When will the damp weather in Hanoi and the northern provinces and cities last?

In late autumn and early winter, Hanoi and the northern provinces and cities are unusually humid. When cold air comes in, this situation will end.

Although it has just entered the beginning of winter (November 7), Hanoi and many provinces and cities in the North are experiencing unseasonably humid days, instead of the typical dry weather of late autumn and early winter. The sky is cloudy, light rain lasts for a long time, the humidity is often above 80%, sometimes exceeding 90%, making the floors and furniture always wet.

Usually, the phenomenon damp only appears in spring, lasting from mid-February to early April every year. Each wet spell usually lasts a few days to a week and only ends when strong cold air flows in or the weather clears up.

Hanoi weather forecast for the next 10 days. (Source: NCHMF)

According to forecast, around November 12-13, cold air will begin to weaken in the North and gradually strengthen on November 16-17. At that time, the humid situation in the Northern provinces and cities will end.

Forecast for November 12, the North will be cold at night and morning, some mountainous areas will be cold. From November 13-14, this area will likely turn cold at night and morning.

Forecast for November 10, central Hanoi area is cloudy, with rain, showers, humidity may continue, daytime temperature is commonly 21-25°C.

On November 11, there will be no rain in this area, the humidity will gradually decrease. From November 12-19, the Hanoi area will be cloudy, no rain, the weather will be clear.

Explaining the dampness in Hanoi, weather expert Dang Tran Trung (former officer of Hai Phong Coastal Information Station) said that this year the change of seasons is out of phase when the cold air mass from the North appeared early but was weak, not strong enough to push the low pressure trough away.

Meanwhile, the hot and humid air mass from the East Sea and the South Central Coast is unusually active, pushing moisture back up to the North. The two air masses meet over the Northern Delta region, creating a low temperature inversion layer, preventing water vapor from escaping upwards; the humidity is saturated, creating a damp, sticky feeling.

In addition, the indirect impact of post-storm circulation and westerly wind troughs when low vortices and tropical storms continuously appeared in the East Sea in recent times has disrupted the wind field in the Northern region.

Currently, the upper westerly wind trough still exists, while the lower level is affected by the humid easterly wind from the sea, creating a "humid sandwich" situation: the upper level has thick clouds, the lower level is heavily humid, the air is stuffy, humid, there is little sunlight, and the temperature is higher than average.

Weather expert Dang Tran Trung pointed out another factor causing unusual humidity is that in Hanoi, the ground and concrete structures absorb heat during the day and radiate heat at night, causing the air temperature to not drop low enough to dry the surface. When encountering humid east winds, this warm air mass has more difficulty evaporating water, creating a humid, stuffy feeling even without rain.

Source: https://baolangson.vn/nom-am-o-ha-noi-va-cac-tinh-thanh-mien-bac-keo-dai-toi-khi-nao-5064458.html