Report on Severe Tropical Storm Nalgae (2222)

Severe Tropical Storm Nalgae (2222)
26 October - 3 November 2022

Nalgae was the sixth tropical cyclone affecting Hong Kong in 2022. The Observatory issued the third No. 8 Gale or Storm Signal in 2022 during the passage of Nalgae. Moreover, Nalgae was the third tropical cyclone necessitating the issuance of the No. 8 Signal in November since 1946.

Nalgae formed as a tropical depression over the western North Pacific about 1 390 km east of Manila on the morning of 26 October. It moved generally west-northwestwards towards the Philippines and intensified gradually. Nalgae intensified into a severe tropical storm in the small hours on 29 October and moved across the Philippines. It weakened into a tropical storm next day and entered the central part of the South China Sea. Nalgae turned to move north-northwestwards that night and intensified gradually again. Nalgae re-intensified into a severe tropical storm on the afternoon of 31 October and attained its peak intensity with an estimated maximum sustained wind of 110 km/h near its centre. Nalgae continued to edge closer to the coast of Guangdong on 2 November. However, it weakened into a tropical storm in the afternoon due to the influence of the northeast monsoon. Nalgae skirted past the waters south of Hong Kong that night and made landfall over Zhuhai the next morning. It degenerated into an area of low pressure over the western part of Guangdong thereafter.

According to press reports, the passage of Nalgae left 155 deaths, 129 injuries and 34 missing in the Philippines. Over 2 million people were affected and economic loss exceeded 120 million USD.

The Standby Signal No. 1 was issued at 10:10 p.m. on 30 October, when Nalgae was about 800 km south-southeast of Hong Kong. Local winds were fresh northerlies, occasionally strong offshore overnight. With Nalgae edging closer to the coast of Guangdong and gradually intensifying, the No. 3 Strong Wind Signal was issued at 4:20 p.m. on 31 October, when Nalgae was about 600 km south-southeast of Hong Kong. Under the combined effect of Nalgae and the northeast monsoon, local winds were generally strong northerlies that night and next day, occasionally reaching gale force on high ground.

Although Nalgae began to weaken gradually when it approached the coast of Guangdong, as Nalgae was expected to come rather close to the vicinity of the Pearl River Estuary with tropical storm strength later on 2 November, the No. 8 Northwest Gale or Storm Signal was issued at 1:40 p.m. that day when Nalgae was about 160 km southeast of Hong Kong. As the extent of gales associated with Nalgae was rather small, local winds maintained generally strong north to northwesterlies, reaching gale force on high ground in that afternoon. In the evening, Nalgae began to take on a more westerly track and local winds gradually veered to northeasterlies. The No. 8 Northeast Gale or Storm Signal was issued at 8:40 p.m. on 2 November. With Nalgae skirting past the waters south of Hong Kong, together with the combined effect of the northeast monsoon, local winds strengthened significantly overnight. Winds were generally strong to gale north to northeasterlies, once reaching storm force offshore over the southern part of the territory and on high ground.

Nalgae came closest to Hong Kong at around 2 a.m. on 3 November, when it skirted past about 40 km southwest of the Hong Kong Observatory. As Nalgae moved to the southwest of the territory, local winds veered to southeasterlies. The No. 8 Southeast Gale or Storm Signal was issued at 2:40 a.m. that day. Nalgae made landfall over Zhuhai at around 5 a.m. on 3 November. With Nalgae weakening and moving inland, local winds soon subsided. The No. 8 Southeast Gale or Storm Signal was replaced by the No. 3 Strong Wind Signal at 5:20 a.m. and all tropical cyclone warning signals were cancelled at 6:20 a.m. that day.

Under the influence of Nalgae, maximum hourly mean winds of 92, 87 and 85 km/h and gusts of 132, 112 and 123 km/h were recorded at Ngong Ping, Waglan Island and Cheung Chau respectively. A maximum sea level (above chart datum) of 3.00 m was recorded at Tsim Bei Tsui and a maximum storm surge (above astronomical tide) of 0.73 m was recorded at Tai Miu Wan. The lowest instantaneous mean sea-level pressures recorded at some selected stations are as follows:

Locally, it was dry with sunny periods on 31 October. Affected by the outer rainbands associated with Nalgae, there were occasional squally showers in Hong Kong on 1 – 3 November. More than 40 millimetres of rainfall were generally recorded over Hong Kong in these three days and rainfall even exceeded 100 millimetres over the urban areas and the eastern part of the territory.

In Hong Kong, one person was injured during the passage of Nalgae. There were also 11 reports of fallen trees. A tree fell in Mong Kok and hit a lamp post.