Vietnam is entering the most dangerous phase of the current weather episode after the tropical depression itself has weakened. The circulation that crossed central Vietnam was downgraded to a low-pressure area on Sunday evening, with maximum winds below 39 km/h. The official cyclone bulletin was then closed. The rainfall threat, however, remains active.
More than 230 mm already measured overnight
Vietnam’s National Center for Hydro-Meteorological Forecasting (NCHMF) reported very heavy rain between 7 p.m. on 13 September and 8 a.m. on 14 September. Hóa Thanh in Quảng Trị recorded 232.2 mm, Kỳ Thượng in Hà Tĩnh 188 mm and Xuân Thủy in Ninh Bình 166 mm.
Those are observed totals. The next part of the story is a forecast: much larger accumulations are possible as the rain episode continues.
Local totals above 500 mm are possible
From 14 September through the night of 15 September, the southern part of the northern delta, southern Phú Thọ and the corridor from Thanh Hóa to Nghệ An are forecast to receive 150 to 300 mm, with isolated totals above 450 mm. Looking at the full period from 14 to 16 September, the official forecast reaches 180 to 350 mm, locally more than 500 mm in the hardest-hit zone.
Rainfall intensity is another concern. NCHMF warns that more than 100 mm could fall within three hours in some places, a rate capable of producing rapid runoff even before multi-day totals are reached.
Flash-flood and landslide warnings are active
The weather service warns of flooding in low-lying areas, cities and industrial zones, flash floods on small rivers and streams, and landslides on slopes. A short-range hazard warning also names Lào Cai, Thanh Hóa, Nghệ An, Hà Tĩnh, Quảng Trị and Huế among areas at risk of flash floods, landslides or ground subsidence.
In the heavy-rain bulletin, the natural-hazard risk is set at level 2 for Thanh Hóa and Nghệ An, while level 1 applies to the broader severe-rain and thunderstorm threat described in the bulletin.
Weaker cyclone does not mean lower rainfall risk
The tropical system is no longer the headline because of its wind strength. It is the amount and intensity of rain that now matters. The official material reviewed for this update does not provide a new confirmed casualty or evacuation toll, so the situation should be followed as an evolving flood and landslide threat rather than described as a confirmed large-scale disaster.