TROPICAL CYCLONES IN 2009

3.2	Tropical Storm Nangka (0904): 23 - 27 June 2009

Nangka was the second tropical cyclone that necessitated the issuance of a tropical cyclone warning signal in Hong Kong in 2009.

Tropical Depression Nangka formed over the western North Pacific about 860 km east-southeast of Manila on 23 June. Moving west-northwestwards, it intensified into a tropical storm that afternoon. Nangka crossed the central Philippines the next day and entered the South China Sea in the evening. It turned to move generally northwestwards across the South China Sea on 25 June and reached its peak intensity in the same morning with estimated maximum winds of 85 km/h near its centre, but weakened slightly in the afternoon and at night. Nangka moved generally north-northwestwards on 26 June approaching the coast of eastern Guangdong and weakened into a tropical depression that evening. It made landfall over the coastal areas of Daya Bay in the small hours of 27 June. Nangka moved further inland and weakened into an area of low pressure that morning. According to press reports, Nangka triggered landslides and overturned fishing boats in the Philippines where at least eight people were killed and 11 others missing. A passenger boat was also overturned off Mactan Island in the central Philippines but all 13 people on board were rescued.

Tropical Storm Nangka weakened slightly after it entered the South China Sea but continued to move closer to the south China coast, posing a threat to Hong Kong. The Standby Signal No. 1 was issued at 7:15 a.m. on 26 June when Nangka was about 410 km south-southeast of Hong Kong. As Nangka was expected to continue to move closer to Hong Kong, the Strong Wind Signal No. 3 was issued at 3:40 p.m. that day when Nangka was about 190 km to the southeast. Local winds were moderate to fresh easterlies at first that day and strengthened in the afternoon to become occasionally strong offshore and on high grounds. The winds gradually turned to the northwest at night. Nangka was closest to Hong Kong between about 11 p.m. and 1 a.m. the next day when it passed about 60 km to the northeast of the Hong Kong Observatory. During the period, the Hong Kong Observatory Headquarters recorded the lowest instantaneous mean sea-level pressure of 1000.1 hPa at 11:03 p.m. on 26 June. Local winds subsided as Nangka made landfall and weakened over Guangdong, and all tropical cyclone warning signals were cancelled at 5:25 a.m. on 27 June. The maximum winds recorded at various stations during the passage of Nangka are given in Table 3.2.1.

The weather in Hong Kong was cloudy at first with squally showers developing during the day on 26 June. There was occasional heavy rain and a few squally thunderstorms on 27 June.

Information on the daily rainfall and maximum sea level in Hong Kong during the passage of Nangka is given in Tables 3.2.2 and 3.2.3 respectively. Figures 3.2.1 - 3.2.4 show respectively the track of Nangka, the rainfall distribution for Hong Kong, a satellite and radar imagery of Nangka.

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