MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY MAY, 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.) *********************************************************************** MAY HIGHLIGHTS --> Short-lived intense super typhoon churns Western Pacific waters --> First Eastern Pacific hurricane forms *********************************************************************** NEW FEATURE - TOPIC OF THE MONTH I am planning to add a new feature to these monthly summaries, a sort of "topic of the month" article, discussing some interesting topic in the tropical cyclone arena. I don't intend for this feature to be very lengthy--just a few paragraphs at most. For some subjects I may be able to provide links and/or addresses where interested persons can look for more information. ***** Topic of the Month for May ***** WHATEVER HAPPENED TO THE NEUTERCANE? As a result of some conversations I found myself involved in at the recent AMS 24th Conference on Hurricanes and Tropical Meteorology in Fort Lauderdale, Florida, I learned that there are quite a few younger meteorologists and graduate students (and some not quite so young) that have never heard the term "neutercane", or if they had, had no idea what it was or when it made its brief sojourn into the annals of North Atlantic weather history. Simply put, the word was coined by former NHC Director Dr. Robert Simpson to describe a certain class of small, mesoscale subtropical cyclones that usually form in horizontal shear zones near dying cold fronts or else near the centers of old, occluded extratropical cyclones (what Paul Hebert termed a Type B subtropical cyclone). In 1972 NHC began issuing public subtropical cyclone bulletins and designated the storms with the phonetic alphabet. In late May of that year a larger subtropical cyclone off the southeastern U. S. coast was dubbed Alpha but the term neutercane was not publicly used. However, in late August a small subtropical cyclone formed in the western Atlantic and bulletins were issued for Neutercane Bravo. (Bravo eventually developed full tropical characteristics and was redesignated Hurricane Betty west of the Azores.) In late September another similar system was named Neutercane Charlie. However, Dr. Simpson retired in 1973 (I believe I'm correct here) with Dr. Neil Frank assuming the directorship of NHC, and the term was not publicly used again. Subtropical cyclones were designated with the phonetic alphabet that year (with Subtropical Cyclone Bravo in October evolving into Hurricane Fran), but in 1974 that practice was dropped also. Many years ago I read an article in the Bulletin of the AMS dealing with cyclone classification, and the neutercane was mentioned. The writer of that article raised a couple of objections to the term: (1) the use of "cane" as a syllable implies that hurricane is a compound word, which it is not; and (2) "neuter" has to do with gender, not an intermediate quality between two opposites or extremes (the proper term for that is "neutral"). In spite of its official usage in only one hurricane season, the neutercane received a fair amount of publicity. I have in an old scrapbook a newspaper clipping with the headline "Satellite Spots Sea-Going Storm That's Half Hurricane, Half Tornado"! The World Almanac for 1973 had a short article describing the neutercane, and the word found its way into some dictionaries. This apparently has been sufficient to keep the term alive to some degree, as I have seen it crop up in various places over the years, especially in some informal discussions and e-mails. Next Month: A Source for State and Local Hurricane Histories *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for May: 1 subtropical depression Atlantic Activity for May ------------------------- The month of May lies outside the nominal hurricane season in the Atlantic basin, although since 1886 twelve tropical storms, including three of hurricane intensity, have been tracked. The last named tropical storm in the Atlantic basin was Tropical Storm Arlene in 1981 which formed in the northwestern Caribbean on 5 May. There have been several years since (1987, 1988, 1990, 1993) in which a tropical depression formed late in the month, but none of these were able to intensify to tropical storm intensity. However, subtropical (hybrid) activity tends to be more frequent during the month and 2000 was no exception. Michael Pitt sent me some information on a LOW-pressure area on 19-21 May which formed a few hundred miles southeast of Bermuda. The Air Force Weather Association issued Dvorak satellite classifications on this LOW for about a day and a half, and TPC/NHC referred to it in their Tropical Weather Discussions as a complex system with an upper- level LOW with supporting fronts and an associated surface LOW. A track for this system was included in the May cyclone tracks file. Michael later sent me some excerpts from TPC/NHC Discussions which I forwarded to David Roth, a meteorologist at HPC. David researched the system and sent me a GOES infrared image of the system taken at 0015 UTC on 20 May. In that picture the LOW appears as a typical subtropical-type system with a band of convection somewhat removed from the center extending from the northwest quadrant around to the eastern side of the LOW. According to David the system entered the subtropical phase on 19 May when moisture and temperature gradients were disappearing. In David's estimation peak winds around the system were 30 kts during the initial non-tropical phase and about 25 kts during the subtropical phase. The system began to shear on the 21st and 22nd as it drifted eastward, and lost its closed circulation soon after 22/0600 UTC. (A special thanks to Michael and David for the information they provided on this system.) *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for May: 1 hurricane 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. Northeast Pacific Activity for May ---------------------------------- The Northeast Pacific tropical season got started a little earlier than normal in 2000. Since 1966 (the year that is considered to have been the beginning of complete operational satellite coverage) the first Eastern Pacific tropical storm has appeared in May sixteen times (including 2000). Of the 35 years from 1966 through 2000, in only seven seasons did the first tropical storm appear earlier in the month than this year's Hurricane Aletta. The write-up for Hurricane Aletta was prepared by John Wallace, a student at the University of Texas in San Antonio who has had a keen interest in tropical cyclones and climatology for several years. Although he didn't initially plan to, John tells me that now he is seriously considering majoring in meteorology. John is interested in tropical climatology and patterns of storm formation, and has a special interest in the Northeast Pacific region. Last year he wrote for me the narrative for Tropical Storm Irwin in October, the final storm of the 1999 season in the Northeast Pacific. A special thanks to John for writing the Aletta summary--it helped me out enormously. (John has already sent me his write-ups for Bud and Carlotta in June, so hopefully I'll be able to get the June summary out a little earlier than usual.) Hurricane Aletta (TC-01E) 22 - 28 May -------------------------- Hurricane Aletta was the first May "named" storm since 1996. However, the 1996 storm was retroactively upgraded to storm status (i.e.,unnamed). With this in mind, Aletta was the first May storm actually warned on as a tropical storm since 1991. It was the first May hurricane since 1990, and the strongest May hurricane since 1983's Hurricane Adolph, which peaked at 95 kts--the current record-holder for intensity in May since the beginning of the era of complete satellite coverage in the late 1960s. A tropical LOW developed in the wake of an easterly wave late in the second week of May. The LOW generated only sporadic convection through the 21st and remained nearly stationary during that time. Even so, by 0000 UTC on 20 May there was definite loose, spiral banding, while the convection fluctuated in an apparent diurnal bursting pattern. The synoptic conditions were favorable for development, with light shear, modest ridging aloft, very warm SSTs, and no dry air intrusion at the mid- to upper-levels. Though convection was strong on the 20th, it weakened greatly on the 21st, so much so that it looked for a moment like the LOW would not develop, though conditions became increasingly favorable. Satellite presentation notwithstanding, the estimated CP of the LOW was stable at 1008 mb from the 20th through late on the 21st. There was a dramatic nocturnal increase in convection starting at 0600 UTC on 22 May, concurrent with the development of a slow easterly track. Between 0600 and 1400 UTC, the LOW deepened and changed from a broad spiral of low clouds to a robust, well-organized cyclone with a CDO nearly centered over the LLCC. The LOW was upgraded to Tropical Depression One-E at 1500 UTC on 22 May when the center was located about 225 nm south-southeast of Acapulco. Conditions were highly favorable for further development as an upper-level anticyclone centered itself over the depression. The cyclone's west-northwesterly track was influenced by a mid-level ridge to its north, and this was forecast to keep it parallel to but safely offshore from Mexico until a strong trough to the northwest was expected to induce a more northerly motion. The track on the whole was expected to conform closely to climatology. The depression intensified slowly through the 22nd and into the 23rd; its forward speed decreased by almost half accordingly as steering currents weakened. By 0900 UTC on 23 May Tropical Depression One-E was upgraded to Tropical Storm Aletta as the Dvorak T-number reached 2.5. The newly-named tropical storm was located about 315 nm south-southeast of Manzanillo, Mexico. The track, initially parallel to the Mexican coast, changed to a more westerly one as storm intensity was reached. The last public advisory was issued since the storm now presented no significant threat to the mainland. Conditions remained favorable for slow strengthening, though University of Wisconsin CIMSS data indicated seemingly more favorable conditions than NHC noted in its advisories. Convection intensified and overall organization increased markedly after the upgrade, though the center remained difficult to locate in the developing storm. Aletta's central pressure fell a respectable 15 mb in the 24 hours from 1500 UTC on 23 May to 1500 UTC on the 24th, when the storm was upgraded to hurricane status about 300 nm south-southwest of Manzanillo. A diffuse, cloud-filled eye was apparent in visible imagery by 1745 UTC on the 24th; a TRMM overpass at 1609 UTC confirmed a 30-nm diameter eye. A SSM/I overpass at the same time showed a closed eyewall, though it disappeared on visible and infrared imagery soon after. Hurricane Aletta intensified quickly, reaching its peak 90-kt MSW and CP of 970 mb just 18 hours later, at 0900 UTC on 25 May, roughly 275 nm southeast of Socorro Island. It briefly sustained this intensity until 1500 UTC when a slow weakening trend began. The intensification trend occurred even though synoptic conditions were less favorable than they had been earlier. The upper-level anticyclone that fostered Aletta's initial development had weakened slightly and moved north over Mexico by 0000 UTC on the 24th, creating light easterly shear. The SSTs were still warm, however, and there was no entrainment of stable air. Soon after Aletta peaked in intensity, the CDO became less symmetric as convection was displaced west of the center by easterly shear, exposing the center and low-level banding in its eastern semicircle. Strong low-level southwesterly flow exacerbated the easterly shear. The beginning of the weakening trend coincided with an almost complete collapse of steering winds. Aletta was already embedded in a broad col between a strong subtropical ridge over the Gulf of Mexico and Caribbean, and the Pacific subtropical ridge far to the west; a strong upper-level trough west of Baja California, well to the northwest, had eroded the mid-level ridge to the north that had provided most of Aletta's steering. The stall was well-forecast by certain models, but caught the NHC official forecasts slightly by surprise. Aletta became quasi-stationary by 0000 UTC on the 26th, and scarcely moved until the last advisory was issued. Aletta became increasingly ragged on the 26th as the shear became more northeasterly. The upper-level anticyclone responsible for the shear had weakened since Aletta's peak, but was apparently strong enough to make life difficult for the weakening hurricane. Aletta weakened very rapidly on the 27th, dropping below hurricane intensity by 0300 UTC, and to a depression by 1500 UTC when no deep convection remained. The last advisory on the weak, low-level vortex was issued at 0300 UTC on 28 May, as it drifted northward to cooler waters. An ill-defined, mid- to low-level vortex persisted in the same location until 1 Jun, after which the remnant circulation was unidentifiable in any satellite channel. Aletta's rapid weakening trend is a minor mystery. Shear over the system was not strong, and by the time Aletta had dissipated was actually favorable. Water vapor imagery from 1200 UTC on 26 May shows northeastward advection of moisture from Aletta's vicinity, but this jet apparently had little or no direct impact on the storm. There was no evidence of entrainment of more stable air--as evidenced in visible imagery by extensive stratiform clouds--if it was a culprit, it was subtle. Nor was there any evidence of dry air entrainment in water vapor imagery. However, water vapor imagery from 1200 UTC on 27 May showed that the moisture content of the atmosphere over Aletta's rough position was slightly drier than that of its surroundings. The import of this on Aletta's dissipation is unknown, or indeed if it was even a real feature. If it was a real feature, though, it would indeed be unfavorable, perhaps indicating subsidence. Imagery from 1215 UTC the following day suggests it was a real feature. As for SSTs, they were not unfavorably cool, roughly 27 C; anomaly imagery shows little significant upwelling, a surprise given Aletta's stall. A minor mystery, but enough to pique the curiosity. No casualties or damage are known from Aletta at this time. The storm did briefly present the threat of heavy coastal rains to Mexico, but as the system was compact these apparently did not occur. NOTE from Gary: I let John's next-to-last paragraph stand basically as he wrote it--exploring reasons why Aletta weakened so rapidly in the absence of any obvious hostile environmental factors. I have since learned from Jack Beven that Richard Pasch, in his preliminary report on the storm, concluded that upwelling after all was likely the primary culprit contributing to the rapid weakening of Aletta on 26 and 27 May. *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for May: 2 tropical depressions 1 tropical storm 1 super typhoon 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 JMA (Japan) and the Philippines (PAGASA) 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. 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 Activity for May ---------------------------------- After lying quiet for the first four months of the year, the North- west Pacific suddenly became quite active, producing one of the most intense super typhoons ever noted during the month of May. Three other tropical depressions formed, but only one of these attained tropical storm intensity. Damrey and Longwang became the first storms to be named from the roster of Asian typhoon names. (More information on these new names can be found in the global summary for December, 1999.) Tropical Depression 03W (named Konsing by PAGASA) formed on 20 May about 300 nm southeast of Hong Kong (or roughly the same distance northwest of Manila). This depression never generated winds higher than 30 kts as it moved east-northeastward through the Luzon Strait. The final warning (from PAGASA) at 22/0600 UTC placed the weakening center about 300 nm east-northeast of the southern tip of Taiwan. Tropical Depression 04W formed on 30 May in the South China Sea just off the coast of southern Vietnam about 200 nm south-southeast of Da Nang. This weak system drifted generally north-northwestward, paralleling the Vietnamese coast. Maximum winds were estimated at no more than 25 kts most of the time, briefly reaching 30 kts at 1200 and 1800 UTC on the 31st. The final JTWC warning at 1800 UTC on 1 Jun placed the dissipating center just off the coast in the Gulf of Tonkin about 175 nm south-southeast of Hanoi. JTWC was the only warning agency to issue bulletins on this system. Super Typhoon Damrey (TC-01W / TY 0001 / Asiang) 5 - 12 May ------------------------------------------------- The waters of the Western North Pacific were quiet for the first four months of 2000, but then exploded with a bang. The first tropical depression of the year became the first tropical storm, which then became the first typhoon, which in turn became the first super typhoon and the second strongest May typhoon on record (dating back to 1945). Capt. Jim Parsons, a Typhoon Duty Officer at JTWC, checked the JTWC Best Track database and also the consolidated world- wide Tropical Cyclone database (maintained at the National Climatological Data Center in Asheville, North Carolina), and reported that the only May typhoon to have exceeded Damrey's peak intensity of 155 kts was Typhoon Phyllis in 1958 (160 kts). Also, Typhoon Iris in May, 1951, reached a peak intensity of 150 kts. But the opinion has often been expressed that many of the MSW estimates in earlier years were too high, so the possibility exists that Damrey was in fact the most intense May typhoon on record. (A special thanks to Jim for looking this up for me.) On 3 May JTWC issued a STWO at 1400 UTC which indicated that an area of convection had developed south of Yap and had persisted for more than 18 hours. A QuikScat pass indicated a broad, weak LLCC with good outflow. A few hours later the center of action was determined to be farther west--about 125 nm southeast of Palau--with convection increasing in areal coverage. The system's potential for development was upgraded to Fair. The area of convection passed over Palau around 04/0600 UTC, and at 2330 UTC JTWC issued a Formation Alert. The LLCC was partially exposed with most of the convection to the west of the center which was embedded in the monsoon trough. The disturbance continued to trek slowly northwestward on 5 May, gradually becoming better organized, and JTWC issued the first warning on Tropical Depression 01W at 1800 UTC with the center estimated to be located about 250 nm north-northwest of Palau. PAGASA initiated warnings at 0000 UTC on 6 May (naming the depression Asiang), and JMA began issuing warnings at 0600 UTC. TD-01W continued to move slowly northwestward on 6 May. By 1200 UTC animated imagery showed that the system was rapidly intensifying and JTWC upgraded the depression to a tropical storm with 40-kt winds, located about 325 nm north-northwest of Palau. PAGASA upgraded the system to a 35-kt tropical storm (10-min avg winds) at 1800 UTC, and JMA followed suit at 07/0000 UTC, naming the storm Damrey. JTWC had increased the MSW to 60 kts by this time, based upon satellite intensity estimates of 55 and 65 kts. Animated imagery showed that Damrey was continuing to organize and had developed outflow channels to the north and south of the system. JTWC upgraded Damrey to a typhoon at 07/0600 UTC when the center was located about 450 nm east of Catanduanes Island in the Philippines. Damrey by this time had moved into a weakness in the subtropical ridge and was moving very slowly in a general northward direction. The MSW estimate reached 75 kts at 1800 UTC with the storm now drifting very slowly northeast- ward. A TRMM pass at 1819 UTC suggested that a weak eye feature was beginning to form with a strong convective band to the north and west of the LLCC. JMA upgraded Damrey to a typhoon at 08/0000 UTC. At 0600 UTC a banding eye was visible in animated satellite imagery as well as in SSM/I imagery. The typhoon had reached the westernmost point in its track around 0000 UTC on 8 May when it was centered about 425 nm east of Catanduanes Island. From this point onward Damrey's motion was always to the northeast or east-northeast. By 1800 UTC a 17-nm diameter ragged eye was visible and the typhoon was beginning to rapidly intensify as it had moved underneath the upper-level ridge axis. JTWC increased the MSW to 105 kts based upon Dvorak estimates of 102 and 115 kts. (JMA's 10-min avg MSW estimate at this time was 75 kts.) Damrey continued to deepen and by 0600 UTC on the 9th had reached super typhoon intensity of 130 kts about 600 nm west of Saipan. The storm had picked up some in forward speed and was moving northeastward at 13 kts. Satellite imagery revealed a round, cloud-free eye approximately 8 nm in diameter with impressive outflow in all quadrants. Based upon current intensity estimates of 140 and 155 kts, JTWC further increased the MSW to 150 kts at 1200 UTC. Damrey at this time displayed a 14-nm wide cloud-free eye with two convective bands approximately 200 nm and 320 nm east of the eye, respectively. Super Typhoon Damrey reached its estimated peak intensity of 155 kts at 1800 UTC on 9 May. The storm at that time was centered roughly 600 nm west-northwest of Guam or about 450 nm southwest of Iwo Jima, moving northeastward at 16 kts. In terms of areal extent Damrey was a rather small typhoon. At its peak gales extended outward 170 nm to the southeast and 135 nm elsewhere. The radii of 50-kt winds were 100 nm to the southeast and 65 nm elsewhere, and 100-kt winds were confined to within about 20 nm of the center. The peak 10-min avg MSW assigned to the storm by JMA was 90 kts from 09/1200 UTC through 10/0000 UTC, and the minimum CP (also from JMA) was 930 mb. As is often the case with small tropical cyclones, Damrey weakened even more quickly than it had intensified. Six hours after peak intensity was reached, JTWC lowered the MSW to 140 kts as the storm was beginning to show signs of weakening in an environment of increased vertical shear. The eye had become ragged and cloud-filled. By 0600 UTC on 10 May animated visible imagery revealed that deep convection had decreased dramatically over the western half of the system. Damrey had moved north of the upper-level anticyclone and moderate to strong southwesterlies overlay the storm. The typhoon's center at this time was about 300 nm southwest of Iwo Jima and winds had dropped to 105 kts. By 1800 UTC there was little deep convection associated with the LLCC, and by 11/0000 UTC, only 30 hours after reaching its peak intensity, Damrey had weakened back to tropical storm intensity of 60 kts. (This is per JTWC's assessment. During the decay phase JMA's 10-min avg MSW estimates were somewhat higher than JTWC's reported 1-min avg MSW values. JMA maintained Damrey as a typhoon through 11/0600 UTC, and was still reporting 50 kts at 12/0000 UTC when JTWC's MSW estimate was only 35 kts.) Caught up in southwesterly flow and in a hostile vertical shear environment, Damrey continued to gradually accelerate to the northeast as it weakened. By 0000 UTC on the 11th the LLCC had become exposed with convection being sheared to the northeast. Damrey passed about 30 nm northwest of Iwo Jima at 0600 UTC with 45-kt winds, moving northeastward at 16 kts. By 0000 UTC on 12 May the former super typhoon was a minimal tropical storm located about 300 nm northeast of Iwo Jima and moving to the east-northeast at 20 kts. JTWC wrote its final warning at 0600 UTC, and (per JMA) Damrey was becoming extra- tropical at 1200 UTC about 525 nm east-northeast of Iwo Jima. Fortunately, this brief but very intense typhoon did not (to the author's knowledge) affect any populated areas. Tropical Storm Longwang (TC-02W / TS 0002 / Biring) 18 - 20 May --------------------------------------------------- On 16 May a broad, weak LLCC was located in the northern South China Sea west of Luzon. The disturbance was located in a monsoon trough extending across the northern South China Sea and was quasi- stationary. Most of the convection associated with the system was well south of the LLCC under moderate to strong vertical shear. A STWO issued by JTWC at 0600 UTC on 17 May mentioned that deep convection appeared to be associated with linear convergence south of the LLCC. A QuikScat pass showed that the stronger winds were located on the outer edge of the circulation. A SSM/I pass at 1247 UTC depicted improved organization with deep convection wrapping around the northern periphery of the LLCC. Synoptic data and satellite imagery indicated that the center was located over land about 100 nm northwest of Manila. CIMSS vertical shear charts and a 200-mb analysis indicated a favorable environment for strengthening, and JTWC upgraded the potential for development to Fair in a special STWO at 2000 UTC. (PAGASA initiated warnings on the developing system at 1800 UTC, naming it Tropical Depression Biring.) By 0600 UTC on the 18th the LLCC was located just off the north- eastern coast of Luzon. JTWC issued a Formation Alert at 0700 UTC as animated visible imagery showed a continued increase in convective organization. At this stage the disturbance displayed monsoon depression characteristics with the deepest convection and strongest winds on the periphery of the LLCC, which was helping to anchor a reverse monsoon trough pattern. Later on 18 May the depression began to develop rapidly about 125 nm northeast of Port San Vincente in the Philippines with the LLCC located about 15 nm west of some deep convection. JTWC wrote the first warning on TD-02W at this time with an initial intensity of 30 kts, based upon satellite CI numbers of 30 and 35 kts. JMA upgraded the depression to Tropical Storm Longwang at 19/0000 UTC with 40-kt winds (10-min avg) and centered about 225 nm northeast of the northeastern tip of Luzon. JTWC upgraded the system to a tropical storm also at 0000 UTC. Deep convection was wrapping around the northern quadrant of the LLCC but was inhibited along the western edge by westerly shear. A SSM/I pass at 2153 UTC depicted a solid band of convection south through northeast of the center with weak convection in the other quadrants. Longwang reached its peak intensity of 40 kts (per JTWC analysis) at 0600 UTC when gales extended outward 45 nm to the southeast of the center and 35 nm elsewhere. The storm was centered about 250 nm south- southwest of Okinawa and moving northeastward at 13 kts. A 200-mb analysis indicated that the upper-level ridge was situated to the south of the system, near Luzon, with weak diffluence noted over the storm. Six hours later Longwang was moving rather quickly (21 kts) to the northeast about 170 nm south-southeast of Okinawa. The MSW was still estimated at 40 kts based upon CI estimates of 35 and 45 kts, but a 19/0908 UTC SSM/I pass depicted a weakened system with convection displaced almost 50 nm east of an exposed LLCC. The western half of the system was virtually cloud-free. At 1800 UTC JTWC dropped the MSW to 35 kts, but JMA's peak 10-min avg intensity of 45 kts was assigned at this time. The JMA analyzed position for 1800 UTC was about one degree to the northeast of JTWC's position, and with the storm undergoing strong southwesterly shearing, it seems likely that the JMA analyst placed the LLCC underneath the convection. By 20/0000 UTC JTWC had downgraded Longwang to a tropical depression located about 355 nm east of Okinawa. The system exhibited a small LLCC with the convection sheared to the northeast and was forecast to track rapidly east-northeastward in mid-latitude westerly flow. Six hours later the depression was becoming extratropical and merging with a frontal boundary about 240 nm north-northwest of Iwo Jima as it raced to the east-northeast at 39 kts. *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for May: No tropical cyclones *********************************************************************** SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E Activity for May: No tropical cyclones *********************************************************************** AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E Activity for May: 1 tropical LOW Australian Region Activity for May ---------------------------------- A tropical disturbance formed on 20 May near Rennell Island in the Solomon group and was assigned a number (24F) by the Fiji TCWC at Nadi. The system subsequently drifted westward for a few days into the Australian Region. A tight pressure gradient with a HIGH to the south caused gales to be generated in the southern semicircle of the system and Brisbane issued gale warnings for a couple of days. The LOW drifted slowly westward and the final gale warning at 23/0000 UTC placed the center only about 275 nm west of Rennell Island. The highest Dvorak rating located by the author for this depression was only T1.5. *********************************************************************** SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E Activity for May: 2 tropical depressions Southwest Pacific Activity for May ---------------------------------- There were no named tropical cyclones in the South Pacific region during May, but there were a few depressions/disturbances which the Fiji TCWC assigned numbers to. The first and longest-lived disturbance was Tropical Depression 22F which formed on 3 May about 350 nm south- east of American Samoa. Six hours later the center seems to have reformed about 100 nm farther to the southeast. Initially, the LOW was more extratropical in nature, lying under a 250-mb trough axis, and, while designated as a tropical LOW in warnings, did not receive a number until 5 May when there was an increase in convection fairly close to the center. The depression remained quasi-stationary for several days before drifting slowly to the west-southwest and weakening. The final warning received by the author, at 08/1800 UTC, placed the LOW's center about 500 nm south-southeast of American Samoa. Gale warnings were issued for winds up to 40 kts in the southern semicircle, but the highest Dvorak ratings assigned by JTWC and KGWC were only T1.5. A track is included for this depression in the May tropical cyclone tracks file. Another disturbance between Fiji and Vanuatu was designated as Tropical Disturbance 23F on 6 May. This system was briefly referred to as a tropical depression, but was sheared and did not develop further. No track is given for this system in the tracks file. Finally, a third disturbance was designated as Tropical Disturbance 24F on 20 May near Rennell Island in the Solomon group. This location is near 160E (the boundary of Brisbane's AOR) and the disturbance subsequently drifted westward into the Australian Region where the Brisbane TCWC issued gale warnings for a couple of days. More on this system can be found in the Australian Region portion of this summary. *********************************************************************** 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, but since May was a relatively quiet month, I have included the Glossary at the end of this summary following the Author's Note. *********************************************************************** 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 May as an example: may00.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: may00.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): http://australiansevereweather.simplenet.com/cyclones/ http://www.typhoon2000.com http://www.hurricanealley.net/ http://www.qisfl.net/home/hurricanemike http://www.met.fsu.edu/gsc/Docs/Grads/henning/cyclones/ 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: http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html TROPICAL CYCLONE REPORTS AVAILABLE I have discovered that JTWC now has available on its website the complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999 season for the Southern Hemisphere). Also, ATCRs for earlier years are available also. The URL is: http://199.10.200.33/jtwc.html 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 Eastern North Pacific cyclones are now available. The URL is: http://www.nhc.noaa.gov Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays) *********************************************************************** *********************************************************************** GLOSSARY of ABBREVIATIONS and ACRONYMS AOML/HRD - Atlantic Oceanographic and Meteorological Laboratory/ Hurricane Research Division, located on Virginia Key, Miami, Florida, U.S.A. AOR - area of responsibility CDO - central dense overcast CI - current intensity CIMSS - Cooperative Institute for Meteorological Satellite Studies (University of Wisconsin-Madison) CP - central pressure CPHC - Central Pacific Hurricane Center, Honolulu, Hawaii, U.S.A. FLW - flight level wind (or winds) FTP - file transfer protocol HPC - Hydrometeorological Prediction Center, Camp Springs, Maryland IMD - India Meteorological Department (RSMC New Delhi, India) JMA - Japanese Meteorological Agency (RSMC Tokyo, Japan) JTWC - Joint Typhoon Warning Center, formerly on Guam, now at Pearl Harbor, Hawaii kt - knot = 1 nautical mile per hour LLCC - low-level circulation center m - meter, or metre mb - millibar, numerically equivalent to hectopascal (hPa) MFR - Meteo France on Reunion Island mm - millimeter MSW - maximum sustained wind(s) (either 1-min avg or 10-min avg) nm - nautical mile = 6076.12 feet or 1852.0 meters NPMOC - Naval Pacific Meteorological and Oceanographic Center, Pearl Harbor, Hawaii, U.S.A. PAGASA - Philippines' Atmospheric, Geophysical & Astronomical Services Administration RSMC - Regional Specialized Meteorological Centre SST - sea surface temperature STS - severe tropical storm (MSW greater than 47 kts) STWO - Significant Tropical Weather Outlook - bulletin issued daily by JTWC giving information about various areas of disturbed weather and the potential for tropical cyclone development TC - tropical cyclone TCWC - Tropical Cyclone Warning Centre (generic term) TD - tropical depression TPC/NHC - Tropical Prediction Center/National Hurricane Center, Miami, Florida, U.S.A. TS - tropical storm WMO - World Meteorological Organization, headquartered at Geneva, Switzerland UTC - Universal Time Coordinated, equivalent to Greenwich Mean Time or Zulu (Z)