TROPICAL CYCLONES IN 2009

3.5	Severe Tropical Storm Goni (0907): 1 - 9 August 2009

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

Goni developed into a tropical depression over the western North Pacific about 720 km east-northeast of Manila on the early hours of 1 August. Tracking west-northwestwards, it crossed northern Luzon that night and entered the South China Sea the next morning. On 3 August, Goni slowed down and its track became erratic but generally moved towards the coast of Guangdong. It intensified into a tropical storm that evening. Goni intensified further into a severe tropical storm and reached its peak intensity with estimated maximum winds of 95 km/h on the late afternoon of 4 August. It made landfall over western Guangdong near Taishan on 5 August and weakened into a tropical storm. Goni then turned to move west or west-southwestwards across the coastal areas of western Guangdong and weakened into a tropical depression on 6 August. On 7 August, Goni moved southwestwards and entered Beibu Wan after crossing the Leizhou Peninsula. It intensified into a tropical storm again on 8 August. Under the influence of Typhoon Morakot over the western North Pacific, Goni turned to move eastwards that night. Goni crossed the northern part of the South China Sea on 9 August. It weakened into a tropical depression in the morning and further into an area of low pressure over the northern part of the South China Sea about 280 km north-northeast of Xisha that afternoon.

According to press reports, Goni triggered landslides and floods in the Philippines, killing at least eight people with four others missing. In Guangdong, two people were killed, a total of 7 cities and 230 towns and 88 800 people were affected, over 1 300 houses collapsed, and 110 000 hectares of farmland were damaged during the passage of Goni. Four fishing vessels were damaged and another vessel missing off the seas near Hainan Island, causing four deaths and 18 people missing.

In Hong Kong, the Standby Signal No. 1 was issued at 3:15 p.m. on 3 August when Goni was about 380 km to the south-southeast. Winds in Hong Kong were moderate to fresh easterlies, occasionally strong offshore and on high ground. Goni moved closer to Hong Kong on 4 August and the Strong Wind Signal No. 3 was issued at 11:15 a.m. Winds strengthened in the afternoon and became generally strong east to southeasterlies, occasionally reaching gale force offshore and on high ground in the evening. At the Hong Kong Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 993.5 hPa was recorded at 5:03 p.m. when Goni was about 130 km to the south-southwest. As Goni strengthened into a severe tropical storm and continued to move closer to Hong Kong, the No. 8 Southeast Gale or Storm Signal was issued at 9:40 p.m. Winds were strongest in the western parts of Hong Kong with gales offshore and on high ground. Goni was closest to Hong Kong between about 8 p.m. and 10 p.m. when it passed about 110 km to the southwest. With Goni moving gradually away from Hong Kong thereafter, local winds became southeasterlies and gradually subsided. The No. 8 Signal was replaced by the Strong Wind Signal No. 3 at 3:40 a.m. on 5 August, followed by the No. 1 Signal at 5:40 a.m. Goni weakened into a tropical storm overland in the afternoon and local winds continued to subside. All tropical cyclone warning signals were cancelled at 4:00 p.m. that day. The maximum winds recorded at various stations and the periods of strong and gale force winds during the passage of Goni are given in Tables 3.5.1 and 3.5.2 respectively.

The weather in Hong Kong was mainly fine and very hot at first on 3 August. Under the influence of the outer rainbands of Goni, there were squally showers and thunderstorms in the afternoon. It was mainly cloudy with squally showers on 4 August and the following day. The Amber Rainstorm Warning was issued at 8:40 p.m. on 5 August.

In Hong Kong, four people were killed and ten people were injured during the passage of Goni, including two men drowned and another injured when a barge capsized off Shek O during the squally thunderstorms, and two people killed when they fell off from the scaffolding they were working at Western District and Kwun Tong respectively. A tree was reported collapsed in Fo Tan Road, Fo Tan, but no one was injured. At the Hong Kong International Airport, 4 flights were cancelled and 17 flights were delayed.

Information on the daily rainfall and maximum sea level in Hong Kong during the passage of Goni is given in Tables 3.5.3 and 3.5.4 respectively. Figures 3.5.1 - 3.5.5 show respectively the track of Goni, the rainfall distribution for Hong Kong, time series of pressure recorded at the Hong Kong Observatory, a satellite and radar imagery of Goni.

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