According to the National Center for Hydro-Meteorological Forecasting, satellite imagery, weather radar and lightning detection data show convective cloud systems developing over the wards and communes of Tay Ho, Xuan Dinh, Ngoc Ha, Giang Vo, Hoang Liet and Dai Thanh.

Within the next three hours from the issuance of the forecast at 8:25 a.m. on June 30, these areas are expected to experience showers and thunderstorms before the storm clouds spread to other parts of Hanoi. The storms may be accompanied by whirlwinds, lightning and strong wind gusts.

The weather agency also reported that overnight and into the morning of June 30, northern Vietnam recorded moderate to heavy rain and thunderstorms, with some locations experiencing very heavy rainfall. Between 7 p.m. on June 29 and 8 a.m. on June 30, rainfall totals exceeded 150mm at several monitoring stations, including Xuan Minh 2 Station in Tuyen Quang Province with 265.2mm, Hong Ha Station in Quang Ninh Province with 208mm and Ngoc Chan Station in Lao Cai Province with 166mm.

From June 30 through the night of July 1, the northern mountainous and midland regions, along with Quang Ninh Province and Hai Phong City, are forecast to receive moderate to heavy rain and thunderstorms, with widespread rainfall of 50-100mm. Some locations could record more than 250mm, with the heaviest rain expected during the evening, overnight and early morning.

Elsewhere in northern Vietnam, from June 30 to the morning of July 1, rainfall is forecast to range from 20-50mm, with isolated areas receiving more than 100mm. Rain is expected to be concentrated during the evening, overnight and early morning.

Forecasters also warned of the risk of extremely intense rainfall exceeding 100mm within a three-hour period.

In addition, scattered showers and thunderstorms are expected on the afternoon and evening of June 30 across Thanh Hoa Province, Nghe An Province, the area stretching from Hue City to Lam Dong Province, and southern Vietnam. Rainfall is forecast at 10-30mm, with isolated locations receiving more than 70mm.

Heavy rainfall is expected to gradually ease from July 2.

The weather agency warned that thunderstorms could bring whirlwinds, lightning, hail and strong wind gusts. Heavy rain may trigger flooding in low-lying areas, urban and industrial zones, as well as flash floods on small rivers and streams and landslides on steep slopes.

Water levels on several rivers in Lao Cai, Thai Nguyen, Tuyen Quang and Cao Bang provinces are continuing to rise. Some rivers have exceeded the first flood warning level, while others have risen above the second warning level. From June 30 to July 1, small rivers and the upper reaches of major river systems in northern Vietnam are expected to experience a flood wave with water levels rising by 2-4m. The weather agency warned of a high risk of flash floods and landslides across the northern mountainous and midland provinces.

Bao Anh