GARY PADGETT'S MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY JUNE, 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.) *********************************************************************** JUNE HIGHLIGHTS --> Relatively weak tropical storm causes devastating flooding with significant loss of life in southeastern U. S. --> Two damaging typhoons strike China --> Unusual small midget cyclone forms in Mozambique Channel *********************************************************************** ***** Feature of the Month for June ***** RESULTS OF TROPICAL CYCLONE SURVEY - PART 2 CLASSIFICATION OF TROPICAL VS SUBTROPICAL CYCLONES As promised I'm going to summarize some of the responses to my little survey on the subject of subtropical/hybrid cyclones. In general the comments seemed to focus primarily on two separate issues: (1) warning strategies for subtropical systems and (2) meteorological classification for climatological purposes. I'm going to split this topic into two monthly features and focus on the second subject for this month. James Franklin of TPC/NHC pointed out the obvious but sometimes troublesome fact that there are no well-defined boundaries between cyclone types. With regard to energy sources, cyclones come in a continuous spectrum, but forecasters (at least at NHC) have to pigeonhole them into three categories: tropical, subtropical, or non-tropical (extratropical). In deciding whether a particular storm is tropical or subtropical, James indicates that he would first look at the structure of the wind field. If the highest winds appear to be the result of central core convection, then it would be tropical. If they result from synoptic-scale gradients or forcing, then the system would be subtropical. Thermal structure is also important, but the data to definitively answer that question is often not available. (NOTE: It should be pointed out that, while in some circles the terms subtropical and hybrid are often used synonymously, this tends to not often be the case at NHC. Since its inception in public warning terminology in 1972, the term "subtropical storm" has become increasingly restricted in its application to hybrid-type marine cyclones. In other words, a subtropical cyclone is a hybrid between classical extratropical and tropical cyclones, but not all hybrids are considered subtropical storms.) Jack Beven, also of NHC, states that he considers three main characteristics in deciding whether or not a given system is tropical or subtropical: satellite appearance, amount and behaviour of central convection, and any available information on how frontal a system is. He admits that all three are rather subjective quantities. Chris Landsea of AOML/HRD feels that a tropical cyclone should be called such when there is convection near or over the center of the system (within about one degree of latitude/longitude), it is warm core in the lower troposphere, is non-frontal, and has a relatively small radius of maximum winds (smaller than about 2.5 degrees of latitude/longitude). David Roth of HPC feels that for classification as a tropical cyclone, a system should have no large dry slots, no cold fronts or stratus clouds, and should have deep central convection. In David's opinion, the (usually) small cyclones sometimes seen in the Atlantic (and also often in the Mozambique Channel) which may contain eye features but have shallow convection and shallow warm cores with cold cores aloft should be classed as subtropical rather than as tropical cyclones. Commenting also on the topic of classification of tropical cyclones, Rich Henning, a meteorologist at Eglin AFB and a member of the Hurricane Hunters squadron, suggested that perhaps there should be a sliding scale based on the latitude of the system and the time of year. Rich writes, "For example, for a system at a high latitude in November, there had better be a burst of deep convection at or near the center of the vortex that creates some evidence of a warm core and the establishment of a tighter pressure gradient near the center that can be traced to the convective event, i.e., that can be distinguished from the larger-scale mid-latitude cyclone gradient in which it may be embedded. For lower latitudes and/or when formation is from July to October, this may not be as strictly enforced, especially when cyclo- genesis occurs over water that is warmer than or equal to 26.5 C. For cooler water temperatures, I am always skeptical about a system in the absence of deep, persistent convection at or near the vortex core." Another perspective on the subject of classification of subtropical cyclones is the issue of entering them into the official tropical cyclone database (Best Tracks file). Rich Henning feels that subtropical systems should be included in the Best Tracks file so that it will contain a complete tropical cyclone climatology for research purposes. It is generally admitted that in the Atlantic basin (and likely in other basins also) before the satellite era, many subtropical/hybrid systems were treated as tropical cyclones. This is the primary reason that in the early 1970s, while not being named operationally, subtropical storms were added to the Atlantic database so as not to skew the climatology of tropical cyclones in years following the introduction of the subtropical concept. David Roth also feels that subtropical storms and subtropical portions of named tropical cyclone tracks should be added to the Best Tracks file. Most of the comments from Southern Hemisphere forecasters dealt with improved warning strategies for subtropical/hybrid systems, and many of their comments will be covered in next month's Feature. However, Steve Ready of the New Zealand Meteorological Service, in commenting on the recently modified definition of a tropical cyclone for WMO Region 5 ("a non-frontal cyclone of synoptic scale developing over tropical waters and having a definite organised wind circulation with a maximum 10-minute average wind of 34 knots (63 km per hour) or greater"), points out that many disturbances satisfy the wind criteria but don't have the classical look in satellite imagery for officially naming as tropical cyclones. This is especially true for systems forming outside the normal hurricane season or in the subtropical latitude band or in a strongly sheared environment. Steve feels that systems whose status is debateable should not be named. As he puts it, "If in doubt, leave out!" *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for June: 1 tropical storm NOTE: Some 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. Atlantic Tropical Activity for June ----------------------------------- Over the past century of records, a tropical storm or hurricane has appeared in June about once every other year on the average. The last Atlantic tropical storm to form in June was Tropical Storm Arlene in 1999, so according to the long-term average it was time for another one this year. Tropical Storm Allison developed rather suddenly just off the Texas coast on 5 June--just a few days after the official hurricane season had begun. Within 24 hours after making landfall Allison had been downgraded to a depression, but instead of moving well inland and dissipating, Allison's remnants hung around the coastal area of southeastern Texas, and over the next several days dropped enormous amounts of rainfall, leading to disastrous flooding. One of the hardest hit areas was the city of Houston, where some of the free- ways were under 5.5 m of water following Allison's deluge. Damage figures from Allison's flooding are not complete, but the storm surely will go down in the annals of weather history as the most destructive tropical storm (i.e., not of hurricane intensity) on record in the United States. Tropical Storm Allison (TC-01) 5 - 19 June ------------------------------- What initially appeared to be a relatively minor landfalling tropical storm event in southeastern Texas turned out to be a major disaster-in-the-making for Texas. As the weakening Allison stalled and lingered in the region, very heavy rains soaked the region for several days, leading to a major flooding disaster for the state. Then, after putting much of Houston under water, the weak remnant LOW drifted back offshore and began to march eastward across the northern Gulf Coast, strengthening back to gale force over south- eastern Louisiana. Heavy rains drenched all the Gulf states as the rejuvenated storm accelerated eastward. Upon nearing the Atlantic coast, a blocking HIGH stalled Allison's remnants once more, allowing heavy rain to spread throughout the Southeast and Mid-Atlantic regions--even up into New England. There is no doubt that Allison is the most destructive tropical storm of less than hurricane force to ever affect the United States. Coincidentally, another Tropical Storm Allison twelve years earlier made landfall in the same region and dumped heavy rains for several days over southeastern Texas and western Louisiana. 1989's Allison, however, occurred the last week in June. Damage from the earlier storm was estimated to have exceeded $500 million, primarily from flooding. Another tropical storm named Allison, formerly a minimal hurricane, made landfall on the Florida Panhandle near St. Marks on 5 June--six years earlier to the day that this year's Allison developed. The Allison of 1995 was far less destructive than the storms of 1989 and 2001. Most of the report given below was taken from an excellent and thorough summary of Allison written by David Roth, a meteorologist at the Hydrometeorological Prediction Center (HPC) in Maryland. David's report is quite lengthy and very detailed, so only an abbreviated version is included here. The full report can be obtained at the following URL: Some information on the early stages of Allison was gleaned from the monthly summary of tropical activity for June prepared by the staff of TPC/NHC. That report can be found at the following URL: A. Origins ---------- Allison's origins appeared to lie with a tropical wave that left the west coast of Africa on 21 May. The wave tracked westward across the Atlantic and Caribbean, reaching the western Caribbean on the 29th, later crossing into the Eastern Pacific. A weak low-level circulation formed along the tropical wave south-southeast of Veracruz, Mexico, on 3 June, later moving into the Bay of Campeche on the 4th as an area of strong thunderstorms. The LOW was guided by a nearby upper-level LOW towards the north-northwest through the western Gulf of Mexico. Thunderstorm activity increased and the system became a depression on the morning of the 5th. The area of thunderstorms became increasingly organized, so much so that reconnaissance aircraft, along with ship and buoy reports, indicated the formation of a tropical storm located only 70 nm from Galveston, Texas. Surface winds of 40-50 kts were being reported on the east side of the system. Even though the storm was more like a hybrid than a purely tropical system, it was upgraded to the first tropical storm of the 2001 Atlantic tropical cyclone season. B. Track and Intensity History ------------------------------ Initially steered by the subtropical ridge centered east of Florida, the cyclone moved northward, making landfall on the east end of Galveston Island during the evening of 5 June. The highest winds reported on land were to the northeast of the center in the area with the tightest pressure gradient. At Sea Rim State Park sustained winds reached 42 kts at 06/0250 UTC and gusts peaked at 53 kts at 0242 UTC. Tropical storm-force winds were reported from Galveston eastward to the Sabine River during the night of the 5th and on the morning of the 6th. The peak MSW reported in the NHC advisories was 50 kts during the afternoon and evening of 5 June. Allison had weakened to a depression by 06/0900 UTC and the responsibility of issuing advisories was handed over to HPC--standard procedure when a weakening depression drifts inland and constitutes a flooding threat. Allison drifted as far inland as Lufkin, Texas, during the morning of the 7th, dropping large quantities of rain along and to the east of its path. Much of southeast Texas and south-central Louisiana had already received over 255 mm of rain by the morning of 8 June. In parts of Louisiana much of this rain fell within a 12-hour period on the 6th. During the night of 6-7 June, heavy rains deluged northwest Jefferson and Orange Counties in southeast Texas when 150-250 mm fell in less than five hours. On the morning of 7 June the subtropical HIGH off Florida weakened and drifted to the south while a ridge over New Mexico was intensifying. This caused Allison's remnants to transcribe a clockwise loop that morning, followed by a slow south- westerly drift toward the coast, a movement which brought more heavy rainfall to Texas and Louisiana over the next couple of days. The center finally exited the Texas coast near Palacios during the evening of the 9th, becoming the first known tropical cyclone to make landfall in Texas only to later re-emerge back over the Gulf. Upper- level westerlies associated with the southern fringe of the subtropical jet stream guided the LOW east-northeastward, moving it into the marshes and bayous of southeastern Louisiana on the morning of 11 June. On the 11th the LOW that was formerly Allison accomplished a rare feat--intensifying over land. This was mainly due to a jet streak riding along the subtropical jet to its north and northeast, enhancing the outflow which in turn led to a stronger surface LOW. By 0600 UTC on the 11th the system had regained gale-force winds which were spreading over the Mississippi River delta area. By 1200 UTC an eye-like feature had developed on radar while the system was entering southwestern Mississippi. The MSW increased to 40 kts with gusts to 50 kts in the main inflow band east of the center. As the LOW edged farther inland that afternoon, it finally weakened and lost the eye feature. (NOTE: The monthly summary for June from NHC states that Allison's remnants re-organized as a subtropical cyclone before moving back inland. Operationally, the system was treated as neither a tropical nor subtropical storm during this brief period of re-intensification, but rather was handled as a LOW with gale-force winds.) Allison tracked out of Mississippi into southern Alabama on the afternoon of 11 June, continuing its quick east-northeasterly movement. The forward motion began to slow as it encountered a blocking ridge of high pressure sitting off the New England coast. The LOW came to a halt as it was nearing the Atlantic coast near Wilmington, North Carolina, on the morning of 14 June. Heavy rains fell on parts of Georgia and South Carolina, and as the system slowed to a crawl in North Carolina, flooding became a major problem in that state. Some locally severe weather was also reported in Georgia and the Carolinas on the 13th and 14th. Several areas reported hail, and high winds downed power lines and trees throughout the region. Also, dangerous rip currents developed in the Outer Banks as the winds became perpendicular to the shore. Allison's remnants later moved slowly northward along the Delmarva Peninsula. (The Delmarva Peninsula is the peninsula which separates Chesapeake Bay from the Atlantic Ocean. The states of Delaware, Mary- land and Virginia all occupy portions of the peninsula, hence the name: "DEL" from Delaware, "MAR" from Maryland, and "VA"--the official abbreviation for Virginia.) A cold front moved in from the west, allowing moisture from Allison to pool along the front to the north of the center. This set the stage for heavy rains across the northern Mid-Atlantic region and southern New England. As the system turned to the east-northeast and paralleled the coast, rainfall amounts of 50-100 mm fell on portions of New Jersey, southern New York, Connecticut, Massachusetts and Rhode Island. The last of the rains associated with Allison's remnants moved out of eastern Maine during the early morning of 18 June as the LOW accelerated off to the east-northeast. By the 19th the LOW had weakened and lost its identity south of the Canadian Maritimes. C. Meteorological Aspects ------------------------- Although rainfall was the big story in connection with Tropical Storm Allison, there were plenty of reports of gale-force winds or higher. The winds measured at Sea Rim State Park have already been mentioned above. As Allison's remnants underwent the intensification over Louisiana and Mississippi on 11 June, quite a few buoys and stations reported winds exceeding tropical storm force. BURL1 (28.9N, 89.3W) reported sustained winds exceeding 33 kts from 11/0700 to 1300 UTC--the maximum of 40 kts occurring at 1300 UTC. Winds were 39 kts at 1100 and 1200 UTC. Peak gusts reached 49 kts around the same time. GDIL1 (29.3N, 89.9W) reported 34 kts at 11/0900 UTC with peak gusts over the previous hour reaching 45 kts. Several other locations had peak gusts in the 45-50 kt range. Eglin AFB, near Valparaiso, Florida, reported a peak gust of 47 kts shortly before local noon (1700 UTC). Along the Atlantic coast I have been unable to locate any reports of sustained gale-force winds. The strongest I'm aware of was a report of 32 kts sustained at Diamond Shoals Lighthouse at 17/0300 UTC. There were many reports of gusts in the 25-30 kt range with a few higher. An offshore buoy near St. Simons Island, Georgia, reported gusts to 31 kts during the afternoon of 12 June as the LOW was crossing Georgia. Inland, Vidalia reported a gust to 28 kts at 2000 UTC. Gusts to 30 kts were reported along the South Carolina coast on the 13th, and Atlantic City, New Jersey, reported sustained winds of 25 kts with gusts to 34 kts at 0200 UTC on the 17th. Chris Bedford of Sailing Weather Services in Watertown, Massachusetts, sent some information to David Roth after David's final storm summary had been posted on HPC's website. Several boats participating in a race from Annapolis to Newport reported quite strong northwesterly winds on Saturday, 16 June, after leaving Chesapeake Bay. Crew members on board the winning boat (Farr 60 Carrera) claimed they experienced winds greater than 48 kts for one hour with gusts to 54 kts. One boat reported 68-kt gusts while another was retired from the race after having its sails ripped in 40-kt sustained winds with gusts to 60 kts. Chris adds, however, that the instrumentation could be suspect. The stiff winds resulting from the interaction between Allison's remnants and the cold front apparently were such that they helped the boats make good time. The winner bested the previous record for the race (set in 1999) by almost five hours, and the runner-up arrived only 23 minutes later. As Allison's center approached the Houston area for a second time on 8 June, rain intensified across southeastern Texas. Conroe measured 209 mm during a six-hour period during the afternoon of the 8th. In the Houston area over 500 mm fell within a 12-hour period. The highest storm total reported from Texas was 939.5 mm at the Port of Houston. Allison ranks as the fourth wettest tropical cyclone in Texas history, the others being Tropical Storm Amelia of 1978 (1168 mm), Tropical Storm Claudette of 1979 (1143 mm), and an unnamed hurricane in 1921 (1016 mm). In Louisiana Allison ranks second behind a 1940 hurricane as the wettest tropical cyclone in that state's history. The maximum rainfall amounts occurred in the Vermilion and Atchafalaya basins of south-central Louisiana with heavy rains falling each day from the 5th through the 11th. The highest storm total amount of 758.4 mm was measured at Thibodaux. Salt Point in St. Mary Parish recorded 699.8 mm. Several locales recorded rainfall amounts exceeding 500 mm. (The peak storm total rainfall for the 1940 hurricane alluded to above was 856.2 mm at Crowley.) As Allison marched eastward, heavy rains continued to fall but the accumulations were much less due to the system's more rapid forward motion. Gulfport, Mississippi, had recorded 304.5 mm by 1800 UTC on the 11th with the majority falling within a 24-hour period. The main rain band moved eastward and then stalled near Tallahassee, Florida, where a 24-hour total of 250.4 mm was netted between the mornings of 11 June and 12 June. As the LOW tracked through the southeastern U. S., the area of heaviest rainfall shifted to its northwestern quadrant each night. Siloam, Georgia, picked up 146.1 mm in the 24-hour period ending on the morning of the 13th. At a location just to the east of Columbia, South Carolina, a local fire department reported on the 13th that its rain guage had overflowed with over 305 mm of rain in fourteen hours. In North Carolina Askewville recorded 216 mm of rain in a 16-hour period on the 15th. A Doppler radar at Morehead City estimated that up to 535 mm fell across the Bertie/Hertford County border as well as in Halifax and Martin Counties. Farther north the heaviest rains fell on the 16th. Willow Grove Naval Air Station in Pennsylvania recorded 215.1 mm of rain mainly in the 8-hour period between 1800 UTC and 0200 UTC on the 17th. Willow Grove and Chanfont reported 24-hour totals of 258 mm, ending on the morning of the 17th. Finally, as mentioned above, rainfall amounts of 50-100 mm fell across portions of the Mid-Atlantic region and southern New England during Allison's last fling. D. Storm Effects ---------------- Allison turned out to be the major flood event on record in the Houston area. Portions of U. S. Highway 59 and Interstate 10 were deeply submerged--up to 5.5 meters in places. Flooding of similar magnitude occurred in the Beaumont area as well. At least 22 persons perished in the Houston area from the flooding. Damage from Houston and surrounding communities alone totalled in excess of $2 billion, perhaps considerably more. Although the main threat from Allison's remnants was heavy rain, tornadoes touched down in Louisiana northwest of Zachary in East Baton Rouge during the early morning of 7 June. One person was killed when a tree fell onto his vehicle. In southeast Louisiana the Comite River recorded its third highest river stage on record on the 9th, cresting at 8.87 meters at Comite. Severe weather associated with Allison became more frequent during and following its re-intensification on 11 June due to stronger winds aloft interacting with the circulation. Two tornado touchdowns were reported in Mississippi on the 11th--one destroyed a manufactured home and caused major damage to a two-story home in George County. And, as noted earlier, some severe weather was reported in Georgia and the Carolinas on the 13th and 14th. Hail fell at Mountain Rest, Landrum and Anderson, South Carolina. The total damage in the United States resulting from Tropical Storm Allison has been tentatively estimated at between $2.5 and $4 billion. Thirty-two fatalities have been directly attributed to the storm with an additional 11 deaths indirectly associated with Allison. *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for June: 1 tropical storm 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 Tropical Activity for June -------------------------------------------- Over the period 1971-2000 the Eastern North Pacific has produced an average of 2.2 tropical storms per year with an average of 1.2 reaching hurricane intensity. This year only one tropical storm developed during the month, so activity was somewhat below normal. Tropical Storm Barbara formed farther west than most June tropical cyclones have formed and moved across 140W into the Central North Pacific as it weakened to a tropical depression. As the month opened former intense Hurricane Adolph was a rapidly weakening tropical storm located several hundred miles south of Mexico's Baja California peninsula and had dissipated by the 2nd. The following summary on Barbara was written by John Wallace of San Antonio, Texas. A special thanks to John for writing the report on this storm. Tropical Storm Barbara (TC-02E) 20 - 23 June -------------------------------- A. Origins ---------- The origins of Barbara are somewhat uncertain. The storm might have been spawned by a tropical wave that left the African coast on 2 June. More likely, though, it developed from a wave that was first noted in the central Caribbean on 10 June. The wave tracked steadily westward, entering the Pacific on the 12th. A tropical LOW had formed along the wave axis by 18 June and conditions favored further development. By 0300 UTC on 20 June, the LOW's organization had increased enough to warrant its upgrade to Tropical Depression Two-E while located some 1375 nm west-southwest of Manzanillo, Mexico. The depression tracked westward, under the steering influence of a mid-level ridge to its north. Its relatively unimpressive organization and convection increased enough to justify its upgrade to Tropical Storm Barbara at 2100 UTC on 20 June while located roughly 1575 nm west of Manzanillo. This made Barbara the earliest storm on record to form so far west in the Northeast Pacific. Its initial westward track took a west-northwesterly turn as the system began to "feel" the effects of a large, strong upper-level LOW to its northwest. B. Track and Intensity History ------------------------------ Barbara strengthened markedly after its upgrade in an initially favorable environment. The storm reached its peak MSW of 50 kts, with a CP of 997 mb, at 1500 UTC on 21 June about 1200 nm east of Hilo, Hawaii. Even then, a weakening trend had already begun, due in large part to increasing southerly shear. The presence of the LOW, along with cooler SSTs along the track, had ensured from the beginning that Barbara was living on borrowed time. The weakening trend was slow at first. Ship V2FA2 reported a northeast wind of 47 kts and 7.9 m seas at 0000 UTC on the 22nd. As the ship was then 105 nm northwest of the center, the report raised interesting possibilities about Barbara's true intensity. However, once ship motion was factored out, the report fell more in line with the satellite estimates. Barbara steadily weakened in the face of increasing shear and cooler SSTs. Nevertheless, it succeeded by a nose in becoming the first Northeast Pacific storm to enter the CPHC's AOR in June. It was downgraded to a depression immediately afterward, though. The final advisory on Tropical Depression Barbara was issued at 0300 UTC on 23 June with the weakening center located some 775 nm east of Hilo, Hawaii. The cyclone's remnant vortex brought some unsettled weather and rough surf to the islands on the 25th and 26th; it seems that other effects were negligible. C. Damage and Casualties ------------------------- No damage or casualties are known to have resulted from Tropical Storm Barbara. *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for June: 1 tropical depression ** 2 typhoons ++ ** - Warnings on this system were issued only by PAGASA, plus a track was received from Roger Edson ++ - One of these was not treated as a typhoon by JMA, but was by JTWC, the National Meteorological Center of China, and Hong Kong Observatory 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. Also, some information based upon warnings issued by the National Meteorological Center of China (NMCC) and the Hong Kong Observatory (HKO) is included. The tracks from these agencies were sent to me by Huang Chunliang of Fuzhou City, China. A special thanks to Chunliang for sending me these additional 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 Tropical Activity for June -------------------------------------------- Warnings were issued for three tropical systems during June by the various warning agencies. For one of these systems, Tropical Depression Darna, warnings were issued only by the weather service of the Philippines. However, Roger Edson also sent me a track for this system, so I have covered it below. Two typhoons, Chebi/Emong and Durian, formed and both made rather damaging strikes in China, Chebi in particular. JMA did not upgrade Durian to typhoon status, but HKO and NMCC (Beijing) did along with JTWC. (This storm formed and remained outside PAGASA's AOR.) Tropical Depression Darna 13 - 20 June ------------------------- Darna was a fairly weak, nebulous disturbance for which warnings were issued only by PAGASA. JTWC did not issue any warnings on this system, although four TCFAs were issued. However, Roger Edson sent me a track for the disturbance, which he also considered to have been a tropical depression. JTWC issued a STWO at 0600 UTC on 11 June which mentioned an area of convection developing about 170 nm north of Chuuk. Animated visible satellite imagery depicted disorganized, isolated deep convection drifting westward. Synoptic data revealed tradewind convergence beneath the convection. I do not have any more STWOs saved until the 15th; Roger's track indicates a weak circulation (15 kts) located about 230 nm northeast of Palau at 1200 UTC on 13 June. Any connection with the disturbance mentioned by JTWC on 11 June is uncertain. The weak LOW continued to move westward--by 1200 UTC on 14 June it was centered approximately 220 nm north-northwest of Palau with winds of 20 kts (per Roger's track). A STWO issued by JTWC at 15/0200 UTC mentioned that an area of convection had developed about 450 nm east of Mindanao. Convection was poorly-organized over a broad area; synoptic and scatterometer data suggested that a weak LLCC was located within the monsoon trough. The LLCC had become more defined by 1300 UTC. A QuikScat pass at 0907 UTC revealed possible gusts above 25 kts associated with deep convection north of 15N. The development potential was upgraded to fair. The STWO issued at 16/0600 UTC indicated possible multiple LLCCs. JTWC issued the first TCFA at 16/1430 UTC and PAGASA initiated warnings on Tropical Depression Darna at 1800 UTC. (Darna is a fictional super- heroine, the Filipino version of "Wonder Woman".) PAGASA's track and Roger's track are in fairly good agreement at first, then they diverge greatly. PAGASA's 17/1800 UTC position is just off the east coast of Luzon northeast of Manila, but the 18/0000 UTC position is a relocation of the center to off the west coast of Luzon west-northwest of Baguio. The 18/0600 UTC position is in the same general vicinity, then at 1200 UTC the center was relocated far to the north in the Luzon Strait--well northwest of Luzon. PAGASA's track subsequently takes Darna north-northeastward toward the southern tip of Taiwan and inland. Roger Edson's track, beginning on the 17th, tracks Darna north- northwestward across extreme northeastern Luzon, across the Luzon Strait, and then up the west coast of Taiwan before taking off to the northeast along a frontal trough. As noted above, JTWC did not issue any warnings on this system, but did issue four TCFAs, each at 1400 UTC on the 16th through the 19th. The positions mentioned in the TCFAs roughly agree with Roger's track. The final TCFA was cancelled at 19/2130 UTC as the LLCC was beginning to interact with the mid-latitude front approaching Taiwan. Darna was in a weakly sheared environment for most of its life. No reports of damage or casualties resulting from this system have been received. Typhoon Chebi (TC-04W / TY 0102 / Emong) 19 - 24 June ----------------------------------------- Chebi: contributed by South Korea, is a swallow--a small bird with long wings and a forked tail which eats insects. Each spring the bird visits Korea where it is believed to bring good fortune. A. Origins ---------- An intermediate STWO issued by JTWC at 1400 UTC on 19 June indicated that an area of convection had developed southeast of Yap. Animated infrared imagery indicated an increase in coverage of deep convection over the previous 12 hours. Microwave data indicated a possible weak surface circulation while a 200-mb analysis revealed weak diffluence associated with an upper-level trough. By 1800 UTC the disturbance was centered roughly 150 nm east-northeast of Palau. New bursts of convection were occurring to the north of a broad LLCC in the monsoon trough; the development potential was upgraded to fair. However, shortly afterward early morning visible pictures depicted that significant intensification and development had occurred over the past four hours with a rapidly developing banding feature over the southern quadrant. The first warning on TD-04W was issued at 2100 UTC placing the depression's center about 275 nm north-northeast of Palau at 1800 UTC. The depression had entered PAGASA's AOR by 20/0000 UTC and that agency began issuing warnings on the system as a tropical storm, which was named Emong (a Filipino nickname). Six hours later both JTWC and JMA upgraded the depression to tropical storm intensity with JMA assigning the name Chebi. Tropical Storm Chebi was located about 350 nm north-northwest of Palau at this time. B. Track and Intensity History ------------------------------ A mid-level subtropical ridge extending northward from a HIGH north of the Mariana Islands was the main steering influence on Chebi through most of its life. The storm embarked on a general west-northwestward to northwestward track which it maintained until it turned northward in the Taiwan Strait on 23 June. Winds were up to 45 kts at 0000 UTC on the 21st as Chebi passed about 200 nm east-northeast of Catanduanes Island in the Philippines. JTWC upgraded Chebi to a typhoon at 22/0000 UTC when it was located about 80 nm east-southeast of the northeastern tip of Luzon. Satellite CI estimates were 65 kts and microwave imagery revealed a partial eyewall feature. (JMA upgraded the storm to a typhoon 12 hours later.) Typhoon Chebi passed just off the northeastern tip of Luzon and moved into the Luzon Strait where it continued to intensify. Chebi reached its peak estimated intensity of 100 kts at 23/0000 UTC when it was centered approximately 75 nm west of the southern tip of Taiwan. Gales extended outward 100 nm from the center in the southeast quadrant and up to 75 nm in the northwest quadrant, while 50-kt winds were estimated to extend out 60 nm to the southeast. A mid-latitude system over eastern China began to influence the typhoon and it turned to a northward track which took it inland into eastern China around 1730 UTC just southeast of Fuzhou City, near Fuqing, in Fujian Province. The MSW was estimated at 85 kts near the time of landfall. (This was JTWC's estimate--a report received by the author from Huang Chunliang of Fuzhou City indicates that NMCC estimated the 10-min avg sustained wind at 66 kts near the time of landfall.) As the system accelerated northward it began to interact with a baroclinic zone over eastern China. JTWC issued their final warning on Chebi at 24/0000 UTC with the storm inland and weakening. JMA and NMCC continued to track Chebi for another 12 hours as it accelerated northeastward and back out to sea. The center passed about 70 nm southeast of Shanghai around 0600 UTC, and the final bulletin from the two warning centers placed it offshore approximately 200 nm northeast of Shanghai at 1200 UTC. Typhoon Chebi reached its estimated peak intensity of 100 kts (1-min avg MSW) at 0000 UTC on 23 June. The estimated minimum central pressure (from JMA's bulletins) of 955 mb also occurred at the same time. C. Meteorological Aspects ------------------------- As Typhoon Chebi passed near Taiwan heavy rains fell on portions of the island. Some locations received between 200 and 300 mm during the 24 hours ending at 24/0000 UTC. At Laog, in northern Luzon, 281 mm fell in the 30-hour period ending at 23/0600 UTC. (Thanks to Patrick Hoareau for passing this information along.) Fuzhou City did not report sustained winds of typhoon strength--the peak there was 61 kts at 23/0003 UTC. Typhoon-force winds were reported in Fuqing, Pingtan, Lianjiang, and Luoyuan. Typhoon Chebi dropped 107.9 mm, 108.0 mm, 96.5 mm, and 86.1 mm of rain on Fuqing, Lianjiang, Pingtan, and Changle, respectively, within a six-hour period from 1200 to 1800 UTC on 23 June. (This information taken from a report on the storm sent to me by Huang Chunliang--a special thanks to Chunliang for sending the report.) D. Comparisons between JTWC and Other Centers --------------------------------------------- Center position estimates were in very good agreement between all the various warning agencies throughout the life of Chebi. Intensity estimates between JTWC and JMA agreed fairly well (after adjusting to the same averaging period) except for the peak intensity. JTWC estimated the peak MSW at 100 kts while JMA's estimated peak 10-min mean wind was 75 kts, equivalent to approximately 85 kts 1-min avg MSW. While PAGASA was the first warning center to upgrade the system to tropical storm intensity, their intensity estimates were the lowest near the time of peak intensity: only 65 kts (10-min avg) at 23/0000 UTC when JTWC was reporting 100 kts. HKO's peak 10-min mean wind estimate was 75 kts--the same as JMA's. NMCC was the warning center reporting the highest 10-min avg sustained wind. Their peak of 80 kts is equivalent to about 90 kts 1-min avg MSW---in fairly good agreement with JTWC. E. Damage and Casualties ------------------------ Typhoon Chebi paid a rather deadly visit to China's Fujian Province. Reports indicate that 71 persons died with 83 missing in the Fuzhou area. In Ningde City, to the north of Fuzhou City, two persons died and four were reported missing. A landslide on 26 June due to the heavy rains of Chebi was responsible for 22 deaths in Hangzhou City, the capital of Zhejiang Province. In Fuzhou damage from the typhoon was widespread with 2,144,300 residents seriously affected. Total economic losses were estimated to have been approximately 3 billion yuan in the city. Also, 65,362 hectares of farmland were seriously damaged by the storm. In Ningde City over 320,000 houses were damaged or destroyed--economic losses there are estimated at 503 million yuan. (Again, a big thanks to Huang Chunliang for compiling all this information and sending it to me.) In Taiwan at least nine deaths were attributed to Typhoon Chebi. Also, the typhoon sank a 5300-ton freighter with 23 persons on board. At the time of the report I received, six had been rescued, five were known dead, and 12 were still missing. (This information sent by Matthew Saxby--thanks to Matthew for passing the report along.) Typhoon Durian (TC-05W / STS 0103) 29 June - 3 July ----------------------------------- Durian: contributed by Thailand, is a favorite fruit of Thailand (Durio zibethinus) A. Origins ---------- JTWC issued a STWO at 0000 UTC on 29 June indicating that an area of convection had developed in the South China Sea. Early morning animated visible pictures depicted cyclonically curved low-level cloud lines outlining a LLCC in the monsoon trough which extended over the area. A 200-mb analysis indicated diffluent flow aloft, but moderate vertical shear seemed to be hindering development somewhat. JTWC assessed the development potential as fair. JMA classified the system as a tropical depression at 29/0600 UTC when it was centered about 400 nm south-southeast of Hong Kong. JTWC issued a TCFA at the same hour, noting that synoptic reports indicated pressure falls and increasing winds in the area. JTWC issued their first warning on TD-05W at 29/1800 UTC. The depression was centered about 390 nm south-southeast of Hong Kong and was forecast to track northwestward under the influence of a mid-level subtropical ridge over Taiwan. At 0000 UTC on the 30th JTWC upgraded the depression to a tropical storm based on CI estimates of 30 and 35 kts. The storm was then located 350 nm south-southeast of Hong Kong. Six hours later JMA upgraded the system to Tropical Storm Durian. B. Track and Intensity History ------------------------------ Durian moved on a fairly steady northwesterly track throughout its life as it was guided by a subtropical ridge extending westward from a mid-level HIGH south of Kyushu. JTWC upgraded the storm to typhoon status at 0600 UTC on 1 July when it was centered about 200 nm south- west of Hong Kong. (NMCC and HKO both upgraded Durian to a typhoon at 1200 UTC while JMA never regarded this storm as a typhoon.) Durian reached its peak estimated MSW of 75 kts at 1800 UTC when it was located in Mandarin Bay just east of the Luichow Peninsula. Gales covered an area roughly 150 nm in diameter. Typhoon Durian jogged very slightly more to the west-northwest and crossed over the northern portion of the Luichow Peninsula and into the extreme northern Gulf of Tonkin. The storm skimmed along the southern coast of Kwangtung Province, eventually making landfall just east of the Laotian border as a minimal typhoon. Once inland, the storm began to weaken quickly as it continued on its northwestward track, roughly parallel to the border with Laos. Durian was at its estimated peak intensity of 75 kts from 01/1800 through 02/0600 UTC. The minimum estimated central pressure (from JMA's bulletins) was 970 mb at 01/1800 UTC. C. Meteorological Aspects ------------------------- I did not receive as many rainfall reports or surface wind observations for Typhoon Durian as I normally do from my usual sources. A report on the storm sent by Huang Chunliang indicated maximum 10-min mean winds were 70 kts, gusting to 90 kts, when Durian made landfall near Zhanjiang City in Guangdong Province at 1930 UTC on 2 July. This seems likely to be based on the warnings from NMCC and not a direct observation. One press report mentioned that a foot of rain (305 mm) fell near Zhanjiang. Chunliang's report indicated that several coastal cities in the Guangxi region reported storm total rainfall amounts ranging from 237 to 290 mm. Nanning, the regional capital, recorded 209 mm of rain from the storm. D. Comparisons between JTWC and Other Centers --------------------------------------------- As was the case with Typhoon Chebi, center position estimates between the various warning centers generally agreed closely for most of Typhoon Durian's life. JMA did not upgrade Durian to a typhoon; however, their estimated maximum 10-min mean wind of 60 kts would be equivalent to about 70 kts 1-min avg MSW, which agrees rather closely with JTWC's estimated peak intensity of 75 kts. HKO's peak intensity of 65 kts and NMCC's peak of 70 kts both agree closely with JTWC. JTWC, however, maintained Durian as a typhoon longer than did the other centers. HKO and NMCC downgraded the system shortly after its initial landfall on the Luichow Peninsula, whereas JTWC maintained Durian as a typhoon through 1200 UTC on 2 July when it was well inland in China's Guangxi Zhuang Autonomous Region. E. Damage and Casualties ------------------------ In southwestern Guangdong Province, where Durian initially made landfall, the cities of Zhanjiang, Yangjiang, and Maoming reported heavy damage. Over 13,000 houses were wrecked, affecting 3.72 million residents in some shape or form, and 1800 businesses were forced to close. Direct economic losses amounted to 3.7 billion yuan (equivalent to $448 million U.S.). Transport across the Qiongzhou Strait was shut down for 34 hours with 3000 passengers being delayed. Sugarcane fields and banana trees were wiped out and more than 52,000 farm animals were killed. At least one person was killed and another reported missing in south China's Guangxi Zhuang Autonomous Region. (Some press reports mention three persons missing.) Some 3.36 million persons in this part of China were affected by the typhoon, the worst in 30 years in the region. Direct economic losses caused by Durian are estimated at 812 million yuan (about $978,000 U.S.), including the destruction of 5550 buildings, the inundation of 149,500 hectares of cropland, and the death of 25,000 head of livestock. Patrick Hoareau sent along a report which stated that 22 persons were killed in Vietnam due to floods spawned by Typhoon Durian's rains. The report also indicated that 20,000 homes had been destroyed in the country by the flooding. *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for June: No tropical cyclones North Indian Ocean Tropical Activity for June --------------------------------------------- There were no tropical cyclones in the North Indian Ocean during June, but there was a disturbance in the northern Bay of Bengal from around the 9th through the 12th which possibly was a monsoon depression type of system. The area was mentioned for several days in JTWC's daily STWOs and was assigned a fair potential for development on the 10th when convection was seen to be increasing west of a partially- exposed LLCC and shear was weak. An upper-level HIGH over the region, however, soon shifted to the northeast and vertical shear increased, and the potential for development was downgraded to poor. By 12 June the center was on the coast of northern India near Paradip and apparently continued to move westward and inland. The maximum winds were estimated at 25 kts on 10 June and the minimum pressure was estimated at 997 mb on the 11th and 12th. No track was given for this system in the June tropical cyclone tracks file. *********************************************************************** SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E Activity for June: 1 tropical storm ** ** - System was treated as a tropical storm by JTWC, but at least three tropical meteorologists expressed the opinion that the system was likely a minimal hurricane (cyclone). MFR classified the system only as a tropical depression, but indicated that gale-force winds likely occurred in limited areas within the circulation. Tropical Cyclone (TC-21S / MFR #11) 20 - 23 June ------------------------------------ The Mozambique Channel was the scene of two interesting but unrelated phenomena on 21 June. The moon's umbral shadow raced across the Channel in the first total solar eclipse of the new millennium (after having crossed Africa), and an extremely small midget cyclone, sporting an eye and well-organized, although shallow, convection developed suddenly off the African coast to the south of the eclipse track. (NOTE: I've used the term "tropical cyclone" in the title line above in a generic sense, not meaning to imply that the official WMO-sanctioned warning agencies, La Reunion and Madagascar, upgraded the system to tropical cyclone (i.e., hurricane) status.) The primary track for the cyclone included in the tropical cyclone tracks file for June, as well as the 1-min avg MSW estimates, were for the most part provided by Dr. Karl Hoarau of Cergy-Pontoise University near Paris. Karl based his intensity estimates on his own Dvorak analysis, plus QuikScat data. A. Origins ---------- The origin of the midget system isn't exactly clear. Karl's track locates a weak 20-kt LOW at 0000 UTC on 20 June about 325 nm east- southeast of Durban, South Africa. The LOW moved initially somewhat quickly north-northeastward to a point about 175 nm east-northeast of Durban by 1800 UTC. Karl estimates the 1-min avg MSW to be 35 kts at this point. Tony Cristaldi of the NWS office in Melbourne, Florida, indicated that he had some satellite imagery which depicted a mature/ dissipating baroclinic wave cyclone spawning the subtropical vortex which became TC-21S. This is the first known instance of a tropical cyclone developing in the Mozambique Channel in the month of June since the advent of the satellite era (1967-1968 season in the South Indian Ocean). B. Track and Intensity History ------------------------------ Based on Karl's track, by 0600 UTC on 21 June the system had reached a point about 300 nm northeast or Durban or 500 nm west-southwest of Tulear on the southwestern coast of Madagascar. At 21/0455 UTC a QuikScat pass indicated winds of 60 kts. In Karl's estimation, the MSW had reached 65 kts at this point. Roger Edson and Chip Guard also expressed the opinion that the midget cyclone likely contained winds of hurricane intensity. MFR initiated warnings at 1200 UTC, assigning a maximum 10-min avg wind of 30 kts and designating the disturbance as Subtropical Depression #11. JTWC issued the first of four warnings at 1800 UTC, estimating the MSW at 45 kts. By the time the warning centers had begun issuing warnings, the system was beginning to come under some shear from a polar disturbance to its south and was weakening. After the cyclone's rapid deepening on 21 June, it turned abruptly eastward and for the next couple of days moved rather slowly east-northeastward across the Mozambique Channel. It was centered about 200 nm southwest of Tulear at 22/1800 UTC when MFR issued their last bulletin, and was about 100 nm southwest of the city when JTWC issued their final warning at 23/0600 UTC. C. Meteorological Aspects ------------------------- At the time of the initial explosive deepening on 21 June, the small system displayed very well-organized convection with a visible eye, spiral banding, and a symmetrical CDO. However, the convection was considerably shallower than that normally seen in tropical cyclones with cloud top temperatures in the -40 to -45 C range. Philippe Aliaga, a forecaster at RSMC La Reunion, felt that with such shallow convection, a standard Dvorak analysis was not possible, so it was difficult to determine the windspeeds near the center. Philippe indicated that the system certainly generated winds near gale force (30 kts), and could have contained winds somewhat stronger (>40 kts). Another aspect of this system was its very small size. According to Karl Hoarau, the entire cloud system was about 90 nm in diameter at its maximum intensity. Brian McNoldy of Colorado State University made the observation that if the midget cyclone were superimposed on the United States, most of it would fit in the southern tip of Florida from Lake Okeechobee southward. The lowest central pressure reported in MFR warnings was 1000 mb. In his analysis of the system, Karl Hoarau estimated that the minimum pressure was likely around 990 mb. One final interesting aspect of the system was that its rapid intensification occurred over SSTs of 24 to 25 C--an event not all that uncommon in the North Atlantic subtropics. D. Damage and Casualties ------------------------ No damage or casualties are known to have resulted from this small out-of-season tropical system. *********************************************************************** NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E Activity for June: No tropical cyclones *********************************************************************** NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E Activity for June: No tropical cyclones *********************************************************************** SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E Activity for June: 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 June as an example: jun01.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: jun01.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 (1999-2000 season for 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 2000 Atlantic and Eastern North Pacific tropical cyclones; also, preliminary storm reports for all the 2000 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) *********************************************************************** *********************************************************************** 08.29.01 / Typhoon2000.com