Overview of Tropical Cyclone in August 2024

Six tropical cyclones occurred over the western North Pacific, but none of them occurred over the South China Sea in August 2024. During most of the month, the location of the subtropical ridge over the western North Pacific was further east than normal. Meanwhile, the seas south of Japan was under the influence of a broad area of low pressure. Thus, the genesis locations of tropical cyclones tended to be further east and north than normal. Tropical cyclones formed over the western North Pacific were likely to be steered towards the vicinity of Japan and the Korean Peninsula. Besides, an anticyclone aloft was affecting the South China Sea most of the time, suppressing deep convections there. Hence, tropical cyclone formation was not favoured over the South China Sea in the month.

Maria formed as a tropical depression over the western North Pacific about 160 km north of Iwo Jima in the small hours of 7 August and then moved generally eastwards. It intensified into a tropical storm in the small hours of the next day and turned to move generally northwards towards the seas east of Honshu, Japan. Maria further intensified into a severe tropical storm in the small hours on 9 August, and attained its peak intensity with an estimated maximum sustained wind of 105 km/h near its centre that afternoon. It turned to move west-northwestwards or northwestwards on 11 August and weakened gradually upon crossing Tohoku, Japan on 12 August. It finally degenerated into an area of low pressure over the seas north of Honshu, Japan on the morning of 13 August.

According to press reports, Maria brought torrential rain and squalls to Tohoku, Japan. A record-breaking 48-hour rainfall of 481.5 millimetres was recorded in Kuji of Iwate Prefecture. At least 2 000 people were evacuated. Water and electricity supply to more than 200 and 4 000 households were disrupted respectively. Railway and air traffic were also affected, with at least 80 flights cancelled.

In mid-August, three tropical cyclones, namely Son-tinh, Ampil and Wukong, formed one after another in the western North Pacific southeast of Japan.

Son-tinh formed as a tropical depression over the western North Pacific about 1 370 km east-northeast of Iwo Jima on the morning of 11 August and moved generally northwards. It intensified into a tropical storm and attained its peak intensity with an estimated maximum sustained wind of 65 km/h near its centre in the small hours of the next day. Meanwhile, it turned to move northwestwards towards the seas east of Honshu, Japan. Son-tinh weakened gradually on the night of 13 August, and finally degenerated into an area of low pressure over the seas east of Honshu, Japan in the small hours on 14 August.

Ampil formed as a tropical depression over the western North Pacific about 430 km west of Iwo Jima in the small hours on 13 August and moved northeastwards. Ampil intensified rapidly into a severe tropical storm on the night of 13 August, and turned to move northwards across the seas south of Honshu, Japan on the afternoon of 14 August. It intensified into a severe typhoon in the small hours on 16 August, and attained its peak intensity with an estimated maximum sustained wind of 165 km/h near its centre that morning. Ampil turned to move northeastwards in the following two days, and finally evolved into an extratropical cyclone over the western North Pacific to the east of Japan on the morning of 19 August.

According to press reports, Ampil brought torrential rain and squalls to eastern Honshu, Japan. Four people were injured. Electricity supply to more than 13 000 households was disrupted. Railway and air traffic were affected, with at least 900 flights cancelled.

Wukong formed as a tropical depression over the western North Pacific about 860 km east-northeast of Iwo Jima on the morning of 13 August and then moved generally northwards. It intensified into a tropical storm and attained its peak intensity with an estimated maximum sustained wind of 65 km/h near its centre that afternoon. Wukong weakened into a tropical depression the next afternoon, and finally evolved into an extratropical cyclone over the seas east of Honshu, Japan on the afternoon of 15 August.

Jongdari formed as a tropical depression over the western North Pacific about 250 km southwest of Okinawa in the small hours on 19 August. It took a northerly track across the East China Sea and the Yellow Sea, towards the vicinity of the Korean Peninsula in the following two days. Jongdari intensified into a tropical storm in the small hours on 20 August, and attained its peak intensity with an estimated maximum sustained wind of 75 km/h near its centre that morning. It weakened gradually that afternoon. Jongdari finally made landfall over the west coast of the Korean Peninsula, and degenerated into an area of low pressure on the morning of 21 August.

According to press reports, Jongdari left one person injured in the Republic of Korea during its passage. Ferry services to and from Jeju Island were suspended. More than 100 flights were delayed at Jeju International Airport.

Shanshan formed as a tropical depression over the western North Pacific about 390 km north-northwest of Guam on the night of 21 August. It took a northerly track across the seas south of Japan and intensified gradually in the following three days. Shanshan turned to move northwestwards or west-northwestwards towards the vicinity of the Ryukyu Islands in the small hours on 25 August. It intensified into a severe typhoon on the morning of 27 August. Shanshan further intensified into a super typhoon, attaining its peak intensity with an estimated maximum sustained wind of 185 km/h near its centre that night. It gradually turned to move northwards towards Kyushu, Japan. Shanshan moved across the vicinity of Kyushu, Japan and weakened gradually on 29 August. It then turned to move generally eastwards across Shikoku and the coastal areas in southern Honshu, Japan in the following two days.