According to the National Center for Hydro-Meteorological Forecasting, the tropical depression weakened into a low-pressure area after making landfall in Quang Tri on the evening of September 13. It then moved into central Laos and gradually dissipated.

However, its circulation, combined with an intertropical convergence zone, continues to bring heavy rain to northern and central Vietnam, with the heaviest rainfall shifting northward.

Northern Vietnam is expected to experience three days of heavy rain from September 14-16, with rainfall exceeding 500mm in some areas. In central Vietnam, the affected area is gradually narrowing, with heavy rain now concentrated mainly between Thanh Hoa and Ha Tinh.

Torrential rain from northern Vietnam to Ha Tinh

From the night of September 13 through the morning of September 14, areas from southern Nghe An to northern Quang Tri received heavy to extremely heavy rain.

Rainfall generally ranged from 60-100mm, but some locations recorded much higher totals, including 225mm in Hoa Thanh, Quang Tri, and 184mm in Ky Thuong, Ha Tinh.

From the morning of September 14 through the night of September 15, the southern Red River Delta and areas from Thanh Hoa to northern Ha Tinh are forecast to receive 150-300mm of rain, with more than 450mm possible in some places.

Other parts of the Red River Delta, southern Son La and Phu Tho, and Ha Tinh are forecast to receive 100-180mm, with isolated totals exceeding 250mm.

From the evening of September 14 through the night of September 15, the northern midlands and southern parts of Tuyen Quang and Lao Cai are expected to receive 50-100mm, with isolated totals above 150mm.

Forecasters warned that rainfall intensity could exceed 100mm within three hours.

On September 16, moderate to heavy rain and thunderstorms are expected to continue across the northern midlands and Red River Delta, Phu Tho, Thanh Hoa and Nghe An, as well as southern areas of Son La, Tuyen Quang and Lao Cai.

Rainfall is forecast at 20-40mm, with isolated totals exceeding 70mm.

Total rainfall from early September 14 through September 16 is forecast to reach 180-350mm across the southern Red River Delta and from Thanh Hoa to northern Ha Tinh, with some areas receiving more than 500mm.

The northern midlands, other parts of the Red River Delta, Phu Tho and southern areas of Son La, Tuyen Quang and Lao Cai are forecast to receive 100-200mm, with isolated totals exceeding 300mm.

Hanoi is expected to receive moderate to heavy rain and thunderstorms from the morning of September 14 through the night of September 15, with rainfall of 40-120mm and isolated totals above 150mm.

Nguyen Ngoc Huy, an expert on climate change and disaster warnings, said the circulation of the former tropical depression would bring heavy rain to coastal areas from Nghe An to Hai Phong on the morning of September 14.

From later in the day through September 16, heavy rain is expected to persist in Thanh Hoa, Ninh Binh, Hung Yen and Hai Phong while spreading to Hanoi, Quang Ninh and Hoa Binh.

Residents in low-lying areas, including parts of Hanoi and Ninh Binh, should be alert to flooding as river levels rise, Huy warned.

“People often become complacent after hearing that a storm or tropical depression has dissipated, but its circulation can still cause widespread and prolonged heavy rain,” he said.

Rivers rising as landslide threat grows

Water levels in rivers from Quang Tri to Hue are gradually falling, according to the national weather agency. The Thach Han River was 0.72 metres below the third warning level.

A new flood wave could develop on rivers from Thanh Hoa to Hue through September 16.

Water levels on the Ngan Sau and Ngan Pho rivers in Ha Tinh could reach the second to third warning levels, while the Thach Han River is expected to continue falling and fluctuate around the first to second warning levels.

Western areas of Thanh Hoa, Nghe An, Ha Tinh and Quang Tri face a particularly high risk of flash floods and landslides on September 14.

The threat is greatest in mountainous areas, on steep slopes and in places where heavy rainfall has accumulated over several days.

Bao Anh