Report on Tropical Storm Nongfa (2514)

Tropical Storm Nongfa (2514)
28 to 31 August 2025

Nongfa was the eighth tropical cyclone affecting Hong Kong in 2025.

Nongfa formed as a tropical depression over the central part of the South China Sea about 410 km east-southeast of Xisha on the afternoon of 28 August, and moved generally west-northwestwards. It turned to track westwards across the seas south of Hainan Island on the night of the next day. Nongfa intensified into a tropical storm over the seas southwest of Hainan Island on the morning of 30 August, attaining its peak intensity with an estimated maximum sustained wind of 65 km/h near its centre. It made landfall over the central part of Vietnam that afternoon and weakened gradually. Nongfa finally degenerated into an area of low pressure in the northern part of Thailand on the morning of 31 August.

According to press reports, Nongfa and the southwest monsoon brought heavy rain to the Philippines. More than 250 000 people were affected and over 470 houses were damaged. The heavy rain associated with Nongfa also caused at least one death in Vietnam, and two deaths and more than 490 houses damaged in Thailand.

The Standby Signal No. 1 was issued at 7:10 p.m. on 28 August, when Nongfa was about 740 km south of Hong Kong. Under the combined effect of Nongfa and the ridge of high pressure over southeastern China, local winds were fresh east to northeasterlies that night and the next day, occasionally reaching strong force over parts of the territory. Nongfa came closest to Hong Kong at around 5 p.m. on 29 August, skirting past about 650 km south-southwest of the territory. With Nongfa gradually departing from Hong Kong, it no longer posed a threat to Hong Kong and all tropical cyclone warning signals were cancelled at 6:10 p.m. on 29 August. But under the influence of the ridge of high pressure over southeastern China, strong easterly winds were still affecting parts of the territory. The Strong Monsoon Signal was issued thereafter and lasted till 9:45 a.m. the following morning.

Nongfa did not cause any significant damage when it affected Hong Kong. At the Observatory Headquarters, the lowest instantaneous mean sea-level pressure of 1007.0 hPa was recorded at 7:22 p.m. on 28 August. Under the influence of Nongfa, a maximum sea level of 2.41 m (above chart datum) was recorded at Tsim Bei Tsui and a maximum storm surge of 0.28 m (above astronomical tide) was recorded at Tai Po Kau.

Locally, it was mainly cloudy with a few showers and squally thunderstorms on 28 August. It was very hot with sunny periods on 29 August.