TROPICAL CYCLONES IN 2003

Imbudo was the first tropical cyclone that necessitated the issuance of the No. 8 Gale or Storm Signal this year.

Imbudo developed as a tropical depression about 730 km southwest of Guam on 17 July. Tracking mainly towards the west-northwest, it intensified into a tropical storm the same night. Imbudo attained severe tropical storm intensity on the morning of 19 July and further strengthened into a typhoon the next morning. The maximum sustained wind speed near its centre reached 185 km/h on 21 July. Imbudo swept through Luzon on 22 July, killing 22 people and injuring hundreds. More than 14 000 people were evacuated. Power supplies and telecommunication network in some places were temporarily cut off. Over USD 35 millions of crops were ruined by flash floods.

Imbudo entered the South China Sea on the night of 22 July and continued to move west-northwestwards towards the South China coast. On the morning of 24 July, it made landfall near Yangjiang of western Guangdong and weakened into a severe tropical storm that afternoon. Imbudo weakened into a tropical storm over land on the morning of 25 July and then dissipated in Guangxi the same day. In Guangdong and Guangxi, the death toll due to Imbudo reached 20, with three people missing. Near 6 000 houses collapsed and more than 10 millions hectares of crops were damaged. More than 7.4 million people were affected. The estimated economic loss was over 1.9 billion RMB. 16 flights were cancelled and 54 flights were delayed in Guangzhou Baiyun International Airport.

In Hong Kong, the Standby Signal No. 1 was issued at 8.20 p.m. on 22 July when Imbudo was located about 760 km to the southeast of Hong Kong. As Imbudo moved towards the South China coast, local winds began to strengthen on the morning of 23 July. The Strong Wind Signal No. 3 was issued at 1.40 p.m. Imbudo moved closer to Hong Kong that night with gale force east to northeasterly winds blowing offshore and on high ground. The Hong Kong Observatory issued the first No. 8 NORTHEAST Gale or Storm Signal this year at 10.40 p.m. on 23 July. Imbudo was closest to Hong Kong at about 5 a.m. on 24 July when it was about 280 km to the southwest. Locally, winds were strong to gale southeasterlies reaching storm force in Cheung Chau. The No. 8 SOUTHEAST Gale or Storm Signal was issued at 5.15 a.m. on 24 July. During the approach of Imbudo, maximum hourly wind speed of 83 km/h and 101 km/h were recorded at Waglan Island and Cheung Chau respectively. The lowest instantaneous mean sea-level pressure of 997.5 hPa was recorded at the Hong Kong Observatory at 4.33 a.m. and 4.34 a.m. on 24 July.

As Imbudo started to move away from Hong Kong and local winds began to weaken, the No. 8 SOUTHEAST Gale or Storm Signal was replaced by the Strong Wind Signal No. 3 at 8.15 a.m. on 24 July. Following the landfall of Imbudo near Yangjiang, local winds subsided further. All tropical cyclone warnings were cancelled at 12.40 p.m. the same day.

Locally, one man was killed after being blown by high winds into the sea from a 6-metre high working stage. Several cases of falling objects and 83 cases of fallen trees injured 11 people. Another 34 people aboard a jetfoil bound for Macau were injured when the boat travelled through the rough sea near Lantau Island. The Government Flying Services rescued 16 crew members from a mainland container vessel which suffered a loss of power near Daya Bay. At the airport, over 20 flights were cancelled and more than ten flights were delayed. Ferry services to outlying islands and bus services for some routes were also suspended.

Information on maximum wind, daily rainfall and maximum sea level during the passage of Imbudo is given in Tables 3.2.1 - 3.2.3. Figures 3.2.1 and 3.2.2 show the track of Imbudo and the rainfall distribution in Hong Kong respectively. The time series of the wind speed recorded at Waglan Island is given in Figure 3.2.3. Figures 3.2.4 and 3.2.5 are the satellite and radar imagery of Imbudo.

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