FLASH UPDATE #1 – Tropical Depression Seventeen
Countries under monitoring: Lao PDR, Thailand, Viet Nam
OVERVIEW:The low pressure area, INVEST 91W, monitored over the East Sea has developed into Tropical Depression Seventeen. According to Viet Nam’s National Center for Hydro-Meteorological Forecasting (NCHMF), as of 1600H UTC+7, the centre of the tropical depression was located at about 19.6 N, 107.7E, about 50 km south of Bach Long Vi special zone.
STRENGTH & MOVEMENT: According to NCHMF Tropical Depression News update at 1700H UTC+7 today:
The strongest wind near the center of the tropical depression is level 6-7 (39-61km/h), gusting to level 9 ; moving in the North-Northwest direction at a speed of about 15km/h.
FORECAST: According to NCHMF Tropical Depression News update at 1700H UTC+7 today:
- By 0400H on 19 August 2025, the Tropical Depression is forecast to continue moving north-northwest at 10-15 km/h over the coastal area of Quang Ninh-Hai Phong with wind strength at level 6 and gusts up to level 8.
- By 1600H of 19 August 2025, it is forecast to move northward at 10-15 km/h as it gradually weakens into a low pressure area over Guangxi, China.
HAZARDS:
- LAO PDR: The Department of Meteorology and Hydrology (DMH) of Lao PDR has issued a warning from until 19 August for light to moderate thunderstorms in general, and heavy to very heavy rains with strong winds in some areas in Vientiane Capital, Vientiane province, Xaysomboun, Bolikhamxay, Khamouanne,Savannakhet, Saravan, Champasak, Sekong, Attapeu, Phongsaly, Houaphanh, Xiengkhouang, Oudomxay, Bokeo. Luang Namtha, Luang Prabang, and Xayaboury. Continuous heavy rainfall for several days may cause flashfloods, landslides, and urban flooding.
- THAILAND: According to the Thailand Meteorological Department (TMD), heavy rain is expected in some areas of the North and Northeast. Residents, particularly those in Bueng Kan, Sakon Nakhon, Nakhon Phanom, and Mukdahan provinces, are advised to be wary of the dangers of heavy rain and accumulated rain, which could lead to flash floods and mudslides. This is particularly true in areas on hillsides near waterways and lowlands, as the monsoon trough is passing through the North and upper Northeast, combined with the approaching strong low-pressure area (Tropical Depression Seventeen) over the Gulf of Tonkin.
- VIET NAM: According to the NCHMF, the coastal areas of Quang Ninh and Hai Phong have winds gradually increasing to level 6, gusts of level 8. The Gulf of Tonkin area (including Bach Long Vi, Cat Hai, Co To and Van Don special zones) has thunderstorms and strong winds of level 6-7, gusts of level 9, and rough seas with waves 2.0-3.5 m high. From tonight up to the night of 19 August, the Northeast and Thanh Hoa will have moderate rain, heavy rain and thunderstorms with common rainfall of 50-150mm, some areas with very heavy rain over 300mm. In Nghe An, there will be moderate rain, heavy rain and thunderstorms with common rainfall of 20-40mm, and some areas with very heavy rain over 80mm.
ANTICIPATED RISK:
- Based on current forecasts, potentially affected areas are same areas affected by the recent tropical cyclones and southwest monsoon.
- The tropical depression may influence the Southwest Monsoon, which may bring more rainfall in the affected areas.
PREPAREDNESS AND RESPONSE:
- LAO PDR: DMH Lao PDR is closely monitoring the weather disturbance and regularly releases warning and advisories. NDMO Lao PDR is also closely monitoring the weather conditions and coordinates with relevant ministries in preparation for the potential impacts of the tropical depression. Communities in high risk areas have been pre-emptively transferred to safer locations.
- THAILAND: TMD is closely monitoring the weather disturbance and regularly releases updates. DDPM closely monitors the situation and coordinates with relevant ministries.
- VIET NAM: NCHMF is closely monitoring the weather disturbance and regularly releases warning and advisories. The VDDMA issued official dispatches on the implementation of dike protection work, ensuring the safety of the dike system; organising text messages to warn 9.1 million users in the affected area, and proactively respond to the tropical depressions in the East Sea.
The AHA Centre will continue to monitor for further developments and issue necessary updates
DATA SOURCES
ASEAN Disaster Monitoring & Response System (DMRS), ASEAN Disaster Information Network (ADINet); Pacific Disaster Center (PDC Global); ASEAN Specialised Meteorological Centre (ASMC);
Lao PDR: NDMO Lao PDR, DMH;
Thailand: DDPM, TMD;
Viet Nam: VDDMA, NHCMF;
Verified news media agencies
