TROPICAL CYCLONES IN 2003

3.1 Severe Tropical Storm Koni (0308) : 16 - 23 July 2003

Koni was the first tropical cyclone necessitating the issuance of the Standby Signal No. 1 by the Hong Kong Observatory this year.

Koni developed as a tropical depression at about 1 000 km east-southeast of Manila on 16 July. Tracking to the west-northwest, it moved across the central part of the Philippines on 17 July. In the Philippines, Koni caused two deaths and two others missing during its passage. Koni entered the South China Sea and intensified into a tropical storm on 18 July. An aircraft enroute from Kota Kinabalu of Malaysia to Hong Kong encountered severe turbulence that afternoon the same day when it passed about 300 km west-northwest of Koni. Fifteen persons were injuried.

On 19 July, Koni turned to the northwest and intensified further into a severe tropical storm the next day with a maximum wind speed of about 100 km/h near its centre. While moving towards west-northwest on 21 July, it traversed Hainan that night and entered Beibu Wan the next day. In Hainan, several people were injured during the passage of Koni. 35 flights were suspended and 28 flights were cancelled due to the inclement weather associated with Koni.

On the night of 22 July, Koni weakened into a tropical storm after making landfall in northern Vietnam. Over land, it further weakened into a tropical depression on the early morning of 23 July and dissipated about 100 km west of Hanoi. Three people were killed and 18 were injured in northern Vietnam. The torrential rain and high winds damaged more than 1 000 houses and thousands of hectares of crops. Power supplies and telecommunication network were also temporarily cut off. 19 fishing and passenger boats were sank near the northern coast of Vietnam.

In Hong Kong, the Standby Signal No. 1 was issued at 5.40 a.m. on 20 July when Koni was about 710 km to the south. Koni was closest to Hong Kong on the early morning of 21 July when it was about 500 km to the south-southwest, local winds became fresh east to southeasterly winds with occasional strong winds offshore and on high ground. The outer rain bands of Koni also brought scattered squally showers and over 40 mm of rainfall to parts of the territory on 20-21 July. The lowest instantaneous mean sea-level pressure of 1003.9 hPa was recorded at the Hong Kong Observatory at about 4 p.m. on 20 July. As Koni moved away from Hong Kong, the Standby Signal No. 1 was canceled at 8.15 p.m. on 21 July.

Information on maximum wind, daily rainfall and maximum sea level during the passage of Koni is given in Tables 3.1.1 - 3.1.3. Figures 3.1.1 - 3.1.3 show the track of Koni, rainfall distribution in Hong Kong and satellite imagery respectively.

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