TROPICAL CYCLONES IN 2003

Dujuan was the first tropical cyclone that necessitated the issuance of the Increasing Gale or Storm Signal No. 9 since 1999.

When Dujuan developed as a tropical depression over the Pacific on the early morning of 29 August, it was slow-moving. It intensified into a tropical storm on the early morning of 30 August and strengthened further into a severe tropical storm the same day. Accelerating towards the west-northwest on 31 August, Dujuan attained typhoon strength and moved towards the seas near southern Taiwan. After crossing the seas south of Taiwan on 1 September, Dujuan headed westwards towards the South China coast. The maximum sustained wind speed near its centre reached 175 km/h. In southern Taiwan, three people were killed, one found missing and eight injured during the approach of Dujuan. Electricity supply to about 590 000 families were interrupted. All transportation services in southern Taiwan were temporarily suspended and the agricultural loss reached NT$200 millions.

Dujuan entered the South China Sea on the early morning of 2 September and moved westwards towards the coast of Guangdong. While crossing the northern part of the South China Sea, it exhibited a double eye wall structure (Figure 3.4.5). The diameter of the inner and outer eyes were about 20 km and 100 km respectively. On the night of 2 September, Dujuan skirted the north of Hong Kong and hit Shenzhen. It then continued to move westwards crossing Guangdong. Dujuan weakened rapidly into a tropical storm on the morning of 3 September and became an area of low pressure over Guangxi afterward. 40 people were killed and about 1 000 were injured as Dujuan rampaged across Guangdong. Power supplies in 90 % of the area in Shenzhen were interrupted. The direct economic loss caused by Dujuan was some 2.3 billions RMB.

In Hong Kong, the Standby Signal No. 1 was issued at 10.15 p.m. on 1 September when Dujuan was located about 750 km to the east of Hong Kong. With Dujuan moving towards the South China coast, the Strong Wind Signal No. 3 was issued at 10.40 a.m. on 2 September. As Dujuan moved quickly towards Hong Kong from the east, the Hong Kong Observatory issued the No. 8 NORTHWEST Gale or Storm Signal at 2.20 p.m. the same day. Dujuan was about 230 km to the east of Hong Kong at that time. Local winds were strong northwesterlies in the afternoon, reaching gale force towards the evening.

On the night of 2 September, Dujuan skirted 30 km to the north of the Hong Kong Observatory Headquarters. The Hong Kong Observatory issued the Increasing Gale or Storm Signal No. 9 at 8.10 p.m. Local winds, in particular those over the northern part of the New Territories, strengthened from gale to storm force. Winds at Lau Fau Shan even reached hurriance force for a short period of time. Gale to storm force winds were also recorded in other parts of the territory, including Victoria Harbour.

Strong to gale southerly winds prevailed over the territory when Dujuan moved to the west of Hong Kong. The signal No. 9 was replaced by the No. 8 SOUTHWEST Gale or Storm Signal at 10.10 p.m. the same night. As Dujuan weakened rapidly over Guangdong overnight, local winds abated generally. The Strong Wind Signal No. 3 was issued at 1.30 a.m. on 3 September to replace the signal No. 8. Local winds subsided further as Dujuan moved further away from Hong Kong. All tropical cyclone warning signals were cancelled at 3.20 a.m. the same day.

The outer rainbands of Dujuan also brought squally heavy rain and thunderstorms to Hong Kong. The Amber Rainstorm Warning Signal was issued at 9.05 p.m. on 2 September and cancelled at 5.00 a.m. the next day. More than 50 millimetres of rainfall were recorded over most parts of the territory, the rainfall in Lautau Island exceeded 90 millimetres.

The approach of Dujuan resulted in 24 people injured. Four mainland fishermen in a boat were found missing off Sai Kung. A total of 85 cases of fallen trees and a few cases of falling objects were reported. A power failure in Yuen Long area affected about 300 households. At the Hong Kong International Airport, 221 flights were cancelled and 139 flights were delayed.

Information on maximum wind, daily rainfall and maximum sea level during the passage of Dujuan is given in Tables 3.4.1 ?3.4.3. Figures 3.4.1 and 3.4.2 show the track of Dujuan and the rainfall distribution in Hong Kong respectively. The time series of the wind speed recorded at Lau Fau Shan and Star Ferry, Kowloon are given in Figures 3.4.3.a and 3.4.3.b. The time series of the pressure recorded at Ta Kwu Ling and Lau Fau Shan are given in Figures 3.4.3.c and 3.4.3.d. Figures 3.4.4 and 3.4.5 are the satellite and radar imageries of Dujuan.

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