Heavy rain forecast as monsoon strengthens; Typhoon Ragasa spares Thailand

The Thai Meteorological Department reported on Wednesday that the monsoon trough extends across northern and northeastern Thailand, while the moderate southwest monsoon prevailing over the Andaman Sea, the South, Central region, East, and Gulf of Thailand is strengthening.

Isolated heavy to very heavy rainfall is expected in northern and northeastern areas, while scattered thundershowers may occur in the South. Residents in the upper regions are advised to beware of flooding and river overflows, particularly along foothills, waterways, and low-lying areas.

Sea conditions:

Upper Andaman Sea: waves 2–3 metres high, exceeding 3 metres during thundershowers. Small boats should remain ashore until 26 September.

Lower Andaman Sea and upper Gulf: waves around 2 metres, rising above 2 metres during thundershowers. All vessels should navigate with caution and avoid thundershower areas.

Typhoon update:

Typhoon Ragasa, currently over the South China Sea, is expected to pass near Hong Kong and approach southern China, moving through the Gulf of Tonkin on September 25. The storm is forecast to weaken into a tropical storm before making landfall in northern Vietnam. Ragasa is expected to downgrade rapidly due to an extending high-pressure system over China on September 25-26. The storm is not expected to affect Thailand.

As a result of Typhoon Ragasa, the monsoon trough and southwest monsoon over Thailand are forecast to strengthen further between September 24-26, increasing rainfall and wind activity.

The weather forecast for the next 24 hours is as follows:

North: Fairly widespread thundershowers and isolated heavy rain in Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Lampang, Lamphun, Tak, Kamphaeng Phet, Phichit, and Phetchabun. Minimum temperature 22-25 °C. Maximum temperature 31-34 °C.

Northeast: Fairly widespread thundershowers and isolated heavy to very heavy rain in Nong Khai, Bueng Kan, Sakon Nakhon, Nakhon Phanom, Mukdahan, Maha Sarakham, Yasothon, Amnat Charoen, Surin, Sisaket, and Ubon Ratchathani. Minimum temperature 23-25 °C. Maximum temperature 30-33 °C.

Central: Scattered thundershowers and isolated heavy rain in Nakhon Sawan, Uthai Thani, Lopburi, Saraburi, and Kanchanaburi. Minimum temperature 23-26 °C. Maximum temperature 33-35 °C.

East: Fairly widespread thundershowers and isolated heavy to very heavy rain in Nakhon Nayok, Prachinburi, Chanthaburi, and Trat. Minimum temperature 24-28 °C. Maximum temperature 28-34 °C. Wave height about 2 metres and above 2 metres in thundershowers.

South (East Coast): Isolated thundershowers mostly in Phetchaburi, Prachuap Khiri Khan, Chumphon, and Surat Thani. Minimum temperature 22-26 °C. Maximum temperature 33-35 °C. Wave height 1-2 metres, about 2 metres offshore and above 2 metres in thundershowers.

South (West Coast): Scattered thundershowers mostly in Ranong, Phang Nga, and Phuket. Minimum temperature 24-26 °C. Maximum temperature 30-33 °C. Wave height 2-3 metres and above 3 metres in thundershowers.

Bangkok Metropolitan: Scattered thundershowers. Minimum temperature 25-27 °C. Maximum temperature 32-35 °C.