Tropical Storm Diamu
Posting Date: 13 August 2010
Location: South China Sea
Peril: Windstorm
UPDATED 11 AUGUST
Tropical Storm Dianmu made landfall over the southern coast of South Korea within the six hours prior to 00:00 UTC on Wednesday, 11 August. According to Korea’s National Emergency Management the storm has resulted in 3 deaths, and torrential rains associated with the system have flooded 100 homes and resulted in flight cancellations.
As of 00:00 UTC on Wednesday, 11 August, the center of Tropical Storm Dianmu was located close to 35.2°N 127.9°E over South Korea approximately 70 miles (110 km) west of Pusan (South Korea’s second largest city). At this time the Joint Typhoon Warning Center (JTWC) reported that Dianmu had maximum sustained winds of 46 mph (74 km/hr), classifying the system as a weak strength tropical storm on the Saffir-Simpson Hurricane scale, and a tropical storm on the Japan Meteorological Agency (JMA)’s Tropical Cyclone Intensity scale. The JTWC also reported that tropical storm strength winds were extending outwards from the center of Dianmu up to 50 miles (80 km), mainly to the northeast and southeast of the system.
According to the JTWC, during the previous 6 hours, Dianmu had tracked towards the northeast with a forward speed of 23 mph (37 km/hr). The system is forecast to continue tracking towards the northeast over the next 36 hours during which time it will track over the Sea of Japan, before making a second landfall over northern Japan on Thursday, 12 August. The Japan Meteorological Agency (JMA) is consistent with (the storms current position and) this forecast track.
Over the past 6 hours the system has fragmented due to interaction with South Korea’s southern terrain and exposure to increased vertical wind shear – however the storm’s intensity has not significantly deteriorated. Despite moving within an area of moderate winds shear the JTWC are expecting Dianmu to maintain tropical storm intensity, primarily due to warm sea surface temperatures that the system will be tracking over, and to be the equivalent of a ‘weak’ tropical storm on the Saffir-Simpson Hurricane scale on landfall over northern Honshu, Japan. The system will however, begin extratropical transition during the next 36 hours and is expected to become fully extratropical within 48 hours.
Korea’s Meteorological Agency reported that in northwestern Seoul 120 mm of rainfall, associated with Dianmu, fell within 3 hours on Tuesday, 10 August. As of Wednesday, 11 August the Korean Emergency Management Agency have reported 3 deaths, with 100 homes flooded leaving 200 people stranded. The agency has also reported that 74 flights were cancelled due to heavy rain conditions over South Korea and 91 ferry trips were suspended. According to the Korean Meteorological Agency the storm is expected to bring further heavy rain to the south of the country as to tracks towards the Sea of Japan. The Chinese Meteorological Agency reported heavy rain from Dianmu over the northeast coast of China during Tuesday, 10 August as the system tracked to the east over the East China Sea.
Satellite images show an area of heavy rain, concentrated around the system and a band of heavy rain stretching away from the system to the northeast. The JMA has issued heavy rain warnings for 8 prefectures in northern Honshu, with flood warning for 6 of the prefectures.
In 2006 Typhoon Ewiniar made landfall close to the landfall location of Dianmu, though as a stronger system than Dianmu. Ewiniar is reported to have caused damage (in 2006 of) up to USD1.4 billion. According to AXCO, Korea has high levels of under-insurance and non-insurance (particularly in the domestic sector) which normally limit insured typhoon and flood losses to between 2% and 3% of total economic losses.
RMS will continue to monitor Dianmu’s progress
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