Heavy rain intensifies across Bangkok, North and Northeast

The Thai Meteorological Department (TMD) has warned of heavier rain across Thailand on Wednesday (August 19), with thunderstorms forecast to cover 70% of Bangkok and surrounding provinces, the North and the Northeast.

Heavy to very heavy rain is expected in parts of the upper North, upper Northeast and East during the 24-hour period from 6am on August 19 to 6am on August 20.

The conditions are being driven by a monsoon trough extending across the upper North and upper Laos towards a low-pressure area along the coast of upper Vietnam. A relatively strong south-westerly monsoon is also prevailing over the Andaman Sea, Thailand and the Gulf of Thailand.

The monsoon trough and strengthening south-westerly monsoon have repeatedly brought heavy rain and rough seas across Thailand this month.

Residents in affected areas have been advised to watch for heavy and accumulated rainfall, which could trigger flash floods, forest run-off and overflowing waterways, particularly on foothill slopes near waterways and in low-lying areas.

Rough seas warning

Winds and waves are strengthening in the Andaman Sea and Gulf of Thailand.

• Waves in the upper Andaman Sea and upper Gulf are forecast at two to three metres.
• Waves may exceed three metres in thunderstorm areas.
• Mariners should proceed with caution and avoid areas experiencing thunderstorms.
• Small boats in the upper Andaman Sea should remain ashore during this period.

Regional forecast

• Bangkok and surrounding provinces: Thunderstorms across 70% of the area, with isolated heavy rain. Temperatures will range from 25–27C to 34–36C, with south-westerly winds of 10–25km/h.

• North: Thunderstorms across 70% of the region. Heavy rain is forecast in Mae Hong Son, Lamphun, Uttaradit, Sukhothai, Tak, Phichit, Phitsanulok and Phetchabun. Very heavy rain is expected in Chiang Mai, Chiang Rai, Phayao, Nan, Phrae and Lampang. Temperatures will range from 23–28C to 29–34C, with south-westerly winds of 10–20km/h.

• Northeast: Thunderstorms across 70% of the region. Heavy rain is expected in Loei, Nong Bua Lamphu, Udon Thani, Khon Kaen, Maha Sarakham, Roi Et, Yasothon, Chaiyaphum, Amnat Charoen, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani. Very heavy rain is forecast in Nong Khai, Bueng Kan, Nakhon Phanom, Sakon Nakhon, Mukdahan and Kalasin. Temperatures will range from 22–25C to 28–33C, with south-westerly winds of 10–20km/h.

• Central region: Thunderstorms across 60% of the area, with isolated heavy rain in Nakhon Sawan, Ayutthaya, Lop Buri, Saraburi, Kanchanaburi and Ratchaburi. Temperatures will range from 25–26C to 34–36C, with south-westerly winds of 10–25km/h.
   
• East: Thunderstorms across 70% of the region. Heavy rain is forecast in Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao, Chonburi and Chanthaburi, with very heavy rain in Trat. Temperatures will range from 24–28C to 30–33C. Waves will be about two metres and may exceed two metres during thunderstorms.
   
• South, east coast: Thunderstorms across 40% of the region, mainly in Prachuap Khiri Khan, Chumphon, Nakhon Si Thammarat, Yala and Narathiwat. Temperatures will range from 23–25C to 33–35C. Waves will reach one to two metres, rising to about two metres offshore and exceeding two metres in thunderstorm areas.
   
• South, west coast: Thunderstorms across 60% of the region, with isolated heavy rain in Ranong and Phang Nga. Temperatures will range from 24–27C to 29–34C. From Phuket northwards, south-westerly winds will reach 20–40km/h, with waves of two to three metres rising above three metres during thunderstorms. From Krabi southwards, winds will reach 20–35km/h, with waves of about two metres rising above two metres during thunderstorms.