Heavy rain and rough seas forecast as monsoon strengthens; Typhoon Ragasa downgrades

The Thai Meteorological Department reported on Thursday that the monsoon trough stretches across northern and northeastern Thailand, while a moderate to rather strong southwest monsoon prevails over the Andaman Sea, the South, Thailand’s Central region, the East, and the Gulf of Thailand.

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 take precautions, as accumulated rainfall could lead to flash floods 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 September 26.

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

Typhoon update:

Typhoon Ragasa, now downgraded to a severe tropical storm, is currently over southern Guangdong, China, and is expected to move into northern Vietnam today. The storm is forecast to weaken rapidly due to the extension of China’s high-pressure system on September 25-26.

The storm is not expected to affect Thailand, but its presence will strengthen the monsoon trough and the southwest monsoon, resulting in increased rainfall and wind activity across the country on September 25-26.

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

North: Fairly widespread thundershowers and isolated heavy rain in Chiang Rai, Phayao, Nan, Uttaradit, Tak, Kamphaeng Phet, Phitsanulok, Phichit and Phetchabun. Minimum temperature 23-25 °C. Maximum temperature 30-33 °C.

Northeast: Fairly widespread thundershowers and isolated heavy to very heavy rain in Nong Khai, Bueng Kan, Udon Thani, Sakon Nakhon, Nakhon Phanom, Mukdahan, Yasothon, Amnat Charoen and Ubon Ratchathani. Minimum temperature 23-25 °C. Maximum temperature 31-33 °C.

Central: Scattered thundershowers and isolated heavy rain in Kanchanaburi and Ratchaburi. Minimum temperature 23-25 °C. Maximum temperature 32-34 °C.

East: Fairly widespread thundershowers and isolated heavy rain in Nakhon Nayok, Prachinburi, Rayong, Chanthaburi and Trat. Minimum temperature 24-27 °C. Maximum temperature 30-34 °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 23-26 °C. Maximum temperature 33-36 °C. Wave height 1-2 metres, about 2 metres offshore and above 2 metres in thundershowers.

South (West Coast): Scattered thundershowers and isolated heavy rain in Ranong and Phang Nga. Minimum temperature 24-26 °C. Maximum temperature 29-34 °C. Wave height 2-3 metres and above 3 metres in thundershowers.

Bangkok Metropolitan: Scattered thundershowers. Minimum temperature 25-27 °C. Maximum temperature 32-34 °C.