Tropical Cyclones in 2019 > Report on Tropical Storm Wipha (1907): 30 July – 3 August 2019

3.2 Tropical Storm Wipha (1907): 30 July – 3 August 2019

Wipha was the second tropical cyclone affecting Hong Kong in 2019. Although tropical storm Wipha skirted past at about 310 km of the territory, its extensive circulation and asymmetric wind structure necessitated the issuance of the only No.8 Gale or Storm Signal this year. Wipha is also the farthest tropical storm necessitating the issuance of No.8 Gale or Storm Signal in Hong Kong since 1961.

Wipha formed as a tropical depression over the northern part of the South China Sea about 510 km south of Hong Kong on the afternoon of 30 July. It drifted northwards slowly during that night and next morning. Wipha intensified into a tropical storm on the morning of 31 July, later reaching its peak intensity with an estimated maximum sustained wind of 85 km/h near its centre. It started to pick up speed to move west-northwest towards Hainan Island in the afternoon. Wipha slowed down on the early morning of 1 August, making an anti-clockwise loop around the northeastern coast of Hainan Island. It picked up its speed to move northward again in the morning and then moved westward across the Leizhou Peninsula that night. Wipha moved across the coast of Guangxi and the vicinity of Beibu Wan on 2 August and weakened gradually. It degenerated into an area of low pressure over the northern part of Vietnam the next night.

After Wipha developed into a tropical depression over the northern part of the South China Sea on the afternoon of 30 July, the Hong Kong Observatory issued the Standby Signal No. 1 at 3:40 p.m. when Wipha was about 500 km south of Hong Kong. Local winds were fresh easterlies, reaching strong force offshore and on high ground in the afternoon. With Wipha intensifying gradually, the No. 3 Strong Wind Signal was issued at 9:15 p.m. that night when Wipha was about 500 km south of Hong Kong. Local winds became fresh to strong east to northeasterly during the night. As Wipha adopted a more northerly track and edged closer to the coast of Guangdong and intensified further on the morning of 31 July, the No. 8 Northeast Gale or Storm Signal was issued at 1:40 p.m. when Wipha was about 340 km south of Hong Kong. Under the influence of the intense outer rainbands in the right semicircle of Wipha, strong to gale force east to northeasterly winds generally affected the territory in the afternoon. Wipha came closest to Hong Kong at around 5 p.m. that day, skirting past about 310 km south-southwest of the territory. With Wipha departing gradually from Hong Kong and local wind moderating, the No. 3 Strong Wind Signal was issued at 11:40 p.m. that night. Wipha lingered around the northeastern coast of Hainan Island at first on 1 August and the rainbands associated with Wipha continued to affect Hong Kong. Strong east to southeasterly winds persisted over Hong Kong that morning, occasionally reaching gale force offshore and on high ground. Wipha moved towards Leizhou Peninsula in the afternoon and local winds abated gradually. The Standby Signal No.1 was issued at 7:20 p.m. on 1 August, before all tropical cyclone warning signals were cancelled at 8:40 a.m. on 2 August.

Under the influence of Wipha, maximum hourly mean winds of 88, 72 and 70 km/h and maximum gusts of 131, 108 and 117 km/h were recorded at Tai Mo Shan, Cheung Chau and Waglan Island respectively. A maximum sea level (above chart datum) of 3.47 m was recorded at Tsim Bei Tsui, and a maximum storm surge (above astronomical tide) of 0.64 m was recorded at Shek Pik. The lowest instantaneous mean sea-level pressures recorded at some selected stations are as follows:

The heavy rain and squalls associated with the outer rainbands of Wipha lashed the territory during 30 July to 2 August. Overall, more than 250 millimetres of rainfall were generally recorded over the territory, with rainfall exceeding 350 millimetres over the Lantau Island and parts of the New Territories. Amber Rainstorm Warning was issued on 31 July, 1 August and 2 August. The rain was particularly heavy on the night of 31 July, necessitating the issuance of the Red Rainstorm Warning, Landslip Warning and Special Announcement on Flooding in Northern New Territories by the Observatory.

In Hong Kong, at least 20 people were injured during the passage of Wipha. There were more than 850 reports of fallen trees, 3 reports of flooding and 3 reports of landslides. Under high winds, a tower crane in Sham Shui Po was blown down and one person was injured by falling objects. Scaffoldings at Sai Kung, Tung Chung and Aberdeen were blown down. During the stormy weather, one person was injured while swimming in Shek O and required the assistance of lifeguards. Villagers in Kam Tin were trapped by flood waters in and were taken to safety by firemen. Part of the false ceiling in Central Market collapsed under heavy rain. A retaining wall at Tai Tong also collapsed, damaging a metal hut. About 300 hectares of farmland in the New Territories were affected. 693 flights were cancelled, 25 flights were delayed and 14 flights diverted at the Hong Kong International Airport.

According to press reports, at least six people were injured in Macao during the passage of Wipha. Wipha also brought torrential rain to the northern part of Vietnam, which triggered extensive flooding. At least 10 people were killed and 11 were reported missing.