Report on Tropical Depression(16 to 19 August)
Tropical Depression
16 to 19 August 2025
A tropical depression formed over the central part of the South China Sea on the night of 16 August and was the sixth tropical cyclone affecting Hong Kong in 2025.
A tropical depression formed over the central part of the South China Sea about 130 km southeast of Xisha on the night of 16 August, with an estimated maximum sustained wind of 45 km/h near its centre. It tracked northwestwards or west-northwestwards towards the seas south of Hainan Island. Skirting past the southwestern coast of Hainan Island on 18 August, the tropical depression entered Beibu Wan and gradually turned to move northwards. It made landfall over the northern part of Vietnam in the small hours of 19 August, and finally degenerated into an area of low pressure area in Guangxi that night.
According to press reports, under the combined effect of the tropical depression and a ridge of high pressure over southeastern China, there were torrential rain and squalls over Guangdong, Guangxi, Hainan Island and the northern part of Vietnam.
The Standby Signal No. 1 was issued at 10:20 p.m. on 16 August, when the tropical depression was about 700 km south-southwest of Hong Kong. Local winds were fresh easterlies the next day. But under the influence of the outer rainbands associated with the tropical depression, winds over parts of the territory occasionally reached strong force. The tropical depression came closest to Hong Kong at around 5 a.m. on 17 August, skirting past about 650 km south-southwest of the territory. With the tropical depression departing from Hong Kong, it no longer posed a threat to Hong Kong and all tropical cyclone warning signals were cancelled at 8:20 p.m. on 17 August. However, under the combined effect of the ridge of high pressure over southeastern China and the tropical depression, strong southeasterly winds were still affecting parts of the territory, occasionally reaching gale force offshore and on high ground. The Strong Monsoon Signal was issued thereafter and lasted till 12:30 p.m. the following day.
The tropical depression did not cause any significant damage when it affected Hong Kong. Under the influence of the tropical depression, a maximum sea level of 2.47 m (above chart datum) was recorded at Tsim Bei Tsui and a maximum storm surge of 0.30 m (above astronomical tide) was recorded at Tai Po Kau. At the Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 1007.6 hPa was recorded at 4:01 p.m. on 17 August.
It was mainly fine in Hong Kong on 16 August. Under the influence of the outer rainbands associated with the tropical depression, there were squally showers and thunderstorms over the territory on 17 August. More than 20 millimetres of rainfall were recorded over many places.