Overview of Tropical Cyclone in September 2021

Five tropical cyclones occurred over the western North Pacific and the South China Sea in September 2021.

A tropical depression formed over the western North Pacific about 900 km northwest of Wake Island on the night of 1 September and moved west-northwestwards. The tropical depression reached its peak intensity on the morning of 2 September with an estimated maximum sustained wind of 55 km/h near its centre. It turned to move northeastwards gradually in the following two days. The tropical depression finally evolved into an extratropical cyclone over the western North Pacific to the east of Japan on 4 September.

Conson formed as a tropical depression over the western North Pacific about 960 km east-southeast of Manila in the small hours on 6 September. It moved northwestwards and intensified gradually. Conson intensified into a severe tropical storm and reached its peak intensity on the morning of 7 September with an estimated maximum sustained wind of 90 km/h near its centre. After sweeping across the central part of the Philippines, Conson turned to track westwards on the night of 8 September and moved across the central part of the South China Sea in the following two days. It weakened into a tropical storm on the morning of 11 September. Conson then slowed down and lingered over the central part of the South China Sea to the east of Vietnam. Conson finally degenerated into an area of low pressure over the coastal waters of the central part of Vietnam in the small hours on 13 September.

According to press reports, Conson left 20 deaths, 24 injuries and at least 7 missing in the Philippines during its passage. Besides, about 9 000 buildings were damaged.

Chanthu formed as a tropical depression over the western North Pacific about 1 880 km east of Manila on the afternoon of 6 September. It moved west or west-northwestwards at first and intensified rapidly. Chanthu intensified into a super typhoon on the morning of 8 September and reached its peak intensity on the night of 10 September with an estimated maximum sustained wind of 240 km/h near its centre. Chanthu then weakened gradually and turned to move northwards across the seas east of Taiwan. It slowed down and lingered over the East China Sea on 14 and 15 September. Chanthu started to pick up speed and turned to move east to northeastwards on 16 September. It swept across Kyushu and Shikoku of Japan next day and finally evolved into an extratropical cyclone over the seas east of Honshu, Japan on 18 September.

According to press reports, there were more than 80 000 households without electricity supply in Taiwan under the influence of Chanthu. Railways and aviation services in Japan were suspended during the passage of Chanthu.  

Dianmu formed as a tropical depression over the southern part of the South China Sea about 460 km south-southeast of Xisha on the night of 22 September. It moved west-northwestwards and intensified gradually. Dianmu intensified into a tropical storm on the night of 23 September and reached its peak intensity with an estimated maximum sustained wind of 65 km/h near its centre. Dianmu weakened and turned to move westwards after it made landfall over the central part of Vietnam in the small hours on 24 September. It degenerated into an area of low pressure over Indochina Peninsula during the day.

Mindulle formed as a tropical depression over the western North Pacific about 290 km southeast of Guam on the morning of 23 September. It moved west-northwestwards and intensified gradually. Mindulle developed into a severe tropical storm on the night of 24 September. It turned to move northwestwards and intensified rapidly. Mindulle further developed into a super typhoon on 26 September and reached its peak intensity with an estimated maximum sustained wind of 220 km/h. It tracked northwards in the following three days and turned to move northeastwards towards the seas east of Japan on 30 September.