OVERVIEW:A low pressure area, INVEST 93W, has developed into Tropical Depression 20W over the Viet Nam East Sea. According to Viet Nam’s National Center for Hydro-Meteorological Forecasting (NCHMF), as of 0700H UTC+7, the centre of 20W was located at approximately 15.8°N latitude and 113.5°E longitude, over the southeastern sea area of the Hoàng Sa Archipelago.
STRENGTH & MOVEMENT: According to NCHMF, maximum sustained winds near the centre were at level 6–7 (39–61 km/h), with gusts reaching level 9. 20W is moving northwestward at a speed of around 15 km/h.
FORECAST:
- By 0700H UTC+7 on 30 August, 20W is forecast to be located at 17.3°N, 109.0°E, over the sea area from Nghe An to Hue City. It is expected to move northwest at a speed of about 20 km/h, with maximum sustained winds at level 8 and gusts reaching level 10. 20W is likely strengthen into a tropical storms and make landfall over Central Viet Nam on Saturday (30 August).
- By 0700H UTC+7 on 31 August, 20W is forecast to be at 17.9°N, 104.5°E, over central Lao PDR, continuing northwestward at about 25 km/h. Its intensity is expected to weaken into a tropical depression, and weaken into.
HAZARDS:
- LAO PDR: According to the Department of Meteorology and Hydrology (DMH) of Lao PDR, due to the influence 20W, from 29 to 31 August 2025, Lao PDR will experience rain, thunderstorms, and strong winds across most regions. Heavy rainfall is expected in some areas, particularly in the central and southern regions, which may cause flash floods and landslides in vulnerable areas. According to MRC, in the next 5 days, 30 Aug to 01 Sept, the thunderstorm and moderate to heavy rainfall are likely to occur in the central part of the LMB including the central part of Lao PDR.
- THAILAND: According to the Thailand Meteorological Department (TMD), during the period of 30 August to 3 September, rainfall will increase across Thailand, with heavy to very heavy rain in parts of the North, Northeast, East, and the western South. This is because the monsoon trough will shift southward to lie across the lower North, Central, and Northeast regions into 20W over the Viet Nam East Sea, while the southwest monsoon prevailing over the Andaman Sea, Thailand, and the Gulf of Thailand will strengthen. According to MRC, in the next 5 days, 30 Aug to 01 Sept, the thunderstorm and moderate to heavy rainfall are likely to occur in the central part of the LMB including the northeastern part of Thailand.
- VIET NAM: According to the NCHMF, in the western waters of the northern East Sea (including the Hoang Sa Archipelago), severe thunderstorms are expected with strong winds of level 6–7. Near the storm’s centre, winds may reach level 8 with gusts up to level 10. Wave heights will range from 2.0 to 5.0 metres, and seas will be very rough. From the night of 29 August, the sea area from Nghe An to Hue City (including Hon Ngu Island and the Con Co area) will experience severe thunderstorms. Winds will gradually strengthen to level 6–7, and near the storm’s centre, winds may reach level 8 with gusts up to level 10. Wave heights will be 2.0 to 5.0 metres, with very rough sea conditions.
REPORTED IMPACTS:
PHILIPPINES:
- According to the NDRRMC, as of 29 August at 0700H (UTC+7), the combined effects of the southwest monsoon, Tropical Cyclone 20W (locally named “Jacinto”), and LPA 08f have affected approximately 29,700 families (143,700 persons). Of these, around 575 families (2,083 persons) are currently being accommodated in 11 evacuation centres (ECs), while 19,884 families (99,396 persons) are receiving assistance outside evacuation centres across Regions V, CALABARZON, MIMAROPA, IX, XII, CARAGA, and BARMM.
- Initial reports indicate impacts to 15 road sections (1 remains impassable) and 1 bridge, along with 413 damaged houses—of which 2 are totally damaged and 311 are partially damaged.
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 situations and coordinates with relevant agencies in preparation for the ongoing impacts of southwest monsoon and previous TC KAJIKI and potential impacts of 20W.
- PHILIPPINES: NDRRMOC remains on Blue Alert due to the impacts of the southwest monsoon, Tropical Cyclones Kajiki and 20W, and LPA 08f. The NDRRMC has conducted a Pre-Disaster Risk Assessment (PDRA), maintained continuous monitoring and coordination with OCD Regional Offices and member agencies, activated both the Virtual Emergency Operations Center and the Inter-Agency Coordination Cell, and disseminated Emergency Alert and Warning Messages.
- 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. According to VDDMA, on 27 August, the Ministry of Agriculture and Environment issued Urgent Telegram No. 6099/C?-BNNMT to the People’s Committees of coastal provinces and cities from Quang Ninh to Khanh Hoa on preparedness and response to 20W and the Ministry of National Defense issued Urgent Telegram No. 4978/C?-TM on 28 August 2025 regarding proactive measures to respond to 20W.
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, DMH;
Philippines: NDRRMC
Thailand: DDPM, TMD;
Viet Nam: VDDMA, NHCMF;
Verified news media agencies
