Report on Typhoon Ma-on (2209)
Typhoon Ma-on (2209)
21 - 26 August 2022
Ma-on was the fourth tropical cyclone affecting Hong Kong this year. The Observatory issued the second No. 8 Gale or Storm Signal in the year during the passage of Ma-on.
Ma-on formed as a tropical depression over the western North Pacific about 730 km east-northeast of Manila on the afternoon of 21 August. It moved west-southwestwards and intensified gradually. Ma-on turned to track west-northwestwards on 22 August and developed into a severe tropical storm in the small hours on 23 August. It moved across the northern part of Luzon that day and entered the northern part of the South China Sea at night. Ma-on tracked west-northwestwards and moved rapidly across the northern part of the South China Sea towards the coast of western Guangdong the next day. Ma-on further developed into a typhoon that night, reaching its peak intensity with an estimated maximum sustained wind of 120 km/h near its centre. Affected by relatively strong vertical wind shear over the northern part of the South China Sea, Ma-on weakened gradually afterwards. It made landfall near Dianbai, Maoming before noon on 25 August and finally weakened into an area of low pressure over the northern part of Vietnam on 26 August.
According to press reports, the rail and shipping services in Zhuhai were suspended under the influence of the torrential rain and squalls associated with Ma-on.
The Standby Signal No. 1 was issued at 9:10 p.m. on 23 August when Ma-on was about 760 km east-southeast of Hong Kong. Local winds were light to moderate north to northeasterlies. With Ma-on approaching the coast of Guangdong quickly, the No. 3 Strong Wind Signal was issued at 12:40 p.m. on 24 August when Ma-on was about 420 km southeast of Hong Kong. Local winds strengthened significantly in the afternoon, becoming generally strong east to northeasterlies and occasionally reaching gale force offshore and on high ground. With Ma-on edging even closer to Hong Kong, the No. 8 Northeast Gale or Storm Signal was issued at 7:25 p.m. that night when Ma-on was about 270 km south-southeast of the territory. Local winds further strengthened at night, becoming generally strong to gale force east to northeasterlies and occasionally reaching storm force on high ground.
Ma-on moved to the southwest of Hong Kong after midnight and local winds veered to east to southeasterlies. The No. 8 Southeast Gale or Storm Signal was issued at 1:40 a.m. on 25 August. Ma-on came closest to Hong Kong at around 2 a.m. on 25 August when it skirted past about 190 km south-southwest of the territory. With Ma-on gradually departing from Hong Kong and local winds moderating, the No. 8 Southeast Gale or Storm Signal was replaced by the No. 3 Strong Wind Signal at 9:20 a.m. on 25 August. As Ma-on continued to weaken and moved further away from Hong Kong in the afternoon, the Standby Signal No. 1 was issued at 2:10 p.m. to replace the No. 3 Strong Wind Signal and all tropical cyclone warning signals were cancelled at 4:10 p.m. that day.
Under the influence of Ma-on, maximum hourly mean winds of 95, 82 and 75 km/h and gusts of 144, 111 and 103 km/h were recorded at Ngong Ping, Cheung Chau, and Waglan Island respectively. A maximum sea level (above chart datum) of 3.27 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 and Tsim Bei Tsui. 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 | 999.4 | 24/8 | 4:11 p.m. |
| Hong Kong International Airport | 999.1 | 24/8 | 4:08 p.m. |
| Cheung Chau | 999.5 | 24/8 | 5:13 p.m. |
| King’s Park | 999.1 | 24/8 | 4:13 p.m. |
| Lau Fau Shan | 999.5 | 24/8 | 4:02 p.m. |
| Peng Chau | 999.3 | 24/8 | 3:49 p.m. |
| Sha Tin | 999.7 | 24/8 | 4:02 p.m. |
| Sheung Shui | 999.1 | 24/8 | 4:21 p.m. |
| Ta Kwu Ling | 999.6 | 24/8 | 4:17 p.m. |
| Tai Po | 999.8 | 24/8 | 4:11 p.m. |
| Waglan Island | 999.0 | 24/8 | 4:00 p.m. |
Under the influence of the subsiding air ahead of Ma-on, the weather of Hong Kong was mainly fine and very hot at first on 24 August. With Ma-on edging closer, the weather became cloudy later that day. The outer rainbands of Ma-on also brought occasional heavy squally showers to Hong Kong on the night of 24 August and on 25 August. More than 50 millimetres of rainfall were recorded over many places.
In Hong Kong, one person was injured during the passage of Ma-on. There were 279 reports of fallen trees and one report of flooding. An aluminium window was blown down by strong winds and fell to a pedestrian crossing place in Hung Hom.