GARY PADGETT'S MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY SEPTEMBER, 2001 (For general comments about the nature of these summaries, as well as information on how to download the tabular cyclone track files, see the Author's Note at the end of this summary.) SPECIAL NOTE: Michael Bath, who lives near the northern coast of New South Wales, has agreed to be my proofreader for the summaries. This should help speed up the preparation time for the summaries a good bit. A special thanks to Michael for agreeing to serve in this capacity. *********************************************************************** SEPTEMBER HIGHLIGHTS --> Atlantic produces four hurricanes--none make landfall as hurricanes --> Northeast Pacific very active with one intense Category 4 hurricane --> Northwest Pacific also very active with five typhoons *********************************************************************** ***** Feature of the Month for September ***** SOUTHERN HEMISPHERE TROPICAL CYCLONE NAMES 2001 - 2002 SEASON TROPICAL CYCLONE NAMES for the AUSTRALIAN REGION The Australian Bureau of Meteorology maintains three Tropical Cyclone Warning Centres (TCWC): Perth, Western Australia; Darwin, Northern Territory; and Brisbane, Queensland. Each centre is allotted a separate list of tropical cyclone names for tropical cyclones forming within its area of responsibility (AOR). In addition a TCWC located at Port Moresby, Papua New Guinea (PNG)--a former Australian territory-- maintains a list of native names to assign to the very rare tropical cyclones which form within its AOR. The AORs of the respective centres are: (1) Perth - 125E westward to 90E. Technically, Perth's AOR is south of 10S with Indonesia being responsible for waters north of 10S, but I believe the plan is that any rare tropical cyclone which might form north of 10S would be named by Perth. (2) Darwin - 125E eastward to 138E and extending northward to the equator. There is a little irregularity with the eastern border in the Gulf of Carpentaria. The Darwin TCWC issues High Seas Warnings for the entire Gulf of Carpentaria, but Brisbane issues Tropical Cyclone Advices and names cyclones in the eastern portion of the Gulf. (3) Brisbane - 138E eastward to 160E and generally south of 10S. The northern border with the Port Moresby AOR is somewhat irregular. (4) Port Moresby, PNG - immediate vicinity of the island of New Guinea and eastward to 160E generally north of 10S although the southern border is somewhat irregular. Names for the 2001-2002 season (** indicates name has already been assigned): Perth Darwin Brisbane Port Moresby ----------------------------------------------------------------------- Alex ** Bonnie Bernie ** Epi Bessi ** Craig Claudia ** Guba Chris ** Debbie Des Ila Dianne Evan Erica Kama Errol Fay Fritz Matere Fiona George Grace Rowe Graham Helen Harvey Tako Harriet Ira Ingrid Upia Inigo Jasmine Jim Jana Kim Kate Ken Larry Linda Monica Monty Nelson Nicky Odette Oscar Pierre TROPICAL CYCLONE NAMES for the SOUTHWEST INDIAN OCEAN and the SOUTH PACIFIC OCEAN The Tropical Cyclone Warning Centre (TCWC) at Nadi, Fiji, has tropical cyclone warning responsibility for the South Pacific east of 160E and from the equator to 25S. The Meteorological Service of New Zealand at Wellington has warning responsibility for waters south of 25S, but almost all tropical cyclones in this basin form north of 25S. When a rare cyclone forms in the Wellington area of responsibility (AOR), it usually will be assigned a name from the Fiji list (such as was done for Tropical Cyclone Gita in February, 1999.) Tropical cyclone warning responsibility for South Indian waters west of 90E are shared by several TCWCs. The Regional Specialty Meteorological Centre (RSMC) for the region is the office of Meteo France on the island of La Reunion. However, following a long-standing practice, the sub-regional centres at Mauritius and Madagascar share the responsibility for actually naming tropical storms with Mauritius naming systems east of 55E and Madagascar covering the area west of 55E. RSMC La Reunion issues warnings for the basin independently of these sub-regional centres, but only advises regarding when or when not to assign a name to a developing cyclone. Names for the 2001-2002 season (** indicates name has already been assigned): Southwest Indian South Pacific ----------------------------------------------------------------------- Andre ** Naly Trina ** Fili Bako ** Orelie Vicky ** Gina Cyprien ** Parina Waka ** Heta Dina ** Quincy Yolande Ivy Eddy ** Roger Zoe Judy Francesca ** Solo Ami Kerry Guillaume Teddy Beni Lola Hary Usha Cilla Meena Ikala Vero Dovi Nancy Jery Wendy Eseta Olaf Kesiny Xora Lalita Yolande Mirana Zaza *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for September: 1 tropical depression 4 hurricanes NOTE: Much of the information presented below was obtained from the TPC/NHC discussion bulletins issued with every regular advisory. All references to sustained winds imply a 1-min averaging period unless otherwise noted. Some information was also obtained from the monthly summary for September prepared by the Hurricane Specialists and available on TPC/NHC's website. In addition, I received a good deal of information from Peter Bowyer of the Canadian Hurricane Centre on the effects several of the tropical cyclones had on Newfoundland and the offshore fishing banks. Some of the information was contained in reports prepared by Chris Fogarty of the Newfoundland Weather Centre. A special thanks to Peter for sending me these reports. Atlantic Tropical Activity for September ---------------------------------------- In contrast to the month of August when no hurricanes formed in the Atlantic basin, four tropical storms formed during September and all reached hurricane intensity--two of these reached Category 3 on the Saffir/Simpson scale. On the average the month of September produces 3.4 tropical storms with 2.4 reaching hurricane intensity and 1.2 attaining intense hurricane status. (These averages based on the period 1950-2000.) Erin, the first hurricane of the 2001 season, reached hurricane intensity on 8 September. This is the latest date the first hurricane of the season has formed since 1984. Hurricanes Erin and Felix both became Category 3 hurricanes, but fortunately both remained well out in the Atlantic, although Erin brushed Bermuda. Tropical Storm Gabrielle formed in the southeastern Gulf of Mexico around mid-month and crossed the Florida Peninsula from west to east, making landfall near Venice at just under hurricane intensity. Gabrielle re-intensified in the Atlantic as it moved away from the U. S. coast and reached hurricane intensity as it passed well west of Bermuda. The final hurricane of the month, Humberto, formed in a residual trough left over from Gabrielle south-southwest of Bermuda. Humberto subsequently passed northward west of the island, eventually turning northeastward across the North Atlantic shipping lanes. A very interesting feature of the Atlantic tropical cyclones this season has been the double peak in intensity all eight of the named systems through the end of September have exhibited. A brief synopsis follows: (1) Allison - peaked at 50 kts off Texas coast, weakened over land, then re-intensified to gale force as a subtropical cyclone over southeastern Louisiana and southern Mississippi. (2) Barry - reached an initial peak of 40 kts before weakening into a tropical depression, then re-intensified to near hurricane force as it moved inland in the Florida Panhandle. (Operationally, Barry was maintained as a minimal tropical storm, but the weakening to depression status will be reflected in the Best Track.) (3) Chantal - actually a triple peak intensity of sorts. Upgraded to a tropical storm east of the Windward Islands but weakened into an open wave later the same day. Redeveloped in the central Caribbean Sea and reached an intensity of 60 kts, weakened slightly due to shear in the western Caribbean, then re-intensified to 60 kts just as it made landfall on the southern Yucatan Peninsula. (NOTE: In a telephone conversation with Jack Beven, Jack indicated that in the Best Track file Chantal will most likely not be considered a tropical storm east of the Antilles.) (4) Dean - developed suddenly just north of the Virgin Islands into a 50-kt tropical storm, but was sheared apart and dissipated the next day. The remnant LOW then moved northward and interacted with an old frontal trough, regaining tropical storm intensity north of Bermuda and almost reaching hurricane intensity before moving over colder SSTs in the North Atlantic. (5) Erin - initially developed into a 50-kt tropical storm in the tropical Atlantic east of the Lesser Antilles, then weakened into a tropical wave due to hostile shear. A new center formed to the north 24 hours later and ultimately developed into Hurricane Erin. (6) Felix - became a tropical depression in the eastern Atlantic but weakened into a tropical wave 24 hours later. Redeveloped a couple of days later and eventually became Hurricane Felix. (Felix was the only one of the eight which did not have a double peak in intensity after becoming a named storm.) (7) Gabrielle - formed in the southeastern Gulf of Mexico, made land- fall near Venice, Florida, just shy of hurricane intensity, weak- ened over land but re-intensified after moving into the Atlantic, ultimately reaching hurricane force west of Bermuda. (8) Humberto - reaching an initial peak intensity of 85 kts while passing west of Bermuda, weakened to minimal hurricane intensity a day later, then very surprisingly underwent a rejuvenation with winds climbing to 90 kts north of the 40th parallel! Interestingly, none of the seven tropical cyclones forming after 1 October displayed a double peak in intensity except for Hurricane Karen, and its initial peak was reached as an extratropical storm before undergoing an evolution into a subtropical and later tropical cyclone. In addition to the four hurricanes, the only other tropical cyclone during September was a short-lived tropical depression in the western Caribbean. A tropical wave was noted approaching the Windward Islands on 15 September. The wave moved through the islands into the eastern Caribbean on the 16th accompanied by showers, thunderstorms, and gusty winds. The disturbance continued westward across the Caribbean during the next few days with little sign of development. As it reached the western Caribbean on the 19th, early morning visible satellite imagery suggested that it had become better organized. Advisories were initiated on Tropical Depression #9 at 2100 UTC. The circulation was broad and there appeared to be two centers--one east of Costa Rica and one about 100 nm east-southeast of Puerto Cabezas, Nicaragua. The strongest and most persistent deep convection was associated with the northernmost center, so that center was considered to be the primary one. Upper-level outflow was very circular and quite impressive. The depression moved steadily westward and by 20/0000 UTC was moving inland near Puerto Cabezas. Although the surface circulation began to quickly weaken over the mountainous terrain, the cloud pattern remained well-organized. The remnants of Tropical Depression #9 subsequently moved across Central America and emerged into the Eastern Pacific where they eventually developed into Hurricane Juliette, which became the second major hurricane of the season in that basin. Hurricane Erin (TC-06) 1 - 17 September ----------------------- A. Origins ---------- A vigorous tropical wave left the west African coast on 30 August, passing south of the Cape Verde Islands the night of the 30th. Environmental conditions were favorable and some of the numerical models were suggesting that tropical cyclone development might occur in a couple of days. The wave remained poorly organized on the 31st but overnight the convective organization improved. TPC/NHC initiated advisories on Tropical Depression #6 at 2100 UTC on 1 September with the center located roughly 650 nm west-southwest of the Cape Verdes. A drifting buoy west of the LLCC had reported a northwest wind of 15 kts and a pressure of 1008.7 mb. Deep convection had increased markedly and this trend continued through the night. By early morning of the 2nd Dvorak numbers were T3.0 from SAB and T2.5 from TAFB, so the depression was upgraded to Tropical Storm Erin with 40-kt winds. B. Track and Intensity History ------------------------------ Erin set out on a westward track, strengthening slightly to 45 kts as the 2nd progressed. The storm remained poorly organized, even though shear was weak and outflow good. Winds were upped to 50 kts at 03/0900 UTC when the cyclone was centered about 950 nm east of the island of Barbados. However, the upper and lower circulation centers were still not vertically aligned. Visible pictures during the morning of 3 September revealed an exposed LLCC southwest of the main CDO feature. At 1000 UTC a drifting buoy about 60 nm west of the center reported 31-kt winds. By 1100 UTC the buoy was reporting north winds of only 20 kts with an attendant SLP of 1008.4 mb. The 1500 UTC discussion noted that tropical storm-force winds were likely confined to the northeast quadrant. As Erin moved westward it moved closer to an upper-level LOW which induced shear over the cyclone. Several bursts of convection were noted, but the cold clouds had an amorphous shape. The MSW was reduced to 40 kts at 2100 UTC. However, by early on 4 September the shear had decreased and the storm appeared better organized. NHC raised the MSW back to 45 kts at 0900 UTC based on a 0200 UTC buoy report of 41-kt winds about 40 nm northeast of the center. Also, outflow had improved and the convective pattern was more circular in appearance. The abatement in the shear, however, was temporary. The first flight into the storm by the Hurricane Hunters on the morning of 5 September found a poorly-defined circulation with a minimum pressure of 1013 mb. A peak flight-level wind of 49 kts was measured east of the center. Tropical Storm Erin was downgraded to a tropical wave at 05/2100 UTC about 250 nm northeast of Guadeloupe, having lost its circulation and deep convection due to a hostile environment. The system appeared to have several weak centers of vorticity along the wave axis. On the morning of 6 September, a Tropical Weather Outlook issued by NHC noted that thunderstorms had increased overnight and that a LLCC might be forming on the southwestern side of the new patch of deep convection. A reconnaissance flight was dispatched into the area during the afternoon and found a poorly-defined LLCC with winds of 30-35 kts at flight level in rainbands. The cloud pattern was gradually becoming better organized with an impressive curved band of convection to the north. Advisories were re-initiated on Tropical Depression Erin at 2100 UTC, locating the new center about 650 nm southeast of Bermuda--well to the north of where the old one had dissipated the day before. Visible satellite imagery on the morning of the 7th indicated that the LLCC and outflow had improved since the previous day. Erin was likely a tropical storm at 1500 UTC, but the forecaster preferred to wait until the Hurricane Hunters investigated the cyclone during the afternoon before upgrading. The reconnaissance crew found a SLP of 1004 mb and flight-level winds of 46 kts northeast of the center, so Erin was upgraded once more to tropical storm status at 2100 UTC. Convection was not particularly deep, but the LLCC was well-defined with good banding and fair outflow. A shortwave trough passing to the north had weakened the steering currents and Erin began a slow drift to the north-northwest. The CP had dropped to 999 mb by 08/0600 UTC with 49-kt winds found at the 925-mb level northeast of the center. Visible pictures during the morning of the 8th indicated a much better-organized storm than 24 hours previously with good banding and deep convection near the center. Dvorak numbers had reached T3.5, so the MSW was upped to 45 kts at 1500 UTC. A strengthening ridge to the north was steering Erin on a slow northwesterly track. Based on the official forecast track, a hurricane watch was issued for Bermuda. During the afternoon visible imagery revealed a well-defined cloud band wrapping around the center, indicating that a banding eye was likely forming. A reconnaissance flight found a pressure of 994 mb with flight-level winds of 76-80 kts, so Erin was upgraded to a hurricane at 2100 UTC when located roughly 350 nm southeast of Bermuda. A flight into the hurricane during the evening found winds of 84 kts and a CP of 992 mb, and concurrent satellite intensity estimates were 77 kts, so the intensity was bumped up to 75 kts at 09/0300 UTC. Erin was sporting an eye 35-40 nm in diameter with good outflow, especially to the north of the center. A reconnaissance flight around 0600 UTC on 9 September found a flight-level wind of 101 kts at 700 mb with an attendant pressure of 982 mb, so the MSW was increased to 90 kts at 0900 UTC, making Erin a Category 2 hurricane on the Saffir/Simpson scale. The eye continued to become better defined, and the next flight into the storm at 1800 UTC found that Erin had deepened into a major Category 3 hurricane. Peak winds at 700 mb were 118 kts while a GPS drop into the north- eastern eyewall showed a spot surface wind of 111 kts with mean boundary layer winds around 100 kts; the official MSW was set to 105 kts as a compromise. The CP had fallen to 968 mb--a little high for 105 kts, but environmental pressures were also rather high. The center of Hurricane Erin was located about 100 nm east of Bermuda at the time it became the season's first major hurricane. The 105-kt intensity was maintained for 24 hours. The cloud tops warmed a bit during the night, but the eye became even better defined. Erin continued moving to the north-northwest, and by 1500 UTC on the 10th was centered approximately 150 nm north of Bermuda, and was displaying the classic signature of a major hurricane with a well- defined eye 30 nm in diameter. A NOAA P3 research plane flew into Erin during the afternoon, and data suggested that the winds had likely weakened a bit to 100 kts or less. Wind profile data indicated that Erin had formed concentric eyewalls. During the evening stepped- frequency microwave radiometer data and GPS drops indicated that surface winds had decreased to around 80 kts, although one drop reported 89 kts at an altitude of 17 m. Dvorak intensity estimates, however, were still 90 kts, so the MSW was lowered to 85 kts at 11/0300 UTC. By 0900 UTC on 11 September, Erin had reached the ridge axis and was preparing to recurve to the northeast. The intensity had dropped to 80 kts, where it remained for 18 hours. By early on 12 September Erin had recurved and was moving in an eastward direction. The intensity was reduced to 75 kts, but as the hurricane was moving over a ribbon of warm water, the weakening process was slow. Large swells from Erin reached the northeastern U. S. during this period. On the 13th the storm turned more to the northeast, although at a slow pace. The eye remained large and well-defined with Erin still moving over 26 C SSTs. The MSW was lowered to 70 kts at 13/0600 UTC and remained pegged there for 24 hours. Late on the 13th the eye was still apparent in infrared imagery, but eyewall convection had become asymmetric, perhaps due to the storm's encountering cooler waters. By early on 14 September Erin had accelerated to 17 kts. The eye was still visible but the MSW was lowered to 65 kts. As the day progressed Erin's eye disappeared and the convection became displaced north of the center--signs that the storm was beginning extratropical transition. Satellite intensity estimates remained at 65 kts however, so the cyclone was maintained as a hurricane. Buoy 44625, located northwest of the center, reported a pressure of 988.2 mb at 1800 UTC. By 15/0300 UTC the remaining convection had become confined to the northwest quadrant. TAFB was still reporting 65 kts, but SAB had classified the storm as extratropical, so the final NHC advisory was issued, downgrading Erin to a 60-kt storm that was rapidly becoming extratropical. Erin at this time was located very near Cape Race, Newfoundland, and the remnant extratropical storm continued moving rapidly northeastward the next couple of days. The last reference to the system in MPC's High Seas Forecasts was at 17/0000 UTC when it was a 40-kt gale near 65N, 35W, still moving northeastward. In summary, the peak intensity of Hurricane Erin (per TPC/NHC's operational advisories) was 105 kts from 09/1800 UTC through 10/1800 UTC. The minimum pressure measured by the Hurricane Hunters was 968 mb at 09/1800 UTC. Gale-force winds extended out from the center 150 nm to the northeast and 100 nm elsewhere while hurricane-force winds reached outward 40 nm in the eastern semicircle and 30 nm in the western semicircle. C. Meteorological Observations ------------------------------ In addition to the reconnaissance data and buoy reports incorporated into the above section, I have received some information from Peter Bowyer of the Canadian Hurricane Centre regarding observations made in southeastern Canada and in offshore waters. The Laurentian Fan Buoy (WMO 44141) reported wave heights to 9 m as Erin passed by early on 14 September. As the storm passed a few miles south of the Nickerson Bank Buoy, seas built to 7 m with a maximum wave height of 14 m being reported at 15/0000 UTC. Rain began falling in Newfoundland late on the 13th from a quasi- stationary frontal zone extending northeast of Erin. The heaviest rain was concentrated along the southern coast of Newfoundland west of the Burin Peninsula where more than 100 mm was recorded at Sagona Island and Burgeo. A second wave of rain, associated with Erin's cloud shield, brought amounts near 75 mm from Bonavista to the Burin Peninsula. A few of the higher storm totals are: Sagona Island - 131 mm Burgeo - 102 mm Bonavista - 78 mm St. Lawrence - 66 mm Lethbridge - 63 mm No hurricane force winds were reported on land. Some exposed coastal stations reported gusts of 58 kts in northwesterlies behind Erin while the strongest winds in the easterlies ahead of the storm were at Cape Race, where a peak gust of 52 kts was recorded at 2124 UTC on the 14th. Both Cape Race and Bonavista reported gusts to 58 kts early on the 15th. St. John's and Grates Cove reported gusts to 45 kts and 49 kts, respectively, also early on the 15th. D. Damage and Casualties ------------------------ No reports of any damage or casualties resulting from Hurricane Erin have been received. Hurricane Felix (TC-07) 7 - 19 September ------------------------ A. Origins ---------- A tropical wave left the African coast on 3 September and marched westward across the tropical Atlantic. This wave never developed into a tropical cyclone, but did influence and interact with the following wave which eventually became Felix. The cyclone tracks file for September contains a track of this leading disturbance which was sent to the author by Roger Edson. No advisories were issued by NHC on this system--it was treated as a tropical wave--although some of the Tropical Weather Discussions indicated that a broad circulation was associated with the wave. Roger estimated that the LOW was accompanied by winds up to 30 kts, which is plausible--many tropical waves are accompanied by winds of 30 kts or stronger without forming a well-defined low-level circulation. The next tropical wave to emanate out of Africa entered the Atlantic on 5 September. A 1009-mb LOW was noted on the 6th as the well- organized disturbance passed south of the Cape Verdes. By the after- noon of the 7th, the system had become better organized with banding features and good outflow and was classified as a tropical depression at 07/2100 UTC when located about 350 nm west of the Cape Verdes. During the night of 7 September Tropical Depression #7 displayed a band of strong convection, but no deep convection was located near the center. By the morning of the 8th the depression consisted of a broad circulation with only a few bands of convection, and by afternoon no evidence of a LLCC could be seen in satellite imagery, so the system was downgraded to a tropical wave and advisories discontinued. In the meantime, the tropical LOW preceding TD-07 had become quasi- stationary in mid-ocean, and by the morning of 9 September the remnants of the depression were combining with the leading wave to produce a broad low-pressure area about 1100 nm east of the Lesser Antilles. Advisories on TD-07 were re-initiated at 0900 UTC on 10 September with the center located about 525 nm west of the earlier final position at 08/1800 UTC, or about 1000 nm east of Martinique. Deep convection had persisted near the LLCC while outflow had become more pronounced. Also, some nearby buoys had reported pressures around 1008 mb. Visible pictures on the 10th brought a complication, however. Two distinct LLCCs were evident, one consistent with the previous west-northwestward motion while a weaker circulation to the southeast was associated with the weaker tropical wave that had preceded the depression. The deepest convection was concentrated east of the northern vortex, which was considered to be the primary center. There was some question during the night of the 10th as to whether or not the system was maintaining a closed circulation, but depression status was maintained pending the availability of visible images the next morning. Organization improved, however, and at 11/0900 UTC all three satellite estimates were near tropical storm strength. By 1500 UTC the LLCC had become better defined under deep convection and the outflow had gradually improved, so the depression was upgraded to Tropical Storm Felix at this time. The newly-christened tropical storm was located about 800 nm east-northeast of Guadeloupe and was moving north-northwestward around the periphery of a subtropical ridge. B. Track and Intensity History ------------------------------ For the first 24 hours of its life as a tropical storm, Felix remained at minimal tropical storm intensity. Convection, while deep, was displaced to the northeast of the LLCC. Morning visible images on 12 September indicated that the cyclone had become better organized with the center embedded in deep convection and an eye-like feature trying to develop. The MSW was increased to 55 kts at 1500 UTC and to 60 kts at 2100 UTC. Felix was upgraded to a 65-kt hurricane at 13/0300 UTC based on Dvorak estimates, partially-contaminated QuikScat data, and a doughnut-shaped feature in SSM/I imagery. The storm by this time was moving north, or slightly east of due north, and strengthened quickly after reaching hurricane intensity. The advisory issued at 13/1500 UTC noted that Felix had developed an eye embedded within the CDO with plenty of banding and fair outflow. Satellite intensity estimates from TAFB and SAB had reached T5.0, so the MSW was increased to 90 kts. By 1800 UTC the satellite presentation of the storm had continued to improve--the eye was distinct and surrounded by very deep convection with plenty of curved bands. TAFB had increased their Dvorak estimate to T5.5, so the MSW was upped to 100 kts, making Felix the second Category 3 hurricane of the season. The storm at this time was centered roughly 1200 nm southwest of the Azores, moving northward. Felix remained at its peak intensity of 100 kts for 18 hours, then began to slowly weaken. By 1500 UTC on the 14th the eye had disappeared in infrared imagery and was not well-defined in visible pictures. Also, water vapor imagery indicated that some southwesterly shear was impinging on the cyclone. The MSW was reduced to 95 kts at 1500 UTC and to 90 kts at 2100 UTC. Felix was by this time moving northeastward at 13 kts, and this motion had become east-northeasterly by 15/0300 UTC. By the morning of 15 September the hurricane was moving eastward and continuing to show signs of weakening. Visible imagery suggested that mid- to upper-level winds were undercutting the impressive cirrus outflow and inducing mid-level shear. The MSW was left at 90 kts, although the discussion noted that this might be on the high side. Around 1500 UTC a drifting buoy (41644) reported a pressure of 975.8 mb in the northwest quadrant of the eye. Although deep convection persisted near the LLCC, the areal coverage had shrunk and, based in part on the buoy report, the MSW was lowered to 85 kts at 2100 UTC. At 16/0300 UTC satellite intensity estimates from TAFB, SAB and AFWA were 90 kts, 77 kts, and 65 kts, respectively, and the eye had reappeared in METEOSAT-7 infrared imagery, so the intensity was left at 85 kts. On the 16th the cloud pattern associated with Felix became more ragged with cloud tops warming and convection eroding over the south- western semicircle--an upper-level trough appeared to be impinging on the western side of the tropical cyclone. The MSW was lowered to 80 kts at 0900 UTC. About this time, drifting buoy 44765 reported a SLP of 981.4 mb from a position about 60 nm northeast of the center. The NHC discussion noted that central convection had decreased, but that the eye had expanded to a diameter of 80 nm. There were indications during the afternoon that the shear over Felix might be lessening--there was a burst of deep convection noted in the north- east quadrant. Drifting buoy 44765 was in the eye of Felix for most of the morning and reported pressures ranging from 973.8 mb at 1100 UTC to 976 mb at 1500 UTC. The intensity was reduced to 75 kts at 2100 UTC and to 65 kts at 17/0300 UTC. Satellite intensity estimates at this time were below hurricane force, but the earlier buoy data had suggested that Dvorak estimates were a little low. The storm's eastward motion had slowed to 8 kts or less by the morning of 17 September as a mid-latitude trough had bypassed the area. At 1500 UTC Felix was located about 250 nm south of the northwestern- most Azores and was drifting to the southeast. Northwesterly shear had displaced the convection to the southeast of the LLCC and the cyclone was downgraded to a 60-kt tropical storm. SSTs in the area were about 24-25 C. Felix continued to slowly weaken as it remained quasi- stationary or drifted slowly southward. Winds were down to 45 kts by 0300 UTC and continued to drop as the day progressed. By 0900 UTC little if any deep convection remained as the storm drifted south- southwestward, retracing its path over waters that had been cooled by upwelling. Felix was being steered by flow on the eastern side of a mid-level subtropical ridge. No deep convection was observed at 1500 UTC and the MSW was reduced to 35 kts. Drifting buoy 44765, which had passed through the eye of Felix two days earlier, again encountered the storm and reported a pressure of 1001.2 mb. Felix was downgraded to a tropical depression at 2100 UTC, based on nearby ship reports of 25 kts. As the 19th began Felix consisted of a broad but rather well- defined circulation devoid of any deep convection. A QuikScat pass indicated maximum winds of 25 kts, and ship KAKF confirmed these winds at a location well south of the center. Since models indicated no chance of regeneration, NHC issued the final advisory on the former Category 3 hurricane at 0300 UTC on 19 September with the remnant LOW drifting slowly southward, well south of the Azores. Hurricane Felix was at its estimated peak intensity of 100 kts from 1800 UTC on 13 September through 1200 UTC on the 14th with the central pressure estimated at 965 mb during this period. At its peak Felix was a large, severe hurricane. Gales covered an area between 300 and 400 nm in diameter and hurricane-force winds reached outward from the center 30-40 nm in all directions. C. Meteorological Observations ------------------------------ No reconnaissance missions were flown into Hurricane Felix. The only surface reports available to the author were the buoy and ship observations mentioned in the preceding section. D. Damage and Casualties ------------------------ No damage or casualties are known to have resulted from Hurricane Felix. Hurricane Gabrielle (TC-08) 11 - 21 September ---------------------------- A. Origins ---------- A Tropical Weather Outlook issued by TPC/NHC on the afternoon of 8 September noted that disorganized cloudiness and thunderstorms extended from the eastern Gulf of Mexico across the Florida Peninsula into the northern Bahamas and adjacent Atlantic waters. This area of disturbed weather was associated with a weak trough of low pressure. The trough and unsettled weather persisted in the area for the next few days, and on the morning of 11 September surface data revealed the existence of a definite closed circulation over the southeastern Gulf of Mexico. The deep convection did not show much curvature, but was near enough to the LLCC to warrant classifying the system as a tropical depression. The first advisory on TD-08 was issued at 2100 UTC with the center located about 125 nm west-northwest of Key West, Florida. The maximum winds were estimated at 25 kts, and with northerly shear over the area and an upper-level vortmax moving south-southeasterly toward the depression, strengthening was forecast to be slow. By the early morning of the 12th the depression was a little better organized. Buoy 42003 in the eastern Gulf reported a pressure below 1009 mb with a 24-hour drop of 4 mb. Deep convection remained to the south of the broad and ill-defined center, but convective banding had increased in the eastern semicircle across southern Florida. As the day wore on an upper-level shortwave trough near the north-central Gulf Coast modified the upper flow over the system, resulting in a decrease in the shear. Satellite imagery revealed increasing organization of the depression and buoy data indicated pressures were continuing to fall, so the MSW was bumped up to 30 kts at 2100 UTC. A reconnaissance plane visited the area during the evening and found a very broad circulation with convection not very well organized near the center, but rather oriented in a linear band extending from the northern Yucatan coast to the southwest Florida coast. Deep convection began to persist near the center on the morning of 13 September, and ship WPKD, located about 70 nm southeast of the center, reported 32-kt sustained winds at 0600 UTC with a pressure of 1006 mb. Outflow was good in the southeastern semicircle but restricted to the northwest due to upper-level shear. Around 1200 UTC ships DCUW and WCZ5238 reported winds of 35 and 40 kts, respectively, and both TAFB and SAB had assigned a T2.5 Dvorak rating, so the depression was upgraded to Tropical Storm Gabrielle with 40-kt winds at 1500 UTC, located about 200 nm west-northwest of Key West. The storm was still experiencing some shear--the center was partially- exposed on the western edge of the deep convection. B. Track and Intensity History ------------------------------ A reconnaissance flight during the afternoon found the center well northeast of the previous position. It was not clear whether the center had reformed or if the storm had been moving northeastward. WSR-88D animation suggested the latter, so warnings were ordered up for portions of the Florida coast. Gabrielle was located in a shearing environment due to an upper-level trough over the eastern Gulf of Mexico. However, the SHIPS model indicated that the storm could become a hurricane before moving inland. The reconnaissance flight at 14/0000 UTC found a pressure of 996 mb and flight-level winds of 52 kts. The system was somewhat sheared with bursts of deep convection forming east of the center. Heavy rainbands from Gabrielle were spreading onshore over the southern Florida Peninsula and the Keys. During the night the center of Gabrielle appeared to keep reforming to the northeast under the convection. The reconnaissance plane at 0600 UTC found a central pressure of 992 mb but encountered winds of 70-75 kts at flight level near the Florida coast. The storm at that time was moving northeastward at 9 kts. The center of Gabrielle reached the southwestern Florida coast near Venice around 1200 UTC on 14 September. The storm almost reached hurricane intensity just before making landfall. Reconnaissance data indicated that the pressure fell to 980 mb, and 700-mb winds as high as 81 kts were measured at flight level. These, however, were near the Venice C-MAN station, which at the time was reporting gusts to only 40 kts. It appears that the higher winds at flight-level were not mixing down to the surface. Gabrielle spent the next 24 hours crossing the Florida Peninsula, emerging into the Atlantic just northeast of Cape Canaveral by around 1200 UTC on the 15th. The convection decreased markedly after the storm made landfall with the strongest remaining convection found in bands well-removed from the center to the north and east. The MSW was maintained at 40 kts during Gabrielle's overland trek, being supported by synoptic observations of 35-40 kts near the Florida East Coast, particularly the St. Augustine C-MAN station. While over Florida Gabrielle began to take on the appearance of an occluded frontal LOW more so than a tropical cyclone. The circulation was large with a non-symmetrical wind field and devoid of any deep convection near the center. The fact that the storm maintained a CP less than 999 mb and winds of 40 kts while over land suggests that its nature was not purely tropical. By 15/1500 UTC the center had moved offshore into the Atlantic near Cape Canaveral. The NHC discussion noted that it resembled a subtropical cyclone with the strongest winds and convection removed from the center and an upper-level cyclone superimposed over the surface center. A reconnaissance flight found winds near 60 kts in the southeast and northwest quadrants with a CP of 998 mb, so the MSW remained at 40 kts. Two ship reports of 43 and 44 kts at 1800 UTC led to the intensity being raised slightly to 45 kts at 2100 UTC. Convection had moved a little closer to the center, but Gabrielle still had a "frontal" look about it. SAB had classified the system as extratropical, and TAFB was calling it a subtropical storm. The cyclone was moving northeastward roughly parallel to the southeastern U. S. coast and by 2100 UTC had accelerated to 13 kts. The intensity was increased to 50 kts at 16/0300 UTC based on ship reports of 50-kt winds in the northwest quadrant near the coast and supported by reconnaissance data and GOES cloud drift winds which indicated winds to 50 kts in other quadrants. Six hours later it appeared that Gabrielle was about to become extratropical--a reconnaissance mission reported that the center had become more elongated with little or no core temperature rise at 850 mb. However, the storm was still moving over warm waters and a slight increase in convection near the center was noted. By 1500 UTC reconnaissance reports and satellite imagery indicated that Gabrielle had become better organized and had strengthened some. At 1140 UTC a pressure of 995 mb was measured and at 1328 UTC a plane found winds of 67 kts northwest of the center, so the MSW was increased to 55 kts. The temperature of the core had also warmed and satellite imagery indicated increasing outflow in the northwest semicircle, suggesting that Gabrielle was still a warm-core tropical cyclone as it sped northeast- ward at 17 kts. During the 16th the storm continued to develop deep convection on the northern side of the ragged, exposed LLCC. Satellite intensity estimates ranged from 35 kts from SAB to 55 kts from KGWC. At 0000 UTC on 17 September a GPS drop made by a NOAA research aircraft reported winds of 68 kts near the center just above the surface, so Gabrielle was upgraded to a 65-kt hurricane at 17/0300 UTC when centered approximately 325 nm west of Bermuda. Even so, the system still appeared to be sheared and asymmetric with the deep convection to the north and east of the center. A dry slot wrapping around into the southern semicircle produced a comma-cloud signature more typical of subtropical storms than tropical cyclones. A reconnaissance flight into Gabrielle around 1200 UTC measured winds to 85 kts at 1500 m along with a pressure of 983 mb, so the MSW was bumped up to 70 kts in the 1500 UTC advisory. By afternoon of the 17th Gabrielle was an impressive system in satellite imagery despite the southwesterly shear affecting the storm. Visible pictures indicated that a banding eye might be trying to form as moderate convection had wrapped 3/4 of the way around the LLCC. Also, the storm had good outflow to the north. However, at 18/0300 UTC Gabrielle was downgraded to a 55-kt tropical storm. The upper-level center was being displaced to the northeast of the LLCC by the south- westerly shear. By 0900 UTC some deep convection had redeveloped just north of the LLCC, so the intensity was maintained at 55 kts. However, Gabrielle was well northeast of Bermuda at this time and beginning to move over progressively cooler SSTs. Six hours later some deep convection still persisted near the center, but the cloud pattern was beginning to look more like an evolving extratropical low-pressure system. The MSW of 55 kts in the 1500 UTC advisory was based on tropical and extratropical satellite intensity estimates of 50 and 55 kts from TAFB and KGWC, respectively. Deep convection continued to persist near Gabrielle's center through the afternoon, but the appearance of the storm was more that of an extratropical LOW. The MSW was increased to 60 kts at 2100 UTC based on a report from ship WMLH, located about 90 nm northwest of the center. Observations from the ship in conjunction with AMSU data indicated that Gabrielle was still a warm-core system. NHC issued their final advisory on Gabrielle at 19/0300 UTC with the storm centered roughly 375 nm southwest of Cape Race, Newfoundland. A recent QuikScat pass had indicated windspeeds near 60 kts, and earlier a buoy had reported a pressure of 977.6 mb, but all cloud tops were warmer than -50 C and there was no deep convection anywhere near the LLCC, so Gabrielle was declared extratropical. At 1200 UTC on the 19th the center of Post-Tropical Storm Gabrielle (the term used by the Canadian Hurricane Centre) passed about 50 nm south-southeast of Cape Race. The last reference to the system in MPC's High Seas Forecasts placed the center near 59N, 31W, at 1800 UTC on 21 September, still generating 50-kt winds. Hurricane Gabrielle's peak intensity of 70 kts was attained at 17/1200 UTC and was maintained for twelve hours with an attendant minimum CP of 983 mb. However, in the Gulf of Mexico phase of Gabrielle, a reconnaissance plane measured a pressure of 980 mb at 14/1009 UTC, shortly before the tropical storm made landfall near Venice, Florida. At the time of Gabrielle's peak intensity on the 17th, gales covered an area about 450 nm in diameter with the radius of hurricane-force winds 25 nm in all directions. Shortly before the storm made landfall in Florida, gales extended outward from the center 125 nm to the northeast and 100 nm to the southeast. C. Meteorological Observations ------------------------------- As Tropical Storm Gabrielle approached the west coast of Florida during the early morning of 14 September, Dry Tortugas reported winds of 38 kts, gusting to 44 kts. Around mid-morning on the 14th the AWS at Venice reported sustained winds to 50 kts with a peak gust of 63 kts. During the afternoon, St. Petersburg on the west coast and St. Augustine on the Atlantic coast both reported gusts to 47 kts. The St. Augustine AWS (elevation 16.5 m) reported sustained winds of 48 kts at 14/2200 UTC and 41 kts at 15/0100 UTC while Gabrielle's center was over the peninsula. At 15/1800 UTC, ships DHER and OZQP2 reported sustained winds of 44 and 43 kts, respectively, while north- west of the center. According to the NHC monthly summary for September, rains in excess of 250 mm fell over portions of west-central Florida and a storm surge of 1.5 m above normal affected the west coast of the peninsula. Bermuda reported wind gusts to 42 kts early on 17 September as Gabrielle passed slightly more than 300 nm west of the island. The storm had just been upgraded to a hurricane at that time. At 1800 UTC on 18 September, when Gabrielle was southwest of Newfoundland, ship WMLH, located about 90 nm northwest of the center, reported a pressure of 984.5 mb with the air temperature 23.9 C and the dew point 22.2 C. This observation, in conjunction with AMSU data, helped to establish that Gabrielle was still a warm-cored system. Gabrielle's center passed over or very near the Laurentian Fan Buoy (44141) just before midnight on 19 September. Wave heights exceeded 9 m and the reported SLP was 977.6 mb and falling. The Nickerson Bank Buoy (44251), located about 80 nm northwest of Gabrielle, reported seas of 5 m. In Newfoundland light rain began falling on the 18th over the southern Avalon and Burin Peninsulas, well north of the storm's center. The rain became heavier on the 19th, and between 0600 UTC and 1200 UTC extremely heavy rain fell across the eastern Avalon Peninsula as Gabrielle approached to within around 70 nm due south of Cape Race. Much of the rain was due to embedded thunderstorms in the circulation around Gabrielle. Cape Race recorded 48 mm in one hour between 0900 and 1000 UTC, and St. John's West measured 27 mm between 0600 and 0700 UTC. Some storm totals include: Cape Race - 162 mm St. John's West - 127 mm St. John's Airport - 119 mm Rainfall amounts west of the Avalon Peninsula were less than 35 mm. Strong northerly winds were experienced over eastern sections of Newfoundland with gusts to 54 kts or higher recorded on all three peninsulas: Avalon, Bonavista, and Burin. Some of the peak winds reported were: Cape Race - 70 kts at 19/1257 UTC (maximum sustained 57 kts at 1200 UTC) St. John's West - 48 kts at 19/1404 UTC St. John's Airport - 47 kts at 19/1114 UTC Grates Cove - 59 kts at 19/1816 UTC Bonavista - 56 kts at 19/1900 UTC Gander - 34 kts at 19/1600 UTC Sagona Island - 54 kts at 19/1247 UTC St. Lawrence - 56 kts at 19/1227 UTC D. Damage and Casualties ------------------------ The heavy rains of Gabrielle led to major river flooding in west- central Florida and on the lower St. Johns River. There was also wind damage to roofs, mobile homes and trees. Total damage was estimated at $230 million. A drowning death along the Alabama coast was attributed to Gabrielle. In Newfoundland extensive damage due to flooding occurred in St. John's. Numerous basements were flooded and some streets were under- mined. Local brooks and lakes swelled beyond capacity, inundating parks and backyards. (No dollar amount of this damage was available.) Hurricane Humberto (TC-10) 21 - 28 September --------------------------- A. Storm Origins ---------------- After Tropical Storm Gabrielle had crossed Florida and moved on to the northeast and strengthened as a sort of quasi-subtropical storm, a residual trough, somewhat resembling a front, continued advancing southeastward, reaching the general area between Puerto Rico and Bermuda by 19 September. On that date a Tropical Weather Outlook issued by NHC at 1530 UTC noted that a weak LOW accompanied by some scattered convection was located about 475 nm northeast of Puerto Rico. Afternoon satellite pictures indicated a circulation might be forming, although environmental pressures were quite high. By midday on the 20th convection was better organized around a well-defined surface LOW about 350 nm northeast of Puerto Rico. The LOW gradually became better organized through the night, and advisories were initiated on Tropical Depression #10 at 1500 UTC on 21 September. The system had moved west-northwestward to a position roughly 450 nm south of Bermuda by this time. Both TAFB and SAB were estimating winds at 25 kts and deep convection was developing near the center. The depression had a very impressive satellite signature with plenty of banding, convection and cirrus outflow, but a reconnaissance flight during the afternoon did not find a well-enough defined LLCC to make a formal fix. Wind observations, however, did show a weak surface circulation about 40 nm west-southwest of the upper-level circulation center. An upper-level LOW to the southwest of TD-10 was still inducing some shear over the system. At 22/0000 UTC the intensity estimates from TAFB and SAB were both 35 kts, but ship KAKF, located near the depression's center, reported winds of only 22 kts with a pressure of 1011.8 mb. By 0600 UTC, SAB's estimate had reached 45 kts, and the system displayed a nicely curved convective band in the eastern semicircle. However, multispectral infrared imagery showed some exposed low-level cloud lines west of the main convection. The 1200 UTC Dvorak estimates from all three agencies were T3.0 (45 kts), and the cloud pattern was well-organized with curved bands and fair outflow, but since on the previous day the system was not as intense as satellite estimates had suggested, the forecaster chose to maintain depression status pending the next reconnaissance mission. The winds, however, were increased to 30 kts. An early afternoon reconnaissance flight into the cyclone found a fairly strong tropical storm with flight-level winds of 57 kts in the west quadrant and a central pressure of 998 mb. A special Tropical Update at 1830 UTC upgraded the depression to Tropical Storm Humberto, located about 250 nm south-southwest of Bermuda and moving north- westward at 10 kts. The initial intensity was set at 50 kts, and the 2100 UTC discussion noted that Humberto had a well-defined, tightly- wound surface center. The storm was forecast to gradually turn to the north around the periphery of the subtropical ridge to the east. B. Track and Intensity History ------------------------------ By 0300 UTC on 23 September a CDO feature had developed, although the MSW remained at 50 kts. A drifting buoy about 40 nm northwest of the center had reported winds of 25 kts and a SLP of 1011.9 mb at 23/0000 UTC, indicating that Humberto was a rather small tropical cyclone. The 0600 UTC reconnaissance flight found a pressure of 994 mb with 65-kt winds at 450 m both east and west of the developing 25-nm diameter eye. Convection had consolidated near the center and outflow was good, so the intensity was upped to 55 kts. By mid-morning on the 23rd Humberto displayed a cold symmetric CDO with good banding north and east of the center, and an 1100 UTC SSM/I pass revealed a doughnut-like eye feature. Estimates from TAFB and SAB had reached 65 kts, but the MSW was increased to only 60 kts since another plane was due to reconnoiter the storm at 1800 UTC. The reconnaissance flight at midday on the 23rd found a central pressure of 984 mb and peak flight-level winds of 86 kts at the 700-mb level northeast of the center, but a concurrent GPS drop near the eye- wall measured only 56 kts at the surface. However, the mean boundary layer windspeed was 79 kts, so the MSW was increased to 70 kts, making Humberto the fourth hurricane of the season and also for the month of September. Humberto was then centered approximately 125 nm west- southwest of Bermuda, moving northward at 9 kts. Observations during the evening from a multi-aircraft mission indicated that Humberto had strengthened further. Eyewall dropsonde data from a NOAA research airplane showed winds of 87 kts at the surface in the northeast quadrant. Stepped-frequency microwave radiometer data also indicated similar winds, so the MSW was increased to 85 kts at 24/0300 UTC, making Humberto a Category 2 hurricane on the Saffir/Simpson scale. The minimum pressure was 983 mb--a little high for 85 kts--but the cyclone was embedded in a higher-than-normal sea-level pressure environment. Humberto's tenure as a Category 2 hurricane, however, was quite brief. The reconnaissance plane at 0600 UTC found that the pressure had risen to 989 mb, and the highest flight-level wind encountered was 68 kts. Satellite imagery suggested some southwesterly shear impacting the hurricane. The MSW was lowered to 80 kts, and was further reduced by 5 kts on each subsequent advisory until Humberto was a minimal 65-kt hurricane at 25/0300 UTC. Oddly, during the morning of the 24th, Objective Dvorak numbers were slightly higher than during the night. Cloud tops warmed significantly during the day, and another multi-aircraft mission into the storm during the evening indicated that Humberto had weakened into a minimal hurricane. GPS drops measured surface winds around 62-64 kts and radar observations indicated that the eyewall was open over most of the southern semicircle. The weakening trend halted, however, and throughout the 25th Humberto held on to hurricane intensity, displaying an intermittent eye-like feature surrounded by deep convection. The hurricane had recurved and was moving northeastward in the general direction of Newfoundland. Weakening and eventual extratropical transition were forecast, but Humberto had one more trick up its sleeve. The NHC discussion at 0900 UTC on 26 September noted that an eye surrounded by deep convection had persisted throughout the night, and with TAFB rendering a Dvorak number of T4.5 (77 kts), the MSW was increased to 70 kts. This improvement in Humberto's appearance coincided with a jog to the north, probably in response to ridging near the cyclone downstream of a large cutoff LOW over the Great Lakes. By 1500 UTC the 15-nm eye had become better defined and cloud tops had cooled even more. Dvorak numbers from both TAFB and SAB had reached T5.0, so Humberto's winds were bumped up to 90 kts, making the storm once more a Category 2 hurricane. The hurricane at this time was north of the 41st parallel about 300 nm southeast of Halifax, Nova Scotia. This strengthening at such a northerly latitude was most unusual. Humberto was located over SSTs of 25-26 C just south of a sharp SST gradient, and a building upper-level ridge near and north of the storm had apparently sheltered it from stronger westerlies. However, like its first flirtation with Category 2 intensity, Humberto was not able to maintain the 90-kt intensity for very long. By afternoon the eye was becoming indistinct and the MSW was lowered to 80 kts at 2100 UTC. The convective pattern was becoming asymmetric with most of the cold clouds shifting to the northeast semicircle. Humberto was likely feeling the effects of cooler SSTs and stronger westerly flow, its forward speed having increased to 13 kts. The Canadian Laurentian Fan Buoy (44141) reported a pressure of 990 mb at 2100 UTC, and a SSM/I overpass at 2310 UTC showed a partial eye- wall to the north. Although Dvorak intensity estimates remained at 90 kts, Humberto's organization was decreasing and the intensity was reduced to 65 kts at 27/0300 UTC. Based on buoy reports, SSTs along and near the forecast track of Humberto were ranging from 15-20 C. On the 27th Humberto's track took an almost due eastward turn. The storm was downgraded to a 60-kt tropical storm at 0900 UTC. The convection was showing less banding and was becoming amorphous as the cyclone accelerated eastward. Satellite intensity estimates were still at hurricane intensity, but given the stabilizing cool SSTs, it was deemed unlikely that any hurricane-force winds were making it down to the surface. During the morning westerly flow aloft increased, and by 1500 UTC Humberto was sailing eastward along a sharp SST gradient at 28 kts. During the afternoon the cloud pattern deteriorated with the convective cloud mass becoming elongated and distorted and removed from the LLCC. NHC issued the final tropical advisory on Humberto at 2100 UTC with the storm located about 500 nm east-southeast of Cape Race and racing slightly south of due east at 27 kts. The storm was rapidly becoming extratropical and was forecast to be absorbed into a very large cyclonic circulation over the North Atlantic during the next day or two. Hurricane Humberto reached its first peak in intensity at 0300 UTC on 24 September when the MSW and central pressure, based upon data from a reconnaissance flight, were 85 kts and 983 mb, respectively. Hurricane-force winds extended out 25 nm northeast and southeast of the center and 15 nm elsewhere. Gales reached outward 90 nm in the eastern semicircle and 35 nm in the western semicircle. Humberto's primary peak occurred after the surprise re-intensification on the morning of 26 September, but the 90-kt MSW and 970-mb central pressure were only estimates based on satellite imagery. At the time of this second peak in intensity, winds to hurricane force extended outward 30 nm from the center in all directions while 34-kt winds reached out 60 nm in the northern quadrants and 120 nm to the southeast. C. Meteorological Observations ------------------------------ I have received no synoptic reports associated with Humberto other than the buoy observation referenced in the above section. D. Damage and Casualties ------------------------ No reports of damage or casualties resulting from Hurricane Humberto have been received. According to information from Peter Boywer of the Canadian Hurricane Centre, Humberto was exclusively a marine event and had no impact on inland areas in the Canadian Maritimes. Like its predecessors, however, Humberto did pass over the Laurentian Fan and Southwestern Grand Banks marine areas, being the fourth tropical cyclone in less than a month to bring storm or hurricane-force winds to those areas. ADDENDUM TO AUGUST SUMMARY Impact of Tropical Storm Dean in Southeastern Canada ---------------------------------------------------- Since the August summary was issued, Peter Bowyer of the Canadian Hurricane Centre has sent me some information on the effects of Tropical Storm Dean in Newfoundland and on the Canadian marine banks. As Dean crossed the southwestern Grand Banks on 28 August, many ships and buoys to the right of the storm track and out to 200 nm reported gale-force winds. There were no confirmed gales to the left of the track, however. Hibernia (WMO 44145) reported south-southeasterlies of 47 kts at an anemometer height ot 139 m just before Dean passed to the north. A large area of 4 to 6-metre seas was produced to the southeast of the track across the southern Grand Banks. Ship PDHY (41.7N, 49.5W) at 28/1800 UTC reported a wave of 5.7 m while Tail-of-the-Bank Buoy (44140) experienced seas of 5.7 m at 1600 UTC approximately 120 nm to the right of the track. At about the same distance to the left of the storm's track, seas built to 3.5 m at the Nickerson Bank Buoy (44251) at 1800 UTC. Only light southeasterly winds of 10-15 kts were experienced over Newfoundland. A band of rain displaced well to the north (250 to 300 nm) of Dean's track remained quasi-stationary over the eastern portion of the island. Heavy rains occurred between midnight and midday on the 28th from the Bonavista Peninsula to the Burin Peninsula. Some of the highest storm totals include: Bonavista - 107 mm Lethbridge - 76 mm St. Lawrence - 72 mm The capital of Newfoundland, St. John's, recorded a much lower 24 mm while Gander netted only 19 mm. *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for September: 2 tropical depressions 2 tropical storms 3 hurricanes NOTE: Much of the information presented below was obtained from the TPC/NHC discussion bulletins issued with every regular advisory (CPHC for locations west of 140W.) All references to sustained winds imply a 1-min averaging period unless otherwise noted. The narratives for all of the named storms were written by John Wallace of San Antonio, Texas. Because of the interaction between Gil and Henriette, those cyclones are covered in a single report. A very special thanks to John for devoting much of his school holiday time to working on the summaries. Northeast Pacific Tropical Activity for September ------------------------------------------------- The month of September was quite active in the Northeast Pacific basin. Five tropical storms/hurricanes formed during the month, well above the annual average of about three. Three of the storms reached hurricane intensity with one becoming a major hurricane. The averages for September are two hurricanes with one reaching major hurricane intensity (Category 3+ on the Saffir/Simpson scale). Early in the month Hurricane Gil and Tropical Storm Henriette moved in close proximity to each other and engaged in a binary interaction. Around mid-month Tropical Storm Ivo formed near the Mexican coast and prompted the issuance of tropical storm warnings for portions of the Mexican coastline. The storm, however, remained offshore with minimal impact onshore. The most significant cyclone of the month was Hurricane Juliette. USAF Reserves Hurricane Hunters flew some missions into the hurricane, and on one of these, measured a central pressure of 923 mb--the second lowest pressure ever actually measured in an Eastern Pacific hurricane. Juliette later brought tropical storm and hurricane conditions to portions of the Baja California Peninsula. In its last gasp, Juliette, after weaking to below depression status, exceptionally re-intensified over the northern reaches of the narrow Gulf of California. The system never regained tropical storm status but did generate some well-organized, albeit shallow, convection. The final named cyclone was short-lived Hurricane Kiko, which was a minimal hurricane for only six hours. In addition to the five systems mentioned above, two tropical depressions formed in the Central North Pacific west of 140W. The first of these, TD-01C, was very brief, being in advisory status for only 18 hours on 11 September. The first advisory, issued by the CPHC at 11/0000 UTC, placed the center about 400 nm southeast of Hilo. The system was moving westward fairly quickly and was not forecast to reach tropical storm intensity. By 1200 UTC the depression had lost all its convection and the final advisory was issued at 1500 UTC, placing the dissipating center about 400 nm south-southeast of South Point on the Big Island. Tropical Depression 02C formed about 750 nm southeast of Hilo on 23 September. Unlike its predecessor, TC-02C was forecast to intensify into a tropical storm; however, this did not happen. The depression sailed west-northwestward at a low latitude, passing about 500 nm due south of South Point at 1200 UTC on the 24th. The forecast for strengthening did not verify due to shear associated with an upper- level trough west of the Hawaiian Islands, along with interference from a weak disturbance near Johnston Island. The final CPHC advisory was issued at 0900 UTC on 25 September and placed the dissipating center about 650 nm south-southwest of Honolulu. Hurricane Gil (TC-08E) 4 - 9 September ----------------------- AND Tropical Storm Henriette (TC-09E) 4 - 8 September ---------------------------------- A. Storm Origins ---------------- The track and development history of Hurricane Gil and Tropical Storm Henriette is a classic case of direct tropical cyclone interaction, also known as binary interaction, or the Fujiwhara effect. Because of their interaction and almost identical life spans, the two systems will be covered in a single summary. The origin of Gil appears to be unrelated to a tropical wave. A cyclonic disturbance first became apparent along the ITCZ on 2 September and steadily organized. By 0900 UTC on 4 September, the LOW's organization on satellite imagery was sufficient to warrant its upgrade to Tropical Depression Eight-E about 1075 nm west of Manzanillo, Mexico. The tropical cyclone tracked slowly west- northwestward, turning more westward as it was upgraded to Tropical Storm Gil at 1800 UTC on 4 September, located some 1125 nm west of Manzanillo. Henriette's origin can apparently be traced back to a vigorous tropical wave that exited the African coast on 24 August. It quickly weakened, however, and tracked uneventfully across the basin. A LOW formed along the wave axis on 1 September as it entered the tropical Eastern Pacific and slowly organized. By 1500 UTC on 4 September Dvorak estimates justified its upgrade to Tropical Depression Nine-E, just six hours after Eight-E's first advisory, while located approximately 275 nm west-southwest of Manzanillo. Its initial west- northwesterly track turned more westward on the 5th. Easterly shear from the same ridge that was its primary steering influence hindered intensification. Nine-E was poorly-organized, and its future was in doubt until a QuikScat pass supported its upgrade to Tropical Storm Henriette at 2100 UTC on 5 September about 700 nm west of Manzanillo. At this time, Gil and Henriette presented an odd pair--Henriette was the larger circulation, but Gil was much better organized. B. Track and Intensity History ------------------------------ Gil's westward motion slowed on the 5th, and it briefly stalled while Nine-E/Henriette tracked steadily westward. At 0300 UTC on 6 September, Gil was upgraded to hurricane status while Henriette remained a 40-kt tropical storm centered east-northeast of Gil. Exactly when Gil and Henriette first interacted is uncertain, but the interaction manifested itself in earnest beginning on the 6th. Henriette's track changed from westerly to west-northwesterly while accelerating slightly around Gil's northeast flank, in spite of being the larger cyclone. Gil tracked slowly due west (perhaps "held back" by Henriette) and strengthened, reaching its peak MSW of 85 kts and minimum CP of 975 mb at 2100 UTC on 6 September roughly 1175 nm west- southwest of Cabo San Lucas. Henriette intensified as well on the 6th and reached its peak MSW of 55 kts, with a CP of 994 mb, at 0300 UTC on 7 September while centered roughly 825 nm west of Cabo San Lucas. At the time of its peak, Henriette was 460 nm northeast of Gil. The overall track of both systems remained westerly, since it appears that they were both embedded in a larger-scale gyre south of the subtropical ridge. Henriette weakened soon after its peak, in spite of excellent out- flow, after crossing into unfavorably cool waters. It continued to track west-northwestward at a brisk pace on the 7th to finally overtake Gil in longitude on the 8th. Some detail should be given to the events on the 7th and 8th, as these were arguably the most interesting days of the interaction between the two systems. Gil weakened on the 7th as well, due to interference from Henriette's outflow. It maintained hurricane strength while it made an abrupt turn to the northwest, bearing north-northwestward by the end of the day. The magnitude of Henriette's influence on Gil is interesting, considering that by 2100 UTC on the 7th, Henriette was generating only weak convection while Gil remained a solid hurricane. This suggests that the size of a tropical cyclone's circulation is more important than its intensity in binary interaction. Perhaps Gil's influence was dominant, however, and the necessarily reciprocal nature of binary interaction only made it appear as if Henriette was the dominant circulation. Given Henriette's ultimate fate, this is a possibility. Perhaps more likely is that Henriette was the dominant circulation at first but that it was eventually usurped by Gil by virtue of its deterioration. A weak Henriette overtook Gil in longitude early on the 8th. Gil's forward motion, deliberate for most of its life, accelerated briefly but dramatically to the north-northwest, peaking at 22 kts at 1500 UTC on the 8th, at which time it weakened to tropical storm strength. Gil's acceleration coincided with Henriette's comparably dramatic acceleration and turn to the west-southwest as the two systems co-revolved. The final advisory on Henriette, as a tropical depression, was issued at 1500 UTC on 8 September with the center located about 1125 nm east of Hilo, Hawaii. By the time of its last advisory, Henriette was little more than a convectionless vortmax lacking a closed circulation, centered some 250 nm west of Gil. Gil scarcely fared better on the 8th. Shear, probably coupled with cool SSTs, took a heavy toll on the tropical storm, and by late that day Gil was a weakly convective whorl. Gil turned west-northwestward on the 8th as part of the continued co-revolution with Henriette's remnant LOW. On the 9th Gil was downgraded to a depression as it turned west-southwestward. It feebly held on to tropical cyclone status as stable air intruded into the system, further eroding its already weak convection. The final advisory on Tropical Depression Gil was issued at 2100 UTC on 9 September, placing the center about 970 nm east of Hilo. At the time of the final advisory, Gil's and Henriette's remnants comprised two co-revolving LOWs embedded in a larger cyclonic gyre. Henriette's remnant LOW apparently had dissipated, or had been absorbed by Gil's remnant LOW, by the 10th. Gil's remnant, however, remained identifiable until the 15th, after which it dissipated in the Pacific well north of Hawaii. C. Damage and Casualties ------------------------ No casualties or damage are known to have been caused by Gil or Henriette as the two cyclones performed their do-si-do far removed from any populated shores. Tropical Storm Ivo (TC-10E) 10 - 14 September ---------------------------- A. Storm Origins ---------------- Ivo developed from a tropical wave--possibly of African origin--that was first noted in the eastern Caribbean on the 3rd of September. It tracked uneventfully across the Caribbean and Central America and entered the eastern tropical Pacific on the 7th. A LOW formed along the wave axis on the 10th and organized enough to warrant its upgrade to Tropical Depression Ten-E at 2100 UTC that day, centered roughly 100 nm south-southwest of Acapulco, Mexico. The cloud envelope of the incipient disturbance and Ten-E itself were massive, but it was only superficially healthy. Initial Dvorak ratings were low for a depression while easterly shear interfered with its circulation. Ten-E tracked westward at first, south of a mid-level ridge. At 0600 UTC on the 11th, ship ZDBE2 reported 37-kt easterly winds and a 1006.5 mb pressure while located 135 nm north- northeast of the center. This data, along with a Dvorak rating of 2.5 from TAFB, supported Ten-E's upgrade to Tropical Storm Ivo at 0900 UTC on 11 September about 225 nm south-southeast of Manzanillo. B. Track and Intensity History ------------------------------ Ivo's track bent to the west-northwest after its upgrade, around the periphery of the ridge to its north. This prompted the government of Mexico to issue a tropical storm warning for the Pacific coast from Acapulco to Cabo Corrientes at 0900 UTC on the 11th. The warnings were discontinued east of Lazaro Cardenas at 1500 UTC and east of Manzanillo at 2100 UTC the same day as Ivo paralleled the coast. At 0300 UTC on the 12th, a tropical storm warning was issued for Baja California from Cabo San Lucas to Cabo San Lazaro. Mexico dropped the watches for the coast from Manzanillo to Cabo Corrientes at 0900 UTC on the 12th, roughly coinciding with Ivo's turn to the northwest. Ivo peaked at 1800 UTC on 12 September about 175 nm south of Cabo San Lucas with a minimum CP of 998 mb and a 45-kt MSW. This slight strengthening occurred in spite of continued mild northeasterly shear. Ivo maintained this intensity for little more than a day before weakening due to shear and cooler SSTs. At 2100 UTC on the 13th, all warnings for Baja California were dropped. Ivo weakened quickly as its convection collapsed--a ship just east of its center at 0600 UTC on the 14th reported southeasterly winds of only 20 kts. This report justified its downgrade to a depression at 0900 UTC that day with the cyclone's track bending back toward the west as low-level steering winds became dominant. The final advisory on the convection-free vortex of Tropical Depression Ivo was issued at 2100 UTC on 14 September and placed the dissipating center about 425 nm west- northwest of Cabo San Lucas. QuiKScat data indicated that Ivo's winds were no higher than 25 kts at this time. Ivo's remnants were indiscernible by late on the 16th. C. Casualties and Damage ------------------------ Though rainbands from Ivo impacted the Mexican coast, no casualties or significant damage are known at this time. Hurricane Juliette (TC-11E) 21 September - 3 October ---------------------------- A. Storm Origins ---------------- The origin of Juliette is uncertain. Ostensibly, Juliette was a redevelopment of Caribbean Tropical Depression Nine. There are a few people in the meteorological community, however, who feel that Juliette only formed within the larger convective envelope of the post-Nine tropical disturbance and is thus only indirectly related to TD Nine. For simplicity and clarity, in this summary it will be presumed that Juliette was at least loosely related to Tropical Depression Nine. Tropical Depression Nine may have developed from a strong tropical wave that exited the African coast around 12 September, though the evidence linking it to TD Nine is tenuous. The wave that definitively spawned TD Nine was first noted just east of the Lesser Antilles on the 15th. On the 19th, a LOW formed along the wave axis--later that day, satellite and surface analyses supported its upgrade to Tropical Depression Nine at 2100 UTC. Even then its outflow was excellent and its cloud pattern robust. Tropical storm watches were briefly issued for the entire Caribbean coast from Nicaragua to Belize. They were dropped when the depression made landfall on Nicaragua's sparsely- populated Mosquito Coast near Puerto Cabezas at 0300 UTC on the 20th. This was also the last advisory issued on Tropical Depression Nine. The central convection of the remnant disturbance weakened over Central America on the 20th. South of the center, however, convection flared up over the extreme eastern Pacific as early as 1800 UTC that day. By 0000 UTC on the 21st, this new convective center intensified south of Guatemala and had a distinct cyclonic signature. Convection was strong, but apparently the system's organization was insufficient to issue warnings on. It was with some surprise that a Hurricane Hunter mission into the system later that day found flight-level winds of 52 kts at ~1520 m, corresponding to a surface wind of 40 kts. Stepped-frequency radiometer data indicated a limited surface MSW of 50 kts. On the basis of this data, the disturbance was upgraded directly to Tropical Storm Juliette in a special 1800 UTC advisory on 21 September while located some 190 nm southeast of Puerto Angel, Mexico. Juliette tracked west-northwestward, south of a mid-level ridge. Though outflow was not impressive, very warm SSTs favored further strengthening, though no one forecast the actual course of events. B. Track and Intensity History ------------------------------ Juliette's proximity to land prompted the hoisting of watches and warnings for the southwestern Mexican coast, beginning with Juliette's first advisory. These extended roughly from the Gulf of Tehuantepec to Manzanillo and shifted westward on the 21st and 22nd. The watches and warnings were dropped at 1500 UTC on the 22nd as Juliette pulled away from the coast. The storm failed to thrive on the 22nd--deep convection weakened and became asymmetric in spite of moderately favorable upper-level conditions. A surprising development was an abrupt southward shift of the center, while the overall heading shifted to due west. This coincided with Juliette's weakening convection. NHC staff stated that it was probably due to downslope flow from the Isthmus of Tehuantepec. A sustained intensification trend began late on the 22nd as outflow improved and convection re-intensified over the center. The first hints of an eye were apparent in satellite imagery by 2215 UTC that day. Juliette's intensity took off on the 23rd--satellite microwave imagery indicated that an eyewall was forming by about 0300 UTC, while at 1500 UTC satellite data warranted Juliette's upgrade to hurricane status when located about 280 nm south-southeast of Manzanillo. Juliette reached major hurricane intensity only six hours later. A hurricane watch was concurrently issued for the south- west coast of Mexico. Juliette continued to explode in intensity on the 24th. At 0300 UTC the three-hour average Objective Dvorak T-number (ODT) was 7.0, equivalent to a MSW of 140 kts. The constraints of the Dvorak technique, however, meant that the official intensity was "only" 115 kts--the wind field needed time to "catch up" to the satellite estimates. Juliette had a pinhole eye surrounded by a compact, extremely cold CDO at this time. Its eye diameter was only 5 nm, though its circulation was large and imposing. Juliette reached its 125-kt first peak in intensity at 0900 UTC on the 24th with an estimated CP of 936 mb when located some 260 nm south-southeast of Manzanillo. Juliette's CP dropped 53 mb in 24 hours for an average rate of 2.2 mb per hour; this qualifies as rapid deepening. Between 2100 UTC on the 23rd and 0900 UTC on the 24th, the CP fell at an average rate of 2.41 mb per hour, just short of the 12-hour mininum criterion for explosive deepening (2.5 mb/hr for 12 hrs). Juliette's intensity and organization flagged after its peak, apparently due to an eyewall replacement cycle. A Hurricane Hunter mission found flight-level winds (FLW) of only 90 kts in its southeast quadrant at 1800 UTC and a 94-kt FLW in its northeast quadrant later that day. Its estimated MSW dropped first to 100 kts, then to 90 kts by 2100 UTC while its central pressure rose accordingly. The hurricane soon re-intensified, however, and regained major hurricane strength by 0300 UTC on the 25th. By 0900 UTC the three-hour ODT was once again 7.0, and this time it was supported by a T7.0 from the TAFB. Once again, however, the NHC intensity estimate remained conservative until the Hurricane Hunters reached the system. The conservatism was also based on an earlier upward bias of satellite estimates, as determined by reconnaissance on the 24th. The Hurricane Hunters finally reached Juliette late on the 25th and found a Category 4 hurricane that was more intense than expected. They recorded a FLW (at 700 mb) of 131 kts, and measured a surprisingly low CP of 923 mb in Juliette's 9 nm-wide eye. Though lower CPs have been estimated in NEP storms before (e.g., the 902 mb CP of Hurricane Linda (1997)), this is the second-lowest CP actually measured by reconnaissance, after 1973's Hurricane Ava (915 mb). Although the conversion factor for FLW to surface MSW (0.9) suggested surface winds of 120 kts, the 923 mb CP justified the NHC's increase of the official MSW to 125 kts. This was Juliette's "true" peak intensity, attained 415 nm south-southeast of Cabo San Lucas at 2100 UTC on 25 September. Dvorak intensity estimates from TAFB and the AFWA were as high as 140 kts by 0300 UTC on the 26th while SAB estimated 127 kts; the intensity remained 125 kts, however. Juliette was a large hurricane, particularly for the NEP basin. Hurricane-force wind radii were an impressive 60 nm, and 12 ft+ seas extended as far as 325 nm from the center in its southern quadrant at 0300 UTC on the 26th. Ship data from around 0000 UTC that day revealed 34-kt wind radii as large as 225 nm in its eastern semi- circle, placing storm-force winds perilously close to the Mexican coast (18 nm offshore of Manzanillo). Tropical storm warnings were accordingly re-issued for the southwest Mexican coast at 0300 UTC. After tracking slowly west-northwestward for over two days, Juliette made a long-forecast northwestward turn on the 26th, due to the ridge to its north shifting eastward while a trough eroded its western limb. The first watches were issued for Baja California at 0600 UTC that day. Juliette weakened from its earlier peak, though it remained a major hurricane throughout the 26th. Satellite imagery indicated, and a reconnaissance mission found, concentric eyewalls on the 26th. A flight late that day found an amazing three concentric eyewalls, though they found no FLW higher than 93 kts. For a hurricane to have three eyewalls is not unprecedented--three were found in the Atlantic's Hurricane Edouard in 1996 (1)--but they are definitely one of the curios of tropical meteorology. In any event, on the basis of their data, Juliette was downgraded below major hurricane intensity at 0300 UTC on the 27th. The estimated MSW of 95 kts was considered generous given the Hurricane Hunters' findings, but it was rather low for a central pressure that was still as low as 942 mb. According to the NHC's official statements, the discrepancy was probably due to the broad central windfield of Juliette which didn't generate a strong pressure gradient. NOTE--A nice radar picture of the three concentric eyewalls can be found at: The Mexican government issued the first hurricane warning for Baja California at 0900 UTC on the 27th as Juliette turned due north. In spite of persistent forecasts of a westward turn, Juliette continued on this heading. The NHC considered its motion anomalous; indeed, one forecaster said that Juliette seemed to be moving straight through a ridge. Juliette slowly weakened as it tracked straight towards Baja California. By 0300 UTC on the 28th, Juliette was only 45 nm west-southwest of Cabo San Lucas, putting the region well-within the radii of hurricane-force winds. Early on the 28th, the Hurricane Hunters found a minimal hurricane whose CP had risen approximately 1 mb per hour since their last fix. Ship 4XFD reported 67-kt winds in the same region where reconnaissance had reported FLW of 79 kts (the ratio of the surface winds to FLW, 0.85, agreed very well with the classic formulae for the conversion). Again, reconnaissance found a central pressure that seemed to be too low (971 mb) for the winds they found, supporting the NHC's conjecture that the windfield was too broad to generate a higher MSW. Juliette slowed on the 28th. Its motion became erratic, and it had stalled by 2100 UTC as it weakened to tropical storm-strength some 65 nm west-northwest of Cabo San Lucas. The Mexican weather service reported 52-kt sustained winds at Cabo San Lucas at this time as well as a 93-kt gust at 0100 UTC the previous evening. An automatic station at Cabo San Lucas reported a 76-kt wind at 0100 UTC on the 28th, though it is unclear if this were a sustained wind or a gust (probably the latter)(2). The erratic motion was probably due to Juliette finally "feeling" a ridge over the American Southwest while the trough off California weakened and a ridge built in. This left the storm in a col, a weak steering environment where it lingered near the coast. It was the shape of things to come, as it turned out. Juliette surprised forecasters by re-intensifying to hurricane strength at 0300 UTC on 29 September, 65 nm northwest of Cabo San Lucas, while remaining stationary. Satellite estimates suggested that the storm intensified even as it was mostly over land, though that fact was key to the NHC's conservatism in the intensity estimate. Both Cabo San Lucas and La Paz reported only light rain and below- storm-force winds at this time. Apparently most of Juliette's rain and winds were over remote, mountainous regions. Juliette weakened again to a tropical storm at 1500 UTC on the 29th, apparently just over the west coast of Baja California near Todos Santos. Weakening began apace on the 29th, due to dry air entrainment, land interaction, and wind shear. Juliette's center passed very close or over the island of Santa Margarita, just off the west coast of Baja California, at 0000 UTC on the 30th as it finally moved out of its stall and assumed a meandering, roughly northwestward track offshore. Juliette weakened to a depression as it turned north again on the 30th, making landfall at Cabo San Lazaro at approximately 0800 UTC. It tracked northward, straddling the coast, and moved inland over the peninsula. Steering currents remained light as the system was apparently embedded in a mid-level ridge. Though its central convection was weak, convection persisted over the Gulf of California and the adjacent land areas. A 40-kt gust recorded at Santa Rosalia was discounted by the NHC as spurious, since it was discordant with earlier data from that station and inconsistent with satellite data. At 2100 UTC on the 30th, Juliette's center re-formed over the Gulf of California, roughly 15 nm southeast of Tiburon Island. Even so, satellite and surface data discrepancies made pinpointing its location and intensity difficult. Juliette was embedded in a larger cyclonic gyre that had a significant influence on its motion. The final advisory on Juliette was issued at 0300 UTC on 1 October after its low-level circulation decoupled from the rest of the cyclone. Its poorly-defined center was placed inland over the Sonoran coast, some 20-25 nm north of Tiburon Island. In yet another surprise for forecasters, the remnant LOW's convection and circulation regenerated over the Gulf of California on the 1st, warranting its re-upgrade to a depression at 0300 UTC on 2 October some 55 nm south-southeast of Puerto Penasco, Mexico. Althought Juliette was almost unclassifiable by the Dvorak technique, WSR-88D data from Yuma, Arizona, revealed good banding and winds as high as 35-50 kts at 0900 UTC. The latter winds, however, were well above sea level, and it was deemed unlikely that the high winds would have worked down to the surface due to the system's weak convection. Juliette meandered toward the northwest over the far northern Gulf of California on the 2nd before weakening once again. It turned southwestward late on the second, as the deep-layer LOW it was embedded in was deflected southwards by a ridge over the Pacific. The second final advisory on Tropical Depression Juliette was issued at 0300 UTC on 3 October as it made landfall about 80 nm south-southeast of San Felipe, Mexico. C. Meteorological Observations ------------------------------ Juliette lingered off southern Baja California for days, resulting in some impressive rainfall totals for a usually arid region. One government official was quoted as saying that Cabo San Lucas received 457 mm of rain in four days, equivalent to the total of four average rainy seasons. The highest 24-hour totals were: 136 mm at Santiago (Baja California Sur) on the 27th, 167.5 mm at Enpalme (Sonora) on the 30th, and 207.2 mm at San Felipe (Baja California) on 2 October (3). D. Damage and Casualties ------------------------ The estimated damage in Baja California was minor, roughly $12 million according to press reports. The Associated Press stated that in Cabo San Lucas, a resort city of 25,000, Juliette smashed docks, uprooted trees and power lines, and broke the city's water mains. Many tourists were stranded in Cabo San Lucas for the storm's duration as floodwaters washed out the main bridge to the mainland and blocked smaller roads. Damage to the homes of the poor was significant, while most luxury hotels received only minor damage. One hotel, however, suffered 90% damage according to AP sources. In southwestern Mexico, heavy rains from Juliette flooded 200 homes in the state of Michoacan and downed many trees. There was minor flooding and tree damage in Acapulco, while rain-swollen rivers knocked out two bridges in the state of Oaxaca. Three deaths resulting from Juliette are known at present. One man drowned when his boat capsized near the Mexico mainland while a fisher- man from Acapulco was lost in high seas. A Colorado surfer drowned in rough waves and was the only American casualty. E. References ------------- (1.) Weatherwise. February/March 1997, p. 40. (2.) "Ciclon Tropical Juliette." Servicio Meteorológico Nacional (3.) Ibid. Hurricane Kiko (TC-12E) 22-25 September ------------------------ A. Storm Origins ---------------- Kiko developed from a tropical wave that was first noted in the Eastern Pacific on 19 September. By late on the 21st, a definite cyclonic disturbance had formed along the wave axis. The organization of this disturbance improved, warranting its upgrade to Tropical Depression Twelve-E at 0300 UTC on 22 September about 800 nm west- southwest of Manzanillo, Mexico. Although conditions seemed to be favorable for significant strengthening at first, easterly shear slowed intensification while an approaching trough restricted its outflow. This combination of factors made positioning the center difficult. Early on, an initial west- northwestward track was found to be northwesterly when the first good visible imagery became available on the 22nd. Difficulties aside, the depression became organized enough to be upgraded to Tropical Storm Kiko at 2100 UTC on 22 September when located about 950 nm west of Manzanillo. About this time Kiko's track became due westerly as it moved south of the climatological subtropical ridge. The NHC stated that the westward turn may have been due to the realignment of Kiko's LLCC with its deep convection as outflow improved. B. Track and Intensity History ------------------------------ Kiko intensified slowly through the 23rd, perhaps due to the entrainment of stable air into its western semicircle late that day. Even so, microwave satellite imagery revealed eye formation late on the 23rd. Therefore, at 0900 UTC on 24 September, Kiko was upgraded to hurricane status roughly 1225 nm west of Manzanillo with 65-kt MSW and a CP of 987 mb. This was Kiko's peak intensity. At this time, microwave imagery revealed a 20-nm eye, supported by infrared imagery and Dvorak intensity analyses. Kiko's upgrade coincided with a brief west-northwestward jog before a westward track resumed late on the 24th. Interestingly, the NHC also speculates that the decrease in Kiko's forward motion commencing on the 23rd may have also been due to the re-organization and regeneration of its central convection. Kiko weakened to tropical storm-strength soon after its peak due to cooler waters and increased shear. Kiko's deterioration was relatively rapid and it was downgraded to a depression at 1500 UTC on the 25th. The final advisory on Tropical Depression Kiko was issued at 2100 UTC on 25 September when it was located some 1425 nm west of Manzanillo. Kiko was arguably more remarkable in death than it was in life. The storm's remnant was recognizable long after the final advisory was issued and generated intermittent deep convection until the 28th as it drifted westward across the Pacific. The low-level vortmax persisted longer still, and its convection even flared up once again as an extra- tropical cyclone approached. A cold front associated with the LOW finally absorbed Kiko's remnant by 0600 UTC on 2 October, well north- east of Hawaii. C. Damage and Casualties ------------------------ No casualties or damage are known to have resulted from Kiko. *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for September: 2 tropical depressions ** 5 typhoons ** - Both of these systems were treated as tropical depressions by JMA and some of the other Asian TCWCs, but not by JTWC NOTE: Most of the information on each cyclone's history presented in the narrative will be based upon JTWC's advisories, and references to winds should be understood as a 1-min avg MSW unless otherwise noted. However, in the accompanying tracking document I have made comparisons of coordinates with some of the Asian warning centers when their positions differed from JTWC's by usually 40-50 nm or more. A special thanks to Michael V. Padua, owner of the Typhoon 2000 website, for sending me the PAGASA and JMA tracks. Also, a special thanks to Huang Chunliang of Fuzhou City, China, for sending me tracks based on warnings from the National Meteorological Center of China (NMCC), the Hong Kong Observatory (HKO), and the Central Weather Bureau of Taiwan (CWBT). In addition, Roger Edson of the University of Guam sent me tracks for two tropical depressions which were warned on by some of the Asian TCWCs but not by JTWC. A special thanks to Roger for the information he sent. In the title line for each storm I plan to reference all the cyclone names/numbers I have available: JTWC's depression number, the JMA-assigned name (if any), JMA's tropical storm numeric designator, and PAGASA's name for systems forming in or passing through their area of responsibility. Northwest Pacific Tropical Activity for September ------------------------------------------------- The Northwest Pacific basin was very active during the months of September. Five tropical cyclones were named by RSMC Tokyo and all reached typhoon intensity. Typhoon Danas clipped the southeastern corner of Japan and caused a few fatalities and some flooding. Two of the storms, Nari and Lekima, brought destructive floods to Taiwan with Nari being especially deadly. Typhoons Vipa and Francisco both recurved northeastward into the North Pacific with no effects on land. Two additional systems were tracked as tropical depressions by JMA and some of the other warning centers. Roger Edson also provided me with tracks for these systems. Since these depressions were operating simultaneously and, based on Roger's assessment, there is a possibility they could have reached minimal tropical storm intensity, in the tracks file I identified them with the Greek letters "Rho" and "Sigma". The first system, "Rho", was active in some form or another from the 5th until the 12th of September. It originated as a weak LOW in the Gulf of Tonkin east of Hanoi, drifted very slowly eastward across the Luichow Peninsula, reaching a point about 225 nm south-southwest of Hong Kong by 1200 UTC on 8 September, then drifted southward and eventually back to the west. The system became slightly better organized on the 9th, and on 10 September made landfall around 0200 UTC near Lingshui Li Autonomous County of Hainan Province. The depression continued westward across Hainan Dao, re-entering the Gulf of Tonkin once more, and eventually moved inland into southern China where it dissipated on the 12th. Qiongshan City recorded 160 mm of rain from the night of the 7th through the afternoon of the 8th, and a three-day storm total in excess of 210 mm. Wenchang City recorded 115 mm in an eight-hour period on the 8th and 217 mm in a 54-hour period ending at 0600 UTC on 10 September. Haikou City measured 127 mm of rain during the same 54-hour period and 155 mm for a three-day total. One person was injured and 15 houses destroyed in a tornado which lasted a few minutes in Xiuying District, Haikou City around 0840 UTC on the 10th. (The above information was sent to me by Huang Chunliang.) The second depression, "Sigma", formed south of Taiwan on the 7th and moved generally northeastward over the next several days. JMA elevated the 10-min avg winds to 30 kts for a 24-hour period beginning at 09/0000 UTC when the system was located about 100 nm east-southeast of the southern tip of Taiwan. It was at this juncture that Roger Edson assigned a 1-min avg MSW of 35 kts. The most notable aspect of this depression was its interaction with Typhoon Nari which was likely one of the factors contributing to Nari's highly erratic track. The depression continued moving northeastward, passing south of Okinawa on the 10th, and had weakened into a weak LOW south of Japan by the 12th. Both "Rho" and "Sigma" were mentioned by JTWC in their daily STWOs, but no warnings were issued on either system. Typhoon Danas (TC-19W / TY 0115) 2 - 14 September --------------------------------- Danas: contributed by the Philippines, is a Tagalog word meaning "to feel" or "to experience" A. Storm Origins ---------------- JTWC issued a STWO at 0200 UTC on 2 September which noted that an area of convection had formed about 450 nm west of Wake Island. A LLCC with persistent convection was developing in a col area south of a TUTT cell. Diffluence southeast of the trough was creating a fairly favorable environment for development. Although the first JTWC warning was not issued until 03/0000 UTC, the JMV file (a sort of working Best Track) indicates that the system had become a 25-kt depression at 0600 UTC when located about 500 nm west of Wake Island. A TCFA was issued at 2130 UTC as an increase in the areal coverage of deep convection had been noted during the previous few hours. JTWC issued the first warning on Tropical Depression 19W at 0000 UTC on 3 September. The system was centered about 600 nm west of Wake Island or about 570 nm east of the Northern Marianas. Maximum winds were estimated at 25 kts and the depression was moving westward at 5 kts. Convective organization was increasing, and at 1200 UTC the MSW was bumped up to 30 kts with deep convection building over the LLCC. At 0000 UTC on the 4th both JTWC and JMA upgraded the strengthening tropical cyclone to tropical storm status with JMA assigning the name Danas. The newly-christened Danas was then located about 450 nm east of the Northern Marianas, moving westward at 10 kts. B. Track and Intensity History ------------------------------ Initially steered westward by a subtropical ridge to the north, Danas gradually slowed and turned northward as a baroclinic trough east of Honshu moved eastward. The cyclone intensified rather quickly after reaching tropical storm strength. The intensity estimates at 0600 and 1200 UTC on 4 September are good illustrations of the situation often faced by forecasters when they must choose between widely varying satellite intensity estimates. At 04/0600 UTC both JTWC and JMA reported 45 kts (1-min and 10-min averages, respectively). Satellite CI estimates at the time were 30, 45, and 55 kts. Six hours later JTWC's 1-min avg MSW was 60 kts and JMA's 10-min mean MSW was 55 kts--satellite estimates ranged from 45 to 65 kts. JTWC upgraded Danas to typhoon status at 1800 UTC with the center located approximately 350 nm east of the Northern Marianas. The intensity was upped to 80 kts at 05/0000 UTC while at the same time JMA classified the storm as a 70-kt typhoon. Danas by this time was moving northward at 6 kts. JTWC increased the MSW to 85 kts at 05/1800 UTC. A 05/2006 UTC SSM/I pass depicted a small eye feature with good convective banding in the eastern semicircle. Upper-level outflow was good, especially toward the southeast. By 0600 UTC on the 6th satellite imagery revealed a 15-nm round cloud-filled eye in the center of the CDO. The trough which had brought about the northward turn began to fill and the ridge to the north of the typhoon began to strengthen--by 1200 UTC Danas was beginning to move in a north-northwesterly direction which gradually became northwesterly. The storm reached its peak intensity of 115 kts (per JTWC's warnings) at 0000 UTC on 7 September when the eye was centered approximately 400 nm east- northeast of Iwo Jima. The MSW was based on CI estimates of 115 and 127 kts. Danas maintained its peak intensity for 18 hours. A SSM/I pass at 07/1023 UTC revealed a tight, symmetrical system with an 8-nm diameter cloud-filled eye and a primary banding feature over the southeast quadrant. By 08/0000 UTC Typhoon Danas was moving due westward as it was being steered by an intense mid-level HIGH situated east of Japan. The intensity had come down a bit to 105 kts at 1800 UTC on the 7th, although one satellite intensity estimate was still at 127 kts. JTWC lowered the MSW to 100 kts at 0600 UTC, but raised it back to 105 kts at 1200 UTC based on Dvorak intensity estimates ranging from 90 to 115 kts. At 08/1800 UTC Danas had turned to the northwest as it passed about 235 nm due north of Iwo Jima. The storm was also located about 430 nm south-southeast of Tokyo and was beginning to pose a distinct threat to Japan. Typhoon Danas continued moving northwest- ward toward southwestern Honshu until it reached its point of recurvature around 0000 UTC on 10 September about 235 nm southwest of Tokyo. An approaching mid-latitude trough had weakened the ridge which had been steering the storm, allowing it to recurve rather abruptly to the north-northeast. Fortunately, Danas began to weaken steadily as it approached Honshu. The MSW was down to 85 kts by 0000 UTC and continued to drop as the typhoon approached the Tokyo area. At 1200 UTC the 35-nm diameter banding eye of Danas was located about 150 nm southwest of Tokyo and moving north-northeastward at 7 kts. The MSW was 75 kts at that time and had dropped to an estimated 70 kts by the time the eye reached the coast just southwest of Yokosuka at 11/0035 UTC. (Yokosuka is a short distance south of Tokyo on a point of land extending out into Tokyo Bay.) The NAVPACMETOCCEN Yokosuka reported sustained winds of 65 kts from the southeast gusting to 75 kts as the storm made landfall. (JMA's 10-min avg MSW at 0000 UTC was 55 kts.) Danas moved across the peninsula southeast of Tokyo and by 0600 UTC was moving out into the Pacific about 60 nm northeast of Tokyo. JTWC downgraded Danas to a 60-kt tropical storm at this time. (Interestingly, one satellite intensity estimate was still as high as 77 kts.) After crossing extreme south- eastern Honshu the former typhoon accelerated northeastward and weakened as it began to transition into an extratropical cyclone. The final JTWC warning on Danas was issued at 12/0600 UTC. The storm had completed extratropical transition and was located well east of Hokkaido and south of the Kuril Islands, racing northeastward at 22 kts. The extratropical gale continued to moved northeastward, then curved eastward as it approached the 49th parallel. By 0600 UTC on 14 September the system was still a 45-kt gale south of the south- western Aleutian Islands. Typhoon Danas was at its peak intensity of 115 kts from 07/0000 through 07/1800 UTC. The minimum central pressure estimated by JMA was 950 mb. Danas was an average-sized typhoon. At its peak intensity storm-force winds extended outward from the center 80 nm in the eastern semicircle and 50 nm to the west while gales covered an area about 300 nm in diameter. By the time the typhoon was approaching Japan the gale-force radii had expanded--gales extended outward 190 nm to the northeast and southeast and 160 nm to the north- west of the center. C. Meteorological Observations ------------------------------ The only report available was the observation from Yokosuka which was referenced in the above section. D. Comparison Between JTWC and Other Centers -------------------------------------------- Center position coordinates between the various warning centers were in very good agreement for Typhoon Danas. Intensity estimates between JTWC and JMA were in good agreement except for the storm's most intense phase. JMA's peak 10-min avg MSW was 80 kts, and was kept at this value for a full four days, from 06/0000 through 10/0000 UTC, except for a six-hour period on the 8th when it was lowered to 75 kts. JTWC's 1-min avg MSW estimates were at 100 kts or greater for most of this period, peaking at 115 kts on the 7th. NMCC's peak estimated intensity (10-min avg) was 90 kts, from 0600 UTC on 8 September through 0000 UTC on the 10th. During the time when JTWC's MSW was at 115 kts, NMCC's 10-min mean wind was 80 kts. E. Damage and Casualties ------------------------ According to press reports, five persons died in Japan as a result of Typhoon Danas. Four of the deaths were due to mudslides--the other fatality was a 50-year-old man who fell from the roof of his house while carrying out repairs. In addition, fifteen persons were injured, mainly by flying debris. The town of Nikko, north of Tokyo, recorded in excess of 870 mm of rain over a four day period. Flooding was reported by 148 homeowners in several prefectures, and over 220 households were advised to evacuate due to the threat of floods and mudslides. Several trees were blown down across streets in the downtown Akasaka area, crushing one car, but no injuries were reported. Ferry services between Honshu and outlying islands were disrupted, more than 140 domestic and international flights cancelled, and services on a number of train lines in and around Tokyo cut back. Danas' high winds and heavy rains also shut down some of the high-speed bullet trains, leaving thousands of passengers stranded. Typhoon Nari (TC-20W / TY 0116 / Kiko) 5 - 21 September --------------------------------------- Nari: contributed by South Korea, is the lily, a wildflower commonly observed in the summer in Korea A. Storm Origins ---------------- The disturbance which became the long-lived and erratic Nari had its origin in the Philippine Sea in late August. An area of convection had formed by 0600 UTC on 31 August roughly midway between northern Luzon and the Northern Marianas. A broad cyclonic circulation with westerly winds equatorward of the center was located in the region, and there was some isolated convection noted along the southern periphery of the circulation. A 200-mb analysis and CIMSS products indicated moderate vertical shear over the region. The disturbance remained quasi-stationary and by 2 September had weakened and was no longer considered a suspect area for tropical cyclogenesis. On the 3rd the area of convection redeveloped farther west in association with a monsoon trough in the region. A QuikScat pass on the 4th depicted a weak LLCC located about 150 nm north of the previous day's position. Things got interesting on the 5th! Based on JTWC's STWO, the disturbance moved northwestward to a position east of southern Taiwan. JMA, however, classified the system as a weak tropical depression at 1200 UTC, located about 265 nm west-southwest of Okinawa. At 1800 UTC winds were increased to 30 kts (10-min avg). JTWC had assessed the potential for development to be fair at 1200 UTC, and at 1930 UTC a TCFA was issued, noting an improvement in the coverage and organization of deep convection. At 0000 UTC on 6 September JMA upgraded the system to Tropical Storm Nari, located about 200 nm west-southwest of Okinawa. At the same time JTWC initiated warnings on Tropical Depression 20W with 25-kt winds. JTWC's position was about 55 nm west-northwest of JMA's, or about 100 nm east of Taipei, Taiwan. The JTWC warning noted that the center was fully-exposed to the east of a line of deep convection. JMA's intensity remained at 35 kts throughout the 6th while JTWC kept the system at depression status, based on CI estimates of 25 and 30 kts. Enhanced infrared imagery depicted a very weak, diffuse system with a partially-exposed center. Several bursts of deep convection were noted around 1800 UTC, so JTWC increased the MSW to 30 kts. Radar imagery revealed a well-defined mid and lower-level circulation center near the bursts of deep convection. An amended 1800 UTC warning was soon issued upgrading Nari to tropical storm status based on synoptic reports from Okinawa which showed rapid pressure falls and winds near gale force. (Satellite CI estimates at the time were still 25 and 30 kts.) Nari was centered at this time only about 50 nm west of Okinawa, moving east-northeastward at 7 kts. B. Track and Intensity History ------------------------------ The track of Tropical Storm/Typhoon Nari over the next 5 or 6 days after it was named was extremely erratic and convoluted with twists, turns, and loops within loops. It remains to be seen if the final "best track" for Nari will smooth out any of the kinks, but during this period the storm was within easy radar coverage range from Okinawa and the coordinates from JTWC, JMA, and NMCC were in excellent agree- ment. Later, as the storm approached Taiwan, the Taipei radar helped to pinpoint the eye, so again there was little discrepancy between the warning centers as to the exact location of Nari's center. In order to try to present the Nari saga as it unfolded in a clear and orderly manner, I am going to adopt an approach which I've considered on several occasions in the past but have never implemented--a daily diary format. (Dates represent day boundaries in UTC.) September 7th: At 0000 UTC Nari's center was located approximately 13 nm south of Kadena AB, moving slowly eastward at 7 kts. The MSW was estimated at 45 kts, based mainly on synoptic reports--satellite intensity estimates were lower. The storm continued drifting eastward and by 0600 UTC had reached a point about 25 nm east of Kadena where it remained essentially stationary for several hours before reversing its motion and drifting back toward the west. Nari also intensified as bursts of deep convection developed near the center, leading to the MSW being upped to 50 kts at 1200 UTC. By 1800 UTC the storm's center had drifted back westward and was located essentially over Kadena AB. Based on synoptic reports JTWC upgraded Nari to a 70-kt typhoon at this time while JMA and NMCC had increased their 10-min avg MSW estimates to 55 kts and 50 kts, respectively. Nari was a small cyclone with 50-kt winds confined to a zone within 20 nm of the center. September 8th: For most of 8 September Nari drifted initially north- westward, later turning to a westerly track. By 1800 UTC the typhoon's center had reached a point about 140 nm west-northwest of Kadena AB. JTWC brought the MSW down to 65 kts at 1200 UTC where it remained for 24 hours while JMA's and NMCC's intensity estimates remained at 60 kts. Nari had entered Taiwan's AOR by 1800 UTC and CWBT assessed the 10-min avg MSW at 60 kts also. The storm remained small with gales covering an area no more than 100 nm in diameter. September 9th: Nari's westward motion came to a halt early on the 9th and the storm sat essentially stationary at a position about 150 nm west-northwest of Kadena AB. The storm's organization improved during the day with satellite intensity estimates reaching T4.5 (77 kts). An 08/2151 UTC TRMM pass had depicted tightly-wrapped but narrow convective banding. JTWC increased the MSW to 75 kts at 0600 UTC and NMCC upgraded Nari to typhoon status at the same time. At 1200 UTC NMCC increased their 10-min avg MSW estimate to 70 kts while HKO and CWBT both upgraded Nari to a typhoon. JMA had dropped their reported intensity early in the day, but bumped it back up to 60 kts at 1200 UTC. Nari's areal dimensions had increased somewhat by 1800 UTC with gales covering an area over 150 nm in diameter. September 10th: Nari commenced a southward drift early on the 10th which later became east-southeastward. By 1800 UTC the storm had moved to a point roughly 85 nm west-southwest of Kadena where it then remained quasi-stationary for about 48 hours. Nari weakened some, likely due to the upwelling of cooler water in the area where it had been loitering. JTWC reduced Nari's intensty to 65 kts at 0000 UTC while NMCC made a more drastic reduction from 70 to 50 kts. JMA's 10-min avg MSW estimate remained at 60 kts through the 10th. As the storm pulled away from the area where it had sat stationary on the 9th, it began to show signs of intensifying once more. NMCC upped their intensity to 60 kts at 1200 UTC, and JTWC increased their 1-min avg MSW to 75 kts once again at 1800 UTC. September 11th and 12th: On these two days Typhoon Nari was quasi- stationary approximately 40-50 nm west of Kadena. The storm wiggled about some, seeming to describe a very tight clockwise loop within a larger counterclockwise loop. The re-intensification trend noted on the 10th continued--at 11/0000 UTC satellite imagery indicated that a 5-nm irregular eye had developed with an increase in deep convection over the eastern quadrant. The eye diameter had increased to 10-nm by 0600 UTC and CI estimates had reached 102 kts. At 1200 UTC satellite intensity estimates were 102 and 115 kts, so JTWC upped the MSW to 100 kts, which was the peak intensity for Typhoon Nari. The storm's eye at this time was only about 35 nm west of Kadena and 50-kt winds reached outward 35 nm from the center. A gradual weakening trend began afterward, once more likely due to upwelling of cooler waters, and winds had come down to 75 kts by 1800 UTC on the 12th (per JTWC). A SSM/I pass at 12/1236 UTC indicated that the convection associated with the vortex had expanded and weakened. JMA's peak intensity for Nari was 85 kts while NMCC's was slightly lower at 80 kts. Both these warning centers had reduced Nari to a 60-kt tropical storm by 1800 UTC on the 12th. The area covered by gales had expanded to cover a zone almost 200 nm in diameter. September 13th: By 13/0000 UTC Nari was located about 70 nm west of Kadena and had begun to track slowly toward the west-northwest. At 1200 UTC the typhoon was about 120 nm west-northwest of Kadena and had crossed its track of five days earlier, completing a counterclockwise loop which contained a tiny clockwise loop. The storm had briefly moved northwest to this point, then moved little for the remainder of the 13th. Nari's intensity remained basically static--JTWC decreased the MSW to 65 kts at 0600 UTC but bumped it back up to 70 kts at 1800 UTC. JMA's and NMCC's 10-min avg MSW remained pegged at 60 kts, and after Nari re-entered CWBT's AOR at 0600 UTC, that agency estimated the intensity at 60 kts. September 14th: On 14 September Nari weakened slightly, being down- graded to a 60-kt tropical storm by JTWC at 1800 UTC. The other warning centers' 10-min avg MSW estimates likewise remained under typhoon intensity, including that from HKO (Nari had re-entered that center's AOR by 14/0600 UTC). The slow northwestward motion seen the previous day came to a halt about 235 nm northeast of Taipei, and by 1800 UTC a slow southwestward drift had begun. September 15th: Nari turned more to the south-southwest as the 15th began, and for much of the day moved in that direction at a steady 6 kts, but slowed and turned slightly back to the west-southwest late in the day. By 1800 UTC the storm's 22-nm diameter eye was centered approximately 115 nm east-northeast of Taipei. The weakening observed on the previous day proved to be temporary--late on the 14th animated satellite imagery revealed a redeveloping banding eye feature and CI estimates were 65 kts, so JTWC upgraded Nari back to typhoon status after only six hours as a tropical storm. As the day progressed the eye became more distinct and the areal coverage of deep convection increased. JTWC had increased the MSW back to 80 kts by 1800 UTC, and all the other agencies had re-upgraded Nari to typhoon status by 1200 UTC. September 16th: By 16/0000 UTC Nari was located about 100 nm east- northeast of Taipei and drifting westward at 3 kts. This motion later became southwesterly at a slightly faster pace as the day wore on. JTWC increased the MSW to 90 kts at 0000 UTC based on CI estimates of 77 and 102 kts. Gales reached out about 100 nm from the 25-nm round eye. By 1200 UTC Nari's eye was nearing the coast of northeastern Taiwan and made landfall around 1500 UTC just east of the city of Lo Tung. JTWC estimated the maximum winds at landfall to be 85 kts sustained, gusting to 105 kts. By 1800 UTC the center was inland and weakening as it tracked to the southwest at 8 kts. JMA did not increase Nari's intensity (10-min avg) above 65 kts during this secondary peak, but both NMCC and CWBT raised their estimates to 80 kts, and HKO was reporting 75 kts just before landfall. September 17th and 18th: Nari had weakened to a tropical storm by 17/0000 UTC (according to all warning centers) as it drifted slowly south-southwestward over Taiwan. Whereas the center coordinates from the various warning agencies agreed exceptionally well during the time Nari was fairly well-organized and within radar range of Kadena and/or Taipei, during the 17th and 18th the position estimates became rather divergent--not unexpected with a weakening system over land. But in general all the TCWCs except JMA tracked Nari's center down the western side of the island. JMA, however, tracked the storm's center southward just off the eastern coast of Taiwan. JTWC's positions at 0600 and 1200 UTC on 18 September abruptly jumped eastward to near the eastern side of the island, but the 1800 UTC position was back to just west of southwestern Taiwan. All the warning agencies maintained Nari at tropical storm intensity throughout the 17th and 18th except for JTWC and NMCC, who downgraded the storm to depression status at 18/1800 UTC. While the exact location of the center may not be known with certainty during these two days, the storm's slow drift down the backbone of Taiwan led to very heavy rainfall over the island which had disastrous consequences. More on this below. (By 16/1800 UTC Nari had entered PAGASA's AOR and that agency began issuing warnings on the cyclone, naming it Kiko--a Filipino nickname.) September 19th: After all the surprises which this long-lived and erratic cyclone had brought, Nari still had one more trick up its sleeve. After clearing Taiwan Tropical Depression Nari turned westward across the Taiwan Strait. Satellite CI estimates were initially at 30 kts, but the JTWC warning issued at 1200 UTC noted the receipt of a 35-kt CI estimate. By 1800 UTC intensity estimates had reached 45 kts, so JTWC upgraded Nari to a 45-kt tropical storm located about 225 nm east of Hong Kong. A 19/1628 UTC SSM/I pass depicted the possible development of a banding eye. The cyclone had by this time exited the AORs of Taipei and Manila, so those TCWCs were no longer players. NMCC also upgraded Nari back to tropical storm status at 19/1800 UTC with the 10-min avg MSW estimated at 40 kts. HKO, which had never downgraded Nari, raised its intensity estimate back to 40 kts. September 20th: Early on the 20th animated visible and infrared imagery revealed a developing banding eye and improving organization of the deep convection. JTWC increased the MSW to 55 kts at 20/0000 UTC with Nari centered about 155 nm east of Hong Kong. HKO upped their 10-min avg MSW estimate to 50 kts, and NMCC raised theirs to 60 kts, which, following the standard 10-min to 1-min conversion rule, would imply a 1-min avg MSW of about 70 kts. Nari's westward motion picked up some as it neared the Chinese coast. At 0600 UTC the center of the storm was just making landfall about 80 nm east-northeast of Hong Kong with 55-kt winds based on JTWC's warning. HKO's and NMCC's 10-min avg MSW estimates had fallen to 40 kts, but both those agencies were placing the center to the north and west of JTWC's position and hence a little farther inland. As Nari continued westward into China the convection began to weaken rapidly, and by 0000 UTC on 21 September the system was a weak 20-kt LOW located about 150 nm west-northwest of Hong Kong. Interestingly, during this final encore to Nari's long performance, JMA never increased the intensity above 30 kts, somewhat surprising considering the consensus among the other warning centers that the cyclone re-intensified markedly prior to its final landfall in China. C. Steering Influences on Typhoon Nari -------------------------------------- With Nari following such an extremely erratic track--which looked rather like a strand of cooked spaghetti which had been dropped onto a platter--I thought it would be interesting to take a look at some of the circulation features which helped to steer Nari on its long and winding road. The initial JTWC warning on TD-20W noted that the system had formed within a weakness in the subtropical ridge with weak steering currents. Slight interaction with a weak ridge building over China or else an indirect interaction with Typhoon Danas to the east were considered possibilities. Nari's initial eastward motion which carried it across Okinawa the first time was due to the influence of a mid-level ridge to its southeast, between the storm and Typhoon Danas. As the larger and more intense Danas approached, this ridge began to erode and a mid-level ridge began to build near the Chinese coast, leading to Nari's turning back to the west-northwest and crossing Okinawa a second time. However, the Chinese ridge did not build far enough east at that time to induce Nari to follow a more protracted westerly or south- westerly course. The typhoon remained within a weakness in the sub- tropical ridge, resulting in slow, erratic motion. The move back to the southeast which brought the cyclone again near Okinawa as it reached its peak intensity was in part apparently due to interaction with an exposed circulation southeast of the typhoon on 9 and 10 September. This system was carried as a tropical depression by JMA, and the author also received a track from Roger Edson. (This was the depression which I dubbed "Sigma" in the tracks file for September.) Another player in Nari's eastward motion toward Okinawa was the mid-level Chinese ridge, which had become poleward-oriented and extended northeastward from the South China Sea. By the 11th this ridge was weakening and Nari's eastward motion came to a halt. The storm was still located within a weakness in the subtropical ridge, but an extension of the ridge was forecast to build slightly over the East China Sea over the next couple of days as a baroclinic system over the Sea of Japan lifted out toward the north. By 14 September the tropical cyclone had come under the influence of a mid-level ridge over central China and was tracking westward. As this ridge built to the north of Nari, the storm turned to the southwest toward Taiwan. The equatorward flow associated with the mid-level ridge situated by now over eastern China was the primary influence which steered Nari into Taiwan and southward down the backbone of the island. The fact that the system was weakening, plus the distortion due to terrain effects, led to considerable uncertainty at times in the location of the center. As the system re-organized in the Taiwan Strait, it came under the influence of a building low and mid-level ridge over southern China which steered it westward and into the Chinese mainland. D. Comparisons Between JTWC and Other Centers --------------------------------------------- Normally I try to report on the significant differences in intensity between JTWC and other warning agencies in a separate section, but due to the manner in which I detailed Nari's history, I have incorporated those comparisons into the daily diary of the storm in Section B above. E. Meteorological Observations ------------------------------ (1) Okinawa I have no rainfall amounts from Okinawa, and the only wind and SLP report available was one referenced in a e-mail from Mark Lander. As Nari moved westward over the island the second time, Kadena Air Base recorded wind gusts in excess of 87 kts with a minimum pressure of 974 mb. (2) Taiwan I have available some extensive rainfall records from Taiwan--far too many to present here. These were sent to Huang Chunliang by Chun-Chieh Wu of the National Taiwan University, and Chunliang forwarded them to me. Below are some of the totals for various periods at several different stations (all amounts are in mm). (a) For the 24-hour period ending at 16/1500 UTC: Chutzhu 638 Shun-Chi, Taipei County 546 Tien-Mu, Taipei City 438 Pai-Lan, Hsinchu County 425 Kuang-Wu, Miaoli County 419 Kao-I, Taoyuan County 419 Pei-Kuan, Ilan County 321 Nei-Hu 305 Sheuilin, Taichung County 174 (b) For the 48-hour period ending at 17/1500 UTC: Tu-Chang, Ilan County 1051 Chutzhu 1012 Ku-Lu, Ilan County 942 Da-Jan-S, Taipei County 925 Shun-Chi, Taipei County 867 Neo-Tsu, Hsinchu County 850 Nan-Kang, Taipei City 834 Ta-Chi, Taoyuan County 799 Tien-Mu, Taipei City 764 Fong-Mei, Miaoli County 657 Tsaoling, Yunlin County 514 Fenchihu, Chiayi County 505 Shui-Nan, Taichung City 458 (c) Storm totals, from 15/1600 UTC through 17/2100 UTC: Tu-Chang, Ilan County 1255 Ku-Lu, Ilan County 1174 Chutzhu 1145 Da-Jan-S, Taipei County 1024 Nan-Kang, Taipei City 915 Neo-Tsu, Hsinchu County 912 Shun-Chi, Taipei County 892 Tien-Mu, Taipei City 883 Ta-Chi, Taoyuan County 816 Fong-Mei, Miaoli County 676 Hen-Shan, Taichung County 550 Fenchihu, Chiayi County 544 Tsaoling, Yunlin County 535 (d) Storm totals, from 17/1600 UTC through 18/2100 UTC: Chiayi City 775 Kuanzlin, Tainan County 743 Shangder, Pingtung County 510 Niu-Ton, Ilan County 436 Chupei, Hsinchu County 397 Pa-The, Taoyuan County 360 Yueh-Mei, Kaohsiung County 358 Chunan, Miaoli County 353 Pei-Kang, Yunlin County 303 Tung-Tou, Nantu County 277 Anpu, Taipei City 259 (e) Storm totals, from 18/1600 UTC through 19/1200 UTC: Chunjih, Pingtung County 217 Fang-Lia, Pingtung County 146 Hengchun, Pingtung County 97 (3) Chinese Mainland Haifeng City and Shanwei City, located in Guangdong Province, recorded 241.9 mm and 307.9 mm, respectively, during the period from 20/0800 through 21/0800 Beijing time (which is UCT plus 8 hours). Several stations recorded in excess of 100 mm during this period with Guangzhou, the provincial capital, reporting 77.9 mm. A special thanks to Mark, Chunliang, and Chun-Chieh for providing me with meteorological observations from Typhoon Nari. F. Damage and Casualties ------------------------ I received no reports of any damage or casualties from Okinawa. Taiwan was especially hit hard by Typhoon Nari with the storm's rains causing some of the worst flooding ever experienced on the island. According to some information sent to me by Huang Chunliang, there were 93 deaths in Taiwan with 11 missing and 208 injured. Thousands of homes and buildings were damaged by flooding. Water supply to over 1,200,000 households was cut off, electricity to 500,000 homes was disrupted, and 300,000 telephones were disabled. Direct economic losses were estimated to be at least NT$ 30 billion. (Some of this information was taken from the HKO's report on the storm, available at the following URL: Many bridges and railway lines were washed away, and Taipei's Deputy Mayor stated that it might take months to get the city's Mass Rapid Transit system fully operational again. The 93 fatalities resulting from Typhoon Nari rank this storm as one of the deadliest tropical cyclones on record in Taiwan. From some information sent to me by Chunliang, the deadliest typhoons to affect the island since 1958 have been: Ranking Name Date Deaths Missing ------- ---- ---- ------ ------- 1 Gloria 09 Sep 1963 204 88 2 Pamela 12 Sep 1961 158 121 3 Vera 31 Jul 1977 104 10 4 Toraji 31 Jul 2001 103 111 (See Note) 5 Shirley 31 Jul 1960 102 81 6 Elsie 25 Sep 1969 93 12 6 Nari 16 Sep 2001 93 11 7 Fran 06 Sep 1970 89 41 Note: In the summary for July, 2001, I reported the death toll in Taiwan from Typhoon Toraji at 35 with 108 persons missing at the time of the report I had obtained, which was made two days after the storm had struck. The figures above reveal that Toraji turned out to be much more deadly than the preliminary report had indicated. In Guangdong Province, China, where Nari made its final landfall, three persons were reported killed. Direct econmic losses were estimated to have been approximately 60 million yuan in the province. In Huilai County, 154 houses collapsed and 267 were partially damaged. Also, 3400 hectares of farmland were damaged by Nari in the province. Typhoon Vipa (TC-21W / TY 0117) 17 - 23 September -------------------------------- Vipa: contributed by Thailand, is a Thai woman's name A. Storm Origins ---------------- Typhoon Vipa had its origin in a monsoon gyre--a relatively rare mode of the monsoon circulation in the Northwestern Pacific. A long- lived upper-level LOW (TUTT cell), which had originated earlier near Wake Island, had by mid-September migrated westward and was located south of Japan. The LOW had pulled the monsoon trough northward such that its associated cloud band was wrapped around the southern and eastern periphery of the large circulation--the signature of a monsoon gyre. Typhoon Nari at the time was approaching northern Taiwan, and numerical model guidance had been consistently forecasting the development of a large low-level circulation east of the typhoon which would normally be regarded as the next tropical cyclone. Instead, the forecast large LOW turned out to be the gyre. The above information on the monsoon gyre was taken from an e-mail sent by Mark Lander, and Mark noted that a tropical cyclone or two forming in the monsoon cloud band was probably a good bet. An area of convection developed in the monsoon cloud band associated with the gyre on 16 September southwest of Iwo Jima and west-northwest of the Northern Marianas. Deep convection was associated with a possible LLCC, and a 200-mb analysis indicated that an extension of an upper-level ridge was providing good outflow for the disturbance. JTWC upgraded the development potential to fair at 1500 UTC, and a TCFA was issued at 2230 UTC. Deep convection was increasing over the LLCC which was moving north-northeastward at 9 kts. Early morning visible imagery showed low-level cloud lines wrapping in from the north toward the center, which appeared to be located on the northern edge of the convection. The first warning on Tropical Depression 21W, issued at 17/0000 UTC, placed the center about 300 nm west-northwest of the northernmost Marianas Islands. The initial intensity of 25 kts was based upon satellite CI estimates of 25 kts. The MSW was increased to 30 kts six hours later based on synoptic reports. A SSM/I pass at 17/0820 UTC revealed distinct rainbands and a more symmetric appearance to the depression, but the LLCC was still partially-exposed on the northern edge of the deep convection. JTWC upgraded TD-21W to a 35-kt tropical storm at 1800 UTC when the center was located about 85 nm west- southwest of Iwo Jima, moving northward at 6 kts. The system's organization continued to improve, and JMA upgraded the depression to Tropical Storm Vipa at 18/0000 UTC as it was passing about 85 nm west of Iwo Jima. B. Track and Intensity History ------------------------------ The track of Typhoon Vipa was about as smooth and well-behaved as any forecaster could want--starkly contrasting with the incredibly convoluted track of Typhoon Nari. The storm moved north-northwestward from its point of origin, executed a smooth recurvature south of Japan, and then accelerated northeastward on a very straight trajectory. After being upgraded to a tropical storm, Vipa remained at minimal tropical storm intensity for about a day, then intensified rather quickly to typhoon force. The MSW (per JTWC) was still 35 kts at 0600 UTC on 18 September, but was upped to 50 kts six hours later based on satellite CI estimates of 45 kts and a 18/1118 UTC SSM/I pass. At 1800 UTC Vipa became a typhoon about 300 nm northwest of Iwo Jima or about 415 nm south-southwest of Tokyo. Satellite imagery depicted a small, cloud-filled eye. The cyclone was being steered by a subtropical ridge to the east, and was forecast to recurve to the northeast ahead of a baroclinic zone approaching from the west. By the time Vipa was upgraded to typhoon intensity, its forward motion had become northward, and by 19/0600 UTC the storm was moving north-northeastward. Vipa reached its peak intensity of 75 kts at 19/0000 UTC and remained at that level for 18 hours. At 1800 UTC the storm was located roughly 200 nm south of Tokyo and was moving northeastward at 10 kts. Enhanced infrared imagery depicted a slight erosion of the deep convection over the western semicircle--Vipa had begun to track beneath the upper-level southwesterlies. JTWC reduced the MSW to 70 kts and forecast continued weakening and extratropical transition. By 0600 UTC on 20 September Vipa was located about 135 nm east-southeast of Tokyo and had accelerated slightly to 15 kts. The intensity was lowered to 65 kts and the JTWC warning noted that Vipa appeared to be rapidly transitioning into an extratropical cyclone. However, tropical cyclones are rather famous for producing the unexpected, and Vipa was no exception. At 20/1200 UTC a 13-nm diameter eye had re-appeared in satellite imagery and CI estimates were back up to 75 kts, so JTWC raised the MSW back to that value where it remained for another 18 hours. One CI estimate at 1800 UTC was as high as 90 kts. By 21/0600 UTC Vipa was located about 350 nm south of the Kuril Islands and racing northeastward at 39 kts. Although one CI estimate was still 90 kts, the irregular eye had filled and JTWC decreased the intensity to 70 kts. A 21/0731 UTC SSM/I pass revealed erosion of the eyewall and dry air entrainment associated with extra- tropical transition. The MSW was further reduced to 55 kts at 1200 UTC (although one CI estimate was 75 kts), and at 1800 UTC Vipa was declared extratropical about 400 nm east-northeast of the Kuril Islands. The remnant extratropical storm continued northeastward, crossing the Aleutian Islands and entering the Bering Sea where it was still producing 45-kt gales at 23/0000 UTC. In summary, Typhoon Vipa was at its peak intensity of 75 kts (per JTWC) from 0000 through 1800 UTC on 19 September, and also from 20/1200 through 21/0600 UTC. The estimated minimum central pressure reported in JMA's warnings was 970 mb at 19/1800 UTC. At the time of Vipa's first peak intensity, gales extended outward 95 nm in the eastern semicircle and 55 nm to the west, while the radius of 50-kt winds was 25 nm. The storm was only slightly larger in areal extent during its second peak in intensity. C. Meteorological Observations ------------------------------ I have received no surface observations taken from within or near Typhoon Vipa. D. Comparisons Between JTWC and Other Centers --------------------------------------------- JMA and NMCC were the only two Asian warning centers issuing warnings on Typhoon Vipa. JMA upgraded Vipa to typhoon intensity for only one six-hour period beginning at 19/1800 UTC. The 10-min avg MSW was reduced to 55 kts at 20/0000 UTC and further to 50 kts at 0600 UTC where it remained during the cyclone's second intensification phase. NMCC, however, estimated Vipa's peak intensity at 70 kts during the storm's second intensity peak on 20 and 21 September. This compares well with JTWC's estimated peak MSW of 75 kts. E. Damage and Casualties ------------------------ I have received no reports of any damage or casualties resulting from Typhoon Vipa. Typhoon Francisco (TC-22W / TY 0118) 18 - 27 September ------------------------------------- Francisco: contributed by the United States, is a Chamorro man's name (Spanish form of Francis) A. Storm Origins ---------------- JTWC issued a STWO at 15/0600 UTC which noted that an area of convection was developing approximately 200 nm east-northeast of Kwajalein. A recent QuikScat pass had indicated the possible existence of a LLCC. Diffluent flow overlay the region, southeast of a TUTT cell--a scenario somewhat similar to that preceding the development of Typhoon Danas earlier in the month. The disturbance drifted west- ward and by 2300 UTC on the 16th was located 260 nm north-northwest of Kwajalein. Animated infrared and visible imagery indicated that a LLCC was developing with increased convection and good outflow, therefore, the potential for development was upgraded to fair. The STWO issued at 17/0600 UTC relocated the system to a point about 350 nm north of Kwajalein. At 18/0000 UTC JMA began tracking the system as a 30-kt tropical depression located about 275 nm south- southeast of Wake Island. JTWC issued a TCFA at 1200 UTC but placed the partially-exposed center about 100 nm east of JMA's 1200 UTC position. Warnings on Tropical Depression 22W were initiated at 19/0000 UTC with the system centered 390 nm southwest of Wake Island, moving west at 7 kts. The initial MSW of 30 kts was based on satellite CI estimates of 30 kts. The depression's center was located beneath the western edge of the deep convection. TD-22W was upgraded to a tropical storm at 19/1200 UTC. The system had not moved very much and was located about 400 nm southwest of Wake Island. By 20/0000 UTC the cyclone was moving west-northwestward from a point about 880 nm east-northeast of Guam. CI estimates had all reached 35 kts by this time, so JMA upgraded the system to tropical storm status, assigning the name Francisco. B. Track and Intensity History ------------------------------ Tropical Storm Francisco tracked steadily west-northwestward on 20 September, reaching a point approximately 670 nm east of Saipan by 1800 UTC. For the first 24 hours or so after being upgraded to tropical storm status Francisco did not intensify, remaining at minimal tropical storm intensity. However, by 20/1200 UTC deep convection had persisted and increased in areal coverage, so the MSW was increased to 45 kts at this time and raised further to 50 kts at 1800 UTC based on CI estimates of 45 and 65 kts. A 20/1032 UTC SSM/I pass depicted a banding feature developing over the northeastern quadrant. Visible imagery early on the 21st resulted in a relocation of Francisco's center of over 100 nm to the northwest of the previous warning position. The tropical cyclone continued to intensify as the 21st progressed. The MSW had reached 60 kts by 0600 UTC, although multi- spectral imagery revealed that the LLCC became partially-exposed for a few hours. Deep convection began to build once more over the vortex center, however, and at 1200 UTC JTWC upgraded Francisco to typhoon status based on CI estimates of 65 kts. The storm was then centered approximately 300 nm east of the Northern Marianas Islands and moving northwestward at 12 kts. Typhoon Francisco was steered on a fairly smooth track along the southern and western periphery of a large mid-level HIGH centered well to the east of Japan. As a major short-wave in the westerlies approached, the cyclone turned to the north and eventually northeast. Francisco continued to intensify, reaching an intensity of 90 kts by 22/1200 UTC, however, the MSW plateaued at that level for about 24 hours. At 22/1200 UTC the storm was centered about 435 nm east- southeast of Iwo Jima and had begun moving to the north-northwest as it tracked around the periphery of the aforementioned HIGH. A ragged eye 17-nm in diameter was becoming visible by 23/0000 UTC and persisted throughout the day. Francisco passed about 350 nm east of Iwo Jima around 0600 UTC and by 1200 UTC was moving northward as it reached its peak intensity of 100 kts. The typhoon appeared to be well-organized, sporting a 27-nm cloud-filled irregular eye, and animated water vapor imagery indicated a well-defined trough off the east coast of Japan that was helping to create a poleward outflow channel for Francisco. The minimum CP estimated by JMA was 945 mb at 24/0000 UTC. Francisco remained at its peak intensity for 18 hours, then began to weaken. The storm was an average-sized typhoon--gales covered an area about 280 nm in diameter and storm-force winds extended outward about 50 nm from the center. By 1200 UTC on 24 September Francisco was tracking north-northeastward at 16 kts from a point about 700 nm south-southeast of the Japanese island of Hokkaido. Animated satellite imagery depicted a rapid weakening of the deep convection. JTWC lowered the MSW to 90 kts based on CI estimates of 77 and 102 kts. A 24/1124 UTC SSM/I pass depicted tight but discontinuous convective banding. The storm had begun to show signs of extratropical transition by 1800 UTC and this trend continued on 25 September. An SSM/I pass at 24/2056 UTC depicted an eroded eyewall with suppressed convection in the southern semicircle, and JTWC had reduced Francisco to minimal typhoon intensity by 25/0000 UTC when the storm was located about 400 nm east of Tokyo. Francisco had temporarily moved due northward on the 24th but began to accelerate northeastward on the 25th as it got caught up in mid-latitude westerlies. The storm had weakened to 60 kts by 0600 UTC and the intensity continued to drop throughout the day. Dry air began to be entrained into the system and at 1800 UTC, JTWC declared Francisco to be extratropical and issued their final warning, placing the cyclone approximately 550 nm south of the Kamchatka Peninsula and racing northeastward at 36 kts. The extra- tropical storm continued rapidly east-northeastward and by 0000 UTC on 27 September was a 35-kt gale located south of the Aleutians and just east of the Dateline. C. Comparisons Between JTWC and Other Centers --------------------------------------------- JMA's intensity estimates compared fairly well with JTWC's after adjusting for the different averaging periods. JMA was a little on the low side during the period when Francisco was intensifying to typhoon force--JMA reported the 10-min avg MSW at 45 kts at 21/1800 UTC when JTWC was estimating 75 kts (NMCC was 60 kts at this point), and JTWC had increased the MSW to 90 kts by the time JMA upgraded Francisco to a 65-kt typhoon. However, JMA "caught up" and their peak 10-min avg MSW of 85 kts agrees very well with JTWC's peak of 100 kts. NMCC's estimates tended to be higher than JMA's with a peak estimated 10-min avg MSW of 90 kts from 23/0000 through 24/0000 UTC. D. Damage and Casualties ------------------------ No damage or casualties are known to have resulted from Typhoon Francisco. Typhoon Lekima (TC-23W / TY 0119 / Labuyo) 21 - 30 September ------------------------------------------- Lekima: contributed by Vietnam, is the name of a tree whose fruit has only one seed surrounded by a yellow pulp which resembles an egg yolk A. Storm Origins ---------------- A STWO issued by JTWC at 2300 UTC on 19 September noted that an area of convection associated with a monsoon trough had developed a few hundred miles east of Luzon in the Philippine Sea. The convection was disorganized, although there were indications of a possible developing LLCC. The disturbance drifted northward over the next 24 hours and at 21/0000 UTC, NMCC elevated the system to depression status with 30-kt winds located about 275 nm east-southeast of the southern tip of Taiwan. JTWC's daily STWO issued at 0600 UTC indicated that convection was increasing around a broad LLCC. A TCFA was issued at 1900 UTC and the first warning on Tropical Depression 23W followed at 22/0000 UTC. The initial MSW was set at 30 kts based on satellite CI estimates of 25 and 35 kts. JTWC upgraded the depression to tropical storm status on the second warning at 22/0600 UTC based on CI estimates of 30 and 35 kts. The cyclone was then located about 250 nm southeast of the southern tip of Taiwan and was tracking toward the west-southwest at 7 kts. By 1200 UTC all the satellite intensity estimates had reached 35 kts and JMA upgraded the system to tropical storm status, assigning the name Lekima. (PAGASA had also upgraded the system to tropical storm status at 22/0600 UTC and assigned the name Labuyo--the name of a species of extremely hot Filipino pepper.) B. Track and Intensity History ------------------------------ Tropical Storm Lekima continued to drift west-southwestward on the 22nd, becoming quasi-stationary for several hours approximately 115 nm east-northeast of Luzon. The storm resumed a very slow westerly to west-northwesterly motion on 23 September which, by 1800 UTC, had brought the center to a position about 55 nm north of Luzon or about 175 nm south-southeast of the southern tip of Taiwan. Lekima remained a minimal tropical storm for the first 24 hours after it was upgraded, but a steady intensification trend began on the 23rd which resulted in JTWC's upgrading the cyclone to typhoon status at 1800 UTC. The storm intensified slightly early on the 24th with winds reaching 75 kts by 0600 UTC, but then the strengthening trend levelled off and Lekima's intensity remained static for about 24 hours. All the Asian warning centers had upgraded Lekima to typhoon status by 24/1200 UTC with the CWB of Taiwan being the last to do so. Early in Lekima's life steering currents were weak, the primary influence being a mid-level subtropical ridge over China. The typhoon didn't move all that much on the 24th--mainly drifting slowly toward the west-northwest. However, at 1800 UTC JTWC relocated the storm farther to the north (based on microwave imagery) to a point roughly 110 nm south-southeast of Taiwan. Typhoon Lekima was still located within a weakness in the mid-level subtropical ridge situated over China, but a sub-equatorial ridge to the southeast was complicating the steering pattern. At 24/1800 UTC the storm was drifting very slowly north-northeastward, but on the 25th curved back to the north and later northwest toward Taiwan. By 1800 UTC on 25 September Lekima was centered approximately 60 nm southeast of the southern tip of the island. A slight weakening noted late on the 24th proved to be temporary and by 25/0000 UTC the storm's organization appeared to be improving. A TRMM pass at 24/2002 UTC had revealed a small eye feature and a primary band wrapping around the western semicircle. JTWC upped the MSW to 80 kts at 25/0600 UTC and to 90 kts at 1200 UTC. A small banding eye was centrally located within organized convective spiral bands. The intensity remained at 90 kts for the 1800 UTC warning, based on satellite CI estimates ranging from 77 to 102 kts. Based on JTWC's warnings, Typhoon Lekima reached its peak intensity of 95 kts at 26/0000 UTC when it was only about 25 nm off the coast of southeastern Taiwan. The MSW was based on satellite CI estimates of 90 and 102 kts. Gales extended out from the center 140 nm in the southwestern quadrant and around 130 nm in the eastern semicircle. The radius of storm-force winds was estimated to be 60 nm. At 0600 UTC the eye was just about onshore about 170 nm south of Taipei and moving north-northwestward at 6 kts. The storm made landfall around 0900 UTC near the city of Tawu packing MSW of 90 kts, gusting to 110 kts (per JTWC). At 1800 UTC, with the center inland over south- eastern Taiwan, JTWC downgraded Lekima to a 50-kt tropical storm. All the Asian warning centers had also downgraded the cyclone by this time. By 27/0000 UTC the center of Tropical Storm Lekima had crossed over to the southwestern coast of Taiwan, and during the 27th drifted slowly northward along the west coast of the island. The storm slowly weakened, and at 1800 UTC JTWC downgraded Lekima to a 30-kt tropical depression. Interestingly, all the other warning centers were still classifying Lekima as a tropical storm at this point. Exactly what Lekima did on 28 September depends on which TCWC's track one follows. JTWC's operational track takes Lekima on an approximate counterclockwise loop over northern Taiwan. JMA's track also shows some erratic motion and possibly describes a tight loop. However, neither NMCC or HKO show this jaunt to the east over northern Taiwan. CWBT's track ends with the downgrading of Lekima to a depression at 28/0000 UTC, but the final position was in the Taiwan Strait west of the northern end of the island. JTWC re-upgraded Lekima to a minimal tropical storm for a 12-hour period beginning at 28/0600 UTC based on some synoptic reports of 35 kts. By 29/0000 UTC, JTWC, JMA, HKO and NMCC were all in agreement that the center of the weakening cyclone was over water west of Taiwan. Lekima continued drifting northward, brushing the Chinese coast before turning northeastward into the East China Sea. HKO had downgraded Lekima to a depression at 28/0600 UTC, but JMA maintained it as a minimal tropical storm for another 30 hours, and NMCC did not downgrade Lekima until 29/1800 UTC. The final NMCC warning, issued at 0000 UTC on 30 September, placed the 30-kt depression well east of the coast of China, roughly midway between northern Taiwan and Kyushu. C. Comparisons Between JTWC and Other Centers --------------------------------------------- Some of the major differences between the various warning agencies in Lekima's track during its weakening phase have already been noted. With regard to intensity comparisons, the storm's history can be looked at in three stages. From Lekima's inception up through around 1800 UTC on 24 September, the MSW estimates (10-min avg) from the Asian warning centers were basically in good agreement with each other and, after adjusting for the different averaging time, agreed well with JTWC. And, as was noted earlier, during the storm's decaying phase, JMA and NMCC continued to classify Lekima as a tropical storm for 24 or more hours after JTWC's final downgrade of the system to tropical depression status. The period from around 25/0000 UTC until Lekima had made landfall in Taiwan at 0900 UTC on the 26th is very interesting. JTWC increased the typhoon's intensity from 75 kts at 25/0000 UTC to the peak of 95 kts at 26/0000 UTC. JMA estimated their peak 10-min avg MSW of 75 kts at 24/1800 UTC (when JTWC was reporting 70 kts), then decreased Lekima's intensity to 65 kts during the period when JTWC was intensifying the storm. NMCC peaked the storm at 75 kts at 25/1200 UTC, then reduced the winds slightly to 70 kts until landfall. PAGASA's peak 10-min avg MSW of 75 kts was reached at 25/1200 UTC, but that agency also weakened Lekima to 65 kts before the storm made land- fall. HKO and CWBT both estimated a peak intensity for Lekima of 70 kts around the time of JTWC's 95-kt peak MSW. (Anyone interested in trying to sort out these differences in further detail should consult the track for Typhoon Lekima in the cyclone tracks file for September.) D. Meteorological Observations ------------------------------ As was the case with Typhoon Nari, Chun-Chieh Wu of the National Taiwan University sent some extensive rainfall records to Huang Chunliang, who then forwarded them on to me. Below is a summary of some of the rainfall totals for various stations for several different periods of time (all amounts are in mm). (a) For the 24-hour period ending at 23/1500 UTC: Taipin-S, Ilan County 328 Ku-Lu, Ilan County 294 Hsi-Ceiu, Hsinchu County 229 Tatung, Taipei County 156 Chutzhu 139 Yu-Li, Hualian County 138 (b) For the 48-hour period ending at 24/1500 UTC: Ku-Lu, Ilan County 430 Taipin-S, Ilan County 412 Chutzhu, 273 Yu-Li, Hualian County 272 Hsi-Ceiu, Hsinchu County 266 Da-Jan-S, Taipei County 249 (c) For the 72-hour period ending at 25/1500 UTC: Ku-Lu, Ilan County 912 Taipin-S, Ilan County 792 Hsi-Ceiu, Hsinchu County 594 Da-Nung, Hualian County 458 Hualian City 432 Chutzhu 426 Taipin, Taipei County 348 Chengkung, Taitung County 234 (d) Storm totals, from 22/1600 UTC through 26/0500 UTC: Ku-Lu, Ilan County 1167 Taipin-S, ILan County 973 Hsi-Ceiu, Hsinchu County 695 Da-Nung, Hualian County 590 Chutzhu 582 Hualian City 494 Taipin, Taipei County 483 Chengkung, Taitung County 405 (e) For the 24-hour period ending at 26/1500 UTC: Tai-An, Hualian County 508 Lu-Yeh, Taitung County 460 Ceietuan, Ilan County 437 Ku-Lu, Ilan County 338 Kuang-Gu, Hualian County 308 Anpu, Chutzhu 297 Taitung City 295 Fushan, Taipei County 238 Mu-Tan, Pingtung County 223 Ken-Ting, Pingtung County 216 (e) For the 48-hour period ending at 27/1500 UTC: Pu-Lo-Wan, Hualian County 616 Ceietuan, Ilan County 529 Ku-Lu, Ilan County 498 Lu-Yeh, Taitung County 482 Tung-Men, Hualian County 425 Shi-Nan, Kaohsiung County 375 Fushan, Taipei County 365 Mu-Tan, Pingtung County 364 Anpu, Chutzhu 344 Taitung City 310 Ken-Ting, Pingtung County 264 Patrick Hoareau sent me some observations from Basco in the Batan Islands where the eye of Lekima passed very near to. At 24/2100 UTC Basco was reporting a SLP of 974 mb with north-northeast winds of 51 kts. At 25/0100 UTC the wind report was north-northwest at 51 kts with a SLP of 971 mb. In Fujian Province on the Chinese mainland, seven counties reported rainfall amounts exceeding 100 mm for the period 28/0000 UTC through 29/0300 UTC. Among these, Xiapu County reported the highest rainfall accumulation with 268 mm being recorded. E. Damage and Casualties ------------------------ Being a slow-moving typhoon and coming right on the heels of the destructive Nari, the potential for another disaster on Taiwan was very real, but it seems that Lekima was much less destructive than its predecessor. The storm did bring some very heavy rains, but the author has located only scanty references to damage caused by the storm. Landslides blocked some highways, and 5600 persons were with- out power at one point. The only Taiwanese fatalities I could find were two fishermen who drowned when their boat capsized in heavy seas generated by the storm. A third person on board was missing and presumed drowned. One man perished on Luzon in a river swollen by heavy rains spawned by Typhoon Lekima as it brushed that area. On the mainland a landslide on 29 September triggered by the heavy rains of Lekima was responsible for one death (with another missing) near Wenzhou in Cangnan County, Zhejiang Province. If any further reports of damage or fatalities associated with Typhoon Lekima become available later, I shall include them in a future summary. *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for September: 1 tropical cyclone of gale intensity NOTE: The tracking and intensity information for North Indian Ocean Basin tropical cyclones is based primarily upon operational warnings from the Joint Typhoon Warning Center of the U. S. Air Force and Navy (JTWC) at Pearl Harbor, Hawaii. Occasionally some information may be gleaned from the daily Tropical Weather Outlooks and other bulletins issued by the Indian Meteorological Department (IMD), which is the WMO's RSMC for the basin. The MSW are based on a 1-min averaging period, which is used by all U. S. civilian and military weather services for tropical cyclone warnings. For synoptic observations in the North Indian region, both 10-min and 3-min average winds are employed, but IMD makes no attempt to modify the Dvorak scale for estimating tropical cyclone intensity; hence, a 1-min avg MSW is implied. In the North Indian basin JTWC usually does not initiate warnings until a system is well-organized and likely to attain tropical storm status within 48 hours. Tropical Cyclone (TC-02A) 25 - 28 September -------------------------- A. Storm Origins ---------------- An area of convection developed on 24 September about 200 nm west- southwest of Bombay, India. Satellite imagery depicted improving organization with weak convective banding. A 24/0038 UTC QuikScat pass indicated the existence of a well-defined LLCC on the eastern edge of the convection. The disturbance was located under a 200-mb subtropical ridge axis in an environment of weak vertical shear. The MSW was estimated at 25 kts (which would have qualified it for tropical depression status in the NWP basin). The development potential was considered to be fair. JTWC issued a TCFA at 1100 UTC based on a 24/0514 UTC SSM/I pass which indicated developing banding west of the LLCC. The Indian Meteorological Department (IMD) classified the system as a depression on the 25th, the center being located about 325 nm west- southwest of Bombay at 0300 UTC. JTWC issued a second TCFA at 25/1100 UTC. Earlier TRMM and SSM/I passes had failed to clearly define a LLCC, but multi-spectral animated imagery depicted weak cumulus lines outlining a partially-exposed LLCC just inside the eastern edge of the convection. The LOW continued to move west-northwestward across the Arabian Sea, and by 26/0000 UTC animated visible imagery indicated that the LLCC had moved under the deep convection. Satellite intensity estimates were 30 kts, but synoptic reports warranted upgrading the system to a 35-kt tropical cyclone. The first JTWC warning placed the center of TC-02A about 350 nm west-southwest of Bombay, moving west- northwestward at 6 kts. (NOTE: Information available to the author from IMD is quite sketchy, but that agency also classified TC-02A as a cyclonic storm (i.e., tropical storm) on 26 September.) B. Track and Intensity History ------------------------------ Initially the cyclone was forecast to strengthen into a 50-kt system and make landfall on the southern end of the Arabian Peninsula, but this scenario never materialized. Easterly shear inhibited significant strengthening of the tropical cyclone and eventually brought about its demise. By 1800 UTC on the 26th the LLCC was exposed approximately 45 nm east of the convection. The JTWC warning at 27/0600 UTC still anticipated some slight strengthening, but by 1200 UTC the official forecast was calling for no additional intensification and gradual dissipation. The center of TC-02A was then located about 230 nm east- southeast of Masirah Island off the coast of Oman. At 1800 UTC on the 27th the MSW was lowered to 30 kts, based on satellite CI estimates of 25 and 30 kts. Animated infrared satellite imagery depicted weakening convection 35 nm west of the LLCC. The system drifted westward during the next 24 hours as it slowly weakened. By 28/0600 UTC satellite imagery depicted a fully-exposed LLCC with no associated deep convection. JTWC issued the final warning on this system at 1800 UTC, placing the dissipating center about 100 nm east- southeast of Masirah Island. C. Damage and Casualties ------------------------ No damage or casualties are known to have resulted from this weak tropical cyclone. *********************************************************************** SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E Activity for September: No tropical cyclones *********************************************************************** NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E Activity for September: No tropical cyclones *********************************************************************** NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E Activity for September: No tropical cyclones *********************************************************************** SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E Activity for September: No tropical cyclones *********************************************************************** EXTRA FEATURE In order to shorten the amount of typing in preparing the narrative material, I have been in the habit of freely using abbreviations and acronyms. I have tried to define most of these with the first usage in a given summary, but I may have missed one now and then. Most of these are probably understood by a majority of readers but perhaps a few aren't clear to some. To remedy this I developed a Glossary of Abbreviations and Acronyms which I first included in the July, 1998 summary. I don't normally include the Glossary in most months in order to help keep them from being too long. If anyone would like to receive a copy of the Glossary, please e-mail me and I'll be happy to send them a copy. *********************************************************************** AUTHOR'S NOTE: This summary should be considered a very preliminary overview of the tropical cyclones that occur in each month. The cyclone tracks (provided separately) will generally be based upon operational warnings issued by the various tropical cyclone warning centers. The information contained therein may differ somewhat from the tracking and intensity information obtained from a "best-track" file which is based on a detailed post-seasonal analysis of all available data. Information on where to find official "best-track" files from the various warning centers will be passed along from time to time. The track files are not being sent via e-mail. They can be retrieved in the following manner: (a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206] (b) Login as: anonymous (c) For a password use your e-mail address (d) Go to "data" subdirectory (Type: cd data) (e) Set file type to ASCII (Type: ascii) (f) Transfer file (Type: get remote_file_name local_file_name ) (The files will be named with an obvious nomenclature--using September as an example: sep01.tracks) (g) To exit FTP, type: quit Both the summaries and the track files are standard text files created in DOS editor. Download to disk and use a viewer such as Notepad or DOS editor to view the files. The first summary in this series covered the month of October, 1997. If anyone wishes to retrieve any of the previous summaries, they may be downloaded from the aforementioned FTP site at HRD. The summary files are catalogued with the nomenclature: sep01.sum, for example. Back issues can also be obtained from the following websites (courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael Pitt, and Rich Henning): OR NOTE: The URL for Michael V. Padua's Typhoon 2000 website has changed. Another website where much information about tropical cyclones may be found is the website for the UK Meteorological Office. Their site contains a lot of statistical information about tropical cyclones globally on a monthly basis. The URL is: TROPICAL CYCLONE REPORTS AVAILABLE JTWC now has available on its website the complete Annual Tropical Cyclone Report (ATCR) for 2000 and a report on the 2000-2001 season in the Southern Hemisphere. ATCRs for earlier years are available also. The URL is: Also, TPC/NHC has available on its webpage nice "technicolor" tracking charts for the 2001 Atlantic and Eastern North Pacific tropical cyclones; also, preliminary storm reports for all the 2001 Atlantic and Eastern North Pacific cyclones are now available, as well as track charts and reports on storms from earlier years. The URL is: Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays) *********************************************************************** *********************************************************************** >> 02-13-02 / Typhoon2000.com