From: Gary Padgett To: Michael V. Padua Subject: March 1998 TC Summary Date: Thursday, May 14, 1998 10:43 AM MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY MARCH, 1998 (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.) HIGHLIGHTS --> South Indian Ocean active but storms remain at sea --> Vanuatu suffers damage from two cyclones *********************************************************************** CORRECTIONS and UPDATES to Earlier Summaries I have received some additional information from the South Indian Basin on February cyclones, a correction to an observation reported in the December summary, and some brief damage reports from French Polynesia. (1) Observations from Mauritius during Tropical Cyclone Anacelle Arvind Mungur of London sent some information regarding the effects of Anacelle as it passed about 65 nm east of Mauritius on 11 Feb. The capital, Port Louis, recorded 125 mm of rain that day. Barometric pressure fell to 986.1 mb, but wind gusts did not exceed hurricane force. No details were given about the effects of this cyclone on St. Brandon. (2) Report on an unnamed tropical depression Arvind Mungur also sent the following information (slightly edited): A low-pressure area deluged Mauritius and especially Reunion in late February. From 18-25 Feb Reunion recorded 1700 mm of rain with 572 mm coming in 24 hrs on the 24th! This deluge caused severe flood damage, landslides and powercuts--the worst rain damage in several years. The peak rainfall in Mauritius occurred on 25 Feb (240 mm in 24 hrs). According to news reports the depression passed about 80 nm southeast of Mauritius on the 25th and caused mean winds of 20 kts with gusts reaching 46 kts. The lack of warnings (the system was not classed as a storm) caught the island by surprise, and there were many complaints directed at weather forecasters and reporters for not warning the public effectively--especially since conditions were as bad as during Anacelle when warnings were in effect. Surface observations suggest that this depression peaked at 25-30 kts on 25 Feb before heading southward. NOTE: I am not sure how this system was handled by the responsible warning agencies in the South Indian Ocean. No warnings were issued on this system by JTWC. (3) Connection between TC-21S and TC-23S (Beltane) Julian Heming of the Bracknell (UK) Meteorological Office sent the following: I thought you might be interested to know that the TC warning centre at La Reunion considered TC-21S and TC-23S (Beltane) to be the same system. I discussed this with Frank Wells of JTWC who thought there was probably enough of a gap when the system was not clearly identi- fiable to justify classifying TC-23S as a new TC. However, La Reunion in their advisories continued to track the system back northward again after JTWC had ended TC-21S. It crossed Madagascar a second time and reformed in the Mozambique Channel when JTWC commenced advisories on TC-23S. (4) Tropical Cyclone Pam (SWP in Dec) observation dated incorrectly Mark Kersemakers of the Fiji TCWC at Nadi uncovered an observation from Rarotonga that had the wrong date. Reference the paragraph in the December summary which begins with "Pam passed about 40 nm south- west of Rarotonga at 0600 UTC on 9 Dec." The text subsequently reports that the lowest pressure of 986 mb wasn't recorded until 10/0600 UTC--with a comment that this was rather strange. Mark sent the following explanation: CORRECTION: the 10/0600 UTC should have been 09/0600 UTC. The information sent by me was wrong due to the forecaster who compiled it not allowing for the dateline change--the barograph was in local time. The time was converted but the date was not. This change no longer makes the pressure strange. (5) Damage report from French Polynesia Steve Ready of the New Zealand Meteorological Service has sent a little information regarding the effects of Tropical Cyclones Ursula and Veli in the area of French Polynesia in early February. These cyclones caused damage to three islands in the Tuamotu group: Mataiva, Rangiroa, and Makatea. Mataiva was the worst struck with 39 houses damaged, bridges down, roads washed away; Makatea had 5 houses damaged while the airstrip on Rangiroa was inconvenienced by wash-up of coral and sand. Ursula was the stronger of the two with damage due to pre- cyclone swell rather than winds. Fortunately there was no loss of life. NOTE: A very special thanks to Arvind, Julian, Mark and Steve for passing the above addenda/corrections on to me. *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for March: No tropical cyclones *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for March: No tropical cyclones *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for March: No tropical cyclones *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for March: No tropical cyclones *********************************************************************** SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E Activity for March: 1 tropical cyclone of gale intensity 1 tropical cyclone of storm intensity 1 tropical cyclone of hurricane intensity NOTE: The only sources of information on South Indian cyclones I have available for the time being are the warnings issued by JTWC. All the winds reported in the narrative are 1-min average maximum sustained winds. Tropical Cyclone Donaline (TC-26S) 6-10 March ----------------------------------------------- The Joint Typhoon Warning Center (JTWC) on Guam issued the first warning on a developing depression in the west-central South Indian Ocean at 1200 UTC on 6 Mar, locating the system about 250 nm northeast of Rodrigues Island. (Rodrigues lies about 315 nm slightly north of due east of Mauritius.) The depression had become a tropical storm with 40-kt winds by 07/0000 UTC. Initially Donaline drifted generally in an eastward direction, but by 0000 UTC on 8 Mar was moving to the south. Peak intensity of 55 kts was reached at this time when the cyclone was centered about 400 nm east of Rodrigues. Afterward Donaline began to weaken and accelerate off to the south-southeast. The low-level circulation center had become completely exposed due to shear by 09/1200 UTC. The system had weakened to below gale force 12 hrs later, and the last warning, issued at 1200 UTC on 10 Mar, located the center about 750 nm southeast of Rodrigues. Tropical Cyclone Elsie (TC-27S) 12-17 March --------------------------------------------- JTWC issued the first warning on a rapidly developing tropical system in the central Indian Ocean at 0000 UTC on 12 Mar. The system was located about 850 nm southeast of Diego Garcia. Scatterometer data from a pass at 11/1720 UTC showed a narrow vortex of 35-kt winds around a low-level center with a band of 30-kt winds in the southeast quadrant. Concurrent satellite imagery showed spiral bands forming west and east of the center. Elsie moved generally in a south- southwesterly direction for the next five days, reaching a peak intensity of 90 kts at 1200 UTC on 13 Mar, only 36 hrs after the first warning was issued. The cyclone at this time was centered about 1000 nm east of Rodrigues Island. Elsie weakened just as quickly as it had intensified--by 14/1200 UTC the storm was experiencing moderate shear and winds had decreased to minimal hurricane force. The south-southwesterly motion came to a halt after 0000 UTC on 17 Mar and the weakening system turned to the southeast. The last JTWC warning, issued at 17/1200 UTC, placed the center about 950 nm east-southeast of Rodrigues. The final warning indicated that extratropical transition was expected to be complete within 24 hrs. Tropical Cyclone Fiona (TC-28S) 17-20 March --------------------------------------------- JTWC issued the first warning on Tropical Cyclone 28-S (to be named Fiona by the Mauritius TCWC) at 0000 UTC on 17 Mar. The center of this rapidly developing cyclone was located about 150 nm northwest of Rodrigues. The initial warning estimated the maximum sustained winds at 40 kts, and mentioned that conditions were ripe for continued rapid strengthening: poleward outflow was linked up with mid-latitude westerlies, a small CDO feature was present, and spiral bands indicated good cross equatorial flow in the north and east quadrants. But the anticipated intensification never happened. A passing shortwave trough inhibited further development and winds were decreased to 35 kts in the next warning. During this time Fiona had drifted westward to a position about 215 nm northeast of Mauritius. The weak storm next moved to the southeast for about 24 hrs but then curved back to the west. After the trough had lifted out Fiona gained a little in intensity, but vertical shear never really lessened enough to allow the cyclone to intensify further. Fiona passed about 75 nm east of Mauritius at around 1500 UTC on 19 Mar with 40-kt winds. Continuing on to the south, the system began to slowly weaken once more with the last warning placing the center about 225 nm east-southeast of La Reunion at 20/1200 UTC. Newspaper reports stated that wind gusts up to 38 kts were recorded in the eastern portion of Mauritius as Fiona passed by, but there were no rainfall nor pressure observations mentioned. (Thanks to Arvind Mungur for passing along this bit of information.) *********************************************************************** AUSTRALIAN REGION (AUS) - From Longitude 90E Eastward to Longitude 160E Activity for March: 1 tropical cyclone of storm intensity 1 former tropical cyclone (extratropical or hybrid) NOTE: Some of the material presented on Tropical Cyclone Nathan is taken from the March Darwin Tropical Diagnostic Statement. Thanks to Sam Cleland for sending that report to me. Unless stated other- wise, references to sustained winds imply a 10-min averaging period. Tropical Cyclone Nathan (TC-30P) 21-31 March ---------------------------------------------- Tropical Cyclone Nathan developed from a LOW embedded in the weak monsoon trough soon after Yali had reached tropical cyclone intensity farther east. Although upper-level outflow was favorable, mid-level shear restricted rapid development. Nathan developed rather quickly initially--the first warning, issued at 0000 UTC on 21 Mar, classified the system as a 40-kt tropical cyclone just east of the northern Cape York Peninsula, or about 300 nm north-northwest of Cooktown on the Queensland coast. During its early stages Nathan dropped up to 400 mm of rain on the northern and eastern portions of the peninsula. Being a small system in an environment of weak steering flow, Nathan moved slowly and erratically--generally eastward away from the coast, and then in a southerly direction, coming to within 100 nm of Cooktown at 23/1200 UTC. The Brisbane TCWC consistently reported Nathan's maximum 10-min average winds at 45-50 kts throughout most of its life, but JTWC briefly elevated the storm to minimal hurricane status at 65 kts (1-min avg) from 1200 to 1800 UTC on the 23rd. After approaching the Queensland coast, Nathan came under the steering influence of the broad monsoon flow that had been dragged south by Tropical Cyclone Yali. The cyclone began moving in an east- northeasterly direction at an accelerated pace, becoming more easterly after 25/0000 UTC. By 0000 UTC on 26 Mar Nathan was located about 275 nm southwest of Honiara on Guadalcanal and was becoming sheared. This shearing process was possibly related to the large extratropical (or hybrid) system to the south which had been Yali. Nathan curved to the south on the 27th and Brisbane downgraded the system to a depression and ceased issuing advices. By 27/1200 UTC the cyclone was located about 200 nm north-northeast of the Chesterfield Islands and was showing some signs of re-intensification. A CDO feature had regenerated and spiral bands were wrapping into a well-defined center; therefore, JTWC upped the winds to 45 kts and continued to issue warnings on Nathan. The system then began to move back to the west and slowly weakened as it approached Australia once more. A scatterometer pass on 29 Mar indicated a small area possibly containing 35-kt winds, and a 30/0000 UTC observation from Willis Island reported 30-kt easterly winds. JTWC kept Nathan as a minimal tropical cyclone until 0000 UTC on 31 Mar, when it was downgraded to a weakening depression about 150 nm north-northwest of Cooktown. Tropical Cyclone Yali (TC-29P) 25-27 March -------------------------------------------- Tropical Cyclone Yali, which had spent most of its life in the Fiji area of warning responsibility, moved westward across 160E around 1200 UTC on 25 March into the Australian region for a couple of days before undergoing rapid deepening as an extratropical cyclone and pommelling New Zealand with high winds and seas and heavy rains. Yali was not a true tropical cyclone by the time it entered Australian waters. It had been captured by an upper LOW and was somewhat like the hybrid storm systems which are occasionally seen in North Atlantic subtropical waters and usually referred to as subtropical cyclones. Fiji and Brisbane regarded the system as extratropical while Guam continued to issue tropical cyclone warnings until 27/0000 UTC. For the complete history of Tropical Cyclone Yali, see the section of this summary covering the Southwest Pacific Basin. *********************************************************************** SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E Activity for March: 1 tropical depression 2 tropical cyclones of hurricane intensity NOTE: Thanks to Steve Ready of the New Zealand Meteorological Service at Wellington for passing along some information on Tropical Cyclone Yali. Also, some of the material on Yali is taken from the March Darwin Tropical Diagnostic Statement. Unless stated otherwise, references to sustained winds imply a 10-min averaging period. Tropical Depression 28 February-2 March ----------------------------------------- A tropical depression had formed in the southeastern Solomon Islands on 28 Feb near Santa Cruz Island. At 0000 UTC on 1 Mar the depression was centered about 350 nm east-southeast of Honiara on Guadalcanal. Over the next couple of days the system drifted generally in an easterly to southeasterly direction without significant strengthening. By 02/0600 UTC the last bulletin issued by Nadi located the depression about 250 nm northeast of Port Vila in Vanuatu. Winds in the eastern semi-circle were forecast to possibly reach gale force on 2 Mar but the system did not develop into an organized tropical cyclone. Tropical Cyclone Yali (TC-29P) 18-27 March ------------------------------------------- A well-defined low pressure system was identified in the Southwest Pacific on 18 Mar and drifted to the west between Vanuatu and the Solomon Islands while slowly strengthening. Yali was named by the Nadi TCWC at 1800 UTC on 19 Mar when located about 350 nm due north- west of Port Vila, Vanuatu. The first JTWC warning at 18/1200 UTC, centering the LOW about 350 nm north-northwest of Port Vila, classified the system as a minimal tropical cyclone with 35-kt (1-min) winds. Up to this time Yali had been tracking to the southwest, but by 0600 UTC on 20 Mar the cyclone had begun moving on a southeasterly track due to a strengthening of the northwest monsoon flow to the north of the storm. For the next two-and-a-half days Yali moved on a southeastward course, passing west of the main islands of Vanuatu but finally coming close enough to brush the southernmost islands of Tanna and Aneityum. Yali reached hurricane force at 21/1200 UTC when located about 100 nm west-northwest of Port Vila. The center of the hurricane passed about 60 nm west of Port Vila around 0000 UTC on 22 Mar but no strong winds were reported. Peak intensity of 70 kts (10-min avg) with an estimated central pressure of 965 mb was attained at 22/0600 UTC when Yali was centered about 80 nm south of Port Vila, which reported winds of only 11 kts and a pressure of 992 mb. (It is possible that the low wind reading was due to poor exposure of the instrument.) By 1800 UTC on 22 Mar Tropical Cyclone Yali had reached its eastern- most position about 200 nm southeast of Port Vila. The upper ridge to its north had intensified, increasing shear and restricting convection; consequently Yali began to weaken, dropping below hurricane force. At the same time a mid-level subtropical ridge to the south began to impact its motion with easterly flow forcing a westward component to its track. As Yali moved to the southwest and slowly weakened, the wind field was becoming quite asymmetric. At 23/0000 UTC gales were reported 90 nm to the north but 150 nm to the south. Matthew Island, about 130 nm southeast of the center, reported east winds of 40 kts. The main convection at this time was about 140 nm south of the center. At 1200 UTC on 23 Mar Yali was located about 125 nm east of Noumea, New Caledonia with 45-kt winds. The weakening cyclone passed just south of New Caledonia late on 23 Mar (UTC) as it continued on its southwesterly track. By 25/0000 UTC an upper LOW had captured the cyclone with cold air cumulus working around the west and north sides of the circulation. Yali had become a hybrid-type cyclone of the type often referred to in the North Atlantic as a subtropical cyclone. Fiji downgraded the system to an extratropical system and discontinued advisories. JTWC continued to track Yali southwestward in the general direction of Australia. The semi-tropical Yali slowed and moved more on a westerly track as it approached and crossed 160E on 24 and 25 Mar. By 26/1200 UTC the center of the large cyclone was about 300 nm east-northeast of Brisbane. Some convection was noted re-developing about 90 nm south of the elongated center with gales likely affecting the Australian coast on 26 and 27 Mar. By 0000 UTC on 27 Mar the cyclone was moving more quickly to the south with the final JTWC warning placing the center about 325 nm east-southeast of Brisbane. Yali underwent a transformation over the Tasman Sea. It came under the influence of a double jet structure (equatorward entrance of one, polar exit of another) and strong cyclonic vorticity advection at 500 mb. The system deepened and moved rapidly towards the southern end of New Zealand's South Island. Its central pressure lay between 970-975 mb as it crossed the coast on 29 Mar. Wind damage was reported over a wide area--roofs lifted, flying debris, trees toppled, power lines down. Heavy rain was experienced in the western and southern portions of the South Island over a 6-12 hr period, but fortunately the fast-moving nature of the storm prevented any significant rain flooding. The passage of Yali coincided with exceptionally high tides, causing sea flooding near Nelson and Westport. One youth was washed into the sea near New Plymouth (central North Island) and drowned. After passing New Zealand the remains of Yali eventually became absorbed into the circumpolar trough between 65S and 75S. Some of the southernmost islands of Vanuatu: Aniwa, the northern and western portions of Tanna, and the southern and western sides of Erromango, suffered rather severe damage from Yali. About 60-70% of the crops and 30% of the houses were badly damaged by winds with some damage to roads on Tanna. Both Tanna and Aniwa had suffered from a drought before the cyclone came along so stocks of food were quite low. Only minor damage was reported elsewhere in Vanuatu. Tropical Cyclone Zuman (TC-31P) 29 Mar--> ------------------------------------------- The tropical depression that was to develop into Tropical Cyclone Zuman was first noted about 300 nm northeast of Port Vila in Vanuatu at 2100 UTC on 29 Mar. The system had become a tropical cyclone and was named at 1200 UTC the next day when centered about 250 nm north- northeast of Vila. Zuman moved westward until around 0600 UTC on 31 March as it steadily strengthened, then took a turn to the south- west and intensified quite rapidly. The cyclone had struck the island of Espiritu Santo by 0000 UTC on 1 Apr with sustained 10-min winds estimated at 80 kts. Early reports indicate that the island incurred rather heavy damage from the cyclone. Next month's summary will contain a full report on Tropical Cyclone Zuman. *********************************************************************** 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) The files will be named with an obvious nomenclature--using March as an example: mar98.tracks 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 March summary is the sixth cyclone summary in this series; the first one covering the month of October, 1997. If anyone did not receive any of the previous summaries, they may be downloaded from the aforementioned FTP site at HRD. The summary files are catalogued with the nomenclature: oct97.sum, for example. Back issues can also be obtained from the following website (courtesy of Michael Bath): The preliminary storm reports for all the 1997 Atlantic and Eastern North Pacific tropical cyclones are available on the Tropical Prediction Center's website: . These reports include the analyzed best-track for each cyclone. The staff of JTWC is also working on an on-line version of their Annual Tropical Cyclone Report for 1997. It is still under construction, but the best-track files are already available for 1997 Northwestern Pacific and North Indian Ocean cyclones. The URL is: Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 *********************************************************************** ***********************************************************************