Thailand on High Alert for Floods as Tropical Storm Bualoi Nears Vietnam Coast
Monsoon trough and tropical remnants fuel heavy, sustained rainfall across the North and Northeast, with flood warnings issued for key areas
- Thailand has issued a high alert for floods due to a forecast of ten consecutive days of heavy rainfall.
- The severe weather is caused by a combination of a strengthened monsoon, the remnants of Typhoon Ragasa, and the approaching Tropical Storm Bualoi.
- While Tropical Storm Bualoi is expected to make landfall in Vietnam, its final stages will bring heavy rain to parts of Northern Thailand.
- Northern and Northeastern regions are at the highest risk for heavy to very heavy rain and potential flash flooding.
Thailand’s weather agency has urged the public to remain on high alert as the country faces ten straight days of continuous heavy rainfall, driven by a strengthening monsoon and the residual effects of recent Pacific storm systems.
The Thai Meteorological Department (TMD) confirmed on September 26, 2025, that the frequency of storm formation is increasing. While Tropical Storm Bualoi is not expected to make landfall in Thailand, its movement is influencing the regional weather pattern.
Bualoi was located over the central Philippines this morning and is moving rapidly at 40 kilometres per hour. It is forecast to enter the South China Sea tonight and head northwest towards the coast of Vietnam and the Gulf of Tonkin.
The TMD has cautioned that geographical features and the presence of a cold air mass could cause Bualoi's trajectory to change between September 28 and 29. The public must closely monitor official announcements once the storm is over the South China Sea.
Flood Risk Across Northern and Northeastern Regions
The continuous heavy rain forecast for the period of September 26 to 30 is primarily driven by a monsoon trough passing across the lower North and upper Northeast regions, combined with a moderate-to-strong southwest monsoon.
Expert analysis from TEAM Consulting Engineering and Management (TEAMG) confirmed that the remnants of the recently dissipated Typhoon Ragasa have also significantly intensified the monsoon, contributing to the severe weather.
Areas at high risk of heavy to very heavy rain and flash flooding include:
Phitsanulok, Phetchabun, Loei, Chaiyaphum, Khon Kaen, Nakhon Ratchasima, Buriram, Amnat Charoen, Ubon Ratchathani, Chanthaburi, and Trat.
Specific warnings have been issued for areas prone to sudden floods and flash floods, particularly in foothills, low-lying areas, and urban communities along the Chao Phraya River, where water levels are already rising and require continuous monitoring.
Rainfall intensity across the country is expected to decrease slightly between October 1 and 5.
Storm Activity Confirmed
The detailed analysis by TEAMG confirms the complex interactions of the recent storm systems:
Typhoon Bualoi (the 20th storm of 2025) is forecast to strengthen to a Category 1 Typhoon on September 27 before making landfall in Vietnam (near Thanh Hóa) on September 28-29, then dissipating over mainland Southeast Asia by September 30. Its final stages will cause heavy rain in upper Laos and parts of Northern Thailand, including Chiang Rai, Phayao, and Nan.
Typhoon Ragasa (the 18th storm of 2025) made a powerful strike on Hong Kong as a Category 4 system on September 23, before weakening. Its remnants caused very heavy rain in upper Laos upon dissipation on September 26, fuelling the monsoon and leading to scattered heavy downpours across Thailand's North and Upper Northeast.
Typhoon Neoguri (the 19th storm of 2025) was confirmed to have reached Category 4 strength but moved across the sea east of Japan and is not a threat to the region.
