GARY PADGETT'S MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY NOVEMBER, 2000 (For general comments about the nature of these summaries, as well as information on how to download the tabular cyclone track files, see the Author's Note at the end of this summary.) *********************************************************************** NOVEMBER HIGHLIGHTS --> Late-season Eastern Pacific tropical storm makes landfall in Mexico --> Philippines affected by typhoon and tropical storm --> Southern India struck by tropical cyclone *********************************************************************** ***** Feature of the Month for November ***** ATLANTIC SUBTROPICAL SYSTEMS OF 2000 (Part 2) ------------------------------------ This is Part 2 of a three-part feature detailing cyclonic systems of 2000 in the Atlantic which were either subtropical storms or depressions or else exhibited some of the features of subtropical cyclones. The information presented below is taken from material supplied by David Roth of HPC. Please refer to Part 1 in the October summary for more background information and some explanations and caveats. This month's feature looks at some of the named tropical cyclones of 2000 which, in David's opinion, exhibited some subtropical features at some point during their histories. For three of these systems (Florence, Leslie, Michael) official NHC "best tracks" designate some portion of the respective tracks as either a subtropical depression or subtropical storm; for Alberto, Gordon, and Helene they do not. I am repeating here the table of subtropical/hybrid systems which David provided. (Numbers in parentheses following the storm designation refer to explanatory notes below.) I. Subtropical Depression May 19-25 II. Alberto (1) August 14-16 III. Subtropical Storm (2) August 28-30 IV. Subtropical Depression September 10-11 V. Florence (3) September 10-12 VI. Gordon (1) September 17-18 VII. Helene (1) September 24-25 VIII. Subtropical Storm (2) September 30-October 3 IX. Leslie (3) October 4-8 X. Michael (3) October 14-17 XI. Subtropical Storm (4) October 25-28 (1) The official NHC "best tracks" do not treat any portion of Alberto, Gordon, or Helene as subtropical. In general, once a tropical cyclone has been named, NHC treats it as a tropical system through- out the remainder of its life--both operationally and in post- analysis--even if at some point it exhibited some subtropical features. (2) According to Jack Beven, these two systems possibly could qualify as subtropical storms pending a careful analysis of all the available data. For the time being they should be regarded as possible subtropical storms. (3) Subtropical portions of the tracks of Florence, Leslie, and Michael are designated in the "best tracks" for these cyclones. The dates of their subtropical phases, however, might not necessarily agree with those David has assigned above. (4) This storm has already been officially recognized as a subtropical storm by TPC/NHC. Since Hurricane Florence, Tropical Storm Leslie, and Hurricane Michael have already been covered in the monthly summaries, and the official storm reports are available on TPC/NHC's website, these storms will not be mentioned further here. Regarding Alberto, Gordon, and Helene, it should be understood that officially, in post-seasonal analysis, TPC/NHC did not designate any portion of the tracks of these cyclones as subtropical storms. However, all three of them did exhibit, at some point in their lives , a few of the features which often characterize subtropical cyclones. Following a practice dating back to the early years of working with subtropical systems (e.g., Tropical Storm Gilda of October, 1973), if an already- named tropical cyclone transforms into a subtropical cyclone and merits public advisories, the system will continue to be treated operationally as a tropical cyclone. In some cases (e.g., Gilda, 1973, and Klaus, 1984), the subtropical portion of the track was so-designated in the "best track" file; in other cases (e.g., Amy, 1975, and Gordon, 1994) the "best track" defines the storm as tropical for its entire history. II. Alberto, August 14-16. Hurricane Alberto had already wandered the Atlantic for ten days prior to the 14th. On that day the cyclone moved into 24 C water as it approached the 40th parallel, convection became shallow, the eye disappeared, and a cold front was swinging around its western periphery but the cool and dry air had not invaded its immediate center. This combination of features gave Alberto an appearance somewhat similar to that of a subtropical storm. Its north- ward motion was blocked by a slow-moving ridge to its north. On the 15th bands of dry air encircled the center as the system began to loop back to the south towards warmer waters with an eye-like feature, but its convection remained shallow. On the 16th bursts of deep convection developed near the immediate center and the stratocumulus shield on its western periphery became multicellular, indicative of the warmer waters it was moving over and an overall warming of its environment. Alberto regained a true eye late that day with a warming core. The storm was upgraded to hurricane status (for the third time) and lived several more days before finally escaping into the westerlies. (NOTE: The August global summary contains a discussion of Alberto written by Eric Blake, and the official storm report on the hurricane, authored by Jack Beven, is available on TPC/NHC's website.) VI. Gordon, September 17-18. While Gordon was a hurricane in the southeastern Gulf of Mexico, an upper-level vorticity maximum became co-located over the surface circulation, totally exposing the surface center in the first morning visible images on the 17th. However, the surface winds were slow to decrease and the pressure remained relatively low until landfall as the system fed off this increase in baroclinic instability (with slightly colder air aloft) while lurking over 31 C water; hence, the suggestion that Gordon was at least partly subtropical. By the 18th it had hooked up with a frontal boundary in the Southeast, ultimately occluding later that day. That completed Gordon's transition to an extratropical cyclone. (NOTE: The September global summary contains a discussion of Gordon, and the official storm report on the system, authored by Stacy Stewart, is available on TPC/NHC's website.) VII. Helene, September 24-25. A tropical storm that made landfall near Fort Walton Beach, Florida, on the night of the 21st/22nd, Helene became linked with a cold air wedge (stationary front) by the evening of the 22nd, transforming the cyclone into an extratropical LOW. As Helene was moving out to sea near the Outer Banks, it left the frontal boundary behind and quickly redeveloped into a subtropical cyclone, embedded within deep southwesterly flow ahead of a frontal system in New England. Its circulation was elongated northeast/southwest and convection was limited in its eastern half. As it moved along the Gulf Stream, it fed off its latent baroclinicity (temperature gradient), deepening into a 55-kt subtropical storm on the night of the 24th/25th. Once the system had moved east of Nova Scotia, it moved into colder waters and frontogenesis occurred with the cyclone quickly occluding on the 25th. (NOTE: The September global summary contains a discussion of Helene, and the official report on the storm, co-authored by Lixion Avila and Eric Blake, is available on TPC/NHC's website. It should be noted that while during Helene's Atlantic Ocean phase the cyclone was not exactly a classic tropical storm, the decision was made in post- storm analysis to treat this portion of the cyclone's history as a tropical storm.) *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for November: No tropical cyclones *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for November: 1 tropical storm NOTE: Much of the information presented below was obtained from the TPC/NHC discussion bulletins issued with every regular advisory (CPHC for locations west of 140W.) All references to sustained winds imply a 1-min averaging period unless otherwise noted. Northeast Pacific Tropical Activity for November ------------------------------------------------ In the Northeast Pacific basin the month of November averages a tropical storm or hurricane about once every four years (the exact average for the Eastern Pacific east of 140W for the period 1971-1999 was 0.28). This year's Tropical Storm Rosa was the first November cyclone in the NEP basin since Hurricane Rick in 1997. Like Rick, Rosa moved northeastward and made landfall in southeastern Mexico, but unlike the former storm, Rosa did not reach hurricane intensity. The tropical cyclone peaked at 55 kts but had weakened to a minimal tropical storm by the time of landfall. The following report on Rosa was written by John Wallace of San Antonio, Texas. A very special thanks to John for writing the discussion for me. Tropical Storm Rosa (TC-19E) 3 - 8 November ----------------------------- Tropical Storm Rosa was a rare November storm, of which the NEP averages only 2.8 per decade--less than the Atlantic rate of roughly 4.4 per decade. Intermittent, strong convection persisted in the southwest Caribbean through much of the month of October. A tropical disturbance formed north of Panama beginning on 28 October. Its convection increased, and hints of cyclonic structure were apparent, resulting in a closed LOW being depicted on the surface analyses by the evening of the 29th. The LOW generated strong convection and maintained fair cyclonic structure as it drifted westward. It weakened substantially early on the 31st as it crossed the Isthmus of Panama, but the LOW apparently reconsolidated under a cluster of thunderstorms west of Panama. The LOW tracked slowly westward under the influence of a mid-level ridge to its north, and had organized enough to warrant its upgrade to Tropical Depression Nineteen-E at 2100 UTC on 3 November when it was located approximately 475 nm southeast of Salina Cruz, Mexico. The depression was slow to intensify, though SSTs and shear were most favorable. A report of a 30-kt MSW and 12-foot seas from ship WMBK, just east of the center at 0000 UTC on the 3rd, justified a slight increase in the estimated MSW to 30 kts on the second advisory. For the most part, though, satellite MSW estimates fluctuated between 25 and 30 kts, based on mercurial convective organization and sometimes conflicting data. The cyclone's organization finally increased enough to justify its being upgraded to Tropical Storm Rosa at 1500 UTC on 5 November, though the forecaster on duty at the time acknowledged that the classification was dubious. The storm was centered by this time about 350 nm south- southwest of Salina Cruz. At the same time, Rosa's track, roughly due west earlier, began to make an expected northwestward turn in response to a strong mid- to upper-level trough to its west. The tropical storm's organization increased significantly between its upgrade and 0900 UTC on 6 November, when it reached its estimated peak MSW of 55 kts about 300 nm south-southeast of Acapulco. Around this time the cyclone's track turned ever more to the north toward the Mexican coast. As Rosa seemed to flirt with the possibility of reaching hurricane intensity, at 1500 UTC on 6 November the government of Mexico issued a hurricane watch for the coast extending from Acapulco to Puerto Angel. Interestingly, at this time there was speculation from one of the forecasters that Rosa's MSW might have been as low as 40 kts, based on Quickscat data that conflicted with Dvorak intensity estimates. Rosa attained its estimated minimum CP of 993 mb at 2100 UTC on 6 November which it maintained through the next advisory. The storm stalled briefly at 0300 UTC on 7 November and began its recurvature as it turned to the north, then north-northeast. A tropical storm warning was added to the hurricane watch area at 0900 UTC on the 7th, while the watch/warning zone was extended east to Salina Cruz at 1500 UTC. Rosa's cloud pattern began to show the effects of southwesterly shear from the same trough responsible for its recurvature and a weakening trend began. The hurricane watches were dropped, while tropical storm warnings were raised for the coast from Punta Maldonado to Tonal at 1800 UTC on the 7th. A reconnaissance mission investigated Rosa around 1600 UTC on the 7th; they found a MSW of 50 knots and a CP of 1000 mb, in excellent agreement with Dvorak estimates, which also averaged 50 knots. It's worth noting that the reconnaissance crew also found a closed, 20-nm eyewall; there was no hint of this in satellite imagery and was unusual for a storm that was well-below hurricane intensity. Rosa made landfall on the Mexican coast near Puerto Angel at 0600 UTC on 8 November with a MSW of 40 knots and CP of 1001 mb. Rosa was only the second November storm since 1971 to make landfall in Mexico (the other being Hurricane Rick in 1997). Already weakening when it made landfall, Rosa was quickly obliterated by the rough terrain. It was downgraded to a depression at 0900 UTC, at which point all warnings were discontinued. The final advisory was issued at 1500 UTC on 8 November, only nine hours after landfall, with the dissipating depression's center located inland about 75 km north of Salina Cruz. No casualties or significant damage are known from Rosa's landfall; if any come to light, the information will be reported in a future summary. The official storm report on Tropical Storm Rosa, prepared by Richard Pasch, is available on TPC/NHC's website at the following URL: . *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for November: 1 tropical depression 1 tropical storm 1 typhoon NOTE: Most of the information on each cyclone's history presented in the narrative will be based upon JTWC's advisories, and references to winds should be understood as a 1-min avg MSW unless otherwise noted. However, in the accompanying tracking document I have made comparisons of coordinates with JMA (Japan) and the Philippines (PAGASA) when their positions differed from JTWC's by usually 40-50 nm or more. A special thanks to Michael V. Padua, owner of the Typhoon 2000 website, for sending me the PAGASA and JMA tracks. In the title line for each storm I plan to reference all the cyclone names/numbers I have available: JTWC's depression number, the JMA-assigned name (if any), JMA's tropical storm numeric designator, and PAGASA's name for systems forming in or passing through their area of responsibility. Northwest Pacific Tropical Activity for November ------------------------------------------------ The Republic of the Philippines was the target of both of the named tropical cyclones forming in the Northwest Pacific basin during November. Early in the month Typhoon Bebinca/Seniang followed a track across southern Luzon almost identical to that taken by Typhoon Xangsane/Reming only a week earlier. And, like the earlier storm, Bebinca caused a considerable amount of damage and several dozen fatalities. Late in the month Tropical Storm Rumbia crossed the southern Philippines and was responsible for a dozen or so fatalities. Another tropical depression (TD-32W) formed on 8 November roughly 100 nm east-northeast of the northern tip of Luzon. This depression formed in an environment of southerly vertical shear which prevented it from strengthening into a tropical storm. The system initially moved northward, later curving to the northeast. By 1800 UTC on the 8th the shear was increasing and dry air was invading the depression's central region, indicating that extratropical transition was underway. The system moved just north of Okinawa around 1200 UTC on 9 November and by 1800 UTC had become an extratropical LOW about 150 nm east- northeast of the island. Finally, as the month opened, Typhoon Xangsane was skirting Taiwan as it raced northeastward and had transitioned into an extratropical gale southwest of Japan by 2 November. See the October summary for the complete report on Typhoon Xangsane. Typhoon Bebinca/Seniang (TC-31W / TY 0021) 31 October - 8 November ------------------------------------------- Bebinca: contributed by Macau, is the name of a Macanese milk pudding served in the Portuguese restaurants of Macau The STWO issued by JTWC at 0600 UTC on 28 October mentioned that an area of convection had formed about 330 nm east of Yap. Synoptic data indicated a developing LOW within the monsoon trough. The disturbance migrated to the west but remained poorly organized with multiple circulation centers evident in the monsoon trough. By the 30th the area of convection was located about 270 nm southeast of Yap and was looking healthier. There was an increase in deep convection associated with cross-equatorial flow south of the LLCC and some isolated deep convection was developing near the center; therefore, JTWC upgraded the development potential to Fair. By 2200 UTC the main area of convection was located near Palau and JTWC issued a Formation Alert as the system had continued to show signs of development and was located within an environment favorable for intensification. By 0000 UTC on 31 October convection had become much better organized about the LLCC and JTWC initiated warnings on TD-31W. The center of the depression was located approximately 85 nm northwest of Palau or about 475 nm east of the Philippine island of Mindanao. Also at 31/0000 UTC PAGASA began issuing bulletins on the depression, naming it Seniang. Tropical Depression Seniang was initially moving to the west-northwest at a fairly good clip (around 15-20 kts), but the forward motion gradually slowed. PAGASA upgraded Seniang to a tropical storm at 31/1200 UTC while JTWC maintained the system as a 25-kt depression through 1800 UTC. The center had been partially-exposed but by 1800 UTC a convective band was beginning to wrap into the LLCC. By 0000 UTC on 1 November satellite intensity estimates had reached 35 kts and microwave imagery revealed deep convection organizing over the LLCC, so JTWC upgraded TD-31W to a tropical storm. At the same time JMA upgraded the depression to a tropical storm and named it Bebinca. Bebinca's center was located roughly 230 nm east-northeast of Surigao on the northern tip of Mindanao. At the time it was named Tropical Storm Bebinca was moving north- westward, but the storm's heading changed more to west-northwesterly with time as it came under the steering influence of the subtropical ridge to its north. The cyclone's organization continued to improve and by 1800 UTC the 1-min avg MSW had reached 55 kts with the storm centered about 115 nm east-southeast of Catanduanes Island. (JMA's maximum 10-min avg wind estimate was 50 kts while PAGASA's was slightly higher at 60 kts.) Bebinca exhibited one interesting feature which Mark Lander pointed out: around 01/1200 UTC the storm blew up a large Central Cold Cover (CCC) with cloud top temperatures colder than -80 C and in some limited areas colder than -90 C. At 0000 UTC on the 2nd the storm's center was located about 40 nm east-southeast of Catanduanes Island and moving west-northwestward at 12 kts. PAGASA upgraded Bebinca/Seniang to a 65-kt typhoon at this juncture, but JTWC did not upgrade the storm to typhoon status until 0600 UTC. A SSM/I pass at 01/2137 UTC revealed a developing eye and animated water vapor imagery depicted improved single-channel outflow south of the system. The center of Bebinca/Seniang apparently passed over or just north of Catanduanes around 0300 UTC--at 0600 UTC it was centered about 50 nm northwest of the island or about 45 nm north-northeast of Naga City (where my associate Michael Padua lives). JTWC upgraded Bebinca at 0600 UTC to a typhoon with the MSW estimated at 75 kts. (PAGASA reported the maximum 10-min avg wind at 70 kts while JMA was lower at 55 kts.) Animated visible imagery had depicted rapid intensification during the previous six hours with a well-developed primary spiral convective band developing over the northern semicircle and contracting around the vortex center. By 1200 UTC on 2 November Bebinca/Seniang's center was located about 65 nm northwest of Naga City or 90 nm east of Manila--just off the coast of Luzon. JTWC upped the MSW estimate to 85 kts while JMA upgraded the storm to a 65-kt (10-min avg) typhoon. A recent observation from Daet (which would have been a short distance south of the cyclone's center) indicated sustained 1-min avg winds of 43 kts with a SLP of 994.5 mb. Outflow was impressive in all quadrants and enhanced infrared imagery revealed a small, cloud-filled eye. The observation from Daet in the preceding paragraph was the only synoptic observation given in any JTWC warning as the typhoon was about to make landfall. Michael Padua of Naga City (13.6N, 123.2E) made hourly observations with his instrumentation during the approach and passage of Bebinca/Seniang. The lowest pressure Michael recorded was 994.6 mb at 02/0700 UTC while the highest 1-min avg MSW of 30 kts from the southwest occurred at 02/0900 UTC when the typhoon's center was 46 nm north-northwest of his site. A peak gust of 39 kts was recorded at 0934 UTC. Also, at 0900 UTC, Daet reported a peak gust of 65 kts with an attendant pressure reading of 986.7 mb. At PAGASA's Bicol River Basin Flood Forecasting Center at Camaligan, 235 mm of rain was recorded in the 48 hours ending at 02/0000 UTC. More information can be found at: . The eye of Typhoon Bebinca/Seniang apparently made landfall along the east coast of Luzon shortly before 1800 UTC at a point about 39 nm (72 km) east of Manila at its peak intensity (per JTWC) of 90 kts. The storm moved westward across a narrow part of Luzon island, passing just south of Manila and across Manila Bay, and by 03/0000 UTC was beginning to emerge into the South China Sea at a point about 33 nm (61 km) slightly south of due west of Manila. JMA had by this time downgraded Bebinca to a 55-kt tropical storm, but JTWC still maintained the MSW at 90 kts based on current satellite intensity estimates. Convection had rapidly weakened but some new central convection was redeveloping southwest of the LLCC. By 0600 UTC the cyclone's center was over water about 85 nm west of Manila. Deep convection had weakened significantly during the previous six hours due to interaction with Luzon, especially in the northern semicircle. JMA downgraded Bebinca to a 45-kt tropical storm while PAGASA and JTWC still main- tained the storm as a typhoon. JTWC's 1-min avg MSW estimate was 80 kts, but the remarks in the warning indicated that this was based on satellite intensity estimates ranging from 55 to 90 kts. It seems likely that JMA's lower intensity estimate was probably more on target as JTWC abruptly dropped the MSW to 55 kts on the next warning. (PAGASA kept Bebinca/Seniang at 65-kts until 1800 UTC.) Most of the remaining convection had decoupled from the LLCC and was located to the east along the windward side of the Zambales Mountain range. As Bebinca began to move northwestward and gradually pulled away from the Luzon landmass, convection began to redevelop near the LLCC. The system was under good diffluence with weak to moderate vertical shear and was forecast to intensify for a couple of days until it began to encounter stronger shear to the north. Throughout 4 November and into the 5th, JTWC and JMA held their respective MSW estimates at 55 kts while PAGASA's 10-min avg MSW was 60 kts. The storm had moved out of Manila's AOR by 05/0000 UTC. Bebinca became quasi-stationary around 0000 UTC about 200 nm west-northwest of Lincayen in the Philippines. A 04/2219 UTC microwave image showed what appeared to be a banding eye, but within 30 minutes the convection had weakened and the eye had filled. By 05/0600 UTC Bebinca had begun a slow northward trek west of Luzon with convection still pulsing near the center. Based on Dvorak intensity estimates of 65 kts, JTWC upgraded Bebinca once more to typhoon status at 1200 UTC when it was centered approximately 275 nm southeast of Hong Kong. (JMA concurrently upped their 10-min avg sustained wind estimate to 60 kts, but never reclassified Bebinca as a typhoon.) Outflow over the system was good, but upper-level winds were continually advecting the convection to the northeast. Cloud tops were beginning to warm by 06/0000 UTC but convection was still well-organized around the center. However, twelve hours later animated satellite imagery indicated that the convection was rapidly dissipating while the northeastern quadrant was being sheared to the northeast. JTWC downgraded Bebinca to a 45-kt tropical storm at 1200 UTC on the 6th with the center approximately 190 nm southeast of Hong Kong. Further reduction to minimal tropical storm intensity took place at 1800 UTC, and Bebinca was downgraded to a depression at 0000 UTC on the 7th. The LLCC was fully-exposed with well-defined low-level cumulus cloud lines to the south of the center. The decaying storm had been tracking generally northward into a weakness in the sub- tropical ridge, but a strengthening low-level ridge turned Bebinca westward during its final depression stage. Some occasional minor bursts of convection were noted, but the system continued to wind down. JTWC issued the final warning at 08/0000 UTC, placing the poorly-defined and convection-free LLCC about 80 nm southwest of Hong Kong, just off the southern Chinese coast. Like Xangsane/Reming a week earlier, Typhoon Bebinca/Seniang left a trail of death and destruction across Luzon. The highest death toll noted by the author was 43 with nine persons reported missing. Of the 43 fatalities, 22 died in landslides, 14 drowned, four died when a concrete wall collapsed on them in Calamba, Laguna, and the others died when they were hit by flying objects. Floodwaters inundated portions of the metropolitan Manila area, forcing 630,000 persons to flee their homes. Government offices, schools and financial markets closed, all airline flights from the capital were cancelled, and power blackouts occurred in much of the city. Tropical Storm Rumbia/Toyang (TC-33W / STS 0022) 27 November - 8 December ------------------------------------------------- Rumbia: contributed by Malaysia, is the name of a type of palm tree which yields sago. The tree commonly grows along riverbanks, in swampy areas, or in areas near water. The first "rumblings" of Rumbia can be traced to an area of convection which developed around 25 November very deep in the tropics about 450 nm southeast of Palau. A weak LLCC was present with some convection to the north, and the disturbance was located beneath light diffluent flow. Over the next couple of days the disturbance moved westward and by 27/0600 UTC was located about 80 nm east of Palau. JTWC upgraded the development potential to Fair, but PAGASA had begun issuing bulletins on the system at 0000 UTC, naming it Tropical Depression Toyang, and by 0600 UTC had already upgraded it to a tropical storm. JMA classified the system as a tropical depression at 1800 UTC, and JTWC issued a Formation Alert at 1900 UTC. A recent QuikScat pass had shown a LLCC embedded in the monsoon trough with 10-15 kt winds near the center but stronger winds in the gradient flow along the periphery. JTWC initiated warnings on the system as TD-33W at 0000 UTC on the 28th with the center estimated to be about 400 nm east of Mindanao. The remarks indicated that QuikScat data showed 20-25 kt winds near the center with stronger winds along the northern periphery. The MSW for the first warning was reported as 30 kts. This implies that the system still had significant monsoon depression characteristics. The author has noted that often with these larger systems originating in the monsoon trough PAGASA is ahead of JTWC and JMA in initiating warnings and upgrading to tropical storm status. Perhaps it is because of the great potential for disastrous flooding such systems may pose that PAGASA does not draw such a fine distinction between monsoon and "tropical" depressions/storms. JMA upgraded 33W/Toyang to a tropical storm at 0600 UTC, naming it Rumbia, and JTWC followed suit six hours later. Dvorak intensity estimates had reached 35 kts, although the stronger winds were still located in the gradient flow to the north. At 1800 UTC JTWC abruptly increased the MSW estimate to 50 kts as convection had continued to intensify and organize around the LLCC. Interestingly, the satellite intensity estimates upon which the MSW was based were 35 and 45 kts. Rumbia was centered at this time about 325 nm east-southeast of Surigao on the northern tip of Mindanao. The storm was moving slowly in a general westerly direction, occasionally jogging to the southwest or remaining quasi-stationary. Throughout 29 November Tropical Storm Rumbia/Toyang maintained its intensity of 50 kts (45 kts 10-min avg) in the face of moderate easterly vertical shear which kept the deeper convection sheared to the western half of the storm. JTWC and PAGASA both increased their respective estimated MSWs to 55 kts at 30/0000 UTC as the convection had increased in areal extent. The center of Rumbia/Toyang was then located approximately 130 nm east of the city of Surigao and moving west-northwestward at 11 kts. Multi-spectral imagery around 0600 UTC depicted low-level cumulus cloud lines east of the deep convection; therefore, the LLCC was estimated to be beneath the eastern edge of the convection. Tropical Storm Rumbia/Toyang reached the vicinity of the small island of Siargao (just off northeastern Mindanao) around 1200 UTC on 30 November at its peak estimated intensity of 55 kts. The exact path of the storm as it moved through the southern Philippines is a little uncertain. PAGASA's and JTWC's positions were in fairly good agreement, and using JTWC's synoptic-hour coordinates, the center of Rumbia/Toyang moved from near Siargao northwestward and was located in the Leyte Gulf around 30/1800 UTC. By 0000 UTC on 1 December the center had crossed Leyte and was near San Isidro on extreme north- western Leyte. The cyclone then seemed to cross Masbate and tiny Tablas islands, and by 01/1200 UTC had reached the Tablas Strait just east of Mindoro where it remained quasi-stationary for several hours. However, at 0000 UTC on the 2nd JTWC relocated the storm's center well to the south of the previous warning position--south of Mindoro and west of Panay, so the actual track taken by Rumbia's center may have been to the south of that described above, possibly crossing Panay Island and even the northern portions of the islands of Cebu and Negros. The JTWC warning at 30/1800 UTC noted that the storm displayed a large, asymmetric cloud shield about 360 nm in diameter and that the LLCC was near the eastern edge of the deep convection about 45 nm into the cloud shield. The MSW was still maintained at 55 kts--the remarks noted that one satellite intensity estimate of 77 kts had been received. Rumbia/Toyang gradually weakened as it moved through the Philippine archipelago. It is interesting to note that PAGASA had downgraded the storm to a 30-kt depression by 01/0000 UTC while JTWC's and JMA's MSW estimates were still 50 kts and 40 kts (10-min avg), respectively. JTWC had reduced the system to a minimal tropical storm by 1800 UTC, noting that the remaining deep convection was moving off the coast of Mindoro into the South China Sea. The next JTWC warning effected the above-mentioned relocation and also downgraded Rumbia to a tropical depression. The LLCC was very weak and both visible and microwave imagery revealed multiple circulation centers. The weakening depression continued to move westward into the South China Sea. Its diffuseness and difficulty in tracking is evidenced by the disparity between some of JTWC's and PAGASA's coordinates: the PAGASA position for 0600 UTC was over 100 nm to the west-northwest of JTWC's locaiton, and the difference was over 150 nm for the next two warnings. The 02/1800 UTC bulletin was PAGASA's final one on Toyang. JTWC continued to issue warnings through 0000 UTC on 4 December as Rumbia sailed rather quickly westward across the South China Sea. The 03/1800 UTC warning had placed the depression's center about 275 nm east-southeast of Cam Rahn Bay, Vietnam, but the (temporarily) final warning at 04/0000 UTC relocated the center to a point approximately 60 nm south-southeast of the previous position--roughly 195 nm west- northwest of the southwestern tip of Palawan Island. Convection near the system was sheared 90 nm to the northwest of the LLCC and the strongest convection was being caused by convergence in the northeast monsoon. The depression was forecast to track southwestward and dissipate over water due to increasing cold air entrainment and increasing vertical shear. The remnants of Rumbia continued to drift westward across the South China Sea, and the STWO issued at 05/0600 UTC rated the potential for redevelopment as Poor. However, the disturbance suddenly re- intensified and JTWC resumed warnings at 05/1200 UTC, directly upgrading the system to Tropical Storm Rumbia, based on satellite intensity estimates of 25 and 35 kts. A SSM/I pass depicted deep convection confined to the western semicircle of the system. Rumbia was centered about 450 nm southeast of Da Nang, Vietnam, or roughly halfway between the Vietnamese coast and northern Borneo. This modest re-intensification of Rumbia likely happened because the disturbance had made its way under an upper-level ridge axis. The cyclone was embedded in a monsoon trough extending eastward from a broad, LLCC over the southern Bay of Bengal. The rejuvenated cyclone tracked slowly west-northwestward and north- westward toward southeastern Vietnam. The center remained partially- exposed with convection sheared to the west of the LLCC. By 1800 UTC on 6 December the center had become fully-exposed with convection sheared 80 nm to the west, so JTWC downgraded Rumbia once more to a tropical depression. The center was located approximately 200 nm east-southeast of Ho Chi Minh City, Vietnam, and was tracking slightly south of due west. By 07/0000 UTC all satellite intensity estimates had fallen below 35 kts and the system continued to slowly weaken as it drifted off the Vietnamese coast. No convection remained near the LLCC after around 1200 UTC and JTWC issued the final warning at 1800 UTC with the weak center near the extreme southern tip of Vietnam. Press reports indicated that 12 persons lost their lives in the Philippines due to Rumbia/Toyang with seven people missing. One report mentioned winds of 74 kts--the source of this report was not given. If the report is valid, the 74 kts likely represents peak gusts. There is no indication that Rumbia reached typhoon intensity, but gusts of 74 kts could reasonably be expected with a 55-kt MSW. Nine towns were flooded in northern Mindanao, and two days after the storm, more than 4100 individuals remained in temporary shelters while more than 1700 homes and several bridges were damaged or destroyed by the flooding and landslides. After writing the bulk of this report, I discovered in my files some e-mail from Mark Lander I'd saved which is interesting. Mark reported that, like Bebinca a few weeks earlier, Rumbia had blown a Central Cold Cover (CCC) with extremely cold cloud tops. For a period of several hours on 28 November (based on replacement tables on METSAT processing equipment) the coldest pixels in the image yielded temperatures of -97.2 C. At 1100 UTC two pixels yielded a temperature of -100.9 C. This is very close to the record of -102 C reported by Ebert and Holland in an analysis of Tropical Cyclone Hilda near Australia in 1990. According to Mark, some typical characteristics of CCCs, at least in the NWP basin, are: (1) they usually begin to form at local sunset, (2) they reach their greatest size and coldest temperatures near local midnight, and (3) they usually occur in weaker cyclones in the 45-65 kt intensity range. NOTE: I e-mailed Mike Padua and asked him if PAGASA makes any distinction between monsoon depressions and tropical depressions. Mike checked with some contacts he has in PAGASA and was told that they do not use the term "monsoon depression" in any warnings or bulletins. Some such systems are referred to as "active low-pressure areas". *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for November: 1 tropical cyclone of hurricane intensity NOTE: The tracking and intensity information for North Indian Ocean Basin tropical cyclones is based primarily upon operational warnings from the Joint Typhoon Warning Center of the U. S. Air Force and Navy (JTWC) 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 WMO's RSMC for the basin. The MSW are based on a 1-min 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 region, both 10-min and 3-min average winds are employed, but IMD makes no attempt to modify the Dvorak scale for estimating tropical cyclone intensity; hence, a 1-min avg MSW is implied. In the North Indian basin JTWC usually does not initiate warnings until a system is well-organized and likely to attain tropical storm status within 48 hours. North Indian Ocean Tropical Activity for November ------------------------------------------------- The Bay of Bengal produced its third tropical cyclone of the fall transition season late in November. The system was also the first to reach hurricane intensity in the NIO basin this year. Tropical Cyclone 03B made landfall in southeastern India as a minimal hurricane where it caused some scattered damage. The system weakened while crossing India but underwent some modest re-intensification in the Arabian Sea, eventually dissipating several hundred miles east of the Somalian coast during the first week of December. Tropical Cyclone (TC-03B) 26 November - 6 December -------------------------- The beginnings of Tropical Cyclone 03B can be traced to a LLCC which developed on 25 November approximately 200 nm west of Phuket, Thailand. A 25/1443 UTC SSM/I pass depicted a fully-exposed LLCC with deep convection sheared west of the center. The disturbance moved westward across the Bay of Bengal with convection gradually improving in organization and increasing in areal extent. JTWC issued a Formation Alert at 26/0700 UTC with the center of the system estimated to be about 700 nm east-southeast of Madras, India. Outflow was improving as the depression moved toward the subtropical ridge axis extending over the Bay. The maximum winds were estimated at 25-30 kts, so in the NWP basin the disturbance would likely have been treated as a tropical depression. (Another tropical disturbance was present at the same time in the Arabian Sea and had been given a Fair development potential, but this system failed to develop further.) JTWC initiated warnings on TC-03B at 1200 UTC on 26 November with an initial warning intensity of 35 kts. Deep convection had weakened some during the previous six hours but the system remained well- organized with deep convection located over the LLCC. The cyclone was located about 540 nm east of Sri Lanka and was tracking west- northwestward at 9 kts. Over the next couple of days the system continued to march to the west-northwest and gradually strengthened. By 1200 UTC on the 27th the MSW had increased to 45 kts, and a 27/1126 UTC SSM/I pass depicted a primary convective band feature wrapping in toward the center from the southwest. Microwave imagery around 28/0000 UTC depicted a well-defined eye feature and the MSW estimate was increased to 55 kts in the 28/0000 UTC JTWC warning. The eye feature persisted and at 1200 UTC the MSW was increased to 65 kts, making TC-03B the first cyclone to reach hurricane intensity in the NIO basin this year. The storm was centered approximately 100 nm southeast of Madras and had turned to a westward course. University of Wisconsin CIMSS charts indicated moderate vertical shear continuing over the system. The shear likely was one factor which prevented the cyclone from intensifying any further beyond minimal hurricane force. The storm continued moving due westward and maintained its 65-kt MSW until landfall in India at 1000 UTC on 29 November near Cuddalore, about 30 km south of Pondicherry. The cyclone weakened quickly over land; by 30/1200 UTC the majority of the convection had moved offshore into the Arabian Sea and the LLCC was difficult to locate. The weakening depression continued west- ward and had moved into the Arabian Sea by 0600 UTC on 1 December. A few diurnal bursts of convection had been noted north of the LLCC, but JTWC anticipated that the system would continue to dissipate and issued the final warning at 0600 UTC. The STWO issued at 1800 UTC on 2 December indicated that the remnants of TC-03B were still weak but that outflow was good and the system had a fair chance of redeveloping. By 0600 UTC on the 3rd the disturbance had undergone some re-intensification with convection increasing in all quadrants. JTWC re-initiated warnings on TC-03B, placing the center about 600 nm southwest of Bombay, India, and moving westward quickly at 17 kts. The MSW was set at 35 kts, based on Dvorak intensity estimates of 30 and 45 kts. The system was well- organized with good outflow aloft. However, the intensification trend was short-lived--at 1800 UTC the MSW was decreased to 30 kts. The LLCC remained well-defined but convection had weakened. The cyclone was tracking west-southwestward across the Arabian Sea and was still under a favorable upper-level environment, so some modest strengthening was forecast for the next 12 hours or so before dry air and increasing vertical shear were expected to begin weakening the system. However, the cyclone never regained tropical storm intensity and continued to weaken as it sailed west-southwestward across the Arabian Sea. A SSM/I pass at 04/1342 UTC depicted only isolated convection near the LLCC. Another SSM/I pass about 12 hours later revealed a fully-exposed LLCC with no deep convection. JTWC issued the final warning (for the second time) on the system at 0600 UTC on the 5th with the weak center located about 400 nm east-southeast of the "Horn" of Somalia. The residual LOW continued to drift westward toward the Somalian coast for another couple of days but showed no signs of redevelopment. Near the port town of Cuddalore, where the cyclone made landfall, all roads leading to the town were rendered impassable. Many trees were uprooted and numerous homes lost their roofs. Many thousands of persons were evacuated from low-lying areas in the Indian states of Tamil Nadu and Andhra Pradesh. Six deaths, mainly drownings, were reported in association with the storm, and Indian authorities reported that 43 fishermen were missing at sea. Heavy rains inundated thousands of acres of rice paddies in the Sirkali and Papanasam areas. Some of the highest storm-total rainfall amounts reported were: Colerron - 235 mm, Sirkali - 201 mm, Manalmedu - 168 mm, and Papanasam - 120 mm. *********************************************************************** SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E Activity for November: 1 tropical depression The primary sources of information upon which the narrative is based are the warnings issued by the TCWC on La Reunion Island, associated with Meteo France, which is the RSMC for the Southwest Indian Ocean basin. However, cyclones in this region are named by the sub-regional centres on Mauritius and Madagascar with longitude 55E as the dividing line between their respective areas. La Reunion only advises these centres regarding the intensity of tropical systems. References to sustained winds should be understood as implying a 10-min averaging period unless otherwise stated. In the accompanying tracks file some position comparisons have been made with JTWC's positions, and warnings from JTWC were used as a source of 1-min avg MSW estimates. Southwest Indian Ocean Tropical Activity for November ----------------------------------------------------- An increase in convective activity was noted across the South Indian Ocean in November, perhaps due to an active phase of the Madden-Julian Oscillation. An area of convection had developed by the 9th several hundred miles east-southeast of Diego Garcia. A LLCC developed and JTWC issued a Formation Alert on the system on 11 November and the first warning on TC-02S at 12/0000 UTC. La Reunion also initiated bulletins on the system at 0600 UTC, numbering it Tropical Disturbance 02 for the SWI basin. The system, although weak, was tenacious, remaining on the charts in one form or another until the 20th. The first JTWC warning located the center about 450 nm east-southeast of Diego Garcia. Over the next several days the disturbance drifted somewhat erratically eastward, remaining quasi-stationary for several hours at times. Eventually the system began to move more to the south or south-southwest--the final bulletin from La Reunion at 18/1800 UTC placed the center about 875 nm east-southeast of Diego Garcia. JTWC issued one warning (12/1200 UTC) estimating the MSW (1-min avg) at 35 kts, and the concurrent La Reunion warning indicated gales were occurring in the southwestern quadrant; however, the next JTWC warning at 13/0000 UTC indicated that the system was rapidly weakening and that no more warnings would be issued unless re-intensification occurred. La Reunion treated the disturbance as a tropical depression from 12/1200 UTC through 13/1200 UTC with maximum 10-min avg winds near the center estimated at 30 kts, but it was downgraded back to a tropical disturbance at 1800 UTC and bulletins discontinued. Bulletins were re-instated 24 hours later when the system appeared to be getting better organized once more, and the disturbance was re-upgraded to a tropical depression at 15/0000 UTC for a 12-hour period. However, at 1200 UTC the system was downgraded once more and was carried as just a tropical disturbance for three more days. JTWC issued several Formation Alerts on the system between the 15th and 19th but never issued any more warnings. (Note: A track was provided for this system in the November cyclone tracks file.) *********************************************************************** NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E Activity for November: 1 tropical LOW The primary sources of information for Australian Region tropical cyclones are the warnings and bulletins issued by the three TCWCs at Perth, Darwin, and Brisbane. Information gleaned from JTWC's warnings is used as a supplement for times when it was impossible to obtain Australian bulletins and for comparison purposes. References to sustained winds should be understood as being based on a 10-min averaging period unless otherwise noted. Northwest Australia/Southeast Indian Ocean Tropical Activity for November ------------------------------------------ During late November the monsoon trough was becoming established to the north and west of Australia. The western region was more active, and for some days there were several weak monsoonal LOWs in the Indian Ocean section of the trough. One of these became sufficiently active for the Perth TCWC to issue Tropical Cyclone Advices for Christmas Island. At 0700 UTC on 28 November the tropical LOW was located about 60 nm east-southeast of Christmas Island. Over the next couple of days the system drifted generally in an eastward direction. By 0400 UTC on the 29th the LOW was about 250 nm east of the island and the final advice was issued. The LOW continued to drift eastward and by 0400 UTC on 30 November was located about 300 nm east of Christmas Island. There were indications that the system might be about to strengthen into a cyclone so a High Seas Gale Warning was issued. However, by 1000 UTC the LOW appeared to be weakening and the gale warning was cancelled. (Note: A track was provided for this system in the November cyclone tracks file.) A special thanks to Carl Smith, who lives on the Gold Coast of Queensland, for sending me a report on this tropical LOW from which some of the above material was taken. *********************************************************************** NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E Activity for November: No tropical cyclones *********************************************************************** SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E Activity for November: No tropical cyclones *********************************************************************** EXTRA FEATURE In order to shorten the amount of typing in preparing the narrative material, I have been in the habit of freely using abbreviations and acronyms. I have tried to define most of these with the first usage in a given summary, but I may have missed one now and then. Most of these are probably understood by a majority of readers but perhaps a few aren't clear to some. To remedy this I developed a Glossary of Abbreviations and Acronyms which I first included in the July, 1998 summary. I don't normally include the Glossary in most months in order to help keep them from being too long. If anyone would like to receive a copy of the Glossary, please e-mail me and I'll be happy to send them a copy. *********************************************************************** AUTHOR'S NOTE: This summary should be considered a very preliminary overview of the tropical cyclones that occur in each month. The cyclone tracks (provided separately) will generally be based upon operational warnings issued by the various tropical cyclone warning centers. The information contained therein may differ somewhat from the tracking and intensity information obtained from a "best-track" file which is based on a detailed post-seasonal analysis of all available data. Information on where to find official "best-track" files from the various warning centers will be passed along from time to time. The track files are not being sent via e-mail. They can be retrieved in the following manner: (a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206] (b) Login as: anonymous (c) For a password use your e-mail address (d) Go to "data" subdirectory (Type: cd data) (e) Set file type to ASCII (Type: ascii) (f) Transfer file (Type: get remote_file_name local_file_name ) (The files will be named with an obvious nomenclature--using November as an example: nov00.tracks) (g) To exit FTP, type: quit Both the summaries and the track files are standard text files created in DOS editor. Download to disk and use a viewer such as Notepad or DOS editor to view the files. The first summary in this series covered the month of October, 1997. If anyone wishes to retrieve any of the previous summaries, they may be downloaded from the aforementioned FTP site at HRD. The summary files are catalogued with the nomenclature: nov00.sum, for example. Back issues can also be obtained from the following websites (courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael Pitt, and Rich Henning): OR Another website where much information about tropical cyclones may be found is the website for the UK Meteorological Office. Their site contains a lot of statistical information about tropical cyclones globally on a monthly basis. The URL is: TROPICAL CYCLONE REPORTS AVAILABLE I have discovered that JTWC now has available on its website the complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999 season for the Southern Hemisphere). Also, ATCRs for earlier years are available also. The URL is: Also, TPC/NHC has available on its webpage nice "technicolor" tracking charts for the 2000 Atlantic and Eastern North Pacific tropical cyclones; also, official storm reports for all the 2000 Atlantic and Eastern North Pacific cyclones are now available. The URL is: Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays) *********************************************************************** *********************************************************************** 02.26.01 / Typhoon2000.com