TROPICAL CYCLONES IN 2009

3.3	Tropical Storm Soudelor (0905): 10 - 12 July 2009

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

Tropical Depression Soudelor formed over the South China Sea about 700 km east-southeast of Hong Kong on 10 July and moved west-northwestwards across the northern part of the South China Sea. Soudelor intensified into a tropical storm on the afternoon of 11 July about 240 km south of Hong Kong and reached its peak intensity with estimated maximum winds of 65 km/h near its centre. Soudelor crossed the southern tip of the Leizhou Peninsula on the morning of 12 July and entered Beibu Wan that afternoon. It made landfall over the coast of northern Vietnam about 170 km east of Hanoi and weakened into a tropical depression that evening. Soudelor further weakened into an area of low pressure over northern Vietnam that night.

In Hong Kong, the Standby Signal No. 1 was issued at 4:45 p.m. on 10 July when Soudelor was about 640 km east-southeast of Hong Kong. Local winds were light to moderate westerlies on that day. Winds strengthened on 11 July becoming fresh easterlies that afternoon and up to strong offshore and on high grounds. The Strong Wind Signal No. 3 was issued at 1:25 p.m. that day. Soudelor was closest to Hong Kong at about 2 p.m. that day when it passed about 240 km to the south. Soudelor gradually moved away from Hong Kong and local winds weakened that evening, although there were still occasionally strong winds offshore and on high grounds. The Standby Signal No. 1 was issued at 9:15 p.m. to replace the Strong Wind Signal. All tropical cyclone warning signals were cancelled at 5:20 a.m. on 12 July as Soudelor moved further away from Hong Kong and local winds gradually moderated. At the Hong Kong Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 999.7 hPa was recorded between 5:27 p.m. and 5:55 p.m. on 10 July, when Soudelor was about 620 km to the east-southeast. The maximum winds recorded at various stations and the periods of strong winds during the passage of Soudelor are given in Tables 3.3.1 and 3.3.2 respectively.

The weather in Hong Kong was fine and very hot on 10 July. Under the influence of the outer rainbands of Soudelor, there were occasional squally showers on the next day. With showers easing off, it became mainly fine and hot on 12 July.

In Hong Kong, there were 20 reports of fallen trees during the passage of Soudelor. A 10-metre tall tree fell into a mini-bus terminal in Ngau Chi Wan and fortunately no one was injured. In addition, a large 20-metre tall tree fell into Hong Chong Road in Tsim Sha Tsui East and caused temporary disruption to the traffic.

Information on the daily rainfall and maximum sea level in Hong Kong during the passage of Souledor is given in Tables 3.3.3 and 3.3.4 respectively. Figures 3.3.1 - 3.3.4 show respectively the track of Soudelor, the rainfall distribution for Hong Kong, a satellite imagery of Soudelor and a radar imagery of the outer rainband of Soudelor.

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