Report on Tropical Storm Nangka (2016)
Tropical Storm Nangka (2016)
11 to 14 October 2020
Nangka was the fourth tropical cyclone that affected Hong Kong in 2020. Although Nangka skirted past at about 440 km south of Hong Kong, its combined effect with the northeast monsoon necessitated the issuance of the second No. 8 Gale or Storm Signal this year. Nangka is also the farthest tropical cyclone with the issuance of No. 8 Gale or Storm Signal in Hong Kong since 1961.
Nangka formed as a tropical depression over the central part of the South China Sea about 500 km southeast of Dongsha on the afternoon of 11 October. It then moved west-northwestwards towards Hainan Island and intensified gradually. Nangka intensified into a tropical storm on the afternoon of 12 October, reaching its peak intensity at night with an estimated maximum sustained wind of 85 km/h near its centre. It moved across Hainan Island on the night of 13 October and weakened gradually. Nangka entered Beibu Wan on 14 October and finally degenerated into an area of low pressure over inland Vietnam at night.
According to press reports, a cargo ship overturned near Qiongzhou Strait when Nangka was hitting Hainan. Two crew members on board died and three were missing. Nangka also brought heavy rain and squalls to Vietnam, leaving at least two deaths and one missing.
In Hong Kong, the Standby Signal No. 1 was issued at 8:40 p.m. on 11 October when Nangka was about 780 km southeast of the territory. Moderate east to northeasterly winds generally affected Hong Kong the next day. With Nangka edging closer to the south China coast, the Strong Wind Signal No. 3 was issued at 5:10 p.m. on 12 October when Nangka was about 480 km south-southeast of Hong Kong. Local winds started to strengthen during the night with winds reaching strong force offshore and on high ground. Nangka came closest to Hong Kong at around 2 a.m. on 13 October with its centre passing about 440 km south of Hong Kong. With Nangka moving gradually to the south to southwest of Hong Kong, local winds were expected to strengthen further under its combined effect with the northeast monsoon. The No. 8 Northeast Gale or Storm Signal was issued at 5:40 a.m. on 13 October when Nangka was about 450 km south of Hong Kong. Local winds were generally strong east to northeasterlies during the day, reaching gale force offshore and on high ground. Overall, winds were generally stronger over the southern part of Hong Kong with numerous places recording gale force wind, while winds were weaker over the northern part of the territory. When Nangka made landfall over Hainan Island and weakened gradually, the Strong Wind Signal No. 3 was issued at 7:40 p.m. on 13 October. After Nangka entered Beibu Wan in the small hours on 14 October and moved far away from Hong Kong, its impact to territory had diminished and all tropical cyclone warning signals were cancelled at 2:40 a.m. on that day. Nevertheless, strong winds still affected many places in Hong Kong under the influence of the northeast monsoon. The Strong Monsoon Signal was issued immediately afterwards and lasted till 10:15 a.m. the following day.
Under the influence of Nangka, maximum hourly mean winds of 82, 66 and 66 km/h and maximum gusts of 97, 90 and 91 km/h were recorded at Waglan Island, Cheung Chau Beach and Green Island in the Victoria Harbour respectively. A maximum sea level (above chart datum) of 2.79 m was recorded at Tai Po Kau, and a maximum storm surge (above astronomical tide) of 0.74 m was recorded at Shek Pik. The lowest instantaneous mean sea-level pressures recorded at some selected stations are as follows:
| Station | Lowest instantaneous mean sea-level pressure (hPa) | Date/Month | Time |
|---|---|---|---|
| Hong Kong Observatory Headquarters | 1006.7 | 12/10 | 3:53 p.m. |
| Hong Kong International Airport | 1006.6 | 12/10 | 3:37 p.m. |
| Cheung Chau | 1006.1 | 12/10 | 3:52 p.m. |
| King’s Park | 1006.3 | 12/10 | 3:15 p.m. |
| Lau Fau Shan | 1006.2 | 12/10 | 3:11 p.m. |
| Peng Chau | 1006.6 | 12/10 | 3:59 p.m. |
| Sha Tin | 1007 | 12/10 | 3:05 p.m. |
| Sheung Shui | 1006.5 | 12/10 | 3:32 p.m. |
| Ta Kwu Ling | 1006.8 | 12/10 | 3:07 p.m. |
| Tai Po | 1007.3 | 12/10 | 3:10 p.m. |
| Waglan Island | 1006.8 | 12/10 | 4:37 p.m. |
Locally, it was mainly fine and dry on 11 and 12 October. With the outer rainbands of Nangka edging closer to the coast of Guangdong gradually, it was cloudy with rain in Hong Kong on the night of 12 October and on 13 October. Although Nangka had moved away, there were still a few rain patches in Hong Kong on 14 October under the influence of the northeast monsoon. More than 20 millimetres of rainfall were recorded over most parts of the territory during 11 – 14 October.
In Hong Kong, at least three people were injured during the passage of Nangka and there were around 250 reports of fallen trees. A taxi and a passenger van were hit by fallen trees at Sham Shui Po and Yuen Long respectively. A village house in Tsuen Wan was damaged by falling branches. An advertisement banner of a commercial building in western District was blown down, disrupting the traffic nearby.