MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY JUNE, 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.) *********************************************************************** JUNE HIGHLIGHTS --> Very intense Eastern Pacific hurricane threatens Mexican coast --> Rare June depression forms in Cape Verde region --> Overnight midget cyclone strikes Hong Kong *********************************************************************** NEW FEATURE - TOPIC OF THE MONTH Last month I began adding 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 June ***** A SOURCE FOR STATE AND LOCAL HURRICANE HISTORIES Back when I was a teenager in the mid-1960s, I began collecting brochures and books on tropical cyclones as well as annual tracking charts of the previous year's Atlantic storms. One publication I ordered fairly early on was entitled "NORTH CAROLINA HURRICANES - A Descriptive Listing of Tropical Cyclones Which Have Affected the State" by Albert V. Hardy and Charles B. Carney. This little booklet quickly became one of my favorites. So much historical hurricane information was in the form of tables and maps, but here was something refreshingly different: narrative descriptions of significant tropical cyclones which had affected the state, taken from old newspapers and other sources. Much information was given on damage and casualties, measurements of wind velocity, marine disasters, general comments about the known history of the storm, etc. I read and re-read the booklet many times. A few years later, after beginning my employment at Eglin AFB, Florida, I obtained a copy of a Hurricane Brochure which had been published by the base Disaster Preparedness Office. This was a similar sort of compilation of tropical cyclones which had affected the western portion of the Florida Panhandle. A few years ago I discovered a website where several such state and local hurricane histories can be accessed, and I thought I would pass along the information for the benefit of those persons who enjoy reading descriptions of historical storms. These can be accessed from Eric Blake's Atlantic Tropical Weather Center, for which the URL is: . Click on the link "Other Hurricane Info" (on the left). The line containing links to the various hurricane histories appears about halfway down the screen. Several of these were compiled and written by David Roth, a graduate of Florida State University who worked for four years at the Lake Charles WFO and is now employed at the Hydrometeorological Prediction Center in Maryland. I had the pleasure of meeting David, along with Eric, at the recent AMS tropical meteorology conference in Ft. Lauderdale. Another of the histories is an expanded and updated version of the aforementioned Northwest Florida storms brochure by Rich Henning, a member of the 53rd Weather Reconnaissance Squadron (Hurricane Hunters) and a Staff Meteorologist at Eglin AFB. The North Carolina hurricane history by James D. Stevenson is an expanded and updated work which incorporates much of the material from the earlier publication by Hardy and Carney. The list also includes a history of hurricanes in southeastern Texas by Joshua Lichter, one for the Savannah, Georgia, area by Patrick Prokop, the histories for Louisiana and Texas by David Roth, and one for the state of Virginia co-authored by David Roth and Hugh Cobb from the WFO in Wakefield, Virginia. Another item which may be of interest to many is a re-analysis of the Great Gale of 1878, a hurricane which swept out of the Caribbean in late October and up the U. S. Eastern Seaboard, and which was rather deadly and destructive in Virginia. This study was performed by David Roth and Hugh Cobb and was presented as a paper by David at the recent Ft. Lauderdale conference. The URL for this paper is: Another interesting tropical cyclone historical paper I stumbled across was a re-analysis of the intense Georgia hurricane of 1898 by Al Sandrik and Brian Jarvinen. Al, the Lead Forecaster at the Jacksonville WFO, is another person whom I had the pleasure of meeting at the AMS conference. The links, first to the full paper, and secondly to a version submitted for publication, are: At the recent conference Al presented a paper, authored by himself, Brian Jarvinen, and Chris Landsea, discussing the major hurricane which struck north Florida on 29 September 1896 and led to very high winds inland. This study is still in progress and is currently not available online, but when it is completed I shall report the address of a URL where it can be accessed. Next Month's Topic - Some Eastern North Pacific Statistics *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for June: 2 tropical depressions NOTE: Much of the information presented below was obtained from the TPC/NHC discussion bulletins issued with every regular advisory. All references to sustained winds imply a 1-min averaging period unless otherwise noted. Atlantic Activity for June -------------------------- Two tropical depressions formed in the month of June in the Atlantic basin. The first development was in one of the favored cyclogenetical areas for June--the southwestern Gulf of Mexico--but the second depression formed very anomalously in the eastern Atlantic a few hundred miles southwest of the Cape Verde Islands, becoming the easternmost June tropical depression on record. Furthermore, the system appeared quite well-organized and there were several meteorologists who seemed to feel that the system may have actually reached tropical storm intensity. A tropical wave left the coast of Africa on 23 May and moved across the Atlantic and Caribbean. By 6 Jun the wave was helping to generate strong convection over the southwestern Gulf of Mexico and the Yucatan Peninsula. A second tropical wave, first detected in the east-central Atlantic on 28 May, followed closely on the heels of the first wave and the two appeared to merge on 7 Jun as a 1009-mb LOW formed in the Bay of Campeche. NHC classified the LOW as a tropical depression at 2100 UTC on 7 Jun and initiated advisories. At 1800 UTC the poorly- defined center was located about 275 nm east-southeast of Tampico, Mexico. An upper-level anticyclone to the south created unfavorable westerly shear over the depression, thereby inhibiting further intensification. The system moved very slowly and erratically toward the west over the next 24 hours. A reconnaissance plane from the 53rd Weather Reconnaissance Squadron of the U. S. Air Force Reserves investigated the depression around midday on 8 Jun and found that the system had degenerated into a broad area of low pressure without a definite center of circulation. A weak remnant area of low pressure was forecast to drift slowly westward or west-northwestward over the following 2 or 3 days. A ship (9VBL) located near 22.9N, 95.5W reported winds to 33 kts at 1400 and 1500 UTC on 9 Jun. Moisture advected northward from the remnants of the depression lead to several days of heavy, tropical rain over south-central Texas. (The parent wave which helped to spawn this depression subsequently moved into the Eastern Pacific where it was instrumental in the formation of Tropical Storm Bud.) Tropical Depression (TD-02) 23 - 25 June ---------------------------- My reason for treating this depression in a separate section is more to discuss some of the debate which ensued over the system's pre- depression stage than to describe the meteorological history of the disturbance. A 1012-mb LOW formed just off the west African coast on 22 Jun and began tracking westward. Although convection was generally not all that deep, on 23 Jun the system presented a very well-organized appearance in satellite imagery. However, the system was not upgraded to a tropical depression at this time since the forecasters at TPC/NHC were not convinced that a surface circulation existed. The first advisory on TD-02 was issued at 1500 UTC on 24 Jun when the depression was located about 500 nm southwest of the Cape Verde Islands. By this time the system was looking less impressive in satellite imagery than on the previous day, but the forecaster on duty was convinced that a surface westerly wind existed south of the center. Some of the models forecast intensification while others indicated that the depression would soon dissipate. The latter scenario verified in this case as visible imagery and cloud wind vectors from CIMSS the next day indicated that the depression no longer had a closed circulation. The final advisory was issued at 1800 UTC on 25 Jun with the system located over 900 nm west-southwest of the Cape Verdes. SSTs were marginal and the depression encountered more stable air as it moved westward. This depression, while short-lived and insignificant, is interesting in that it is the easternmost tropical depression on record to form in the month of June. June tropical cyclones are not unknown in the tropical Atlantic between the Antilles and Cape Verdes--two tropical storms formed there during the 20th century and others are known to have formed in earlier centuries--but nonetheless they are very rare and no June depression has been observed so far east since the advent of satellites. However, it is very possible that tropical depressions/ tropical storms formed in this area during June in pre-satellite years and remained undetected. In 1996 Hurricane Bertha formed in the same general area on 5 July--less than two weeks later into the season. Mark Lander of the University of Guam supplied a visible satellite image taken at 23/1800 UTC which depicts a well-organized cloud system. (This was the day before depression advisories were initiated.) In Mark's opinion the system warranted a Dvorak rating of a strong T2.5 with winds likely 35-45 kts with a definite indication of westerlies to the south of the center. A QuikScat image from Roger Edson taken at 1500 UTC revealed a complete circulation with quite a few wind barbs of 35-40 kts. (There were three at 50 kts, but the general consensus was that these were likely too high.) Roger and Mark, along with some of the researchers at HRD, expressed the opinion that this system was a tropical storm on 23 Jun. This opinion was obviously not shared by the forecasters at NHC, although James Franklin has indicated that in post-storm review the depression stage will quite possibly be extended back earlier in time. Most of the disagreement seems to center around the validity of scatterometer data. Some tropical meteorologists tend to have quite a great degree of confidence in data from the QuikScat satellite (with researchers more prone to fall into this camp) while others are more cautious in accepting the data as "ground truth". Two aspects of the data seem to have been called into question: (1) whether or not the existence of a surface circulation is always accurately portrayed, and (2) whether the reported winds are correct or are subject to rain contamination. Hopefully, these questions will be resolved in the near future to everyone's satisfaction, and the day will maybe soon come when remote sensors will be able to accurately determine the intensity, physical structure, and thermal characteristics of all tropical and subtropical cyclonic systems. Some of the e-mail discussion about this system though brought up another question: If, in the opinion of the responsible forecaster, a system does meet all the criteria of a tropical storm, should it be upgraded and named in all cases, or should a "wait and see" stance be adopted to see if the system persists? In the specific instance of eastern Atlantic systems, there have occasionally been monsoon depressions which have rolled off Africa with well-developed circulations, and perhaps in a few cases accompanied by gale-force winds, but which have died as they moved westward out of the monsoon trough into the tradewind environment--especially true for systems earlier in the season. For such disturbances NHC has often adopted the policy of waiting to see if the system maintains itself and shows signs of strengthening as it moves farther west before upgrading the system and initiating advisories. As Mark Lander points out, to "call it like it is" certainly does a service for shipping in the area, but the forecaster at NHC is ever conscious of how the U.S. public and media will respond to disseminated tropical cyclone information. And this is a point to be considered. It may be difficult for persons outside the U. S. to believe this, but a 35-kt tropical storm in the far eastern Atlantic can really grab the attention of the media and public, at least in the eastern and southern U. S. If a storm is named, and then downgraded only 6 or 12 hours later, some forecasters feel that many in the media/public will believe they "cried wolf" and their credibility may suffer. (This is not quite as much of a problem in the western Atlantic where reconnaissance data, as well as often radar and buoy data, are available.) To do a bit of editorializing (which I rarely do)--in the author's humble opinion, with the increasing public availability of all the remote sensing data from satellite platforms, the best course of action is to "call the shots as they are". I believe that it is not impossible to educate the public and media, without resorting to language that is too technical, to the point where they can understand more about the nature of tropical cyclones and will not be surprised once in awhile if a very brief tropical storm occurs; or will understand why a future "Perfect Storm" that batters the New England coastline might later be reclassified as a hurricane and assigned a name even while it is moving away from the coastline. *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for June: 1 tropical storm 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. The narratives for Tropical Storm Bud and Hurricane Carlotta were written by John Wallace of San Antonio, Texas, who also wrote the narrative for Hurricane Aletta in last month's summary. (A big thanks to John for writing the the reports and also for the special interest he has in this often somewhat neglected tropical cyclone basin.) Northeast Pacific Activity for June ----------------------------------- Tropical cyclone activity in the Northeast Pacific basin during June was near normal. Two tropical storms developed with one of these, Carlotta, becoming a very intense Category 4 hurricane on the Saffir/Simpson scale. In its early stages Carlotta passed close enough to the coast of southern Mexico that some watches and warnings were required for the coastline. Tropical Storm Bud (TC-02E) 13 - 17 June ---------------------------- The origin of Bud seems to have been an African tropical wave that tracked off the continent around 27 May. It tracked uneventfully across the Atlantic for most of the next week, after which it became tied up in strong convection in the western Caribbean and Bay of Campeche. In fact, this wave was apparently the progenitor of Tropical Depression One in the Atlantic. The wave entered the Eastern Pacific by 8 Jun, where it slowly drifted westward. The wave generated strong, but sporadic and disorganized, convection until the 11th, when a tropical LOW developed along the wave axis. The ragged disturbance slowly organized until a ship report and satellite analysis warranted upgrading the LOW to Tropical Depression Two-E at 1500 UTC on 13 Jun about 550 nm south of Mazatlan, Mexico. The tropical depression tracked west-northwestward under the influence of a deep-layer ridge to its north. Two-E was slow to intensify; it was initially under moderate north- easterly shear from a strong upper-level anticyclone to its north which kept the mid- and low-level circulations from aligning. The situation was reminiscent of Aletta's the month before. A ship report from vessel KAOU of 40-kt winds with a 1001-mb SLP 120 nm northeast of the center, Dvorak estimates of storm strength from the TAFB and KGWC, and scatterometer data warranted its upgrade to Tropical Storm Bud by 0300 UTC on the 14th when the center was located roughly 500 nm south- southeast of Cabo San Lucas on the tip of Baja California. The anti- cyclone weakened and moved eastward relative to Bud by late on the 14th, lessening the shear. The sheared cloud pattern in fact misled forecasters; the morning of the 14th showed the tropical cyclone to be on more of a northwesterly track than originally believed, as the LLCC was northeast of Bud's strongest convection. The center remained difficult to pinpoint even in visible imagery, and the track was adjusted eastward throughout the day on the 14th as the LLCC became more co-located with the mid-level center. The storm intensified slightly to 45 kts with a CP of 1000 mb by 1500 UTC on 14 Jun. This was to be Bud's peak wind intensity, and it was maintained until 2100 UTC on the 15th. However, the pressure was adjusted downward twice based on synoptic data, and the first time the CP was estimated to be 995 mb, the lowest value in Bud's lifetime. Bud was a large storm; storm-force winds and 12-foot seas extended 120 to 150 nm from the center through most of its time as a storm. Before it was downgraded, the 12-foot seas radii had expanded to 200 nm while the wind radii contracted during the onset of the weakening trend. The cyclone remained relatively unimpressive in terms of organization as it tracked to the north-northwest. Though upper-level conditions became more favorable, this positive factor was cancelled out by Bud's entry into cooler waters. There was conflicting output about its possible track, and some models suggested that Bud posed a threat to the Mexican coast--specifically Baja California. The storm tracked very near Socorro Island at 0900 UTC on 15 Jun; unfortunately, as with Linda three years earlier, there were no surface data collected at closest approach, though an upper-air observation taken at 0000 UTC helped to better determine its intensity. By this time, however, its convection had already begun a weakening trend. The entrainment of cooler, more stable air and its track into ever-cooler waters eroded the tropical storm. The favorable upper-level environment gave Bud a reprieve, however, and the cyclone's large circulation was slow to spin down. Bud was downgraded to a tropical depression at 0900 UTC on 16 Jun as it became quasi-stationary north of Socorro Island, or about 200 nm south-southwest of Cabo San Lucas, again reminiscent of Aletta. By 1500 UTC on the 16th, Bud's LLCC was completely exposed--the system was devoid of deep convection within 60 nm of the center. By 2100 UTC the cyclone was almost invisible in infrared imagery, although visible images still showed a well-defined low-level vortex. The final advisory on Bud, placing the weakening center about 175 nm south- southwest of Cabo San Lucas, was issued at 1500 UTC on 17 Jun, though a residual whorl of clouds persisted for several days thereafter. Moderate, peripheral rains reached the southern Mexican coast, but whether they were directly related to the storm is debatable. The rains occurred well outside the radius of tropical storm-force winds, and most of Bud's convection was displaced west of the center, away from the coast. The rain may have been as much a result of offshore convergence, orographic lifting and daytime heating as of Bud's presence, although the storm's large circulation must be taken into account. North of Puerto Vallarta the effects were less ambiguous, and it's certain that rains from Bud affected Cabo San Lucas and the mainland. Residual moisture advected northeastward from Bud generated precipitation in Mexico and the American Southwest. No casualties or damages are known from either rain or surf. Hurricane Carlotta (TC-03E) 18 - 25 June ---------------------------- Carlotta seems to have originated from a tropical wave that left the African coast on 8 Jun. However, the wave apparently dissipated as it crossed Central America well east of where the incipient tropical LOW that became Carlotta developed. Admittedly though, the data have a coarse temporal resolution. Another possibility is that Carlotta developed directly from a convective disturbance on the Pacific ITCZ. In either case, a tropical LOW formed just east of Central America on the 16th and tracked slowly west-northwestward. The LOW had a good cyclonic signature and strong convection from the start, and steadily organized. A CDO developed on the 18th; this along with ship reports (and one doubtful report of storm-force winds 50 nm south of the center) justified its upgrade to Tropical Depression Three-E at 2100 UTC on 18 Jun when it was roughly 255 nm south of Salina Cruz, Mexico. Its immediate track was northwestward, parallel to the coast. Three-E's proximity to the coast warranted the issuance of a tropical storm warning for the Mexican coast from Salina Cruz to Acapulco. The issuance seemed prudent, as the depression was upgraded to Tropical Storm Carlotta only three hours after the first advisory, at 0000 UTC on the 19th, roughly 235 nm south of Salina Cruz. The upgrade was based on surface and satellite data; the latter showed a robust tropical cyclone with strong convection. Although light easterly shear (and perhaps interaction with land) prevented the CDO from being symmetrical at first, the strongest convection remained centered over the circulation center, and became more consolidated by the time of the upgrade. Once upgraded, Carlotta began a relentless intensification trend with its central pressure falling an average of 0.6 mb per hour for the next 24 hours. A hurricane watch was issued for the Mexican coast at 0900 UTC on the 19th from Puerto Angel to Zihuatanejo, while a tropical storm warning remained in effect east of Puerto Angel to Salina Cruz. Nevertheless, the radii of tropical storm-force winds remained just offshore; even the impact of rain from Carlotta's spiral bands was modest with much of the rain that did occur being unrelated to its presence. Carlotta's track turned slightly more to the west through the 19th and into the 20th, a development that was well-forecast as the storm was influenced by a strong mid- to upper-level ridge to its north. Though the turn lessened the threat to Mexico, Carlotta remained too close for comfort as it paralleled the coast. Carlotta was upgraded to hurricane status at 0000 UTC on 20 Jun, merely a day after being christened a tropical storm, while 205 nm west-southwest of Puerto Angel or about 175 nm south-southeast of Acapulco. A hurricane watch and tropical storm warning were in effect for the Mexican coast from Puerto Angel to Zihuatanejo, while warnings east of Puerto Angel were discontinued by 2100 UTC on the 19th. The upgrade was warranted based on the first appearance of a ragged eye in visible imagery late on the 19th and a classification of 65 kts from KGWC at 2215 UTC that same day. An increase in the area of deep convection, a persistent warm spot in infrared imagery, and a consensus among satellite analyses of 65-kt intensity were also taken into account. Outflow was excellent through most of its southern semicircle, but restricted elsewhere. Carlotta's intensification trend, though impressive, was downplayed as its convection weakened slightly early on the 20th. By 0900 UTC the threat to the Mexican coast had decreased to the point where the hurricane watch was discontinued; the tropical storm warning was dropped by 1500 UTC the same day. Carlotta continued to intensify in the meantime--the estimated MSW was upped to 75 kts by 0900 UTC and to 90 kts by 1500 UTC on the 20th. Radar from Acapulco at 0900 UTC showed only a partial eyewall, but the hurricane had developed a definite 7-nm diameter eye by 1500 UTC which became increasingly well-defined through the day. The most interesting developments in Carlotta's life occured late on the 20th when a rare Eastern Pacific reconnaissance mission investigated the storm. The Hurricane Hunters found a central pressure of 977 mb and maximum flight-level winds of 87 kts at 1856 UTC on the inbound leg of the flight in the northeast quadrant. A GPS dropsonde deployed later when the plane had reached the west quadrant found mean boundary layer winds of 106 kts about 200 m above the water and surface winds of 91 kts a few seconds later. The NHC adjusted the MSW estimate downward accordingly to 85 kts in the 2100 UTC advisory, a 20-kt under- shot from satellite estimates. This perhaps wasn't too surprising, given the great eye presentation and spiral structure apparent on visible imagery at the time. This discrepancy would become a hot topic of discussion among certain members of the meteorological community, a topic which will be discussed in more detail later in the summary. At the time of the reconnaissance observation, the outflow remained excellent in the southern semicircle as it improved to the north. Even as the Hurricane Hunters reported data back to the NHC, Carlotta had begun a dramatic intensification trend. The central pressure dropped 7 mb in less than three hours between the first and last center fixes while the winds increased to 96 kts at the surface. Carlotta exploded in intensity after 2100 UTC, its central pressure dropping 42 mb in 12 hours for a rate of 3.5 mb per hour. In contrast, the minimum deepening rate required to be considered "explosive" is 2.5 mb per hour for 12 hours. Carlotta reached its peak intensity at 0900 UTC on 21 Jun; estimated MSW were 130 kts with a CP of 935 mb. The hurricane was centered about 250 nm south of Manzanillo, Mexico, at this time. This intensity was maintained until 1500 UTC when a weakening trend began. During Carlotta's peak, the hurricane's CDO had the classic "buzzsaw" appearance characteristic of many of the most intense hurricanes, and a 17-nm diameter eye. The "buzzsaw" is typified by a sharp-edged and symmetrical CDO with a pinpoint eye and uniform intense convection. According to an associate, Patrick Hoareau, Carlotta's 130-kt peak makes it the second most intense June Eastern Pacific hurricane on record, after 1973's Hurricane Ava. (Note: According to TPC/NHC's monthly summary on their website, the peak MSW for Carlotta has been increased to 135 kts on 21 Jun, making Carlotta a very strong Category 4 hurricane on the Saffir/Simpson scale, almost a Category 5.) Carlotta slowly weakened through the 21st as it turned slightly more to the northwest around the periphery of a ridge to its north and entered cooler waters. Northeasterly shear also began to impinge on the system, and Carlotta's superb structure and strong convection deteriorated steadily, as did its eye. The cyclone fluctuated in intensity on the 22nd; it weakened below major hurricane status (100 kt or greater winds) at 0900 UTC, re-attained 100 kts at 1500 UTC, and weakened again to 95 kts by 2100 UTC. Carlotta's forward motion increased slightly beginning on the 23rd, a day in which various model outputs suggested the system could pose a threat to Baja California, though the weakening trend and its small size argued against it. A trough extending southward from a 500-mb LOW off California was expected to maintain Carlotta's northwesterly track. Though Carlotta was on its way out, it maintained hurricane status through the 23rd and into the 24th. Even in its weakening stage, Carlotta remained remarkably well-organized, with a persistent, compact CDO that seemed atypical of a decaying hurricane. A tropical storm watch was issued for Baja California south of Cabo San Lazaro at 0900 UTC on the 23rd; Carlotta was 250 nm south of Cabo San Lazaro at the time with a MSW of 95 kts. The watch proved unnecessary and was dropped later that day at 2100 UTC, at which time Carlotta was only a minimal hurricane located about 200 nm south- southwest of Cabo San Lucas; the system showed no direct indication of being a threat to the peninsula. Indeed, a 500-mb LOW off southern California threatened to deflect the cyclone to the east, but it was considered unlikely that Carlotta would survive long enough for that to happen. Carlotta was downgraded to a tropical storm at 0900 UTC on the 24th as it began a rapid weakening trend over unfavorably cool waters. Its forward motion decelerated accordingly. By 1500 UTC on the 24th, all of Carlotta's deep convection was gone, and only the Dvorak constraints maintained the system. Hints of convective activity early on the 25th also kept it at tropical storm strength longer than it might have otherwise been. The LLCC became completely exposed, resulting in Carlotta's being downgraded to depression status at 0900 UTC on 25 Jun; the final advisory was issued at 1500 UTC the same day with the center about 450 nm west of Cabo San Lucas. The remnant low-level vortex slowly drifted westward in the low-level flow for several days thereafter. No casualties are known by the author at the present time. Heavy rains over Mexico on the 18th were apparently unrelated to Carlotta. Through much of Carlotta's life though, strong ITCZ convection was advected northeastward into Mexico along its southwest flank. The impact of these rains is unknown, as is that of the undoubtedly dangerous seas. Tropical storm-force winds remained offshore throughout the storm's lifetime. In Acapulco 100 families were moved out of high-risk areas when Carlotta reached hurricane strength. Carlotta will be most remembered for the data the reconnaissance mission collected on the 20th. These highlighted a major discrepancy between the Dvorak intensity estimates and the in situ measurements by the Hurricane Hunters. That the Hurricane Hunters caught Carlotta at the beginning of an explosive deepening trend is not disputed, but rather, why the two estimates were so at odds. At the time of the 2100 UTC advisory, when the winds were adjusted downward to 85 kts, satellite intensity estimates were near 100 kts. Less than 30 minutes after the reconnaissance recorded surface winds of 96 kts, satellite estimates from KGWC were 115 kts while the University of Wisconsin's Objective Dvorak Technique (ODT) gave estimates of roughly 135 kts. At Carlotta's peak satellite intensity estimates were near 140 kts, but were adjusted downward because of the earlier discrepancy. In fact, it's possible that Carlotta was much weaker at its perceived peak. The author considers this unlikely, but the lack of flight data means it can't be ruled out. There has been speculation that the Dvorak estimates merely led the actual intensity, and that the reconnaissance missed the convergence between the two estimates; i.e., the winds "caught up" with the Dvorak estimates. Another view is that the satellite estimates were on the money, while another is that neither the Dvorak estimates nor the flight measurements can be fully trusted and that the final estimate will be the result of a reasonably justified judgement call. Carlotta's difficult case also highlights the "if a tree falls in the forest..." paradox that a lack of flight and other in situ data causes with respect to storm strength. The debate is fundamentally about the validity of Dvorak estimates versus reconnaissance data, a topic which has been a problem for tropical meteorologists since the technique was devised. Dvorak estimates are usually in the ball park; such a large deviation is unusual. When compiled, the official Best Track data will show which side the NHC falls on. Note: The monthly summary prepared by TPC/NHC mentions that the Lithuanian freighter LINKUVA, which lost engine power and was caught in the hurricane, remained missing at the time the report was prepared and the crew of 18 are presumed lost. *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for June: 1 short-lived tropical cyclone Northwest Pacific Activity for June ----------------------------------- No tropical depressions, tropical storms, or typhoons entered warning status in the Northwest Pacific basin during June. While it is not common for June to be completely stormless, a quiet June does happen every now and then, the last such occurrence being in 1996. However, it appears that there was a very short-lived small system which reached tropical depression status and perhaps even minimal tropical storm strength. This interesting "micro-midget" system which affected Hong Kong on the night of 18-19 June is described below. ADDENDUM TO MAY TROPICAL CYCLONE SUMMARY ---------------------------------------- When I first received a copy of the list of new Asian typhoon names in late 1998, I decided that whenever the names began to be utilized I would report the contributing country or territory for each name and give the basic meaning of the name. I forgot to do this for the first two NWP systems to be assigned names from the new list. The name "Damrey" is the Cambodian word for elephant; and "Longwang" was contributed by China, being the name of the Dragon King who was the god of rain in Chinese mythology. In ancient times people would offer sacrifices to the Dragon King, praying for timely rainfall and abundant harvests. Hong Kong Midget Tropical Cyclone 18 - 19 June --------------------------------- On 19 Jun I received an e-mail from Phil Smith, an Australian who lives in Hong Kong and works as a computer salesman and consultant, and who is also a dedicated tropical cyclone enthusiast. Phil related how that on the night before, a very small tropical cyclone had formed, rapidly intensified and moved inland right over Hong Kong--all during the night while he slept! According to a report from the Hong Kong Observatory, Tropical Cyclone Warnings were hoisted for only 4 hrs, 30 min--a record short duration, the previous shortest being in association with a tropical depression in Sep, 1958 (9 hrs, 35 min). As early as 14 Jun JTWC had mentioned an area of convection that had formed in the South China Sea with a LLCC located along the tail end of a shear line. The disturbed area remained quasi-stationary for several days with a little increase in convective organization becoming apparent by the 16th. By 18/0600 UTC the STWO indicated that over the previous 24 hours satellite imagery had revealed an increased organization of convection around a small LLCC located about 150 nm southwest of Hong Kong and the potential for development was upgraded to Fair. At 2300 UTC a special STWO was issued reporting that the system was now inland about 50 nm north of Hong Kong with convection persisting about a tightly-wrapped LLCC. By 19/0600 UTC the area was centered about 250 nm north-northeast of Hong Kong, and at 2100 UTC had moved out over the East China Sea and was extratropical. According to the HKO report, the tiny tropical depression formed only about 20 nm from the Observatory. When the depression was closest to Hong Kong, Waglan Island and Tsing Yi reported 10-min avg wind speeds of 29 kts and 22 kts, respectively. The lowest pressure recorded at the Observatory was around 1000 mb. Phil's report indicates that at Shatin (where he lives), winds peaked at 15 kts from 2200 to 2300 local time with a minimum pressure of 999 mb at 2200 Local. At Sai Kung (a few km east of Shatin) the wind peaked at 38 kts (10-min avg) at 2200 Local and had abated to 33 kts an hour later. No pressure reports were available from Sai Kung. (Since Phil indicates all the action occurred whilst he slept, and the HKO report makes it clear the event happened during the evening, I am assuming the times given are local times. Hong Kong time exceeds UTC by 8 hours.) According to Phil's e-mail the storm didn't begin to form until about 2100 Local, although the Hong Kong area had been under the spiralling rain bands of a low-pressure area for the previous couple of days. It appears that the system was no more than 30 nm in diameter. The HKO report refers to the system as a tropical depression. Phil indicates that the wind speeds in his write-up are 10-min averages. If the 38-kt report from Sai Kung is verified, this would indicate that the system may have been a brief tropical storm. If more information comes to light on this very interesting little storm it will be reported in a future summary. *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for June: No tropical cyclones *********************************************************************** SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E Activity for June: No tropical cyclones *********************************************************************** AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E Activity for June: No tropical cyclones Australian Region Activity for June ----------------------------------- No tropical cyclones or LOWs developed in the Australian Region during June, but there was a system which formed east of Queensland around mid-month which, while not a true tropical development, did produce gale-force winds over a wide area. Since the warnings from Brisbane did not classify the system as a tropical LOW, and since to me it did not remotely resemble a tropical cyclone in the satellite imagery which I looked at, I did not save any warnings for the LOW from which a track might have been constructed. However, Jeff Callaghan of BoM Brisbane sent me a summary of the system, so I am including a synopsis of Jeff's write-up below. A very strong upper-level jet stream was located in the southern Coral/northern Tasman Seas on 9 Jun (maximum winds greater than 150 kts) with an upper-trough entering eastern Australia. On the surface a trough was developing and extending southeastwards from the northwest corner of the Coral Sea. During 10 Jun a LOW developed to the west of Ile Loop (WMO 91574) and the maximum 10-min avg wind and lowest SLP at that AWS were 040/32 kts and 1004.0 mb at 10/0900 UTC. The LOW moved southeastward between Ile Loop and Cato Island (WMO 94394) and the maximum 10-min avg wind and lowest SLP at that AWS were 130/38 kts and 1010.8 mb at 10/0600 UTC. The LOW then continued moving rapidly southeastward and by 1200 UTC on the 11th was located approximately midway between Noumea and Norfolk Island. The strongest 10-min mean wind reports on the east coast of Australia were at Cape Moreton AWS (WMO 94594): 140/42 kts at 1504 UTC on the 11th and 120/41 kts at 0521 UTC on the 10th; and 160/43 kts at 11/0208 UTC from Double Island Point AWS (WMO 94584). Little impact was felt on the Queensland coast. Due to the rapid movement of the LOW and the tendency for the strongest winds to be oriented parallel with respect to the coast, the seas were not exceptionally large. The largest peak wave height on the wave rider buoy east of Brisbane was 6 metres. The Byron Bay buoy peaked at just over 7 metres, being a little more open to the southerly swell generated deep in the Tasman Sea. (A thanks to Jeff for sending me this information.) *********************************************************************** SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E Activity for June: No tropical cyclones *********************************************************************** A SLIGHT CHANGE TO SOUTHERN HEMISPHERE REPORTING BASINS ------------------------------------------------------- For the upcoming Southern Hemisphere tropical cyclone season I am planning to implement a slight change to the manner in which I group and report Southern Hemisphere cyclones. As noted in the recent Southern Hemisphere seasonal review for 1999-2000, the basins will be defined as follows: SWI - Southwest Indian Ocean - West of 90E AUW - Northwest Australia/Southeast Indian Ocean - 90E to 135E AUE - Northeast Australia/Coral Sea - 135E to 160E SPA - South Pacific Ocean - West of 160E Note that I have made a slight change to the identifiers for the Southwest Indian and South Pacific Oceans to better reflect the most commonly-used terminology for those regions: SWI and SPA instead of SIO and SWP. The tropical cyclogenetical regions of the Northern Hemisphere are rather neatly divided into distinct basins by landmasses or, in one instance, by a stretch of thousands of miles of the North Pacific where tropical cyclone formation is very rare. But the Southern Hemisphere is not thusly divided. Tropical cyclones form in a continuous band beginning in the Mozambique Channel and continuing eastward across the vast South Indian Ocean, through the seas and gulfs off northern Australia, across the Coral Sea and into the South Pacific proper to well east of the Dateline, and in certain years extending even further eastward into the region of French Polynesia. The Southern Hemisphere cyclogenetical zone spans nearly 200 degress of longitude, and it is neither practical nor desirable to consider it as a single basin for cyclone reporting or statistical studies. Several different schemes for divvying up the Southern Hemisphere into tropical cyclone basins have been followed, including: A. JTWC's Operational Plan 1. South Indian Ocean - West of 135E 2. South Pacific Ocean - East of 135E B. JTWC's Statistical Plan in their Annual Tropical Cyclone Reports 1. South Indian Ocean - West of 105E 2. Australian Region - 105E to 165E 3. South Pacific Ocean - East of 165E C. Plan followed by Charlie Neumann in the "Global Guide to Tropical Cyclone Forecasting" 1. South Indian Ocean - West of 100E 2. Southeast Indian and Northern Australia - 100E to 142E 3. Northeastern Australia and South Pacific - East of 142E (Note: 142E lies essentially along the Cape York Peninsula.) D. Current Boundaries of Various Warning Centre's AORs 1. Southwest Indian - West of 90E 2. Australian Region - 90E to 160E 3. South Pacific - East of 160E (Note: The western boundary of Perth's AOR was originally 75E prior to around 1970, then 80E for the 1970s and 1980s until being set at 90E in the early 1990s.) When I began writing the global tropical cyclone summaries in late 1997, I opted to follow Plan D in order to keep the cyclones grouped together that were warned on by particular national meteorological services. I could see some merit to each of the other plans, but this one seemed simplest and was adequate for my purposes. The only change I'm making is to divide the Australian Region into two sub-regions along 135E. When reporting the cyclones for a given month within the Australian Region, this will prevent the "leapfrogging" back and forth that often occurs when reporting storms chronologically for the whole region. A study of cyclone tracks in the Australian Region dating back to 1960 revealed that the Arafura Sea north of the Northern Territory's Top End in the vicinity of 135E is an area of minimum tropical cyclone formation and movement. Gulf of Carpentaria cyclones seem to have more in common with Coral Sea systems, especially with regard to intensity, than with those of the Timor Sea. Very intense cyclones seem to be rather rare in the Coral Sea and Gulf of Carpentaria, but occur quite frequently in the waters off Western Australia. I specifically made tallies of cyclone tracks falling into three groups: (1) storms which crossed 135E (moving either east or west) over water north of the Northern Territory, (2) systems which crossed 135E over land and re-emerged over water (mostly westward movers but 2 or 3 moved southeastward from the Arafura Sea over the Top End and entered the Gulf of Carpentaria), and (3) cyclones which crossed the Cape York Peninsula moving in either direction. The results were: (1) Crossed 135E over water: 16 (2) Crossed 135E over land: 11 (3) Crossed Cape York Peninsula: 34 Of the 34 systems which crossed the Cape York Peninsula, 5 crossed the peninsula twice, moving in each direction. I realize that using 135E as a line of demarcation for reporting purposes will break Darwin's AOR into two regions, but the Darwin AOR is an area of very low cyclone formation frequency with usually only one or two cyclones forming per season. This past season there were none. The majority of tropical cyclones forming in the Darwin region fall into two distinct groups: (1) those which form in and make land- fall along the shores of the Gulf of Carpentaria (a few of which eventually reach the Timor Sea or move eastward and enter the South Pacific Ocean), and (2) those which form north of the Top End and move westward over water into the Timor Sea or else strike the Northern Territory's northern coastline. *********************************************************************** 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 June 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 June as an example: jun00.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: jun00.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 Another website where much information about tropical cyclones may be found is the website for the UK Meteorological Office. Their site contains a lot of statistical information about tropical cyclones globally on a monthly basis. The URL is: TROPICAL CYCLONE REPORTS AVAILABLE I have discovered that JTWC now has available on its 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: 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: 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) ITCZ - Intertropical Convergence Zone 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 SPCZ - South Pacific Convergence Zone 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 WFO - Weather Forecast Office WMO - World Meteorological Organization, headquartered at Geneva, Switzerland UTC - Universal Time Coordinated, equivalent to Greenwich Mean Time or Zulu (Z)