The North is forecast to welcome two consecutive cold air waves, with long-term thunderstorms

According to the National Center for Hydro-Meteorological Forecasting, after a prolonged heat wave, the North will welcome a weak cold air mass causing thunderstorms. From the evening and night of April 30 to May 7, this area will have scattered showers and thunderstorms, locally heavy rain (the rain will be concentrated from the night of April 30 to May 3 and from the evening and night of May 5 to 7).

Meanwhile, from the evening and night of April 30 to May 7, Son La, Hoa Binh, Thanh Hoa, and Nghe An will have scattered showers and thunderstorms, with some heavy rain (rain will be concentrated from the night of April 30 to May 3 and from the evening and night of May 5 to 7). From May 2 to 3, the Central Highlands will likely have scattered showers and thunderstorms.

The meteorological agency warned that the cold air at the end of the season from mainland China is moving to the North, causing showers, some places with heavy rain, and the hot weather will end. The conflict between the two hot and cold air masses can cause extreme weather phenomena such as thunderstorms, hail, and lightning.

May is the period of weather transition from cold to hot season, dry season to rainy season in the North, so strong thunderstorms with tornadoes, lightning, and hail are most likely to appear during the year. Especially in mountainous areas, due to the impact of terrain, convective clouds can develop strongly, resulting in thunderstorms with tornadoes, lightning, hail and strong gusts of wind. Thunderstorms, tornadoes, lightning, and hail in the North, Thanh Hoa, Nghe An and Ha Tinh areas often appear in the afternoon, evening and night.

The National Center for Hydro-Meteorological Forecasting said that due to the impact of El Nino in the recession phase, the average temperature in May nationwide was 1-2 degrees Celsius higher than the average of many years, and in June it was 0.5-1.5 degrees Celsius higher.

Mr. Nguyen Van Huong, Head of Weather Forecasting Department (National Center for Hydro-Meteorological Forecasting) said that the outbreak of cloud towers appearing during the transitional season caused strong thunderstorms or hail recently. Early next May, thunderstorms, tornadoes, lightning, hail and strong gusts of wind are forecast to recur.

Explaining the cause of the recent occurrence of thunderstorms and hail in many places in the North, Mr. Huong informed that it is currently in the transitional season, there is often a conflict between air masses with different characteristics, the atmosphere becomes more unstable, so thunderstorms also occur more often than at other times of the year.

Earlier, in the evening and night of April 23, there were showers and heavy thunderstorms in Son La, Hoa Binh, Thanh Hoa, and Nghe An. According to satellite data, the estimated temperature of the convective cloud top during the thunderstorm was -81.2 degrees Celsius. This is a sign that the convective cloud tower is developing very strongly. The height of the cloud mass can be over 10km.

The eruption of such cloud towers often appears during the changing seasons and causes strong thunderstorms or hail. The strongly developed cloud area moves slowly, causing hail concentrated in the area bordering Son La and Hoa Binh.

According to some forecast models, currently through analysis of weather maps and models, it is highly likely that the North will receive 2 weak cold air waves accompanied by a low pressure trough. Between the 2 cold air waves, there may be wind convergence before the westerly wind trough. Therefore, the weather after the April 30 - May 1 holiday in the North will turn bad, cloudy with rain, showers, locally heavy rain, beware of thunderstorms, mountainous areas should be careful because there may be flash floods and landslides.

According to the National Center for Hydro-Meteorological Forecasting, after this weak cold spell, the North is expected to continue to receive cold air this weekend. Due to the influence of cold air combined with the high-altitude wind convergence zone, from May 2-8, the North will continue to have scattered showers and thunderstorms, with some areas having moderate to heavy rain, with rain concentrated in the late afternoon and at night.

In addition, the Thanh Hoa-Nghe An area is also affected in this period. This rain is forecast to start around the night of May 30th and early morning of May 1st and last for many days, possibly this whole week and next week there may be another weak cold air coming in. The heat in the Central and Central Highlands will gradually decrease after the holiday. There may be thunderstorms in the evening.

The South is likely to have seasonal rains due to the equatorial trough gradually lifting its axis to the North. According to the model, the highest possibility of thunderstorms may occur at the weekend, with thunderstorms accompanied by lightning, so caution is needed. Regarding the Southwest monsoon, the North Indian Ocean region has not yet established this wind flow next week, so it is likely that the Southwest monsoon will blow to the South around mid-May.

Mr. Nguyen Van Huong, Head of Weather Forecast Department, National Center for Hydro-Meteorological Forecasting, this year's heat wave has 3 main characteristics: it comes early, the number of heat waves is higher than the average of many years, the intensity is more severe than the average of many years; there may be historically high temperature values.

The reason for the early heat wave in the North and Central regions is the impact of the El Nino phenomenon, which causes the average temperature across the country to tend to be higher than the average of many years. The South and Central regions experienced heat waves 1 month earlier. In the North, this year's heat wave came 1 month earlier, with intense temperatures, higher than the average of many years.

Mr. Nguyen Van Huong also said that the early heat wave is an unusual phenomenon, occurring for the third time since 1991. "Under the impact of the El Nino phenomenon, temperatures across the country tend to increase, and the heat wave comes early. We predict that the peak of the heat wave in Hanoi and the North will be in May, June, July, and August," Mr. Huong said.