Kompasu: contributed by Japan, is the compass, a v-shaped device for describing circles or arcs; also the name of the constellation Circinus.
At 0600 UTC on 12 July a weak, cycling area of deep convection was first mentioned in JTWC's STWO and located approximately 500 nm southeast of Okinawa. Animated multi-spectral imagery revealed a possible weak LLCC associated with this system. An upper-level analysis indicated that the disturbance was within an area of weak shear and weak diffluence aloft. The potential for development into a significant tropical cyclone at this point was assessed as poor. This was upgraded to fair status in a re-issued advisory at 12/1930 UTC.
A TCFA was issued at 13/0230 UTC after the system had become better organized. The LLCC was well-developed at this time, but exposed as seen in multi-spectral imagery. A QuikScat pass also showed a well- developed tight vortex with the associated deep convection propagating toward the southern end of an analyzed shear line. The first warning on Tropical Depression 12W was issued at 13/0600 UTC with the centre located 340 nm south-southeast of Okinawa and moving toward the west at 8 kts. Even though this system was exiting an area of high vertical shear, the dynamical aids did not indicate any further development nor did they initialize the storm very well. Pint-sized TD-12W spent the rest of the day tracking westward and accelerating, its forward speed reaching 17 kts by 1800 UTC. The baby tropical cyclone was christened Kompasu following JMA's upgrade to tropical storm intensity at 0000 UTC on the 14th. (PAGASA named the depression Julian at 13/1200 UTC when it entered that agency's AOR.)
JTWC upgraded Kompasu to a tropical storm at 14/0600 UTC when the system was located 180 nm east-southeast of Kaoshiung, Taiwan. Kompasu was still moving briskly toward the west or west-northwest under the influence of a mid-level steering ridge to the northeast. The system continued to exhibit an exposed LLCC due to continued shearing from the east. However, a little strengthening had been occurring and the MSW reached 40 kts at 14/1200 UTC. At this time Kompasu unexpectedly turned west-southwestwards, and this heading ensured that the centre would pass south of Taiwan.
Tropical Storm Kompasu/Julian did not change a great deal during the 15th. A peak intensity of 45 kts had been reached at 14/1800 UTC and this intensity was maintained throughout the following day. The radius of gale-force winds fluctuated in succeeding JTWC warnings, but to give the reader some idea of Kompasu's minute size, 34-kt wind radius never exceeded 50 nm during the maximum intensity. An interesting possibility is that a tropical cyclone, similar to Kompasu, might have escaped unnoticed in the pre-satellite era, especially one which did not make landfall near a population centre like Hong Kong.
At 0000 UTC on 16 July Tropical Storm Kompasu was 85 nm southeast of Hong Kong and moving west-northwestward at 10 kts. The system shifted to a more poleward track and came ashore near Hong Kong at approximately 16/0900 UTC. Kompasu was barely at tropical storm intensity by the time it made landfall. The LLCC proceeded northward, leaving behind the upper-level circulation which was being sheared toward the southwest. The final warning was issued by JTWC at 16/1200 UTC when the centre was continuing northward 40 nm east of Hong Kong. JMA continued to monitor Kompasu as a tropical depression for another six hours before that agency also dissipated the storm.
Waglan Island reported a 10-min sustained MSW of up to 65 kts at 16/0900-1000 UTC. The lowest pressure of 996 mb was recorded between 0500-0600 UTC. (The AWS at Waglan Island sits more than 75 m above MSL.)
The following report was sent by Huang Chunliang.
According to the HKO warnings, Tropical Storm Kompasu (0409) made landfall over Sai Kung at around 16/0700 UTC, when it was about 25 km to the east of Hong Kong Observatory Headquarters, its closest approach, with a MSW of 40 kts and a CP of 990 hPa.
The HKO report on TS Kompasu can be found at the following link:
In Guangdong Province, the coastal region near the mouth of Pearl River reported sustainded winds of Beaufort Force 7 to 8, gusting to Force 9 to 10 during the storm. Pingshan & Longqi, both located in Shenzhen City, recorded peak gusts to 50.5 kts, while the Gulf of Daya (Huizhou City) & Guishan (Zhuhai City) both reported gusts topping 46.7 kts.
News reports indicated that Tropical Storm Kompasu only caused minor damage in Hong Kong. Three people were injured as a result of wind- borne debris. However, many transportation services were either cancelled or ran on reduced schedules, and the stock market, banks and other institutions were closed. Emergency shelters were opened for the homeless.
Following is the MSW comparison table prepared and sent by Huang Chunliang. This was unavailable at the time the July tracks file was sent..
============================================================== == Tropical Storm 12W/KOMPASU/0409/JULIAN (Jul 11-16, 2004) == ============================================================== TCWC Storm ID PEAK MSW (kt) -------------------------------------------------------------- JTWC Tropical Storm 12W (KOMPASU) 45 JMA Typhoon 0409 (KOMPASU) 45 PAGASA Tropical Storm JULIAN 40* NMCC Tropical Storm 0409 (KOMPASU) 45 HKO Tropical Storm KOMPASU (0409) 45 CWB Weak Typhoon 0409 (KOMPASU) 40 Note (*): The MSW is merely the "peak" value based on the limited warnings released only when the storm was travelling within the restricted AOR, so it may have not been the real peak.
(Report written by Kevin Boyle with significant contributions by Huang Chunliang)
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