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MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY SEPTEMBER, 2006 NOTE FROM THE AUTHOR: Almost two years ago I began including links to track graphics prepared by John Diebolt of Tucson, Arizona, and archived on his tropical cyclone website. A few months back John experienced a disk crash which resulted in a error. He had to request assistance from the programmer who had written the map-generation software, but so far has not been able to get the problem solved. As a convenience to users, I've also recently been including links to the individual tabular tracks, prepared by myself, which John had archived on his website. Now, due to family concerns, John has not had time to place the tracks for recent cyclones on the website. I have checked the websites listed at the end of the summaries and found that the entire September track file has been archived on two of them. The links are: (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.) ************************************************************************* SEPTEMBER HIGHLIGHTS --> Atlantic more active--four hurricanes form but all recurve well out in Atlantic--Bermuda, Newfoundland, Azores, Spain, Ireland and Great Britain experience some effects --> Major hurricane strikes mainland Mexico --> Intense typhoon slashes through central Philippines while another strikes Ryukyus --> Strong Arabian Sea tropical storm forms just off western Indian coast ************************************************************************* !!!!!!!!!! EXTRA FEATURE !!!!!!!!!! SOUTHERN HEMISPHERE TROPICAL CYCLONE NAMES 2006 - 2007 SEASON TROPICAL CYCLONE NAMES for the AUSTRALIAN REGION The Australian Bureau of Meteorology maintains three Tropical Cyclone Warning Centres (TCWC): Perth, Western Australia; Darwin, Northern Territory; and Brisbane, Queensland. Each centre is allotted a separate list of tropical cyclone names for tropical cyclones forming within its area of responsibility (AOR). In addition a TCWC located at Port Moresby, Papua New Guinea (PNG)--a former Australian territory-- maintains a list of native names to assign to the very rare tropical cyclones which form within its AOR. The AORs of the respective centres are: (1) Perth - 125E westward to 90E and south of 10S. Currently, and for at least the next few years, the Perth TCWC will issue warnings for any systems north of 10S and south and west of the Indonesian islands. (2) Darwin - 125E eastward to 138E and extending northward to the equator. There is a little irregularity with the eastern border in the Gulf of Carpentaria. The Darwin TCWC issues High Seas Warnings for the entire Gulf of Carpentaria, but Brisbane issues Tropical Cyclone Advices and names cyclones in the eastern portion of the Gulf. Also, currently, and for at least the next few years, the Darwin TCWC will issue warnings for any systems west of 125E and within the Indonesian archipelago in the Banda, Flores, and Java Seas. (3) Brisbane - 138E eastward to 160E and generally south of 10S. The northern border with the Port Moresby AOR is somewhat irregular. (4) Port Moresby, PNG - immediate vicinity of the island of New Guinea and eastward to 160E generally north of 10S although the southern border is somewhat irregular. Names for the 2006-2007 season (** indicates name has already been assigned): Perth Darwin Brisbane Port Moresby ----------------------------------------------------------------------- Isobel ** George Nelson Alu Jacob Helen Odette Buri Kara Ira Pierre Dodo Lee Jasmine Rebecca Emau Melanie Kim Sheryl Fere Nicholas Laura Tania Guba Ophelia Matt Vernon Hibu Pancho Narelle Wendy Ila Rosie Oswald Alfred Kama Selwyn Penny Blanch Lobu Tiffany Caleb Victor Denise Zelia Ernie Alison Frances Billy Greg TROPICAL CYCLONE NAMES for the SOUTHWEST INDIAN OCEAN and the SOUTH PACIFIC OCEAN The Tropical Cyclone Warning Centre (TCWC) at Nadi, Fiji, has tropical cyclone warning responsibility for the South Pacific east of 160E and from the equator to 25S. The Meteorological Service of New Zealand at Wellington has warning responsibility for waters south of 25S, but almost all tropical cyclones in this basin form north of 25S. When a rare cyclone forms in the Wellington area of responsibility (AOR), it usually will be assigned a name from the Fiji list (such as was done for Tropical Cyclone Gita in February, 1999.) Tropical cyclone warning responsibility for South Indian waters west of 90E are shared by several TCWCs. The Regional Specialty Meteorological Centre (RSMC) for the region is the office of Meteo France on the island of La Reunion. However, following a long-standing practice, the Sub-regional Tropical Cyclone Advisory Centres at Mauritius and Madagascar share the responsibility for actually naming tropical storms with Mauritius naming systems east of 55E and Madagascar covering the area west of 55E. RSMC La Reunion issues warnings for the basin independently of Mauritius and Madagascar, but only advises regarding when or when not to assign a name to a developing cyclone. Names for the 2006-2007 season (** indicates name has already been assigned): Southwest Indian South Pacific ----------------------------------------------------------------------- Anita ** Newa Xavier ** Hettie Bondo ** Olipa Yani ** Innis Clovis ** Panda Zita ** Joni Dora Quincy Arthur ** Ken Enok Rabeca Becky Lin Favio Shyra Cliff Mick Gamede Tsholo Daman Nisha Humba Unokubi Elisa Oli Indlada Vuyane Funa Pat Jaya Warura Gene Rene Katse Xylo Lisebo Yone Magoma Zouleha ************************************************************************* ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for September: 2 hurricanes 2 major hurricanes Sources of Information ---------------------- Most of the information presented below was obtained from the various tropical cyclone products issued by the Tropical Prediction Center/National Hurricane Center (TPC/NHC) in Miami, Florida: discussions, public advisories, forecast/advisories, tropical weather outlooks, special tropical disturbance statements, etc. Some additional information may have been gleaned from the monthly summaries prepared by the hurricane specialists and available on TPC/NHC's website. All references to sustained winds imply a 1-minute averaging period unless otherwise noted. Atlantic Tropical Activity for September ---------------------------------------- Following are some statistics for the Atlantic basin during the month of September: September Average Parameter 2006 1950 - 2005 -------------------------------------------------------- Named Storms (NS) 4 3.5 Hurricanes (H) 4 2.5 Intense Hurricanes (IH) 2 1.3 Named Storm Days (NSD) 30.75 23.0 Hurricane Days (HD) 18.25 12.9 Intense Hurricane Days (IHD) 3.00 3.4 The month of September, 2006, was above average in all but the IHD parameter, and that was near normal. The overall net tropical cyclone activity (utilizing all six parameters) was about 132% of the average level normally seen in September, whereas in August overall tropical cyclone activity was only about half of normal. The month was only slightly less active than September, 2005, whose overall tropical cyclone activity level was about 147% of the average. The Northeast Pacific basin, which had been extremely active in August, was well below normal in September. As the month opened, Tropical Storm Ernesto was approaching the coast of North Carolina just shy of hurricane intensity. Ernesto made land- fall in North Carolina early in the morning of 1 September and continued northward through the Mid-Atlantic states as it weakened over the next couple of days. The complete report on Hurricane Ernesto may be found in the August summary. Four hurricanes formed in the tropical Atlantic during the month of September, and all recurved northeastward well east of the United States. Hurricane Florence came the farthest west, passing just west of Bermuda near its peak intensity of 80 kts. Florence then headed toward the island of Newfoundland, and though it became extratropical, remained at hurricane intensity and passed just southeast of the island. Hurricanes Gordon and Helene both became Category 3 hurricanes but passed northward several hundred miles east of Bermuda. Helene did not affect any land areas, but Gordon accomplished the rare feat of passing through the Azores Islands as a hurricane, although none of the islands experienced sustained hurricane-force winds. However, the hurricane's extratropical stage brought very strong winds to the Iberian Peninsula and the British Isles, causing widespread damage. Finally, at the end of the month Hurricane Isaac recurved a few hundred miles east of Bermuda and later brushed Newfoundland's Avalon Peninsula while still a strong tropical storm. Reports on all the September hurricanes follow. The link to the Wikipedia page for the 2006 Atlantic hurricane season is as follows: Detailed reports for Florence and Gordon are available and the links to those appear in their respective summaries below. However, no detailed Wikipedia reports are available for Helene and Isaac, but brief reports with a satellite image and track chart may be found at the above link. HURRICANE FLORENCE (TC-06) 3 - 15 September -------------------------------------- A. Introduction and Storm Origins --------------------------------- Hurricane Florence was the first Cape Verde hurricane of the 2006 Atlantic tropical cyclone season. The storm was notable in its early tropical storm stage for its extremely large size. At one point on 8 September gales covered an area 600 nm in diameter--with the MSW at only 45 kts. Florence eventually consolidated its forces some as it reached hurricane intensity, but still remained a rather large tropical cyclone. The storm passed just west of Bermuda on 11 September, later transforming into a severe extratropical cyclone and bringing winds of hurricane force to southeastern Newfoundland. Florence was the only one of the four September hurricanes to pass west of Bermuda--the remaining three recurved well east of the British colony. A tropical wave moved off the African coast during the final week of August and by late on the 28th was located about 525 nm southwest of the Cape Verde Islands. By the 29th the wave was producing a concentrated area of convection which was showing some signs of organization. However, by the next day the shower activity had become disorganized and no imminent development was anticipated. By the after- noon of the 31st organization had improved once more and slow development was considered possible as the system moved slowly westward. The morning of 1 September found the wave located about 750 nm west- southwest of the Cape Verdes with little change in organization. Shower activity increased once more on 2 September with the system now located about 1050 nm east of the Windward Islands. A second area of disturbed weather was located to the east and the presence of this disturbance was thought to be having a slight inhibiting effect on the westernmost system. The wave located to the east had emerged from the African coast on 29 August and by 2 September was showing distinct signs of increased organization. By 3 September it was becoming apparent that the eastern- most wave was developing, and the first wave, located then only about 350 nm to the west, was forecast to weaken and merge with the second wave. Advisories were initiated on Tropical Depression 06 at 2100 UTC on 3 September with the center located approximately 1325 nm east of the Leeward Islands and moving northwestward at 12 kts. SAB and TAFB were assigning Dvorak classifications of T2.0, and buoy 41026 had reported 32-kt winds late in the morning, so the initial intensity was estimated at 30 kts. The circulation was broad and the center was difficult to pinpoint, and also it was considered likely that multiple swirls were rotating around a common center. The depression continued moving slowly west-northwestward over the next couple of days. Banding features were impressive, but the LLCC was broad with several possible centers. An upper-level trough to the northwest was inducing some southwesterly shear over the cyclone, and in conjunction with some drier air, development proceeded rather slowly. B. Synoptic History ------------------- The depression was upgraded to Tropical Storm Florence at 1500 UTC on 5 September, nearly two days after being classified as TD-06. The upgrade was based primarily on QuikScat and SSM/I data which showed large patches of 30-35 kt uncontaminated winds in the northwest quadrant. Florence at this time was located around 800 nm east of the Leeward Islands and was moving westward at 10 kts. Gales extended out over 100 nm in the northeast quadrant and 90 nm to the northwest. Once named, the large, sloppily-organized tropical storm intensified very slowly. Winds were upped to 40 kts at 05/1800 UTC and to 45 kts at 06/1500 UTC, but remained pegged there for almost three days as Florence continued on a west-northwesterly track. The cloud pattern was at times shapeless with very asymmetric convection, and locating the LLCC was a continuing difficult job. Due to the large size of the storm and given the forecast track, the Bermuda Weather Service issued a hurricane watch for the island at 2100 UTC on 8 September with the center located 550 nm to the south-southeast. Florence began to display some signs of strengthening on the 8th. An Air Force hurricane hunter aircraft reached the storm around 0400 UTC on 9 September and found a CP of 993 mb with a maximum 850-mb FLW of 61 kts about 50 nm northeast of the center, so the MSW was upped to 55 kts at 09/0600 UTC. Satellite intensity estimates had increased to 65 kts from SAB and AFWA and 55 kts from TAFB. However, it was to be 24 hours longer before Florence finally became the season's second hurricane. During the 9th satellite intensity estimates continued to rise, but other considerations led to Florence being held at tropical storm intensity, and later in the day the storm exhibited a slight weakening trend. The MSW was upped to 60 kts at 1800 UTC, but decreased slightly to 55 kts three hours later. Florence was finally upgraded to hurricane status at 0600 UTC on 10 September while located about 315 nm south of Bermuda and moving north-northwestward at 11 kts. A reconnaissance aircraft had found peak FLWs of 84 kts and a CP of 976 mb with a pressure drop of 17 mb in a 12-hour period. Florence continued to strengthen, reaching its peak intensity of 80 kts at 1800 UTC on the 10th while centered about 200 nm south-southwest of Bermuda. This was based on a peak FLW of 96 kts measured by a reconnaissance plane, but using a slightly lower reduction factor than the normal 90% used for reducing 700-mb FLWs to the surface. Dropsonde data suggested that a reduction factor of 80 to 85% would be more appropriate in this case. Florence turned north- ward on the 11th and made its closest approach to Bermuda around 11/1200 UTC, the center passing about 50 nm to the west of the colony. The estimated MSW had dropped briefly to 70 kts, but was upped back to 80 kts three hours later. An elevated observing site in Bermuda reported a peak wind gust of 97 kts. Hurricane force winds extended outward 60 nm from the center in the eastern quadrants and 30 nm to the west. Florence's estimated minimum CP of 972 mb occurred around 11/1800 UTC. The hurricane had shifted to a north-northeastward heading as it was brushing by Bermuda, and the track became increasingly northeasterly as Florence accelerated into the North Atlantic ahead of a mid-level tropospheric trough over the Canadian Maritimes. The storm also began to weaken significantly on the 12th and winds had dropped to minimal hurricane intensity by 0600 UTC. Satellite imagery indicated that Florence was in the early to mid stages of extratropical transition. Dry middle and upper-level air wrapping around the southern periphery had eroded most of the inner-core deep convection. TPC/NHC issued their final advisory on Florence at 12/2100 UTC with the center located about 525 nm southwest of Cape Race, Newfoundland, moving northeastward at 18 kts. The only convection remaining near the center was a band of showers and thunderstorms located about 100 nm northwest of the center. Florence transformed into a powerful extratropical cyclone of hurricane intensity and actually strengthened to 70 kts while near south- eastern Newfoundland. This re-intensification was due to interaction with the upper-level trough located over the Maritimes. The center of post-tropical Florence passed just south of Cape Race with a CP estimated around 963 mb. Sustained hurricane-force winds were recorded on Sagona Island in Fortune Bay with gusts well above hurricane intensity felt on the Burin Peninsula and along the Newfoundland coast from Fortune Bay to Burgeo, including St. Pierre and Miquelon. After passing by Newfoundland the remnants of Florence accelerated eastward across the North Atlantic, slowly weakening. By 1800 UTC on 15 September the former hurricane had weakened into a 35-kt gale roughly halfway between Newfoundland and Ireland. The ex-Florence LOW was eventually forced northward toward Iceland while a weak front associated with the storm's remnants made its way toward Great Britain. C. Meteorological Observations ------------------------------ As noted above, an elevated site in Bermuda (elevation unknown) reported a peak wind gust of 97 kts. In Newfoundland, the following peak wind gusts and storm total rainfalls were reported (data courtesy of Chris Fogarty--thanks to Chris for sending it along): Sagona Island 88 kts St. Lawrence 72 kts 47 mm St. Pierre 69 kts Bonavista 59 kts 33 mm Cape Race 58 kts 25 mm Grates Cove 58 kts Pool's Island 58 kts St. John's 55 kts 48 mm ** Twillingate 54 kts 22 mm Burgeo 53 kts 14 mm Argentia 49 kts 35 mm Gander 42 kts 56 mm Terra Nova Park 58 mm Cape Pine * 41 mm * - private weather station on the southern Avalon Peninsula ** - 48 mm fell at St. John's airport and 52 mm in Mount Pearl D. Damage and Casualties ------------------------ In Bermuda strong winds blew down trees and power lines, leaving over 25,000 homes and businesses without power at the height of the storm. A few houses experienced window and roof damage, and a few injuries were reported. Overall damage, however, was relatively light. During the course of its life Florence produced strong swells and dangerous surf conditions, including rip currents, in the northern Lesser Antilles, Virgin Islands, Puerto Rico, Hispaniola, Bahamas, along the U. S. Eastern Seaboard, and in the Canadian Maritimes. However, no fatalities are known to have resulted from Hurricane Florence. In Newfoundland some damage was reported in the form of blown down trees and damage to shingles and siding of homes. Also, some boats and roadways were damaged in and around the Burin Peninsula from heavy surf conditions. Power outages were also reported in the St. John's area. More information can be found in the online Wikipedia report, from which some of the above information was obtained. The link is: (Report written by Gary Padgett) HURRICANE GORDON (TC-07) 11 - 21 September ------------------------------------- A. Introduction and Storm Origins --------------------------------- Hurricane Gordon became the first intense hurricane of the 2006 Atlantic hurricane season, reaching Category 3 status on the Saffir/ Simpson scale on 13 September while several hundred miles southeast of Bermuda. While an impressive Category 3 hurricane, the most remarkable aspect of Gordon's life was a re-intensification to Category 2 status near latitude 40N after weakening to a minimal hurricane three days earlier. Also unusual was the storm's passage through the central Azores while still a tropical cyclone of hurricane intensity. Finally, in its extratropical stages the cyclone brought very strong winds to Spain, the United Kingdom and Ireland. A tropical wave left the coast of Africa on 1 September and began marching westward across the tropical Atlantic. By the morning of 4 September the system was located several hundred miles west of the Cape Verde Islands and was showing signs of organization. The system looked even better the next day, but by the 6th environmental conditions had become less favorable. The primary inhibiting factor was the proximity of the disturbance to large Tropical Storm Florence. The system continued to move west-northwestward for the next few days and managed to produce disorganized showers and thunderstorms. As the separation between this system and Florence slowly increased, conditions gradually improved and by the afternoon of 10 September thunderstorm activity had become more concentrated near the circulation center about 475 nm east-northeast of the Leeward Islands. The first advisory was issued on Tropical Depression 07 at 0300 UTC on 11 September, the center being located about 455 nm east-northeast of the Leeward Islands and moving westward at 5 kts. The initial MSW was set to 25 kts, based on 0000 UTC Dvorak estimates of T1.5 and a report of WSW 27-kt winds from ship MSJX8 just south of the center. In contrast to Florence, which was a huge tropical cyclone in area, TD-07 was a small cyclone with the entire circulation about 300 nm wide and with deep convection mostly confined to the southern semicircle. The depression gradually turned to a northwesterly track as its organization slowly improved. A reconnaissance mission into the system around midday on the 11th found peak FLWs of 47 kts, corresponding to 38 kts at the surface. Based on this the depression was upgraded to Tropical Storm Gordon at 11/2100 UTC with the intensity estimated at 40 kts. Gordon was then located about 375 nm northeast of the Leewards, moving to the northwest at 8 kts. The storm was quite small: gales extended outward 40 nm from the center to the northeast and 25 nm to the southeast with no gale-force winds found in the western quadrants. B. Synoptic History ------------------- The strengthening Gordon soon turned northward toward a break in the subtropical ridge left in the wake of Florence. And even though the earlier storm was moving out of the way, an upper-level LOW located about 1000 nm to the east-northeast of Gordon was forecast by the global models to move westward and break down the remaining subtropical ridge, allowing the storm to recurve. Gordon was upgraded to a hurricane at 0300 UTC on 13 September while located almost 500 nm north-northeast of the Leeward Islands and moving north at 8 kts. The upgrade was based on the appearance of an intermittent eye feature and Dvorak T-numbers of 4.0 and 4.5 from all agencies. By 1500 UTC Gordon had developed a well-defined eye and the MSW was increased to 80 kts. Although not yet forecast to become a major hurricane, Gordon's satellite signature continued to improve and at 14/0300 UTC the cyclone was upgraded to a Category 3 hurricane with winds of 105 kts and an estimated CP of 955 mb, which proved to be Gordon's peak lifetime intensity. Subjective T-numbers had reached 5.5 while the AODT had been giving 3-hour estimates of T6.0. Gordon had become embedded in mid-latitude westerly flow and was moving north-northeastward at 11 kts from a position about 485 nm east-southeast of Bermuda. Hurricane-force winds were confined to a zone within about 25 nm of the center while gales reached outward over 100 nm in all quadrants. Gordon held on to its 105-kt peak for about 24 hours, then slowly began to weaken as it began to move over gradually cooling waters. By the 15th the low-level ridge to the east of Gordon had weakened and the hurricane was left in an area with very weak steering currents. Consequently, Gordon remained quasi-stationary for over 24 hours as mid-level ridging to the north and east of the hurricane strengthened. The MSW had dropped to 65 kts by 0900 UTC on 16 September, and continued weakening with extratropical transition within 72 hours was forecast. Gordon, however, had other plans. The storm continued to display a ragged eye in infrared imagery for the next day and maintained hurricane intensity. At 1500 UTC on the 17th satellite imagery depicted an eye, deep convection and impressive outflow. TAFB and SAB were both reporting Dvorak estimates of 77 kts with AFWA's being 65 kts, so the MSW was upped to 70 kts. The storm by this time was moving north-northeastward at 9 kts and the track became increasingly eastward at a faster pace as the day wore on. Gordon's winds were upped further to 80 kts at 1500 UTC on the 18th. The storm was located almost 1000 nm west of the Azores, moving north- eastward at 17 kts, and all the models were anticipating a due eastward track as the hurricane was steered by the zonal westerlies north of the subtropical ridge. At 18/2100 UTC a tropical storm watch was issued for the Azores as the official forecast carried the storm over or very near the islands during the next 24 to 36 hours. Hurricane Gordon reached a secondary peak intensity of 90 kts at 19/0900 UTC while located about 550 nm west of the island of Terceira in the Azores, scooting eastward at 24 kts. The eye was remaining distinct and cloud- free and intensity estimates ranged from 77 to 90 kts. Gordon was a healthy Category 2 hurricane bearing down on the Azores--something not seen very often. As the cyclone approached the Azores it began to slowly weaken but was still sporting 75-kt winds as it moved rapidly through the central part of the island chain. At 20/0000 UTC Gordon was located about 210 nm west of Sao Miguel, moving eastward at 29 kts. Six hours later the center was 75 nm south-southeast of Terceira and the MSW had dropped to 65 kts. AMSR-E microwave data indicated that the westerlies had finally begun to affect the vertical structure of Gordon with the center displaced about 60 nm west of the limited deep convection. The cyclone was downgraded to a 50-kt tropical storm at 20/1200 UTC but still had the tropical characteristics of a warm core and deep convection near the center. However, a strong cold front was approaching the core and extratropical transition was just around the corner. TPC/NHC issued its final advisory on Gordon at 20/2100 UTC since the cold front had interacted with the cyclone's circulation. The storm's center was then located about 340 nm west of Lisbon, Portugal, racing eastward at 30 kts. Following extratropical transition, the storm tracked northwestward toward the Iberian Peninsula, turning northward on 21 September towards Great Britain and Ireland. By the 22nd it had become completely absorbed into a large LOW to the west of Ireland. C. Meteorological Observations ------------------------------ As Gordon sped through the Azores, a 10-min avg sustained wind of 49 kts with a peak gust of 71 kts was reported at Santa Maria airport in the eastern Azores. In Spain, as the extratropical stage of Gordon paid a visit to the Iberian Peninsula, gusts up to 89 kts were reported at Fisterra. Also, Castro Vicaludo-Oia reported gusts to 91 kts. Some other peak wind gust reports: Cabo Vilan - 82 kts; Ferrol - 64 kts; Alvedro - 60 kts; Ancares - 55 kts; Oiz - 59 kts. Near Madrid winds to 57 kts were felt at Punto Navacerrada. Heavy rains fell across Spain with 65.5 mm recorded at Canfranc. A pressure of 989.7 hPa was measured at Coruna (unknown if this was adjusted to MSL). Also, waves up to 7 meters were reported. In the UK, a gust of 70 kts was recorded in southwest Great Britain late on the 21st. Also, gusts to 65 kts affected Northern Ireland during the night of 21-22 September. High winds were also felt in Scotland and Ireland from the extratropical remnants of Gordon. D. Damage and Casualties ------------------------ In the Azores damage was relatively light with only reports of toppled trees and power lines. A few communities lost electrical power, particularly on Santa Maria Island. The strong winds experienced over much of Spain blew down trees, traffic lights and signs. One man was injured due to a tree falling on his car, and many roads were blocked by fallen trees. Another report indicated that four people were injured in the Galicia region with 100,000 homes losing power. Portugal also experienced heavy rain and wind gusts that downed trees and caused roof damage. In Ireland around 1500 homes lost power due to the stormy conditions wrought by ex-Gordon, and there was one injury reported. In southwestern England more than 1000 homes lost power in Truro, Cornwall, and a rail line between Exeter and Plymouth was damaged by high surf. Up to 100,000 homes in Northern Ireland lost power as tree branches fell on power lines, and fallen trees blocked many roads with flooding reported in some areas. Additional information can be found in the online Wikipedia report from which some of the above information was obtained. The link is: (Report written by Gary Padgett) HURRICANE HELENE (TC-08) 12 - 26 September ------------------------------------- A. Introduction and Storm Origins --------------------------------- Hurricane Helene, the fourth hurricane of the 2006 Atlantic season, was a classic Cape Verde hurricane in every sense of the word, forming as a tropical depression south of the islands and becoming a large, intense hurricane. Fortunately, unlike many Cape Verde hurricanes of the past, Helene recurved well to the east of Bermuda and did not threaten any populated areas in the western Atlantic basin. Also, the storm was the only one of the September hurricanes which did not affect Newfoundland or the Azores, passing well between those islands. In some aspects the hurricane was similar to its namesake in 1988. However, the Hurricane Helene of that year was somewhat more intense, becoming a Category 4 hurricane as it moved northward through the central Atlantic. This year's Helene became the strongest hurricane of the season, peaking at 110 kts on 18 September--a strong Category 3 hurricane on the Saffir/ Simpson scale (although there is some possibility this value was a little too high--see discussion below). A strong tropical wave emerged from the western coast of Africa on 11 September and immediately began to show signs of developing as a tropical cyclone. By the morning of the 12th the system had become sufficiently organized that advisories were initiated on Tropical Depression 08, located about 160 nm south-southeast of the southernmost Cape Verde Islands and moving west at 16 kts. A well-defined curved convective band had formed over the western semicircle and two ship reports of northerly and southerly winds confirmed the existence of a closed surface circulation. Although it was anticipated that TD-08 would become a tropical storm by early on the 13th, intensification proceeded somewhat more slowly than forecast. The depression was large and somewhat elongated with multiple low-level swirls within a larger circulation gyre. By the evening of 13 September the depression's convective pattern had gradually become better organized and Dvorak T-numbers had reached 2.5 from all agencies; hence, the system was upgraded to Tropical Storm Helene at 14/0300 UTC. Helene was located about 490 nm west of the Cape Verdes and moving quickly to the west- northwest at 19 kts along the southern periphery of a deep-layer ridge. B. Synoptic History ------------------- After reaching tropical storm intensity, Helene was slow to intensify further. Winds remained at 40 kts through 15/0900 UTC, but were bumped up to 50 kts at 1500 UTC after satellite imagery revealed that the cloud pattern had become better organized. With low shear and warm SSTs ahead along the anticipated track, Helene was forecast to reach hurricane intensity within 24 hours. The cyclone was upgraded to the season's fourth hurricane at 16/1500 UTC while centered approximately 1000 nm east of the northern Leeward Islands. Once having reached that milestone Helene began to steadily intensify as it continued to churn northwestward along the southwestern side of the deep-layer ridge toward a weakness in the ridge. Helene became the season's second major hurricane at 18/0300 UTC when winds were upped to 100 kts, and the storm reached its peak estimated intensity of 110 kts at 1500 UTC while centered about 950 nm east-southeast of Bermuda, moving northwestward at 8 kts. Earlier that morning Helene had reached the longitude of Gordon and the storm had temporarily moved on a north-northwestward track for several hours, but by advisory time it appeared that an anticipated westward turn, forecast by the global models, was about to begin. A surprise was in store later that afternoon. A NOAA research aircraft made a pass through the center of Helene and found that the hurricane was not quite as strong as previously estimated by satellite. Based on the reconnaissance findings, the MSW was lowered to 100 kts at 2100 UTC. (It seems very possible to the author that in post-storm analysis Helene's peak MSW may be lowered to 105 or even 100 kts.) On the 19th Helene's motion became westerly as a mid-tropospheric ridge to the north built, but by the 20th the storm was moving northwestward once more. A NOAA aircraft made a pass through Helene early on the afternoon of the 19th and measured a CP of 956 mb. The peak FLW was 98 kts at 850 mb in the northwest quadrant, and two eyewalls were present at radii of 40 nm and 120 nm. Based on these findings Helene's MSW was reduced to 95 kts. This brought the hurricane down to Category 2 status, and even though brief re-intensification to a Category 3 hurricane was forecast, this never materialized. Helene at this stage was a fairly large hurricane with hurricane-force winds extending outward 55 nm to the northeast of the center and 35 nm to the southwest. Gales covered a zone over 300 nm in diameter. Over the next few days Helene continued to weaken very slowly as it moved over gradually cooling SSTs and encountered some drier air. The storm's heading gradually turned to the north and then northeastward ahead of an approaching trough in the westerlies. The MSW was reduced to 85 kts at 21/0300 UTC based upon data from a NOAA P-3 mission during the previous afternoon--satellite intensity estimates at the time ranged from 77 to 90 kts. The storm passed about 485 nm east of Bermuda around 0900 UTC on 22 September, moving northeastward at 13 kts. The intensity was lowered to 70 kts at 21/1500 UTC but was bumped back to 75 kts twelve hours later as cold cloud tops had expanded and become more concentric around the center. However, the satellite presentation soon began to deteriorate once again and Helene was reduced to minimal hurricane intensity at 22/2100 UTC and downgraded to a 60-kt tropical storm six hours later. A QuikScat pass from around 2200 UTC showed 50-60 kt winds southeast of the center. In a manner somewhat similar to Hurricane Gordon, Helene pulled a surprise over the reaches of the North Atlantic. The TPC/NHC discussion at 23/0900 UTC noted that a small burst of convection with cloud tops to -60 C had persisted over the LLCC for more than six hours, and given the forward speed of 22 kts, the intensity could be higher than the advisory MSW of 60 kts. At 23/1200 UTC a special advisory was issued, upping the winds to 80 kts. A recent QuikScat pass had indicated that Helene possessed a large area of hurricane force winds southwest of the center and the data showed some vectors to 80 kts. So Helene was re-upgraded to a hurricane, even though the storm appeared to be in the process of transforming into an extratropical cyclone. The 2100 UTC discussion noted that the cyclone displayed both tropical and extra- tropical characteristics. Helene had a frontal-like and asymmetric appearance in satellite imagery with limited deep convection, yet FSU cyclone phase space diagrams diagnosed the storm with a deep-layer warm core. The MSW remained 80 kts for the 2100 UTC advisory but began to decline after that. The final TPC/NHC advisory on Helene was issued at 1500 UTC on 24 September, placing the center about 515 nm west-northwest of the Azores and moving northeastward at 19 kts. The previous advisory had treated Helene as a 75-kt hurricane, but the final one reduced the system to a 60-kt extratropical storm. Helene by this time had acquired definitive frontal features with extensive cold-air advection over the southwestern semicircle. Also, a QuikScat pass around 0900 UTC had suggested that the strongest winds were becoming removed from the center. Interestingly, microwave data still showed a warm core, but this was believed to be due to a warm seclusion that is common in strong extra- tropical cyclones. The post-tropical Helene continued to speed east- northeastward across the North Atlantic and by 25/0000 UTC was generating hurricane-force winds of 70 kts around a 964-mb center. Thereafter, the system began to slowly weaken and the last information available to the author placed a 980-mb center well north of the Azores at 26/0000 UTC. C. Damage and Casualties ------------------------ No casualties or damage are known to have resulted from Hurricane Helene. (Report written by Gary Padgett) HURRICANE ISAAC (TC-09) 27 September - 4 October -------------------------------------------- A. Introduction and Storm Origins --------------------------------- Hurricane Isaac, the final hurricane of September and (as of this writing--9 November) the final tropical cyclone of the 2006 Atlantic season, followed a similar trajectory to its two predecessors, Gordon and Helene, recurving well east of Bermuda. Isaac, however, didn't recurve quickly enough to miss Newfoundland, and the storm brushed the extreme southeastern tip of the island while still a fairly strong tropical storm shortly before becoming extratropical. If indeed there are no more tropical cyclones this season, 2006 will be the first season since 1963 to produce exactly 9 tropical storms or hurricanes (although in that season one tropical storm was unnamed). The last year to see exactly 9 named storms (down through the letter "I") was 1964. However, during post-analysis 3 unnamed storms were added to the official roster, making a total of 12 tropical storms/hurricanes. (These statistics are based upon the current Best Track database. When the ongoing reanalysis is complete these records may no longer hold.) Isaac's origins can be traced back to a tropical wave which emerged from the African coast on 18 September. By early morning of the 20th the wave was accompanied by a broad surface LOW centered about 390 nm south-southwest of the southernmost Cape Verde Islands. Convective activity had increased and additional development was anticipated over the next couple of days as the system moved west-northwestward. As things turned out, a week elapsed before the system was upgraded to a tropical depression. On the 23rd convective activity became better organized, but by the next day upper-level winds had strengthened and the potential for a tropical depression to form had diminished. During the evening of 25 September the wave was looking a little healthier once more and this trend continued through the 26th and into the 27th. Environmental conditions gradually became more conducive for tropical cyclogenesis and the first advisory on Tropical Depression 09 was issued at 2100 UTC on 27 September. Visible satellite pictures indicated that the LLCC had gradually become better defined and there was sufficient deep convection for the system to be classified as a 30-kt tropical depression. The center of TD-07 was located about 705 nm east- southeast of Bermuda and moving northwestward at 12 kts. The depression was upgraded to Tropical Storm Isaac at 1500 UTC the next morning (28th), located about 575 nm east-southeast of Bermuda and moving northwestward at 7 kts. The upgrade was based primarily on data from a QuikScat pass at 0845 UTC which had shown evidence of 35-kt winds in the system. Isaac was exhibiting some characteristics of a subtropical storm with the radius of maximum winds near 75 nm and with an upper-level LOW almost on top of the system. Some modest intensification was forecast. Even though SSTs in Isaac's forecast track were near 26 C, upper-level temperatures were also colder than normal, which would allow for more instability and more convection. B. Synoptic History ------------------- The subtropical-like features continued on into 29 September. Convection was becoming more consolidated around the center, but the convection was rather weak with only a few cloud tops colder than -50 C. By afternoon of the 29th Isaac was showing definite signs of increasing strength: convection was increasing and attempting to form a ring around the center and outflow was expanding and becoming more symmetric. One factor which had earlier had some inhibiting effect on Isaac's intensification was that it had been moving over cooler waters upwelled by Gordon and Helene. The tropical cyclone was now leaving these cooler waters behind and moving into a region with warmer SSTs and low vertical shear. The 29/2100 UTC advisory was the first to forecast that Isaac would reach hurricane intensity. Isaac was upgraded to a hurricane at 1500 UTC on 30 September while centered about 325 nm east-southeast of Bermuda. The cyclone was still moving on a rather slow northwesterly track at 6 kts. Isaac had formed a ragged eye, and a high-resolution QuikScat pass at 1000 UTC showed one believable wind vector of 63 kts. Since that time, the storm's satellite signature had improved and TAFB was reporting a T-number of 4.0. By 0600 UTC on 1 October Dvorak ratings from TAFB and SAB had reached T4.5, so Isaac's MSW was bumped up to 75 kts--the peak for the storm's history. Hurricane Isaac was then located about 245 nm east-northeast of Bermuda, moving north-northwestward at 8 kts. The cyclone was situated between the southwestern flank of a rather small deep-layered subtropical ridge and a very large trough along the U. S. Atlantic Seaboard. A northward turn was forecast, followed by acceleration to the northeast. Following its peak in intensity Isaac's MSW slowly began to decrease. Twenty-four hours after peaking in intensity Isaac had weakened into a minimal 65-kt hurricane. Microwave imagery revealed that the LLCC was displaced about 30 nm southwest of the mid-level center, and Dvorak ratings from TAFB and SAB had decreased to T4.0 and T3.5, respectively. The storm had recurved and was moving north-northeastward at 26 kts. Isaac was downgraded to a 50-kt tropical storm at 02/1500 UTC, centered about 165 nm south-southwest of Cape Race, Newfoundland, racing north- northeastward at 36 kts. The cyclone passed just south of Cape Race during the afternoon of 2 October, and by 2100 UTC Isaac was beginning to take on extratropical features to the point that TPC/NHC issued their final advisory on the system, which was then located about 45 nm east- northeast of Cape Race. The extratropical remnants of Isaac continued to speed northeastward across the North Atlantic, gradually turning east- northeastward, and by 04/1800 UTC had weakened below gale force several hundred miles west of Ireland. C. Meteorological Observations ------------------------------ The only land area affected by Isaac was the island of Newfoundland. Following is a summary of Isaac's impact in the area sent by Chris Fogarty of the Canadian Hurricane Centre. A special thanks to Chris for sending this write-up. "The centre of Tropical Storm Isaac passed approximately 45 km south- east of Cape Race, Newfoundland, late in the afternoon of October 2nd. Isaac was moving very quickly to the northeast near 70 km/hr. The storm circulation was very small and strong winds were confined to only a short distance to the north of the centre. The storm had maximum sustained winds of 50 knots (92 km/hr) and a central sea level pressure near 993 mb at its closest approach to the Avalon Peninsula. Rain from Isaac quickly spread across the Avalon but did not extend beyond Trinity and Placentia Bays. Isaac was still in its tropical cyclone phase when it passed by the Avalon as seen in radar imagery. There was a rain-free area near the centre, perhaps indicating the remnants of the storm's eye. "The strongest winds on land were reported at Cape Race where gusts reached 96 km/hr (52 knots) with the highest sustained winds of 74 km/hr (40 knots). A peak wind of 76 km/hr (41 knots) was reported at a private weather station on Cape Pine about 30 km west of Cape Race. Because of the compact circulation of the storm and its rapid forward motion, winds were much lighter over most of the Avalon Peninsula. The highest wind gust at St. John's International Airport was 54 km/hr (29 knots). Peak winds from an offshore buoy south of the storm reached 56 knots or 104 km/hr. "Rainfall amounts directly associated with Isaac were generally less than 25 mm due to its rapid forward motion and diminishing amount of moisture. The highest measured rainfall was 26 mm at Cape Race. 19 mm was measured at the Cape Pine location and only 10 mm in the St. John's area. "Forecasting the track and speed of the storm was very challenging, as are most tropical storms and hurricanes moving into our region. Given that Isaac was still a strong tropical storm very near the Avalon Peninsula, a tropical storm warning was issued for the potential for high winds. If the storm had tracked only 50 to 100 km farther north, the St. John's area would have experienced much stronger winds. Isaac also moved faster than originally expected, thus rainfall amounts were less than forecast." D. Damage and Casualties ------------------------ No casualties or significant damage are known to have resulted from Hurricane Isaac. (Report written by Gary Padgett and Chris Fogarty) ************************************************************************* NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for September: 2 tropical depressions ** 1 tropical storm 1 major hurricane ** - both the non-developing tropical depressions formed in the Central North Pacific region Sources of Information ---------------------- Most of the information presented below was obtained from the various tropical cyclone products issued by the Tropical Prediction Center/National Hurricane Center (TPC/NHC) in Miami, Florida (or the Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii, for locations west of longitude 140W): discussions, public advisories, forecast/advisories, tropical weather outlooks, special tropical disturbance statements, etc. Some additional information may have been gleaned from the monthly summaries prepared by the hurricane specialists and available on TPC/NHC's website. All references to sustained winds imply a 1-minute averaging period unless otherwise noted. Northeast Pacific Tropical Activity for September ------------------------------------------------- Following are some statistics for the Northeast Pacific basin during the month of September: September Average Parameter 2006 1971 - 2005 -------------------------------------------------------- Named Storms (NS) 2 3.5 Hurricanes (H) 1 2.2 Intense Hurricanes (IH) 1 1.1 Named Storm Days (NSD) 11.25 17.4 Hurricane Days (HD) 3.75 8.3 Intense Hurricane Days (IHD) 0.75 2.6 The month of September, 2006, was well below normal in the Northeast Pacific basin with the overall net tropical cyclone activity (utilizing all six parameters) being only about 55% of the average level normally seen in September, whereas in August the overall tropical activity had been almost 2.5 times the average. The month also was much quieter than September, 2005, when the overall net activity had been almost twice the average. Interestingly, the Atlantic basin was quiet during August when the Northeast Pacific was active, but was well above normal during September when the Pacific was well below normal. Two named storms developed, Hurricane Lane and Tropical Storm Miriam. Lane was a small but intense hurricane which formed and remained near the Mexican coast and ultimately made landfall near El Dorado as a strong Category 3 hurricane--the first major hurricane to strike the West Coast of Mexico in four years. Miriam was a short-lived minimal tropical storm which formed in an extension of the ITCZ to the west of Lane and never affected land. Reports on both Lane and Miriam follow below. No more tropical cyclones formed east of 140W, but two tropical depressions were classified by the Central Pacific Hurricane Center in Honolulu during the month of September. Tropical Depression 02C formed on the 18th about 675 nm south of Honolulu. This system was initially forecast to reach hurricane intensity within 48 hours, but this forecast failed miserably. TD-02C's winds reached 30 kts at 19/0600 UTC and this was the highest for the depression’s history. The system was never able to completely break away from the ITCZ and unable to develop persistent rainbands and central convection. By 20/1200 UTC the low-level center had become completely exposed with disorganized convection off to the west of the center. Interestingly, some of the models were still indicating that TD-02C would strengthen, but given the observed weakening trend and the appearance, the intensity was lowered to 25 kts at 1500 UTC. The depression continued to weaken as it drifted westward and the final CPHC advisory, issued at 20/2100 UTC, placed the dissipating center about 395 nm southeast of Johnston Island. The remnants of TC-02C continued to move westward and eventually brought some heavy rainfall to Kwajalein Atoll. Some information on this will be included in Part 3 of the September summary, covering the Northwest Pacific basin. Tropical Depression 03C formed on 26 September--the first CPHC advisory at 26/2100 UTC placed the center in the far western portion of the Central North Pacific region about 585 nm west-southwest of Johnston Island. Unlike TD-02C, the initial advisory for this system never called for it to reach tropical storm intensity, and in this case the forecast verified. This depression was never well-organized and CPHC issued only three advisories on the system. The final advisory, issued at 27/0900 UTC, noted that there was doubt as to whether or not a closed circulation existed, and given that the environment was quite hostile with dry mid- level air and increasing shear, any remaining circulation would likely soon dissipate. At the time of the final CPHC advisory TD-03C was about to cross longitude 180, and JMA issued four bulletins on the system as a weak tropical depression through 28/0600 UTC. The online Wikipedia reports for the Eastern Pacific cyclones may be accessed at the following URL: A more expanded report is available for Hurricane Lane. The link to this is included in the report on Lane below. HURRICANE LANE (TC-13E) 13 - 17 September ------------------------------------- A. Introduction --------------- Hurricane Lane was a fairly small but intense tropical cyclone which formed and remained within about 100 nm of the Mexican coastline. Lane became the first hurricane of Category 3 or higher intensity to strike Mexico since the destructive Hurricane Kenna of October, 2002. Kenna had peaked at 145 kts--a Category 5 hurricane--before striking the coast near the fishing village of San Blas as a 120-kt Category 4 hurricane. Hurricane Kenna was the last of three Category 5 hurricanes which roamed Eastern Pacific waters during the 2002 season, the others being Elida and Hernan. B. Synoptic History ------------------- A tropical wave passing several hundred miles south of the Gulf of Tehuantepec spawned an area of disturbed weather on 11 September which persisted as it moved slowly westward. Convection and banding features slowly improved and the system was classified as Tropical Depression 13E at 2100 UTC on 13 September while located about 100 nm southwest of Acapulco. TD-13E slowly intensified and was upgraded to Tropical Storm Lane at 0900 UTC on 14 September while centered about 80 nm off the Mexican coast. Lane continued to strengthen as it moved northwestward around the western periphery of a mid-level ridge centered over Mexico. Throughout its life the cyclone moved on a track roughly parallel to and generally less than 100 nm off the Mexican coastline. Since the storm posed a threat to Mexico, reconnaissance missions were flown into the storm by the U. S. Air Force Hurricane Hunters. Based on a peak FLW of 76 kts and a 90-min pressure drop from 989 to 985 mb, Lane was upgraded to a hurricane at 15/2100 UTC while centered only about 35 nm west-northwest of Cabo Corrientes. Lane's track had by that time shifted more to the north-northwest at about 8 kts. Once having reached hurricane intensity, Lane intensified rapidly--a possibility which had been suggested by the SHIPS model. Only three hours after reaching hurricane intensity, Lane was a Category 2 hurricane with 85-kt winds passing just west of the Islas Marias. Intensification continued and at 16/0900 UTC Lane became the season's fifth major hurricane as the MSW was upped to 100 kts, based on Dvorak ratings of T5.5 from all three agencies. The storm was then located about 45 nm southwest of Mazatlan, Mexico, and moving toward the north- northwest at 9 kts. Hurricane Lane reached its peak intensity of 110 kts at 1500 UTC. The 8-10 nm eye was embedded in cloud tops of -70 to -80 C and had become better defined during the previous few hours. Satellite intensity estimates remained at 102 kts from TAFB and AFWA but had increased to 115 kts from SAB. The center of Hurricane Lane made landfall about 20 nm southeast of El Dorado, Mexico, around 1915 UTC. A reconnaissance plane reached the eye of Lane just before landfall and measured a CP of 955 mb along with maximum 700-mb FLWs of 110 kts in the southeastern eyewall. An eyewall dropsonde in the southern eyewall just after landfall measured a surface wind of 108 kts. Once inland the storm predictably began to weaken rapidly over the mountainous terrain with some southwesterly shear also aiding in the weakening process. Lane was downgraded to a tropical storm at 17/0900 UTC, and the final TPC/NHC advisory on the weakening depression was issued at 17/1500 UTC, placing the dissipating surface center about 150 km east-northeast of Los Mochis, Mexico. Some of the moisture from Lane eventually reached Texas. C. Damage and Casualties ------------------------ Due to Lane's track near the Mexican coast, effects were felt in several areas. In Acapulco, wave action and heavy rains caused flooding in coastal streets. Around 200 homes were flooded and the heavy rains were responsible for a mudslide, resulting in the death of a 7-year old boy. Offshore, strong waves capsized a boat, leaving one person missing. Heavy rainfall in the states of Michoacan and Jalisco (187 mm in Cajon de Pena) also led to flooding and landslides with some fatalities reported. In the landfall area roads were washed away and flimsy homes destroyed with electricity poles, trees, and traffic signs blown down. In Mazatlan strong winds and heavy rain resulted in flooded streets and power outages. The total death toll from Hurricane Lane stands at four with total damages estimated around $110 million (USD). Much of the above information was obtained from the online Wikipedia report on Hurricane Lane, and many more details are available in the report. This excellent and very informative report may be accessed at the following URL: (Report written by Gary Padgett) TROPICAL STORM MIRIAM (TC-14E) 16 - 18 September ----------------------------------------- Tropical Storm Miriam was a short-lived and weak tropical storm which formed in a broad area of disturbed weather extending westward from Hurricane Lane. The system was classified as a tropical depression (14E) at 16/0600 UTC when located roughly 450 nm southwest of Cabo San Lucas on the southern tip of the Baja California Peninsula. TD-14E initially moved slowly northeastward, embedded in southwesterly flow feeding into Hurricane Lane. Operationally, the depression was upgraded to Tropical Storm Miriam at 1800 UTC on the 16th while located approximately 400 nm southwest of Cabo San Lucas. (In post-storm analysis it has been determined that the depression and tropical storm stages were each reached six hours earlier than reported operationally.) Tropical Storm Miriam reached its peak intensity of 40 kts at 17/0300 UTC and maintained this strength for 18 hours. Northeasterly wind shear along with inflow from a cooler and stable environment to the north inhibited further intensification and Miriam began to weaken on the 17th. The system was downgraded to a depression at 18/0900 UTC and the final TPC/NHC advisory written at 18/1500 UTC. The remnant LOW moved northward toward the Baja before dissipating on 21 September a short distance offshore. The official storm report on Tropical Storm Miriam, authored by James Franklin, is available on the TPC/NHC website at the following URL: Some of the information above was taken from this report. No damage or casualties are known to have resulted from Tropical Storm Miriam. (Report written by Gary Padgett) ************************************************************************* NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for September: 1 possible tropical depression or storm ** 3 tropical depressions ++ 1 tropical storm ## 2 typhoons 2 super typhoons && ** - system received repeated Dvorak ratings of T2.5 from both JTWC and AFWA but was never started as a tropical depression, nor so classified by JMA ++ - one of these was classified as a tropical depression by JMA only; another formed late in month and became named tropical cyclone in early October ## - system was classified as a minimal tropical storm by JTWC and CMA only && - one of these was a visitor from the Central North Pacific Sources of Information ---------------------- Most of the information presented below is based upon tropical cyclone warnings and significant tropical weather outlooks issued by the Joint Typhoon Warning Center of the U. S. Air Force and Navy (JTWC), located at Pearl Harbor, Hawaii. In the companion tropical cyclone tracks file, I normally annotate track coordinates from some of the various Asian warning centers when their center positions differ from JTWC's by usually 40-50 nm or more. All references to sustained winds imply a 1-minute averaging period unless otherwise noted. Michael V. Padua of Naga City in the Philippines, owner of the Typhoon 2000 website, normally sends me cyclone tracks based upon warnings issued by the Japanese Meteorological Agency (JMA) and the Philippines' Atmospheric, Geophysical & Astronomical Services Administration (PAGASA). A very special thanks to Michael for the assistance he so reliably provides. In the title line for each storm I have referenced 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 warning responsibility. Northwest Pacific Tropical Activity for September ------------------------------------------------- Waters of the Northwest Pacific basin were literally crawling with tropical systems of various intensities during the month of September. To keep a little order, I am going to arrange this introductory paragraph a little differently from what I usually do. (1) Supertyphoon Ioke: This very long-lived intense tropical cyclone formed well to the south of Hawaii in late August, becoming the first native Central North Pacific hurricane on record to reach Category 5 intensity. The storm struck tiny Johnston Atoll before reaching the superlative level on the Saffir/Simpson scale and later entered the Northwest Pacific basin as a super typhoon. Ioke passed very near Wake Island before gradually beginning to weaken. The storm recurved east of Japan, and in its extratropical stages produced high waves and a severe storm surge along the western Alaskan coastline as well as heavy rainfall over the state. The complete report on Super Hurricane/Typhoon Ioke may be found in the August summary. (2) Wake Island Possible Tropical Storm of 5-7 September: A system in the vicinity of Wake Island in early September received Dvorak classifications supporting tropical storm intensity for a few days, and there were QuikScat winds to 50 kts; yet, no tropical cyclone warnings were initiated by JTWC nor was the system even referenced as a tropical depression by JMA. Karl Hoarau was of the opinion that this system was indeed a short-lived tropical storm. Following is a short report, which includes Karl's track, documenting this system. (3) Typhoon Shanshan/Luis: Shanshan was an intense typhoon which recurved east of Taiwan, passing over some of the southernmost islands in the Ryukyu group. In its later stages the cyclone struck southwestern Japan with rather significant effects. A report on Typhoon Shanshan written by Kevin Boyle follows. (4) Tropical Depression 15W: This was a rather short-lived, weak depression which formed in the South China Sea on 12 September and moved northward and inland in western Guangdong Province around 1200 UTC on 13 September. JMA estimated the winds (10-min avg) in this system at 30 kts, but JTWC reported 30 kts (1-min avg) for only one warning cycle, at 13/0000 UTC. A track was included for this system in the accompanying cyclone tracks file for September. (5) Super Typhoon Yagi: Yagi was the year's fourth typhoon to reach JTWC's super typhoon threshold of 130 kts, peaking at 140 kts as it recurved well southeast of Japan. A report on Super Typhoon Yagi, authored by Kevin Boyle, follows. (6) Tropical Storm 17W: This system was another fairly short-lived South China Sea system, forming in the central portion of the Sea on 22 September per the analysis of the China Meteorological Administration (CMA), the Hong Kong Observatory, and JMA. JTWC initiated warnings on Tropical Depression 17W at 23/0000 UTC. The depression moved on a west-northwesterly track across the South China Sea, making landfall in Vietnam on the 25th. The system passed just south of Hainan and brought heavy rain to that island with the maximum value recorded being 143 mm (according to the Wikipedia report). Satellite classifications from JTWC, SAB and AFWA all reached T2.5 (35 kts), and JTWC upgraded TD-17W to a 35-kt tropical storm 24/0000 UTC. However, the system appeared to weaken under strong vertical shear and JTWC downgraded it back to depression status only six hours later. The CMA also upgraded the system to a tropical storm and maintained it at that status until landfall in Vietnam. According to the online Wikipedia report, this was the 13th time since the new naming procedures were put into place in 2000 that JTWC had recognized a tropical storm not named by JMA. It was also the 3rd time that CMA had recognized a tropical storm not named by JMA, the other cases being in 2000 and 2004. A track for this system may be found in the companion cyclone tracks file. (7) Weak JMA Tropical Depression: A tropical disturbance was located on 24 September a few hundred miles east-northeast of Kwajalein. JTWC mentioned this as an area with 'poor' development potential, noting that deep convection was pulsing over a weak LLCC evident in microwave imagery. JMA referenced this system as a weak tropical depression in their High Seas Bulletin at 24/1800 UTC. However, six hours later it was referenced only as a 'low pressure area'. It was subsequently followed westward for another couple of days but did not develop. (8) Typhoon Xangsane/Milenyo: Xangsane was the first in a series of deadly, destructive typhoons to plague the Philippines during the fall months. Xangsane was notable for its extremely rapid intensification prior to landfall, plus maintaining its strength while crossing the archipelago. A report on Typhoon Xangsane by Kevin Boyle follows. (9) Beginnings of Tropical Storm Bebinca: A system in late September west of the Marianas was classified as a weak tropical depression by JMA. On 1 October JTWC initiated warnings on the system as Tropical Depression 19W, and a couple of days later was upgraded to Tropical Storm Bebinca. A report on Bebinca will be included in the October summary. (10) Remnants of Central North Pacific Depressions: Two short-lived tropical depressions formed in late September in the western portion of the Central North Pacific region. The first, TC-02C, weakened well to the east of the Dateline, but its remnants held together and moved westward into the eastern Marshall Islands. Tom Wright, Chief Meteorologist, 3D Research/RTS Weather on Kwajalein, reports that they received almost 3.5 inches (89 mm) of rain from around 25-27 September from the remnants of TD-02C, and Ailingalaplap (to the south of Kwajalein) received about 4 inches (102 mm) on the 27th alone. However, winds at Kwajalein were only about 12 kts in association with the former tropical depression's remnants. Radar revealed a broad circulation with several small circulations, or eddies, embedded within the larger circulation. Tropical Depression 03C was downgraded by CPHC on 27 September just east of the Dateline, but its remnants continued tracking westward into the Northwest Pacific basin also. JMA picked up the former TD-03C as a weak tropical depression at 13.0N/180.0E at 27/1200 UTC and carried it as a weak depression in their High Seas Bulletins for about 24 hours. The online Wikipedia reports for the Northwestern Pacific cyclones may be accessed at the following URL: More expanded reports are available for Typhoons Shanshan and Xangsane. The links to these are included in the respective reports below. POSSIBLE TROPICAL STORM (NRL Invest 92W) 5 - 7 September ------------------------------------------- A tropical system in the vicinity of Wake Island in early September may very well have been a tropical storm which remained unnamed and unnumbered. JTWC and AFWA both assigned Dvorak ratings of T2.5/2.5, plus there were some QuikScat data showing uncontaminated 50-kt wind vectors within the northern side of the circulation. However, SAB never assigned a CI number greater than 2.0, and neither JTWC nor JMA classified the system as a tropical depression. I asked Dr. Karl Hoarau of Cergy-Pontoise University near Paris to perform a Dvorak analysis of this system and construct a track, which is included below. (A special thanks to Karl for his efforts.) According to Karl's track a 25-kt tropical depression had formed by 05/0600 UTC about 300 nm south-southwest of Wake Island, moving north- northeastward and reaching tropical storm intensity around 06/0000 UTC when centered approximately 250 nm south of the island. Dvorak ratings from both AFWA and JTWC were T2.5/2.5 at 05/2330 UTC, and JTWC issued a TCFA for the LOW at 06/0200 UTC. Convection had continued to develop near a well-defined LLCC, and an upper-level analysis indicated that a TUTT cell to the northwest and near-equatorial ridging to the southwest were providing excellent poleward and equatorward outflow. Also, as noted above, some recent QuikScat data had shown uncontaminated wind vectors of 50 kts on the northern side of the circulation. Based on Karl's analysis, the system was at tropical storm intensity for 18 hours, peaking at 40 kts at 06/0600 UTC. The cyclone reached the easternmost point of its trajectory at 06/1200 UTC when it was located approximately 125 nm southeast of Wake Island. Afterwards, it began to curve to the north-northwest and was located about 100 nm north-northeast of Wake Island at 07/0600 UTC when Karl's track ends. Per his analysis, the system had weakened to 25 kts by that time. However, Dvorak ratings from JTWC and AFWA were still in general holding around T2.5 and JTWC issued a second TCFA at 07/0200 UTC. Convection was still flaring around a partially-exposed LLCC located within an environment of moderate vertical shear. A third TCFA was issued at 08/0200 UTC, the system then being located about 345 nm north of Wake Island and with increasing organization. However, at 09/0030 UTC the TCFA was cancelled with the system then located approximately 450 nm north-northwest of Wake Island. Satellite imagery revealed an elongation and breakdown of the LLCC. The entrainment of drier air in the mid levels on the western periphery, increased vertical wind shear, and the system's movement into a region of cooler SSTs had resulted in a transformation from a barotropic system into a more baroclinic one. It is indeed a little puzzling why, with intensity estimates of 35 kts for more than two days from two different agencies, no warnings were ever issued for this system, even as a tropical depression. However, SAB never estimated the system above T2.0/2.0, and this was at 10/0233 UTC--well after JTWC had cancelled the TCFA. SAB then weakened the system to T1.5/2.0 at 10/0833 and 10/1433 UTC, declaring it extratropical at 11/0233 UTC. Furthermore, JMA never mentioned this system as a tropical depression in their High Seas Bulletins, and typically that agency "starts" systems as tropical depressions before JTWC does. Following are the track positions and intensities supplied by Karl Hoarau: Storm Name: None Cyclone Number: None Basin: NWP (NRL Invest Number 92W) Date Time Lat Lon Cent MSW MSW Remarks (GMT) Press 1-min 10-min (mb) (kts) (kts) ------------------------------------------------------------------------- 07 SEP 05 0600 14.4 N 166.1 E 25 07 SEP 05 1200 15.4 N 166.6 E 30 07 SEP 05 1800 16.2 N 167.0 E 30 07 SEP 06 0000 16.6 N 167.4 E 35 07 SEP 06 0600 17.2 N 167.9 E 40 07 SEP 06 1200 18.0 N 168.2 E 35 07 SEP 06 1800 19.0 N 168.0 E 30 07 SEP 07 0000 19.9 N 167.7 E 30 07 SEP 07 0600 20.9 N 166.9 E 25 Note: Even though JTWC and AFWA were assigning Dvorak intensity estimates implying the existence of a tropical depression or even a tropical storm after 07/0600 UTC, I chose not to attempt to extend the track beyond the time frame of Karl’s analysis. My purpose is primarily to simply document the existence of this system. (Report written by Gary Padgett with track by Karl Hoarau) TYPHOON SHANSHAN (TC-14W / TY 0613 / LUIS) 9 - 22 September --------------------------------------------- Shanshan: contributed by Hong Kong, China, is a fairly common pet name for young girls A. Storm Origins ---------------- Shanshan was initially mentioned as a suspect area in JTWC’s STWO at 1000 UTC 8 September when an area of convection developed approximately 240 nm west of Guam. The disturbance was located under a weak vertical wind shear environment, southwest of a TUTT cell, with weak eastward and moderate equatorward outflow. After further development, a TCFA was issued at 1230 UTC 9 September, followed by the first warning at 10/0000 UTC. Moving northwestwards, Tropical Depression 14W intensified and was upgraded to a 40-kt tropical storm at 10/1200 UTC while located approximately 660 nm southeast of Naha, Okinawa. The tropical cyclone was named Shanshan at the same time when JMA raised their 10-min avg MSW estimate to 35 kts. B. Synoptic History ------------------- Tropical Storm Shanshan continued to intensify as it drifted north- westward at 6-8 kts along the periphery of a subtropical ridge and was upgraded to a 70-kt typhoon at 1200 UTC 11 September, being approximately 530 nm southeast of Naha, Okinawa. The MSW reached 90 kts at 12/0000 UTC, and this intensity was maintained for 24 hours as the storm turned westwards. Typhoon Shanshan weakened on 13 September as convergence aloft suppressed the polar outflow. The tropical cyclone began to strengthen again on 14 September, and shortly after turning northwards towards a weakness in the ridge, reached a peak intensity of 120 kts at 15/1200 UTC. Shanshan passed through the southern Ryukyu Islands late on 15 September while maintaining 120-kt winds and started to accelerate northeastwards on 16 September as it began to interact with a mid- latitude trough over eastern China. The system began to weaken and undergo extratropical transition on 17 September as it raced north- northeastwards towards the Japanese island of Kyushu. Shanshan skirted the western coasts of Kyushu and Honshu and was downgraded to a tropical storm at 17/1800 UTC, the time of JTWC’s final warning. JMA lowered their MSW to tropical storm levels at 18/0000 UTC but maintained Shanshan as a tropical storm for two more days, not declaring the system extratropical until 20/0000 UTC. Shanshan was located in the Sea of Japan at 19/1800 UTC, but by 20/0000 UTC had raced northeastward across northern Hokkaido into the North Pacific. Thereafter the extratropical storm slowed its forward motion and moved slowly up the chain of the Kuril Islands as it gradually weakened. The final reference to the system in Japan’s High Seas Bulletins placed a 25-kt LOW near the southern tip of the Kamchatka Peninsula at 22/1200 UTC. The highest MSW (10-min avg) and minimum CP estimated for Typhoon Shanshan by JMA were 100 kts and 925 hPa, respectively. PAGASA referred to this cyclone as Typhoon Luis, and the peak MSW estimated by that agency during the time that Luis was located within PAGASA's AOR was 80 kts (10-min avg). C. Meteorological Observations ------------------------------ The eye of Typhoon Shanshan passed very near Ishigakijima in the southern Ryukyus around 2100 UTC on 15 September. At 2100 UTC the weather station (24.3N/124.2E, Alt. 6 m) reported a SLP of 929 hPa and an attendant 10-min avg wind of SSE 48 kts. The center of the eye at the time was about 12 nm due west of the station, indicating that the station was likely under the eastern eyewall. An hour earlier the Ishigakijima station reported sustained winds of 88 kts. However, these should be understood to be the winds at that particular hour and not necessarily the strongest winds experienced by the station during the typhoon's passage. The online Wikipedia report on Shanshan indicates that a peak gust of 130 kts was reported on Ishigakijima, while on Iriomote a peak gust of 137 kts was recorded. On Ishigakijima rainfall rates of 50 mm per hour were also reported. Later the eye of Shanshan passed about 120 nm west of Okinawa with Naha reporting SSW winds of 41 kts, gusting to 61 kts. D. Damage and Casualties ------------------------ Typhoon Shanshan brought strong winds and heavy rains to Okinawa, South Korea and Japan. Over 25,000 homes in Ishigaki, Okinawa, were without electricity after high winds brought down utility poles. In Japan, eleven people were reported dead and 260 injured. Typhoon Shanshan caused damages up to US$4.9 million. One death was reported from South Korea where the storm knocked out power to nearly 4000 homes. A very detailed online report on Typhoon Shanshan/Luis may be found at the following URL: (Report written by Kevin Boyle with additions by Gary Padgett) SUPER TYPHOON YAGI (TC-16W / TY 0614) 13 - 27 September -------------------------------------- Yagi: contributed by Japan, is the Japanese word for goat A. Introduction and Storm Origins --------------------------------- The fourth Northwest Pacific tropical cyclone of 2006 to achieve super typhoon intensity, Yagi traced a slow clockwise loop for three days before passing well north of the Marianas and recurving southeast of Japan. On 16 September an area of convection developed approximately 685 nm east-northeast of Guam, and was first mentioned as a suspect area in JTWC’s STWO at 0000 UTC when animated multi-spectral satellite imagery depicted flaring convection south and east of a weak LLCC. The disturbance was located in a weak to moderate wind shear environment under a developing upper-level anticyclone. After further development, a TCFA was issued at 16/1730 UTC followed by the first warning on Tropical Depression 16W at 17/0000 UTC. TD-16W was upgraded to a 35-kt tropical storm at 17/0600 UTC. At the same time, JMA raised their 10-min avg MSW to 35-kts and assigned the name Yagi. (Editor’s Note: JMA first identified the pre-Yagi system as a weak tropical depression in their High Seas Bulletins as early as 13/1200 UTC when it was located near 11.0N/156.0E. That the system was diffuse and difficult to track is attested to by several significant relocations over the next few days before a definite center began to consolidate on the 16th.) B. Synoptic History ------------------- Initially located in a weak steering environment, Yagi slowly executed a slow clockwise loop while intensifying and was upgraded to a 65-kt typhoon at 1800 UTC 18 September while located approximately 845 nm east- northeast of Saipan. After completing the loop, Yagi resumed a westward track as it became increasingly influenced by a building subtropical ridge southeast of Japan. Typhoon Yagi continued to intensify, reaching super typhoon strength at 21/0600 UTC while turning towards the west- northwest. Yagi peaked at 140 kts at 21/1200 UTC and maintained this intensity for 18 hours on 21-22 September, passing well north of the Mariana Islands. At 22/0600 UTC Super Typhoon Yagi was centred approximately 70 nm east of Iwo Jima, the island lying just within the radius of 50-kt winds. Moving progressively poleward on 22 September, Yagi began to weaken due to increasing wind shear associated with the mid-latitude westerlies. The tropical cyclone completed recurvature on 23 September and underwent extratropical transition on 24 September (per JTWC’s analysis). JMA downgraded Yagi to a severe tropical storm at 24/1200 UTC and maintained it as a tropical system through 25/0000 UTC. The extratropical storm continued moving east-northeastwards, crossing the Dateline early on the 27th. The final reference to ex-Yagi in JMA’s bulletins placed a still- potent 50-kt storm just south of the Aleutian Islands at 27/0600 UTC. JMA estimated a maximum intensity of 110 kts (10-min avg) and a minimum CP of 910 mb. This cyclone did not enter PAGASA’s AOR. C. Damage and Casualties ------------------------ There were no damages or casualties reported in association with Super Typhoon Yagi. (Report written by Kevin Boyle) TYPHOON XANGSANE (TC-16W / TY 0615 / MILENYO) 25 September – 2 October ------------------------------------------------ Xangsane: contributed by Lao People’s Democratic Republic (Laos), is the Laotian word for elephant A. Introduction and Storm Origins --------------------------------- The first in a veritable parade of intense, destructive typhoons to strike the Philippines during the fall, Typhoon Xangsane originated from a fairly broad circulation within the monsoon trough east of the Philippines. It intensified quickly to near super typhoon strength before slamming into the Philippines on 27 September. Xangsane remained a powerful typhoon throughout its westward journey across the Philippines and across the South China Sea, finally making landfall on the Vietnamese coast on 30 September. The initial reference to the pre-Xangsane disturbance was in JTWC’s STWO at 0600 UTC 23 September when an area of convection persisted approximately 90 nm north-northwest of Palau. Upper-air analysis revealed a low to moderate wind shear environment and favourable divergence aloft. After the issuance of a TCFA early on 25 September, the first warning on Tropical Depression 18W was released at 25/1200 UTC. TD-18W was quickly upgraded to a 35-kt tropical storm at 25/1800 UTC, located approximately 460 nm east-southeast of Manila, Philippines. The tropical cyclone was christened Xangsane at 26/0000 UTC when JMA raised their 10-min avg MSW to 35 kts. (PAGASA had began issuing statements on the system, dubbed Tropical Depression Milenyo, at 25/0000 UTC.) B. Track History ---------------- Tropical Storm Xangsane intensified on 26 September and was upgraded to a typhoon at 1800 UTC while located approximately 340 nm east- southeast of Manila. From 26/1800 UTC to 27/0600 UTC Typhoon Xangsane/Milenyo underwent an explosive deepening phase before reaching its maximum intensity of 125 kts at 27/1200 UTC, making landfall over Samar, Philippines, around that time. After striking Samar, Milenyo’s west-northwestward track kept the tropical cyclone over land for much of its tenure over the Philippine Archipelago. As a result, the cyclone gradually lost strength, passing over the Metro-Manila area of southern Luzon early on 28 September. Xangsane/Milenyo remained a major typhoon while traversing the Philippines and emerged into the South China Sea at around 28/1200 UTC. Changing onto a westerly course under the steering influence of a mid-level ridge, Typhoon Xangsane began to strengthen once again, attaining a secondary peak intensity of 115 kts at 29/0600 UTC while located roughly a third of the way across the South China Sea. After maintaining a MSW of 115 kts for over 24 hours, the tropical cyclone began to slowly weaken as it approached Vietnam. Continuing westwards, the system came ashore near Hue, Vietnam, early 1 October with a MSW of 80 kts. JTWC issued their final warning at 01/0600 UTC. From there, JMA tracked Xangsane westward across much of southeastern Asia, downgrading it to a tropical storm at 01/1200 UTC and to a tropical depression at 02/0000 UTC. The maximum intensity of Typhoon Milenyo as estimated by PAGASA was 75 kts (10-min avg). JMA estimated a peak intensity of 90 kts (10-min avg) and a minimum CP of 940 mb. C. Damage and Casualties ------------------------ Typhoon Milenyo/Xangsane caused widespread damage in the Philippines, and was the worst storm to affect Manila since Typhoon Angela/Rosing in 1995. A total of 197 lives were lost in the Philippines with damages to property and agriculture totaling 5.9 billion Filipino pesos. Typhoon Xangsane also badly impacted Vietnam. The storm caused nearly 10 trillion Vietnamese dong worth of damage and 71 people lost their lives. As the storm moved into neighbouring Thailand, torrential rains caused severe flooding. There were no reports of casualties. Much more information on the impact of Typhoon Xangsane in both the Philippines and Vietnam may be found in the online Wikipedia report at the following URL: D. Additional Information ------------------------- Following is part of an e-mail posted by Michael V. Padua of Naga City, Philippines, to a tropical cyclone discussion group (slightly edited): "The reincarnation of Xangsane was memorable...the storm struck major cities from southern Luzon up to the Metro Manila. Lucky I am that the eye just passed 30 km to the south of Naga City...and the damage was minimal...not a single scratch was seen on my Davis Vantage Pro (weather station). "Here's an interesting story...my uncle was attending a seminar in Legazpi when Xangsane arrived. He was driving back to Naga when the typhoon arrived. Upon its passage he stopped at a nearby gasoline station around 7:30 pm to take shelter as very strong winds began to rampage near the city of Legazpi or over the town of Daraga. While over the Shell Gas station, a sudden lull occurred from 7:45 pm up to 8:15 pm... a quietness of 30-mins!!! While inside the eye he saw flickering lightning flashes on all sides of the horizon. Then the wind returned with full-force, even stronger than the first. He told me that the eyewall left the place around 10:30 pm (during that time my weather station began recording high wind speeds). Overall, the damage down south of Naga is worst, especially the cities of Iriga and Legazpi. "Before the eye passed over Legazpi, my uncle heard over the radio that 30-foot waves with 20 feet of storm surge began hurling towards the port of Legazpi, reaching into the low-lying areas of the main city proper. Cars and other vehicles were submerged during the surge. Wow! Horrendous indeed!" Some observations recorded by Michael on his weather station follow: (1) Lowest barometric pressure - 986.4 hPa at 27/1530 UTC (2) Highest wind speed - East 57.3 kts at 27/1516 UTC (3) 24-hour rainfall - 83.1 mm from 26/1600 UTC to 27/1600 UTC 78.7 mm from 27/1600 UTC to 28/1600 UTC (4) 48-hour rainfall - 161.8 mm from 27/1600 UTC to 29/1200 UTC (5) Storm total rainfall - 189.2 mm from 25/1600 UTC to 28/1600 UTC (6) Maximum rain rate - 137.1 mm/hr from 27/1721 UTC to 27/1722 UTC (Note that this is the maximum hourly rain rate based on the peak 1-min rainfall measured. No, 5.4 inches did not fall in one minute!) (Report written by Kevin Boyle with an addition by Michael Padua) ************************************************************************* NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for September: 2 depressions ** 1 tropical cyclone of gale intensity ++ 1 severe cyclonic storm ** - no warnings issued on these systems by JTWC ++ - system was treated only as a depression by IMD Sources of Information ---------------------- Most of the information presented below is based upon tropical cyclone warnings and significant tropical weather outlooks issued by the Joint Typhoon Warning Center of the U. S. Air Force and Navy (JTWC), located at Pearl Harbor, Hawaii. Occasionally some information may be gleaned from the daily tropical weather outlooks and other bulletins issued by the Indian Meteorological Department (IMD), which is the World Meteorological Organization's Regional Specialised Meteorological Centre (RSMC) for the basin. The reported maximum sustained winds (MSW) are based on a 1-minute averaging period, which is used by all U. S. civilian and military weather services for tropical cyclone warnings. For synoptic observations in the North Indian Ocean region, both 10-minute and 3-minute average winds are employed, but IMD makes no attempt to modify the Dvorak scale for estimating tropical cyclone intensity; hence, a 1-minute average MSW is implied. In the North Indian Ocean basin JTWC usually does not initiate warnings until a system has become well-organized and likely to attain tropical storm status within 48 hours. North Indian Ocean Tropical Activity for September -------------------------------------------------- The northern Bay of Bengal had been quite prolific during August, producing several weak depressions. This trend continued into early September with IMD identifying a depression on the 3rd, centered at 1200 UTC about 100 nm southeast of Balasore. The system moved westward and crossed the coast near Chandbali around 0100 UTC on 4 September and slowly weakened thereafter. This system was referenced in the STWOs from JTWC as an area with a 'poor' potential for development. A couple of quiet weeks ensued before activity resumed. Based on very sketchy information in the IMD bulletins and on a report on the Wikipedia website, IMD upgraded a low-pressure area near Jamshedpur to depression status on 21 September. This city lies well inland, so likely this system was a monsoon depression. Over the next two days the depression moved northward into the state of Bihar, weakening to a low- pressure area on the 24th. According to the Wikipedia report, torrential downpours associated with this system caused flooding that led to 170 fatalities and left around 375,000 persons homeless. There were two storms in the North Indian Ocean for which warnings were issued. Severe Cyclonic Storm Mukda formed in the northeastern Arabian Sea on 20 September and remained quasi-stationary for most of its existence while intensifying to near hurricane force. During the final days of the month, another weak northern Bay of Bengal system was designated Tropical Cyclone 05B by JTWC. Short reports on Mukda and TC-05B follow. The online Wikipedia reports for the North Indian Ocean cyclones may be accessed at the following URL: SEVERE CYCLONIC STORM MUKDA (TC-04A / ARB0601) 20 - 25 September ----------------------------------------------- Mukda: contributed by Thailand An area of convection developed and persisted on 18 September approximately 170 nm west-northwest of Mumbai (Bombay), India. An 18/1344 UTC QuikScat image revealed flaring convection within an area of surface troughing. Upper-level analysis depicted favorable divergence aloft with low to moderate vertical shear. By the next day the disturbance had moved to a position about 250 nm west of Mumbai and appeared to be have become slightly better organized, so JTWC raised the potential for further development to 'fair'. The system continued to move westward away from India and at 20/1800 UTC lay approximately 350 nm west of Mumbai. Animated multi-spectral imagery depicted a partially-exposed LLCC with deep convective banding wrapping into the western quadrant. Based on satellite intensity estimates, the system by this time was sufficiently organized to be classified as a tropical depression with winds likely around 30 kts. At 20/2300 UTC JTWC issued a TCFA for the system as convective organization continued to improve. The first JTWC warning on TC-04A was issued at 21/0000 UTC with the center located about 315 nm south of Karachi, Pakistan, drifting west at 4 kts with the MSW estimated at 35 kts. The intensity had increased to 45 kts by 21/1200 UTC where it reached a plateau for a day or so. Steering currents had become very weak by 1200 UTC and the storm moved very little over the next few days. At 22/0000 UTC the MSW was still estimated at 45 kts, but there were signs that TC-04A was strengthening. A 21/2107 UTC AMSR-E pass had depicted tightly-curved convective banding and a formative eye. IMD had designated the system as a depression at 21/0300 UTC, upped it to deep depression status at 1200 UTC, and at 22/0000 UTC named the system Cyclonic Storm Mukda. Mukda continued to intensify, reaching an estimated peak intensity of 60 kts by 22/1800 UTC--this being based on JTWC's operational warning intensity. It seems very likely that Mukda reached hurricane intensity on 22 September. JTWC's satellite analyst rendered a Dvorak rating of T4.0/4.0 at 22/1730 UTC, SAB's rating was T4.5/4.5 at 22/1430 UTC, and AFWA returned ratings of T4.5/4.5 for several hours on the 22nd. The IMD upgraded Mukda to a severe cyclonic storm early on the 23rd, implying peak winds between 48 and 63 kts. Regardless of its intensity, Mukda didn't go anywhere--it remained quasi-stationary in the general area roughly 250-300 nm south of Karachi throughout its life as a cyclonic storm. JTWC dropped the MSW to 55 kts at 23/0600 UTC, and Mukda's intensity continued to steadily drop, reaching minimal tropical storm intensity of 35 kts by 24/0000 UTC with the storm still essentially stationary. JTWC issued their final warning on Mukda at 24/1800 UTC, and by 25/0000 UTC, the winds had dropped to about 25 kts based on a consensus of satellite intensity estimates. The remnants of Mukda hung around for several days in the northern Arabian Sea, gradually drifting westward. Convection would occasionally flare up near the still well-defined LLCC, but no serious attempts at regeneration were observed. No damage or casualties are known to have resulted from Severe Cyclonic Storm Mukda. (Report written by Gary Padgett) TROPICAL CYCLONE (TC-05B) 28 - 30 September ------------------------------------- A STWO issued by JTWC at 1800 UTC on 27 September noted that an area of convection had formed approximately 420 nm southeast of Calcutta, India, and was moving westward into the Bay of Bengal. A LLCC was in evidence and vertical wind shear in the region was low. Based on satellite intensity estimates the system had become a 30-kt tropical depression by 28/0600 UTC when located about 300 nm south-southeast of Calcutta. JTWC issued the first warning on TC-05B at 1200 UTC with the system then passing 250 nm south of Calcutta, moving toward the west-northwest at 13 kts. The initial warning intensity was 35 kts, which was the system’s peak intensity per JTWC’s warnings. Guided by a mid-level steering ridge, TC-05B continued westward and made landfall near Gopalpur around 29/1200 UTC. With the center moving inland, JTWC issued their third and final warning on the system at this time. This location is also approximately 290 nm southwest of Calcutta. AFWA returned a Dvorak rating of T3.5/3.5 (55 kts) at 28/1800 UTC, suggesting that the system might possibly have been slightly stronger than analyzed by JTWC. However, the IMD never upgraded this system to deep depression status, implying that in their opinion the MSW never reached 30 kts. No damage or casualties resulting from Tropical Cyclone 05B have been reported. (Report written by Gary Padgett) ************************************************************************* SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E Activity for September: No tropical cyclones ************************************************************************* NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E Activity for September: No tropical cyclones ************************************************************************* NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E Activity for September: No tropical cyclones ************************************************************************* SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E Activity for September: No tropical cyclones ************************************************************************* SPECIAL FEATURE - SOURCES OF TROPICAL CYCLONE INFORMATION The purpose of this section is to list some websites where many and varied types of tropical cyclone information are archived. Many readers will know about these already, but for the benefit of those who don't, I wanted to include them. (1) Aircraft Reconnaissance Information --------------------------------------- Various types of messages from reconnaissance aircraft may be retrieved from the following FTP site: Information regarding how to interpret the coded reconnaissance messages may be found at the following URL: Links are also included to websites with further information about the U. S. Air Force 53rd Weather Reconnaissance Squadron and the NOAA Air- craft Operations Center. (2) Archived Advisories ----------------------- All the advisory products (public advisories, forecast/advisories, strike probabilities, discussions, various graphics) issued by TPC/NHC are archived on TPC's website. For the current year (using 2006 as an example), the archived products can be found at: Links to tropical products archives for earlier years are available at the following URL: JTWC warnings for past storms are archived on the NRL Monterrey website: On the NRL site, the link to past years can be found in the upper left corner of the screen. I am not aware at the moment of any other TCWC which archives all its tropical cyclone warning/advisory products for public access, but if I learn of any, I will add them to this list. (3) Satellite Imagery --------------------- Satellite images of tropical cyclones in various sensor bands are available on the NRL Monterrey and University of Wisconsin websites, courtesy of Jeff Hawkins and Chris Velden and their associates. The links are: On the NRL site, the link to past years can be found in the upper left corner of the screen. For the CIMSS site, a link to data archives is located in the lower left portion of the screen. Additional tropical satellite imagery, along with looping ability for composite microwave imagery for the Western Hemisphere north of the equator, can be found at: (1) For the Eastern North Pacific: (2) For the Atlantic, Gulf of Mexico and Caribbean Sea: I'm sure there are other sites with available imagery available, and as I learn of them, I will add the links to this list. ************************************************************************* 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 August, 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 from the archive sites listed below. (Note: I do have a limited e-mail distribution list for the track files. If anyone wishes to receive these via e-mail, please send me a message.) 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. Back issues can be obtained from the following websites (courtesy of Michael Bath, Michael V. Padua, Michael Pitt, Chris Landsea, and John Diebolt): 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 Annual Tropical Cyclone Report (ATCR) for 2004 (2003-2004 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 2005 Atlantic and Eastern North Pacific tropical cyclones; also, storm reports for all the 2005 Atlantic and Eastern North Pacific cyclones are now available, as well as track charts and reports on storms from earlier years. The URL is: A special thanks to Michael Bath of McLeans Ridges, New South Wales, Australia, for assisting me with proofreading the summaries. PREPARED BY Gary Padgett E-mail: [email protected] Phone: 334-222-5327 Kevin Boyle (Northwest Pacific) E-mail: [email protected] Simon Clarke (Northeast Australia/Coral Sea, South Pacific) E-mail: [email protected] ************************************************************************* ************************************************************************* Posted: 01.28.07 / Typhoon2000.ph, Typhoon2000.com