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Ketsana was the eighth tropical cyclone that necessitated the issuance of a tropical cyclone warning signal in Hong Kong in 2009.
Ketsana formed as a tropical depression over the western North Pacific about 810 km east of Manila during the morning of 25 September and moved westwards. It intensified into a tropical storm on the morning of 26 September and moved across Luzon, entering the central part of the South China Sea that evening. While crossing the South China Sea, it slowed down slightly and intensified into a severe tropical storm on the morning of 27 September with a rather extensive circulation. Ketsana intensified further into a typhoon about 740 km south-southwest of Hong Kong on the morning of 28 September and reached its peak intensity with estimated maximum sustained winds of about 140 km/h near its centre shortly before midnight. Ketsana subsequently made landfall over the central part of Vietnam about 100 km southeast of Danang on the afternoon of 29 September and weakened into a severe tropical storm. It further weakened into a tropical storm and then a tropical depression on 30 September, dissipating near the border between Laos and Thailand that night. According to press reports, heavy rain associated with Ketsana caused severe flooding in the Philippines where at least 293 people were killed and 370,000 people were made homeless. The economic losses were estimated to be about 2.34 billion peso (around HK$0.38 billion). The outer rainbands of Ketsana brought strong winds and heavy rain to Haikou with many trees fallen. At least 132 people were killed and 135 people missing in Vietnam, Laos and Cambodia during the passage of Ketsana.
In Hong Kong, the Standby Signal No. 1 was issued at 10:15 p.m. on 27 September when Ketsana was about 730 km to our south. Under the combined effect of Ketsana and the northeast monsoon, winds in Hong Kong were moderate to fresh northeasterlies, occasionally strong offshore and on high ground, with rough seas and swell over Hong Kong waters. Ketsana was closest to Hong Kong at about 2 a.m. on 28 October when it passed about 720 km to the south. At the Hong Kong Observatory Headquarters, a lowest instantaneous mean sea-level pressure of 1003.0 hPa was recorded shortly afterwards between 4:33 and 4:45 a.m. Ketsana gradually moved away from Hong Kong during the day. All signals were cancelled at 7:15 p.m. when Ketsana was about 750 km to our south-southwest.
The weather in Hong Kong was mainly cloudy with sunny intervals during the day on 27 September. Under the combined influence of the outer rainbands of Ketsana and the northeast monsoon, it was cloudy with rain on 28 September and the rain was heavy at times in the afternoon. More than 50 millimetres of rainfall were recorded in most parts of Hong Kong that day.
No significant damage was reported in Hong Kong during the passage of Ketsana.
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