1. Typhoon ROKE (Auring/02w)                        Print this Article
>> March 13-19, 2005

Talas: contributed by the United States, is a Chamorran male name

Storm Origins

The first typhoon of the year, Roke, formed from a surface trough after only a month's hiatus in tropical cyclone activity in the Western North Pacific. It was also the first straight-runner of the year, moving quite briskly towards the west and across the Philippines before falling to pieces and dissipating in the South China Sea.

The origins of Typhoon Roke can be traced from an area of deep convection that persisted for six hours near 4.5N/152.0E, and this was first mentioned in JTWC's STWO at 2300 UTC 11 March. Animated multi- spectral satellite imagery depicted a weak circulation associated with the thunderstorm activity and QuikScat data identified a weak circulation within a broad surface trough. Upper-level conditions were favourable for further development and a TCFA was issued for the organizing system at 12/2200 UTC, followed by the first warning at 13/0600 UTC which centred Tropical Depression 02W approximately 345 nm south-southeast of Andersen AB, Guam.

Synoptic History

After a quiet 24 hours, Tropical Depression 02W was upgraded to tropical storm status at 0600 UTC 14 March and passed a little under 100 nm north of Yap between 14/1800 UTC and 15/0000 UTC. The system was named Roke by JMA at 15/0000 UTC after that agency upped their MSW to 35 kts. The storm had been only slowly intensifying up to this point, but more significant strengthening ensued during the 15th. Roke became a 65-kt typhoon at 15/1800 UTC, its developing eye centred approximately 700 nm east of Manila, Philippines. (PAGASA named the typhoon Auring at 15/1200 UTC after the tropical cyclone had entered their AOR.)

Continuing westwards under the influence of the mid-level steering ridge, Roke maintained a MSW of 65 kts (its peak intensity) until it made landfall near Tacloban, Philippines, at 16/1800 UTC. Roke crossed the Philippine Archipelago as a strong 55-kt tropical storm and emerged back over water, passing just north of Palawan shortly after 17/1200 UTC. The tropical cyclone continued to weaken as it tracked westward into a pool of cold, dry air located in its path and was downgraded to a tropical depression at 17/1800 UTC, the time of the final warning issued by JTWC. JMA continued to monitor the dying system's progress as a 25-kt tropical depression across the South China Sea almost to the Vietnam coast, ending bulletin transmissions at 19/0600 UTC.

NMCC estimated a peak intensity of 60 kts while the highest MSW estimated by the other Asian warning agencies bar HKO was 55 kts. HKO classified Roke as a 50-kt severe tropical storm. The lowest CP estimated by JMA was 980 mb.

A graphic displaying the track of Typhoon Roke/Auring may be found by clicking this link.

Meteorological Observations

Huang Chunliang sent in one observation from the Philippines. Guiuan, Samar Island (WMO 98558, 11.0N/125.7E) recorded 139.8 mm of rainfall during the 24 hours ending at 17/0000 UTC.

The center of Auring passed about 85 nm south of Naga City on Luzon on the 16th. Michael Padua reported that his weather station recorded a peak wind of 24.5 kts at 16/0650 UTC but with a minimum SLP of 1007.7 mb at 0645 UTC on the 17th. The maximum rainfall rate of 87.1 mm/hr occurred at 16/2327 UTC and the total measured rainfall for the 2-day period was 24 mm.

Michael sent the following links whereby more observations can be accessed:

(1) Passage Data Graph A
(2) Passage Data Graph B
(3) Passage Data & Graph (via Wunderground.com)
(4) T2K Discussion Group (its effects over Visayas)

Damage and Casualties

According to press reports, eight persons were confirmed dead and 11 reported missing after Typhoon Roke scythed its way across the Philippines. Six of the casualties occurred when the commercial vessel MV Esperanza capsized in high winds near Ormoc City Pier. The NDCC indicated that 939 families or 4793 persons were displaced by Roke/Auring, and 1181 houses in Leyte and Eastern Samar were destroyed.

How Strong Was Typhoon Roke?

There were some indications that the midget Typhoon Roke was substantially stronger than 65 kts. Following is an excerpt from an e-mail sent by Dr. Mark Lander:

"I contend that Roke made it to 100 kts at about 0500 UTC March 16. I have appended the Aqua images and the corresponding VIS at that time. The eye was very well-defined, but very small. It only showed up in the 89 (GHz) channel and not the 36 (GHz)--I think because at the lower levels where the 36 (GHz) "sees", the eye diameter was too small--maybe 10 miles or less--then expanding outward to perhaps 15 miles or so at the top where the higher frequency channels could see it. Although in some of the before and after SSMI shots, it was apparent in both the 85 and 37 GHz channels.

"As a midget tropical cyclone, changes in intensity can be very rapid (both ways). By the way, there is a later TRMM pass (16 MAR 1618 UTC) that shows that it still had a nice eye as it made landfall in the central Philippines.

"I'm certain that the peak intensity was substantially higher than 65 kts!"

(Report written by Kevin Boyle with significant contributions by Dr. Mark Lander, Michael V. Padua & Huang Chunliang)

Source: Gary Padgett's Monthly Tropical Cyclone Summary - March 2005

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