MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY JANUARY, 2000 (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 by the AUTHOR I have been cranking out these summaries now for slightly over two years, and from the beginning I have been overwhelmed by the reception they have gotten from the tropical cyclone community--not only from professional forecasters and researchers, but from those involved in catastrophe modelling, insurance risk studies, emergency management, etc, who have found material in the summaries useful to them, and also from those who just have a keen interest in studying and following tropical cyclones as a hobby. The time involved, however, spent in constantly monitoring tropical cyclones, downloading warnings, and preparing and proofreading the summaries is quite substantial; and, considering that I have a long commute to work and am away from home twelve hours every day, the task of writing the summaries becomes very burdensome at times, especially during busy months. In an attempt to continue keeping the summaries coming in the form to which readers have become accustomed, I have enlisted the assistance of some fellows in various countries who, like myself, have studied and followed tropical cyclones for years and have a great interest in the storms. A couple of guys, Matthew Saxby in Australia and Michael V. Padua in the Philippines, limit their work to sending me tracking information already typed in columnar format (which can require a substantial effort in some months). Others, namely Patrick Hoareau in France, Carl Smith in Australia, and John Wallace in Texas have actually written some of the narratives for certain tropical cyclones in recent months. Carl is currently writing reports for cyclones in the Australian Region, and Patrick plans to assist with the North Indian Ocean and at least some of the Northwest Pacific typhoons; and if time permits, John Wallace will write the narrative sections for Northeast Pacific tropical cyclones. Also, it should be mentioned that Alipate Waqaicelua, Chief Forecaster of the Nadi, Fiji, Tropical Cyclone Warning Centre sends me summaries and tracks for most South Pacific tropical cyclones. I am very grateful to all these gentlemen for their assistance (and also to many others who send me various bits and pieces of information about tropical cyclones and their effects). That being said, it should be emphasized that I do carefully read their contributions and edit as I see fit. Each one has his own writing style with emphases on particular things, and I want their individual personalities to shine through--in other words, I don't want to edit and revise to the point everything sounds as if I had written it. But I do try to insure that there is some consistency and that the basic things I've always covered remain. No statement gets through into the final product that I personally object to. One other issue I'd like to address. The Atlantic and Northeast Pacific basins are the only areas which essentially have only one major TCWC issuing advisories/warnings. In all the other basins JTWC issues official warnings for the U. S. Military Services and for the benefit of any other parties who wish to use them. Also, with the exception of the Australian Region, in the other basins there are national meteorological services which issue warnings in addition to the official RSMC and JTWC. From the beginning I have made occasional comparisons between warnings from different warning agencies when there were significant differences in position and/or intensity. Analysis of tropical cyclone center positions and intensity by remote sensing (satellite imagery) is often difficult and very subjective. It is far from being an exact science. But I have always tried to be objective in pointing out these to-be-expected discrepancies such that there is no implied criticism of one TCWC over another, and this rule likewise applies to any narratives written by my assistants. *********************************************************************** JANUARY HIGHLIGHTS --> Intense cyclone threatens Southwest Indian Ocean islands --> South Pacific sees first cyclones of season *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for January: No tropical cyclones *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for January: No tropical cyclones *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for January: No tropical cyclones *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for January: No tropical cyclones *********************************************************************** SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E Activity for January: 1 tropical disturbance 1 tropical depression (from December) 1 tropical cyclone 1 intense tropical cyclone The primary sources of information upon which the narrative is based are the warnings issued by the TCWC on La Reunion Island, associated with Meteo France, and which is the RSMC for the South Indian Ocean basin. However, cyclones in this region are named by the sub-regional centres on Mauritius and Madagascar with longitude 55E as the dividing line between their respective areas. La Reunion only advises these centres regarding the intensity of tropical systems. References to sustained winds should be understood as meaning a 10-min averaging period unless otherwise stated. In the accompanying track file some position comparisons have been made with JTWC's positions, and warnings from JTWC were used as a source of 1-min avg MSW estimates. Also, the comments about satellite imagery and other sources of data such as SSM/I and TRMM were obtained for the most part from the JTWC warnings. A special thanks to Philippe Caroff of the La Reunion TCWC for sending me information on the tropical disturbance #03, and a special thanks to Patrick Hoareau and Jean Marc de Maroussem for passing along some observations from Mauritius and Reunion during the approach of Tropical Cyclone Connie. South Indian Ocean Activity for January --------------------------------------- After getting off to a rather late start (in late December), the tropical cyclone season in the South Indian Ocean became significantly more active during the month of January. Babiola became the first actual tropical cyclone (hurricane force) in the region, and Connie became an intense tropical cyclone and threatened the islands of Mauritius and La Reunion. As the month opened, Tropical Depression Astride (formerly a tropical storm) was still present in the Mozambique Channel. (See the December summary for a full report on Tropical Storm Astride.) In addition to Babiola and Connie, disturbed weather persisted in the Mozambique Channel for a couple of weeks starting just before mid-month. Meteo France on Reunion Island (MFR) issued a couple of bulletins on this system on 12 and 13 Jan, numbering it as disturbance #03. JTWC mentioned the area in its STWOs for a few days, but dropped it on 16 Jan. Beginning on 22 Jan JTWC once again began mentioning an area of convection in the Channel with an associated partially-exposed LLCC. MFR issued a single bulletin at 0600 UTC on 24 Jan, referring to the disturbance as #03 once more, so apparently there was possibly some connection between this flare-up and the earlier disturbance. JTWC continued to monitor the disturbance through 26 Jan when it had weakened significantly. I have attempted to piece together a track for this system in the companion tracks file. Finally, a new disturbance/depression formed at the end of the month and was christened Tropical Storm Damienne on 1 Feb. A report on the short-lived Damienne will be included in the February summary. Tropical Cyclone Babiola (TC-04S / SIO #02) 3 - 12 January -------------------------------------------- A STWO issued by JTWC on 1 Jan indicated that an area of convection with an associated very weak LLCC had formed approximately 130 nm south-southeast of Diego Garcia. Over the next couple of days the disturbed area drifted eastward and by 3 Jan was located about 650 nm east-southeast of Diego Garcia. MFR began issuing bulletins on the developing disturbance at 0600 UTC. Animated visible satellite imagery and scatterometer data indicated weak vertical shearing over the disturbance and animated water vapor imagery indicated fair outflow. JTWC issued the first of three Formation Alerts at 1630 UTC, noting that there had been a significant increase in the areal coverage of convection. SSM/I data revealed deep convection developing around the eastern and southern sides of the LLCC. JTWC issued a second Formation Alert at 04/1430 UTC and a third one on 5 Jan at 1430 UTC. The disturbance had continued to drift slowly eastward (or quite possibly a new center had formed) during this time. The first JTWC warning, issued at 05/1800 UTC, placed the center of the system almost 700 nm east-southeast of Diego Garcia and moving southwestward at 9 kts. The MSW (1-min) was estimated at 35 kts, and convection was consolidating around the LLCC. The system was forecast to track southwestward under the influence of a low- to mid-level subtropical ridge to the south-southeast. MFR upgraded the developing LOW to a tropical depression six hours later with 30-kt winds (10-min avg), and Moderate Tropical Storm Babiola was christened at 0600 UTC on 6 Jan, located about 625 nm east-southeast of Diego Garcia. At 1800 UTC Babiola's intensity was holding steady at 35 kts (45-kts 1-min avg from JTWC) with the LLCC displaced somewhat to the east-southeast of the primary convection. On 7 Jan Babiola continued to move slowly to the southwest and steadily increased in intensity. MSW estimates from both MFR and JTWC had reached 55 kts by 1800 UTC. A TRMM pass indicated a significant convective band extending southeast through north wrapping in toward the LLCC with animated infrared imagery depicting another band forming 180 nm to the west of the LLCC. Babiola began to accelerate toward the west-southwest on the 8th and continued to intensify, reaching cyclone (hurricane) strength at 1200 UTC when centered about 575 nm south of Diego Garcia. A banding eye became apparent, and Babiola presented a rather symmetrical appearance in satellite imagery with an upper-level HIGH over the storm enhancing outflow in all quadrants. The west-southwestward to southwestward motion continued through 9 Jan with Babiola reaching its peak intensity late on the 9th. 200-mb analysis showed that the cyclonic circulation extended into the upper levels with good outflow. At 1800 UTC Babiola displayed a ragged eye 20 nm in diameter with good outflow channels over the western half of the system. The cyclone was by this time beginning to move south- southwestward. JTWC's peak MSW (1-min) of 90 kts was reached at this time, and MFR had upgraded Babiola to its peak intensity of 80 kts at 1200 UTC. This represents a perfect agreement of Babiola's peak intensity between the two TCWCs, corresponding to a Dvorak scale rating of T5.0. The minimum CP estimated by MFR was 954 mb. On 10 Jan Babiola remained intense but began to show signs of weakening. The storm began to move due southward and reached the westernmost point of its trajectory around 1200 UTC when it was located about 250 nm east-southeast of Rodrigues Island (which lies about 315 nm east of Mauritius). Early in the day the eye disappeared and Babiola began to elongate and merge with a trough moving rapidly across the South Indian Ocean. By 1800 UTC the storm was tracking south-southeastward and the MSW was down to 70 kts (65 kts per JTWC). Babiola was becoming less organized due to northwesterly shear. The storm continued to weaken on 11 Jan as it continued toward the south-southeast and experienced strong vertical shear. By 0600 UTC Babiola was merging with the approaching trough and beginning extra- tropical transition (this based upon remarks in the 0600 UTC JTWC warning). Animated satellite imagery and data from a SSM/I pass showed an exposed LLCC with convection sheared 85 nm to the south and east. JTWC issued its last warning on Babiola at 0600 UTC on 12 Jan with winds estimated at only 25 kts, but MFR continued gale warnings for the weakening system through 12/1200 UTC, although the bulletins indicated that the gales were forecast to be occurring well away from the center (up to 120 nm) in the southeast quadrant. Early on the 12th the previously mentioned 500-mb trough was just west of Babiola and was interacting with the system, which was becoming extratropical. MFR issued their last bulletin on Babiola at 1800 UTC, downgrading the system to below gale intensity and locating the center approximately 800 nm southeast of Rodrigues Island. Tropical Cyclone Connie (TC-08S / SIO #04) 25 January - 2 February ------------------------------------------- An area of convection appeared on 24 Jan about 315 nm east of northern Madagascar. SSM/I data indicated a fully-exposed LLCC with disorganized convection. The next day the persistent convection had become more organized and MFR initiated Tropical Disturbance Bulletins at 0600 UTC for disturbance #04. The rapidly strengthening disturbance was upgraded to a tropical depression six hours later and to Moderate Tropical Storm Connie at 1800 UTC with 40-kt winds. Connie was centered about 325 nm northwest of Mauritius at that time. (JTWC issued a Formation Alert at 1000 UTC, and their first warning was issued at 1800 UTC, giving a MSW estimate of 35 kts (1-min).) Convective organization was increasing in an environment of good outflow and weak vertical shear. TRMM microwave imagery depicted banding of deep convection in the northeast through southwest quadrants. The storm had been quasi-stationary for several hours but was forecast to track southwestward under the influence of a mid-level ridge to the south. Connie, however, remained more or less stationary, and actually moved (or was relocated) northward a bit on 26 Jan while slowly strengthening. A TRMM pass at 26/0703 UTC revealed what appeared to be a 27-nm wide eye. At 1800 UTC Connie's intensity had reached 45 kts (55 kts 1-min avg from JTWC) and was still quasi-stationary about 380 nm north-northwest of Mauritius. By 0600 UTC on 27 Jan the by-now severe tropical storm with 60-kt winds was moving south- eastward at 6 kts. A SSM/I pass at 0141 UTC revealed an irregular eye 20 nm in diameter with the eyewall surrounding approximately 4/5 of the vortex. Multi-spectral imagery showed a significant convective band entering the LLCC from the southern half of the system. At 1200 UTC Connie's center was about 300 nm north-northwest of Mauritius and MFR upgraded the storm to cyclone status with 80-kt MSW. (JTWC's concurrent 1-min avg MSW was 85 kts at the time.) The eye diameter by this time had shrunk to 11 nm and convective features were continuing to develop and build in toward the LLCC from the southeast and northeast. With an upper-level HIGH located over the cyclone, the outflow continued to improve and Connie began to strengthen rapidly. By 1800 UTC Connie's well-defined 15-nm wide eye was located approximately 235 nm northwest of Mauritius and had moved south at 7 kts over the previous six hours. There was a surface synoptic report of 10-min avg winds of 31 kts from WMO 61986, located about 140 nm due east of the cyclone. Throughout Connie's life center position estimates between JTWC and MFR were in excellent agreement, and intensity estimates agreed fairly well except that on 28 and 29 Jan, when the cyclone was at its peak, there was some divergence of opinion regarding the cyclone's intensity. At 27/1800 UTC JTWC increased the MSW (1-min) to 115 kts, which equates to T6.0 on the Dvorak scale. MFR's 10-min MSW estimate was 90 kts--equivalent to a Dvorak rating of T5.5--and as everyone in the business knows, a difference in Dvorak analysis of 0.5 T-number represents good agreement. At 28/0600 UTC JTWC began to gradually bring down Connie's MSW while MFR's value held steady at 90 kts. At 1800 UTC Reunion increased its MSW estimate to a peak of 100 kts (T6.0 on the Dvorak scale) while JTWC had brought its value down to 105 kts (T5.5). Remarks in the JTWC warning indicated that this was based upon CI estimates of 102 kts and 127 kts (T5.5 and T6.5). Connie's eye had remained well-defined, but cloud tops had warmed somewhat over the cyclone's center. MFR maintained the 100-kt intensity through 29/0600 UTC and then brought the MSW down to 85 kts at 29/1200 UTC. JTWC's estimates had continued to slowly decline and had reached 80 kts (1-min) by 1200 UTC. The minimum CP in Connie's history as estimated by MFR was 928 mb at 28/1800 UTC. By 0000 UTC on the 29th Connie was centered about 130 nm northwest of Mauritius. The cyclone was maintaining a 10-nm diameter eye, but was showing signs of shearing to the south. Water vapor imagery indicated a weak TUTT to the southwest of the storm which was causing the increase in vertical shear. By 1800 UTC on 28 Jan Connie was moving to the southwest on a track which carried it about 100 nm west of Reunion Island around 1800 UTC on 29 Jan. The MSW was down to 80 kts (both MFR and JTWC) as the eye was no longer apparent and drier air from the TUTT was being injected into the storm's inflow. At 30/0000 UTC Connie was located approximately 145 nm west-southwest of Reunion and moving southwest at 11 kts--a motion which had increased to 18 kts by 0600 UTC. The storm's intensity was down to near minimal cyclone force by this time, and Connie was beginning to recurve to the south-southeast. By 1800 UTC on 30 Jan the storm was moving southward about 265 nm east of the southern tip of Madagascar with 55-kt winds (60 kts 1-min avg from JTWC). Earlier in the day a SSM/I pass had indicated a spiral band of convection to the west of the LLCC, but a TRMM pass at 1331 UTC indicated only isolated convection to the south of the center and Connie was forecast to continue weakening. On 31 Jan Connie began to move in a southeasterly direction, steered by a mid-level subtropical ridge to the northeast and the approaching trough to the southwest. The storm, however, held on to its intensity with the MSW remaining at 55 kts through most of the day. JTWC actually increased its 1-min avg MSW to 65 kts briefly at 1800 UTC based upon satellite intensity estimates. However, any re-intensification was short-lived. Animated visible imagery early on 1 Feb showed a fully-exposed LLCC with rapidly weakening convection about 70 nm to the east of the center. Infrared imagery depicted a rapid warming of cloud tops as well as a significant decrease in the areal extent of deep convection. MFR issued its final warning at 01/0000 UTC since Connie appeared to be rapidly losing strength and was taking on extratropical characteristics. JTWC continued to track the rapidly weakening storm through 0600 UTC on 2 Feb when the MSW was estimated at only 25 kts and the center was located about 725 nm south of Reunion Island. SSM/I data indicated a fully-exposed LLCC with weakening convection displaced about 75 nm northeast of the center. The remnants of Connie were forecast to continue moving southeastward and weaken. Jean Marc de Maroussem, a resident of Mauritius, sent me some observations he'd made during Connie's closest approach to the island. The lowest pressure reported by Jean Marc was 1000.6 with several wind gusts exceeding 55 kts and a peak gust of 65 kts. The average rainfall for the entire island was about 200 mm--a bit of relief for the drought-stricken island but not enough. As far as Reunion Island goes, Patrick Hoareau reported that he'd been listening to the official radio on the internet and wind gusts of around 60-80 kts had been reported. Also 16,000 people were without power. Press reports indicated that Connie was responsible for two deaths on Reunion. One hundred homes were reportedly destroyed with at least 600 persons homeless. *********************************************************************** AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E Activity for January: 2 tropical LOWs 1 hybrid LOW 1 severe tropical cyclone The primary sources of information for Australian Region tropical cyclones are the warnings and bulletins issued by the three TCWCs at Perth, Darwin, and Brisbane. Information gleaned from JTWC's warnings is used as a supplement for times when it was impossible to obtain Australian bulletins and for comparison purposes. References to sustained winds should be understood as being based on a 10-min averaging period unless otherwise noted. Matthew Saxby, a tropical cyclone enthusiast from Queanbeyan, New South Wales, Australia, typed up the tracks for the cyclones and LOWs in the Australian Region. Also, Carl Smith, another dedicated tropical cyclone enthusiast from the Gold Coast of Queensland, authored the narratives for Tropical Cyclones 06S and Kirrily. A very special thanks to Matthew and Carl for their assistance. A description of the Australian Cyclone Severity Scale can be found in Chris Landsea's FAQ on HRD's website: or on Michael Bath's Australian Severe Weather site: Also, I performed some editing on Carl's write-ups. For anyone who is interested in reading his complete cyclone reports, they are available at the following URLs: Australian Region Activity for January -------------------------------------- Tropical cyclone activity in the Australian Region was somewhat on the quiet side. Only one cyclone--Kirrily--was named, and this was late in the month in the Southeast Indian Ocean off Western Australia. Earlier there was a tropical LOW in the same region which persisted for several days and eventually made landfall in Western Australia. JTWC issued one warning of 35-kt winds with this system based upon a ship report. Since Carl submitted a report on this LOW, I have included it below. There was a short-lived tropical LOW in the Coral Sea off the coast of Queensland for which Brisbane issued a few warnings on 10 and 11 Jan. Gale-force winds to 35 kts were forecast for the southern quadrant of the LOW at one point. There was also a gale center on 12 and 13 Jan well east of Brisbane which moved slowly westward toward the southern Queensland coast. This system was likely a hybrid or primarily baroclinic LOW. Tracks are given for these two systems in the companion cyclone tracks file. Additionally, there was an interesting example of a so-called "landphoon"--a tropical LOW whose convective cloud signature seems to improve even after it has moved over land. In mid-January a very weak LOW formed near the coast of Western Australia and tracked southward and inland. The maximum winds and minimum pressure when the system was just off the coast were about 15-20 kts and 999 mb, respectively. The cloud signature seemed to improve somewhat as the LOW moved further inland over the Australian Outback. On Sunday, 16 Jan the center passed just west of the Giles Meteorological Station (25.0 S, 128.3 E) and radar showed the circulation to be very weak. Australia is one of the very few places where weak tropical LOWs can drift inland and "appear" to intensify, even after they have travelled well inland for a day or two. From a satellite perspective these systems look like tropical storms, with persistent central convection and a nice symmetrical pattern of cirrus outflow. It is very possible that in the middle troposphere the circulation does indeed intensify somewhat. From the standpoint of process, it seems as if atmospheric conditions are extremely favorable for tropical cyclone formation, and they do the best they can with land underneath. (The above discussion was taken from some correspondence with Mark Lander of the University of Guam and Andrew Tupper of BoM, Darwin.) Tropical LOW (TC-06S) 18 - 23 January ---------------------- During the 3rd week of January, 2000, a tropical LOW formed in the Gulf of Carpentaria, northwest of Weipa on Cape York Peninsula. It drifted slowly west-northwestward into the Arafura Sea over the next few days, passing to the north of Arnhem Land and Darwin. By the 18th it had moved into the Timor Sea. BoM Darwin issued the first shipping warning at 1200 UTC, indicating that a tropical LOW of 1000 mb was centred within 90 nm of 11.0 S, 127.5 E and moving west at 5 kts. Darwin continued issuing shipping warnings until 19/1200 UTC when responsibility was handed over to BoM Perth as the system was by then off the Kimberley Coast near 12.7 S, 125.3 E, moving southwest at 10 kts. Over the next couple of days the LOW continued moving southwestward towards the Pilbara coast. JTWC issued the first TCFA on the 20th; however, development was generally slower than either JTWC or Perth expected, with JTWC issuing another TCFA later in the day. Perth issued the first Tropical Cyclone Advice at 6:50am WST on the 21st (20/2250 UTC), stating that at 6:00am a tropical LOW was located about 380 km (205 nm) north-northeast of Karratha and moving southwest at 15 kts. The first cyclone warning was issued by JTWC at 21/0300 UTC, indicating that TC-06S had developed in the southeast Indian Ocean about 350 nm northeast of Learmonth and was tracking southwestward at 10 kts within the steering flow of a subtropical ridge to the southeast. The 1st BoM warning for coastal communities was issued at 3:50pm WST (0750 UTC) on the 21st for areas between Roebourne and Exmouth. At 3:00pm (0700 UTC) the LOW with a CP of 1000 mb was estimated to be about 290 km (155 nm) north-northwest of Karratha and moving south- southwestward at 10 kts. At 21/0900 UTC JTWC noted that animated satellite imagery indicated a rapid weakening of TC-06S, and animated water vapour imagery revealed increasing vertical wind shear to the southeast due to a mid-latitude trough and associated support of a strong upper-level jet. The difficulties JTWC had in tracking this marginal tropical cyclone were revealed when it was relocated 60 nm to the east-northeast of the previous warning position at 21/2100 UTC. The warning noted that the system displayed a fully exposed LLCC with deep convection to the southwest (based on DMSP night-time visible imagery), and animated infrared satellite imagery depicted increasing convection over the previous six hours. Over the subsequent 24 hours TC-06S continued its west-southwestward motion towards the Pilbara Coast, slowly deepening to 992 mb, but never quite reaching tropical cyclone strength according to BoM criteria. The only significant change was noted in a JTWC warning issued at 22/1500 UTC, which stated that, based on infrared satellite imagery, the system had taken a turn to the southeast during the previous six hours, and it appeared that the low/mid-level HIGH over the Western Plateau had weakened and shifted further east than model guidance had previously indicated, due primarily to the sudden eastward movement of a mid-latitude trough which had been quasi-stationary off the southwest coast of Australia. Water vapour imagery also indicated that the trough had increased in amplitude. The BoM issued its final warning on this system at 9:50am WST (23/0150 UTC) on the 23rd, stating that the tropical LOW with a CP of 992 mb and wind gusts to 40 kts was, at 9:00am WST, estimated to be about 70 km (40 nm) west-northwest of Port Hedland, moving south- eastward at 14 kts. JTWC issued its final warning at 23/0300 UTC, noting that the system was dissipating over land. NOTE: JTWC only issued one warning (22/0600 UTC) estimating the 1-min avg MSW at 35 kts. Satellite intensity estimates were 25 kts, but the remarks indicated that there was a synoptic ship report of 35-kt winds west of the center. Severe Tropical Cyclone Kirrily (TC-09S) 25 January - 1 February ----------------------------------------- A developing 1002-mb tropical LOW in the Indian Ocean southeast of Christmas Island was first mentioned in an Australian Bureau of Meteorology (BoM), Perth, shipping warning issued at 2157 UTC on 25 Jan when the LOW was centered about 250 nm southeast of Christmas Island, moving east-southeastward at 11 kts. JTWC issued a Tropical Cyclone Formation Alert (TCFA) at 26/2130 UTC with winds estimated to be 25-30 kts. Satellite imagery at 1730 UTC indicated that a LLCC was located about 400 nm north-northwest of Exmouth, Western Australia, moving southeastward at 10 kts. Scatterometer data indicated a well- defined LLCC associated with the convection and 200-mb analysis indicated that the convection was slowly moving under the axis of an upper-level ridge which would be expected to provide good outflow. University of Wisconsin CIMSS Wind Shear charts also indicated decreasing vertical shear in the path of the disturbance in the direction of northwestern Australia. The first tropical cyclone warning was issued by JTWC for TC-09S at 27/0900 UTC. MSW (1-min) were estimated at 30 kts and the centre was placed about 330 nm north-northwest of Learmonth, Western Australia, moving south at 5 kts. Animated multi-spectral imagery depicted new convection building over the LLCC and low-level cloud lines were visible moving in toward the center from the southeast. A mid-level HIGH situated over southwestern Western Australia was forecast to build northwestward over the Kimberley region within 36 hours and should cause TC-09S to track initially south- southeastward, then southwestward. The LOW was named Kirrily by BoM Perth at 28/0016 UTC. The CP was given as 985 mb and the 0000 UTC position was about 300 nm northwest of Exmouth. Kirrily was moving southwestward at 6 kts and was causing rough to very rough seas with moderate swell and 30-40 kt winds within 100 nm of the centre and winds to 50 kts within 30 nm of the centre. The first public Tropical Cyclone Update was issued by Perth at 8:45am WST (0045 UTC) on Friday, 28 Jan, stating that Kirrily, a Category 1 cyclone, was located about 295 nm northwest of Exmouth. At 28/0600 UTC JTWC placed Kirrily's center about 325 nm northwest of Exmouth, moving west at 9 kts with 55-kt winds (1-min avg). A TRMM pass at 0314 UTC indicated that the system was developing an eye and that convective banding was surrounding about 8/10 of the vortex. BoM TC Update #2 at 2:30pm WST (28/0630 UTC) upgraded Kirrily to a Category 2 cyclone that was moving southwestward at 6 kts. Only one more public update was issued since it had become clear that Kirrily posed no real threat to the Western Australian coastline. At 29/0600 UTC JTWC placed Kirrily's center about 600 nm south- southeast of Christmas Island, moving southwestward at 10 kts with MSW (1-min) of 80 kts and sporting a 13-nm wide cloud-filled eye. A minimum CP of 965 mb was estimated by Perth at 1100 UTC when Kirrily was located approximately 625 nm south-southeast of Christmas Island. The BoM warning indicated that winds to 65 kts were likely occurring within 30 nm of Kirrily's centre. By 1800 UTC JTWC had decreased its MSW estimate to 70 kts as the cyclone continued to move to the southwest at 9 kts. Kirrily at this time was located about 675 nm south of Christmas Island or about 470 nm west of Learmonth. Animated satellite imagery showed weakening of the system and elongation to the southeast. A 29/1404 UTC SSM/I pass indicated a very broad LLCC; however, convection was confined to the very center and there was no longer any evidence of any type of eye. A 200-mb analysis indicated that the upper-level ridge axis remained south of the system and an upper-level jet was evident to the southeast. Kirrily was tracking west-southwestward under the steering influence of a mid-level subtropical ridge to the south and was moving into an environment of increasing vertical shear. Subsequent warnings issued by both centres indicated a continued weakening trend, with the final BoM shipping warning being issued at 2225 UTC on 31 Jan. The weakening remnants of Tropical Cyclone Kirrily with a CP of 999 mb were located about 750 nm south of Christmas Island at 2200 UTC and were moving north-northwestward at 4 kts. Winds were forecast to ease below gale force within the next three to six hours. The last warning was issued by JTWC at 2100 UTC on 1 Feb with the MSW (1-min) estimated to be only 25 kts. Infrared satellite imagery indicated a fully exposed LLCC which was moving northwestward at 6 kts. The final JTWC warning placed the dissipating centre about 625 nm west of Learmonth or about 700 nm south-southwest of Christmas Island. *********************************************************************** SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E Activity for January: 2 tropical depressions 2 tropical cyclones of storm intensity Most of the information presented below was taken from the operational warnings and advisories issued by the Fiji TCWC at Nadi. References to sustained winds imply a 10-minute averaging period unless otherwise noted. Also, the basic definition of a cyclone in WMO Region 5 (Australia and the South Pacific) has the unique requirement that a depression must have gale-force winds more-or-less completely surrounding the center before the system is named as a tropical cyclone. Hence, often gales of 35-40 kts may be present in one or two quadrants but the system is not considered a tropical cyclone. Last season Fiji initiated their own numbering scheme for tropical disturbances (01F, 02F, etc) that form in the Nadi AOR. Some of the numbered disturbances never warrant depression status. The reports on Tropical Cyclones Iris and Jo were written by Alipate Waqaicelua, Chief Forecaster at the Nadi TCWC, with only minimal editing by myself. A very special thanks to Alipate for sending me the summaries and the cyclone tracks. I wrote the discussion on Tropical Depression 08F; also, I added some discussion about the extreme Dvorak objective T-numbers generated for Tropical Cyclone Iris. Southwest Pacific Activity for January -------------------------------------- January saw the formation of the first two South Pacific tropical cyclones of the 1999-2000 season. In addition to Tropical Cyclones Iris and Jo, there were a couple of systems carried in warnings from Fiji as tropical depressions. One of these, TD-08F, persisted for several days with associated gale-force winds, so I have included a separate report on this system below. Another depression, TD-06F, formed on 3 Jan near Vanuatu and moved slowly east-southeastward over the next couple of days. The system formed and operated in a sheared environment which did not allow it to strengthen. The depression passed south of Fiji and had weakened just east of the Dateline by 6 Jan. A track is included for this system in the companion cyclone tracks file. (A tropical disturbance numbered 07F was mentioned in Nadi's Tropical Disturbance Summary on 16 Jan, located well to the west-southwest of Tahiti. This disturbance subsequently dissipated without being accorded depression status.) Tropical Cyclone Iris (TC-05P / TC-05F) 7 - 10 January ---------------------------------------- A disturbance was first identified around 03/0600 UTC just north- west of Espiritu Santo, in Vanuatu, embedded in a stationary monsoon trough. The system was located under a moderately sheared environment aloft, with slightly hostile conditions at lower levels. This basically denied the system any chances for further development. For another 36 hours, the system was subjected to shear and diurnal influence, making it at times extremely difficult to locate the general centre. However, after 06/0000 UTC, the outflow around the system improved significantly with convection increasing and getting slightly more organised. Twenty-four hours later, at 07/0000 UTC, convection was getting better organised still, with the LLCC gradually moving under the western edge of the deep convection. Gale warnings were issued but for certain sectors only. Overnight the depression, displaying midget characteristics, intensified further under weakening shear aloft. A compact CDO had also formed which was now moving southeast at 5 kts. The depression continued to develop under favourable conditions, and at 07/2100 UTC was named Tropical Cyclone Iris while located about 180 nm northwest of Port Vila, moving southeast at 5 kts with an intensity of 35 kts (10-min avg) and forecast to increase to 40 kts during the next 6 to 12 hours. The cyclone was anticipated to track more easterly under a westerly steering current. Six hours later, at 08/0000 UTC, winds around the compact centre were estimated to be about 45 kts. Gales were confined to within 60 nm of the centre. Iris reached storm intensity at 08/0600 UTC while located about 130 nm northwest of Port Vila, tracking east-southeastward at 8 kts. The cyclone moved close to or over the island of Epi overnight, but its compactness was quite evident as recorded winds over Vila, about 60 nm due south, were only 15 to 20 kts. No damage reports could be obtained from Vanuatu, but it is most likely that damage, if any, would be minimal. This was despite an intensity of 60 kts at its peak, which occurred around 08/1200 UTC. Iris gradually accelerated eastward as it left Vanuatu, but always tracking more and more south of east with time. The system was also becoming more and more asymmetric as it moved closer to Fiji, evidence of strengthening shear and environmental influence. After 09/0000 UTC, the cyclone began its weakening trend. Intensity was down to a gale 18 hours later, at 09/1800 UTC, when it was located about 210 nm west- southwest of Nadi and moving east-southeastward at 13 kts. After 10/0000 UTC, while only about 120 nm southwest of Nadi, Iris was shunting east-southeastward at 15 to 20 kts into increasing shear and cooler waters. The cyclone was downgraded to a depression 48 hours after it had reached its peak intensity--the final warning placing the centre on the Dateline about 150 nm southeast of Fiji. Though it was expected that as the system weakened gales might expand further out from the centre, only fresh to strong winds and very rough seas with heavy swells were experienced over the western and southern parts of Fiji. Once the system was named, the intensity curve took a rate much steeper than any 'normal' cyclone. This was also the case during the decay phase, though at a much gentler trend. Damage in Fiji, if any, would have been either minimal or negligible. JTWC's positions and 1-min avg MSW estimates agreed very well with Nadi's for Tropical Cyclone Iris. The peak MSW (1-min) from JTWC was 65 kts while the peak 10-min avg MSW estimated by Nadi was 60 kts. However, Iris exhibited some features which hinted that the midget cyclone could have been far more intense for a brief time than either warning centre estimated. According to Dr. Mark Lander, T-numbers obtained with the objective (digital) Dvorak method reached T6.5 or slightly higher for a 4-hour period on 8 Jan from around 0230 to 0630 UTC. The Dvorak scale equates T6.5 with a MSW (1-min) of 127 kts or a 10-min avg MSW of 112 kts. A satellite bulletin from JTWC at 08/0625 UTC assigned a T-number of 4.0, but the comments indicated that there was a great inconsistency between the visible and infrared methods with an IR-derived T-number of 6.0. These extreme T-numbers persisted for only a short time, however. By 0915 UTC the eye had disappeared and a JTWC satellite bulletin indicated that the system had lost much convection over the past two hours. Mark Lander further comments that such rapid strengthening followed by rapid decay seems to be a common occurrence with very small, midget tropical cyclones. They seem unable to remain at peak intensity for very long--often for just a few hours--before beginning to fall apart. Typhoons Ellie (1991) and Virgil (1999) were two recent NWP systems which behaved the same way as Iris. No one will ever know just how intense Iris became since the core of the small cyclone did not pass over any weather station and of course there was no aerial reconnaissance available. Tropical Depression (TD-08F) 20 - 26 January ----------------------------- A tropical disturbance was noted near Apia, Western Samoa, around 0600 UTC on 20 Jan. Over the next few days the system drifted slowly southwestward and gradually became better organized. By 23/1800 UTC the disturbance had become sufficiently developed to be classed as a tropical depression with the Fiji TCWC initiating gale warnings and Tropical Disturbance Advisories. TD-08F was then located between Fiji and the Kingdom of Tonga and displayed a CDO-type cloud pattern. However, the system had moved south of the 250-mb subtropical ridge and was being affected by increasing westerly and northwesterly shear. The depression recurved to a southeasterly course and passed through the southern Tongan islands on 24 Jan. At 24/0600 UTC the LLCC was still exposed and the gale-force winds were confined to the south- eastern semicircle. Six hours later the LLCC had moved closer to the CDO feature and the cold cloud tops had increased in areal extent. By 1800 UTC the LLCC was near the southwestern edge of the deepest convection which had continued to increase in extent with cooling cloud tops. The depression seems to have reached its peak organization about this time but there was still evidence of fairly strong vertical shearing. Gales were reported to be occurring within 40 nm of the center from the north around the eastern side into the southwestern quadrant of the system. Thereafter the LLCC began to be sheared farther and farther away from the convection as the depression continued to move southeastward into a region of increasing vertical shear. By 26/0000 UTC the system was entering Wellington's AOR, and gales were expanding in area, indicating that extratropical transition was beginning. Occasionally, in most tropical cyclone basins, poorly-organized depressions will be seen with little deep central convection but with peripheral gales on the poleward side due to a tight pressure gradient with a neighboring area of high pressure. The basic definition of a tropical cyclone in WMO Region 5 (Australia and the South Pacific) contains the requirement that sustained gale-force winds should surround the center before a developing depression is named as a tropical cyclone. This criterion was ostensibly added to provide some objective guidance for weeding out poorly-organized systems which might contain gale-force winds but which do not have the appearance of a typical, developing tropical cyclone. In the case of TD-08F, the gales never surrounded the center, but they were very close to the center--within 30-40 nm, based upon the warnings from Nadi. In looking at the depression in some infrared satellite imagery, to me it appeared to be similar to some sheared, weak tropical storms which I've seen in the Atlantic; however, I do not have available any Dvorak ratings on this system from any agency. To my knowledge, NPMOC at Pearl Harbor did not issue any warnings or alerts on this depression, which suggests that it was poorly organized with only a very low potential for development. Tropical Cyclone Jo (TC-07P / TC-09F) 23 - 28 January -------------------------------------- A weak disturbance was first identified over the northern parts of Vanuatu on the 19th, embedded in an active and slow-moving monsoon trough. On the 20th the disturbance was located to the south of the 250-mb ridge with northwest winds of 40 kts to 55 kts above it. Strong vertical shear had arrested development, which was also strongly influenced by diurnal effects. However, atmospheric pressure at the surface continued to gradually fall, but within a fairly broad area surrounding the system. At 21/2100 UTC, a LLCC could be located by satellite about 300 nm northeast of Port Vila in Vanuatu and about 340 nm northwest of Nadi in Fiji; hence, the upgrade to tropical depression phase. The potential for development into a tropical cyclone in the next 24 hours was still low as shear was still significant over the system. However, on the 22nd shear was gradually decreasing and pressure was also falling at a steeper rate. By the 23rd convection had significantly increased with slight improvement in organisation. The depression was then located in a relatively weakly divergent area at 250 mb; hence, at 22/2100 UTC the potential for this depression to develop into a cyclone in the next 24 hours was assessed to be moderate to high. The first Tropical Disturbance Advisory on this system was issued at 23/0000 UTC when it was centered about 460 nm northwest of Nadi and expected to drift slowly southeastward. Deep convective tops were cooling and organisation, as well as outflow, was continually improving. Aloft, the depression was placed along the subtropical ridge axis in a very favourable area for further intensification. Gale warnings were also issued around this time, though over certain sectors only. Overnight TD-09F continued to develop while moving slowly southward, with cold spiral bands beginning to wrap around the LLCC. At 24/0300 UTC the depression was named Tropical Cyclone Jo with winds of 35 to 40 kts close to the centre, which was located about 240 nm west of Nadi. The cyclone was moving south-southeastward at about 10 kts. Tropical Cyclone Jo attained storm-force intensity 15 hours later, at 24/1800 UTC, with gales spreading to within 80 nm of the centre. Cold spiral bands were still wrapping tightly around the centre. Warm air intrusion was quite evident on satellite imagery throughout most of the life of Jo while inside Nadi's area of responsibility. This, to an extent, made locating the LLCC a little difficult while also preventing the system from attaining hurricane intensity. Jo's intensity peaked around 26/0000 UTC, while it was situated about 350 nm south of Nadi, with a MSW of 60 kts close to the centre. Gales gradually spread out from the centre to about 180 nm in the southeast semi-circle and to 150 nm elsewhere around 26/1200 UTC. Jo's closest approach to Fiji on its way towards the southeast was on 24 Jan when the centre was located about 240 nm to the west- southwest. The system had originally been tracking more south- southeastward but gradually turned to the southeast under a west to northwest steering flow on the 25th. With gales fanning out more, strong 10-minute average winds to 32 kts with gusts to 50 kts were affecting the western parts of Fiji's largest island, Viti Levu, and nearby islands to its south. Frequent squally rainbands lashed these areas from late on the 24th until late on the 26th, inducing flash flooding. There was no major river flooding reported. On the 25th a building 500-mb ridge from the east prevented any closer approach of Jo to Fiji. This ridge was basically responsible for keeping the cyclone on its southeasterly track, entering Wellington's AOR around 26/1200 UTC. Wellington assumed primary responsibility for warnings on Jo after this time. Tropical Cyclone Jo was finally declared extratropical at 28/0600 UTC when located well over 1000 nm east of New Zealand's North Island and a similar distance southwest of Tahiti. No damage reports from Fiji have been received as yet. If any become available later they will be reported in a future summary. Position and intensity estimates by JTWC compared extremely well with those from Nadi for Tropical Cyclone Jo. As was the case with Tropical Cyclone Iris, JTWC's and Nadi's peak 1-min avg and 10-min avg MSWs were 65 kts and 60 kts, respectively. *********************************************************************** 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 included in the July, 1998 summary. I will include this glossary from time to time, primarily in "lean" months without a lot of tropical cyclone activity to cover. But if anyone missed receiving it and wishes to obtain a copy, send me an e-mail privately and I'll forward 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 January as an example: jan00.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: jan00.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): 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 I have discovered that JTWC now has available on its new website the complete Annual Tropical Cyclone Report for 1997 (1996-1997 season for the Southern Hemisphere). Also, tracks only for the 1998 tropical cyclones are currently available. The URL is: Also, TPC/NHC has available on its webpage nice "technicolor" tracking charts for the 1999 Atlantic and Eastern North Pacific tropical cyclones; also, preliminary storm reports for all the 1999 Atlantic and most of the Eastern North Pacific cyclones are now available. The URL is: Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays) *********************************************************************** ***********************************************************************