Rai – The record-breaking tropical cyclone

Rai – The record-breaking tropical cyclone

Choy Chun-wing

Hong Kong is rarely directly threatened by tropical cyclones in winter, because the water temperatures in the northern part of South China Sea are too low, and the cool, dry northeast monsoon is also unfavourable to the development of storms.

After wreaking havoc in the Philippines, Super Typhoon Rai weakened into a severe typhoon and continued to move westwards across the southern part of the South China Sea. Rai re-intensified into a super typhoon on 18 December 2021, making it the first super typhoon occurring in the South China Sea in December since 1961. With Rai tracking northeastwards towards Hong Kong, the Observatory issued the Standby Signal No. 1 on the morning of 20 December 2021. Breaking the record of Irma in early December 1974, Rai became the latest storm necessitating the issuance of a tropical cyclone warning signal since 1946.

Satellite image of Rai over the South China Sea

(Source: Himawari-8 operated by the Japan Meteorological Agency)