7. Typhoon CHANTHU (Gener/08w) 
>> June 07-15, 2004
Chanthu: contributed by Cambodia, is a type of flower.
Introduction
Typhoon Chanthu was the second significant tropical cyclone in June and the first of the year to adopt a straight-runner track through the Philippines, across the South China Sea en route to Vietnam.
Storm Origins
At 0600 UTC on 5 June an area of convection developed and persisted roughly 360 nm east-southeast of Yap. In response to this development JTWC included this new suspect area in their routine STWO. Animated multi-spectral satellite imagery revealed disorganized deep convection about a weak LLCC. An upper-level analysis indicated weak diffluence and light vertical wind shear and the potential for development was assessed as poor. It was upgraded to fair status at 15/1200 UTC (and the disturbance relocated to a position 290 nm east-southeast of Yap) after convection consolidated over the associated LLCC. However, the disturbance was no longer considered a suspect area at 06/0600 UTC and was dropped from JTWC's STWOs.
The regeneration of the disturbance at 0600 UTC on 7 June prompted JTWC to once again mention the system in their regular STWOs. The potential for development was reassessed as poor. Multi-spectral imagery showed sporadic deep convection occurring over a developing LLCC, which was at this time located 210 nm east of Koror. The development potential was upgraded to fair at 08/0030 UTC, and then raised to good. Since the time of its re-introduction the suspect area had been really motoring westward and was located only 50 nm southeast of Dapa, Philippines, deep within PAGASA's territory at 08/2000 UTC--the time that JTWC issued an TCFA. PAGASA had named the system Tropical Depression Gener at 1200 UTC on the 7th when bulletins were initiated.
Synoptic History
The first JTWC warning was issued at 0000 UTC on 9 June with the system centred 430 nm southeast of Manila and about to make landfall on southern Leyte Island. TC-08W/Gener began its career as a 40-kt tropical storm, but only a 5-kt increase in MSW had occurred by late on the 9th. By the end of the first day of its existence, TS-08W/Gener had completed its journey across the Philippine Archipelago and was about to cross into the South China Sea. JTWC's Prognostic Reasoning message correctly predicted that TS-08W/Gener's intensity would remain constant during its passage across the Philippines, and forecast strengthening as the cyclone moved west through an area of low shear and warmer SSTs in the South China Sea.
Tropical Storm Gener continued its brisk west to west-northwesterly movement along the southwest periphery of the subtropical ridge and its associated tropical easterly flow. At 10/0000 UTC the system was located 190 nm south-southwest of Manila. Gener stuttered a little as the MSW fluctuated between 40-45 kts and the convection became somewhat disorganized for awhile. Although QuikScat imagery showed a well-defined LLCC, enhanced infrared animations showed a partially-exposed centre with cycling convection. During the day Tropical Storm 08W/Gener slowed, and by 1800 UTC was moving west-northwestward at 7 kts.
At 10/1800 Tropical Storm 08W was named Chanthu after JMA finally upgraded the system to tropical storm intensity. Chanthu was centred some 740 nm southeast of Hanoi, Vietnam, and moving west-northwestward at a faster pace again with 45-kt winds. Now that it was moving over the warm waters of the South China Sea, strengthening began. By 11/1800 UTC the MSW had risen to 60 kts, and although poleward outflow was decreasing, animated enhanced infrared imagery indicated that the equatorward exhaust was improving slightly.
Chanthu reached typhoon status at 12/0000 UTC while located approximately 540 nm southeast of Hanoi, Vietnam. Moving westward at 13 to 15 kts, it continued to intensify, reaching a peak of 75 kts at 12/0600 UTC. At this time Chanthu was located 200 nm southeast of Hue, Vietnam. Typhoon Chanthu made landfall near Qui Nhon, Vietnam, at 12/1200 UTC with a MSW of 70 kts. The storm weakened quickly as it moved further inland. Chanthu was downgraded to a 55-kt tropical storm at 12/1800 UTC, and then to a tropical depression the next day at 0600 UTC. The final warning was issued by JTWC at 13/0600 UTC, locating the center 180 nm southwest of Hue, Vietnam. The remnants of Typhoon Chanthu lingered for a few days as it slowly moved northwestward across Southeast Asia. The circulation was barely discernible in satellite imagery by the 15th.
The minimum CP estimated by Japan was 970 mb. JMA, NMCC, the Central Weather Bureau of Taiwan and the Thai Meteorological Department all classified Chanthu as a 65-kt typhoon at its peak. However, the HKO did not upgrade Chanthu to typhoon status, instead estimating the peak intensity at 55 kts (10-min avg).
Meteorological Observations
The following meteorological observations were all sent by Huang Chunliang. A special thanks to Chunliang for sending the information.
(1) Rainfall Observations from Vietnam
Station WMO ID Lat Lon Alt (m) Rain (mm) Time Period (UTC) ---------------------------------------------------------------------------------------------------------------------------- Quy Nhon* 48870 13.8N 109.2E 6 238.9 11/1200 - 12/1200 Hue 48852 16.4N 107.6E 9 124.3 11/1200 - 12/1200
* - very near where Chanthu made landfall.
(2) Rainfall Observations from Thailand
Station WMO ID Lat Lon Alt (m) Rain (mm) Time Period (UTC) ---------------------------------------------------------------------------------------------------------------------------- Khlong Yai 48501 11.8N 102.9E 4 140.2 13/0000 - 14/0000 Ubon R.* 48407 15.3N 104.9E 127 110.5 13/0000 - 14/0000 Bua Chum 48418 15.3N 101.2E 50 106.8 13/0000 - 14/0000 Ubon R.* 48407 15.3N 104.9E 127 115.2 13/0600 - 14/0600 Bua Chum 48418 15.3N 101.2E 50 111.3 13/0600 - 14/0600 Surin 48432 14.9N 103.5E 147 192.6 13/0600 - 14/0600 Tha Tum 48416 15.3N 103.7E 129 112.1 13/0600 - 14/0600 Surin 48432 14.9N 103.5E 147 194.1 13/1200 - 14/1200 Surin 48432 14.9N 103.5E 147 140.6 13/1800 - 14/1800 Phitsanulok 48378 16.8N 100.3E 45 112.2 13/1800 - 14/1800 Phitsanulok 48378 16.8N 100.3E 45 121.1 14/0000 - 15/0000 Ranong 48532 10.0N 98.6E 8 115.8 14/0000 - 15/0000 Kosumphisai -------- 16.2N 103.1E 154 101.1 14/0000 - 15/0000 Phitsanulok 48378 16.8N 100.3E 45 131.5 14/0600 - 15/0600 Ranong 48532 10.0N 98.6E 8 126.5 14/0600 - 15/0600 Nong Khai 48352 17.9N 102.7E 175 121.6 14/0600 - 15/0600 Nong Khai 48352 17.9N 102.7E 175 135.6 14/1200 - 15/1200 Uttaradit 48351 17.6N 100.1E 64 148.5 14/1200 - 15/1200 Ranong 48532 10.0N 98.6E 8 114.2 14/1200 - 15/1200 Nong Khai 48352 17.9N 102.7E 175 134.3 14/1800 - 15/1800 Uttaradit 48351 17.6N 100.1E 64 180.6 14/1800 - 15/1800 Ranong 48532 10.0N 98.6E 8 108.6 14/1800 - 15/1800 Nong Khai 48352 17.9N 102.7E 175 126.9 15/0000 - 16/0000 Uttaradit 48351 17.6N 100.1E 64 193.0 15/0000 - 16/0000 Ranong 48532 10.0N 98.6E 8 114.0 15/0000 - 16/0000 Nan 48331 18.8N 100.8E 201 143.5 15/0000 - 16/0000 Phrae 48330 18.2N 100.2E 162 119.0 15/0000 - 16/0000 Uttaradit 48351 17.6N 100.1E 64 212.7 15/0600 - 16/0600 Ranong 48532 10.0N 98.6E 8 108.0 15/0600 - 16/0600 Nan 48331 18.8N 100.8E 201 216.7 15/0600 - 16/0600 Phrae 48330 18.2N 100.2E 162 197.3 15/0600 - 16/0600 Nan 48331 18.8N 100.8E 201 211.9 15/1200 - 16/1200 Phrae 48330 18.2N 100.2E 162 170.3 15/1200 - 16/1200 Phrae 48330 18.2N 100.2E 162 167.2 15/1800 - 16/1800
* - full name of station is Ubon Ratchathani.
(3) Rainfall Observations from the Philippines
Station WMO ID Lat Lon Alt (m) Rain (mm) Time Period (UTC) ---------------------------------------------------------------------------------------------------------------------------- Roxas 98538 11.6N 122.8E 4 150.2 09/0000 - 10/0000 Iloilo 98637 10.7N 122.6E 8 117.0 09/0000 - 10/0000
Damage and Casualties
According to a news report, Typhoon Chanthu killed seven people and left five persons injured. Five fishermen died when their boat sank off the coast of Binh Dinh province while another was crushed in a separate incident as strong winds forced two boats against the dock. Seven fishermen were reported missing. The typhoon damaged or destroyed more than 180 houses in Binh Dinh province. No damage estimates are available at the time of this writing.
(Report written by Kevin Boyle with significant contributions by Huang Chunliang)
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