25. Tropical Storm TALAS (Zosimo/31w)     Print this Article
>> December 10-21, 2004

Talas: contributed by the Philippines, means 'acuteness' or 'sharpness.'

Storm Origins

At 0130 UTC 9 December a new area of convection developed and persisted approximately 630 nm east-southeast of Kwajalein, a position located deep within the Western North Pacific close to the border with the Central North Pacific. At this time, multi-spectral satellite imagery showed organized deep convection beginning to consolidate over a possible LLCC. An upper-level analysis revealed that the suspect area was within a moderate wind shear environment coupled with some diffluence. Based on this, the development potential for the formation of a significant tropical cyclone was assessed as 'poor'. This was soon raised to 'fair' at 09/0600 UTC, and as the overall organization of the system continued to improve, was followed by a TCFA at 09/2200 UTC. The first warning was issued at 10/0000 UTC, the west-northwest to northwest heading bringing the newly-formed Tropical Depression 31W to within 220 nm east-southeast of Kwajalein.

Synoptic History

Tropical Depression 31W was an immediate threat to Kwajalein, Ailinglaplap and Ujae, and a tropical storm warning was issued for those islands as soon as the first warning was issued by JTWC. Despite exhibiting a partially-exposed LLCC, TD-31W was upgraded to a 35-kt tropical storm at 1200 UTC 10 December while it was passing Kwajalein Atoll with sustained winds reaching tropical storm force. Moving west- ward Tropical Storm 31W's intensity strengthened to 45 kts at 11/0000 UTC and this strength was to be maintained for the next couple of days. In fact, this was to be the peak MSW estimated for this system. The storm was named Talas at 11/0600 UTC when JMA upgraded it to a 35-kt tropical storm. Tracking westward, Talas passed well to the north of Kosrae at 11/0300 UTC, its forward speed increasing to around 23 kts. Although the LLCC was located beneath an almost symmetrical CDO, it became fully-exposed at 12/0000 UTC with a marked decrease in deep convection, which was confined mainly to the western periphery.

At 0000 UTC 12 December Tropical Storm Talas was far to the east- southeast of Guam, being located approximately 665 nm from the island. Its westerly heading, governed by the subtropical ridge to the north, took it a little over 200 nm north of Chuuk at 12/0900 UTC. After what seemed to be a reorganizing phase, the system's centre became partially- exposed again. However, the warning at 13/0000 UTC indicated that the deep convection was becoming better-organized. Nonetheless, Talas lacked a significant outflow pattern. In any case, weakening began at 13/1200 UTC, shortly after Talas had tracked nearly 200 nm to the south of Guam and also well south of Saipan, Tinian, and Rota. The MSW dropped to 35 kts at 13/1800 UTC but picked up a little to 40 kts six hours later. This intensity was maintained through the 14th, a day of little to write about. Talas passed safely north of Yap between 14/1200 UTC and 14/1800 UTC.

At 0000 UTC 15 December Talas slowed somewhat as it continued westward along the southwestern portion of the steering ridge--the storm was located approximately 190 nm northwest of Yap at this time. The intensity had fallen to 35 kts and this was maintained for another six hours before Talas was downgraded to a 30-kt tropical depression at 15/1200 UTC. At this time, the weak tropical system had drifted into PAGASA's AOR and was named Zosimo by that agency. The MSW remained at 30 kts through the 16th as the rather disorganized storm's westward motion persisted, but this changed at 16/1200 UTC as a northwesterly motion commenced. The forward speed slowed further as the steering currents slackened and by 17/0000 UTC Talas was crawling along at 3 kts.

At 0000 UTC 17 December Tropical Depression Talas was located approximately 615 nm east of Manila, Philippines. Initially moving slowly northwestward, the system turned north as it began to nudge into a weakness in the subtropical ridge. At this time, deep convection began to rapidly flare up, resulting in an expanding CDO. The MSW rose to 35 kts at this time and Talas was reinstated as a tropical storm. It soon re-intensified back to its earlier peak intensity of 45 kts at 17/0600 UTC. Continuing slowly northward, Talas' strength started to wane again and fell to 40 kts at 17/1800 UTC. At 18/0000 UTC Tropical Storm Talas was nearly stationary 820 nm southwest of Iwo Jima and weakened a little more to 35 kts at 18/0600 UTC, but held on to minimal tropical storm strength for the rest of the 18th as it began to speed up a little towards the north. The cyclone began to fall apart early on the 19th as the LLCC split from the deep convection. Talas was down- graded to a tropical depression at 19/0600 UTC, and JTWC logged the system for the final time at 19/1200 UTC after 39 warnings--the final position 700 nm west-southwest of Iwo Jima. JMA continued to follow the remnant weak depression eastward along the 20th parallel for a couple more days.

Tropical Storm Talas was an average-sized system with gales extending no further than 110 nm from the centre in any one quadrant.

The peak MSW estimated by JMA, NMCC and CWB was 40-kts (10-min avg) with the lowest estimated CP per JMA warning being 992 mb. During the period that Talas/Zosimo was within PAGASA's AOR the maximum intensity reckoned by that agency was 35 kts. HKO issued no warnings on this system.

A graphic displaying the track of Tropical Storm Talas/Zosimo may be found at the following link:

http://www.tropicalcyclone2005.com/database/tc_besttracks_graphics/PACIFIC_ WEST/2004_31W_BT.gif

Damage and Casualties

There were no damages or casualties reported in association with Tropical Storm Talas.

(Report written by Kevin Boyle)

Source: Gary Padgett's Monthly Tropical Cyclone Summary - December 2004

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