Heavy rain warning as tropical system nears, strong winds and flash flood risk expected

According to the Thai Meteorological Department, a low-pressure cell covering upper Myanmar and upper Laos is combining with the prevailing moderate southwest monsoon over the Andaman Sea, Thailand, and the Gulf of Thailand. This will bring thundershowers across the country on Thursday, with isolated heavy rain expected particularly in the North, Central and Eastern regions.

Residents in these areas are advised to remain vigilant for possible flash floods and overflows, especially near foothills and low-lying areas.

In the upper Andaman Sea, waves are forecast to reach about 2 metres, and 1–2 metres in the lower Andaman Sea. However, wave heights may exceed 2 metres during thundershowers. All vessels in the Andaman Sea and Gulf are urged to proceed with caution and avoid areas affected by thunderstorms.

Additionally, a tropical depression over the eastern Philippines is expected to intensify into a tropical storm. Between July 19 and 24, it is forecast to move across the upper Philippines and into the upper South China Sea. This development is likely to further strengthen the southwest monsoon over the Andaman Sea, Thailand and the Gulf.

As a result, Thailand will see an increase in rainfall nationwide, with isolated areas in the North, upper Northeast, and Central regions experiencing heavy to very heavy showers. Wind strength in the Andaman Sea and upper Gulf is expected to rise, generating waves of 2–3 metres, and over 3 metres in areas affected by storms. Mariners are advised to remain on high alert.

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, Lamphun, Lampang, Phayao, Nan, Phrae, Uttaradit and Tak; minimum temperature 22-26 degrees Celsius, maximum 27-34°C. 

Northeast: Scattered thundershowers mostly in Loei, Nong Khai, Bueng Kan, Nong Bua Lamphu, Udon Thani, Sakon Nakhon, Nakhon Phanom, Kalasin, Mukdahan, Roi Et, Yasothon, Amnat Charoen, Surin, Sisaket and Ubon Ratchathani; minimum 23-26°C, maximum 31-35°C.

Central: Scattered thundershowers and isolated heavy rain in Uthai Thani, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram; minimum 23-26°C, maximum 34-35°C. 

East: Scattered thundershowers and isolated heavy rain in Nakhon Nayok, Prachin Buri, Chachoengsao, Chanthaburi and Trat; minimum 23-27°C, maximum 31-34°C; waves about a metre high and above 2 metres high in thundershowers.

South (east coast): Scattered thundershowers mostly in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani and Nakhon Si Thammarat; minimum 23-26°C, maximum 33-35°C; waves about a metre high and above 2 metres high in thundershowers.

South (west coast): Scattered thundershowers mostly in Ranong, Phangnga, Phuket and Krabi; minimum 23-26°C, maximum 30-34°C; waves about 1-2 metres high and above 2 metres high in thundershowers.

Bangkok metropolitan area: Fairly widespread thundershowers and isolated heavy rain; minimum 24-26°C, maximum 33-35°C.