Report on Tropical Storm Mulan (2207)

Mulan was the third tropical cyclone affecting Hong Kong this year.

Mulan formed as a tropical depression over the central part of the South China Sea about 700 km south-southwest of Hong Kong in the small hours on 9 August. It moved north to north-northeastwards at first. Mulan intensified into a tropical storm in the afternoon and reached its peak intensity with an estimated maximum sustained wind of 65 km/h near its centre. It turned to move northwestwards that night. Mulan skirted past the northeastern part of Hainan Island and the southern part of Leizhou Peninsula on 10 August and moved across Beibu Wan at night. It made landfall over the northern part of Vietnam and weakened into an area of low pressure over inland on 11 August.

After the formation of Mulan in the small hours on 9 August, the Hong Kong Observatory issued the Standby Signal No. 1 at 3:40 a.m. when Mulan was about 670 km south-southwest of Hong Kong. Local winds were moderate to fresh easterlies in that morning, occasionally reaching strong force offshore and on high ground. With Mulan moving northwards and edging closer to the vicinity of Hainan Island, the Strong Wind Signal No. 3 was issued at 11:25 a.m. on 9 August when Mulan was about 590 km south-southwest of Hong Kong. Local winds were generally fresh to strong east to southeasterlies that night and the next day, occasionally reaching gale force offshore and on high ground. Affected by the intense rainbands associated with Mulan, gust of 108 km/h was recorded at Cheung Chau at around 9 p.m. on 9 August. Mulan was closest to Hong Kong at around 8 a.m. on 10 August, skirting past at around 400 km southwest of the territory. With Mulan departing from Hong Kong, local winds moderated gradually during the day on 10 August and all tropical cyclone warning signals were cancelled at 6:20 p.m. on that day.

Under the influence of Mulan, a maximum sea level (above chart datum) of 3.21 m and a maximum storm surge of 0.51 m (above astronomical tide) were recorded at Tsim Bei Tsui and Tai Po Kau respectively. At the Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 1001.5 hPa was recorded at 4:31 p.m. on 9 August.

The broad outer rainbands of Mulan brought heavy showers, violent gusts and thunderstorms to Hong Kong on 9 - 10 August. More than 100 millimetres of rainfall were generally recorded over Hong Kong on these two days and rainfall even exceeded 200 millimetres over parts of Lantau Island.

A number of fallen trees were reported in Hong Kong during the passage of Mulan. A hoarding in Tsim Sha Tsui was blown down under violent gusts. There were toppled trees at Chai Wan and Wan Chai, damaging six minibuses and a street lamp. The fallen trees at Kwun Tong and Happy Valley also blocked traffic lanes, resulting in disruption of traffic.