Xinhua News Agency, Beijing, March 30 (News Analysis): Squall lines, hail, thunderstorms and strong winds appear frequently. Why is the wind and rain in the south so violent?
Xinhua News Agency reporter Liu Shiping
Starting from the night of March 28, the first large-scale severe convective weather this year occurred in southern my country. Thunderstorms, strong winds, heavy rain, and hail took turns. Squall lines and tornadoes also appeared in weather forecasts and warnings. Why was the storm so violent this time? Where are there still risks of severe convective weather? The reporter interviewed relevant experts from the China Meteorological Administration on the 30th.
"This round of severe convective weather began on the night of the 28th, and a squall line system moving from west to east first appeared in Yunnan." Zhang Tao, chief forecaster of the Central Meteorological Observatory, said that on the morning of the 29th, thunderstorms with magnitudes 8 to 10 occurred in Guizhou, with some areas reaching magnitude 11 or above. During the day on the 29th, strong convective weather occurred in Guangdong and Guangxi. During the day on the 30th, thunderstorm winds of magnitude 8 to 10 occurred in central and southern Guangdong, with local magnitudes of 11 to 12.
An extremely destructive squall line can be understood as a group of thunderstorms arranged in a linear or strip shape. Along the squall line, violent weather phenomena such as thunderstorms, heavy rain, strong winds, hail, and tornadoes can occur. From appearance to disappearance, the typical life history of a squall line is only 6 to 12 hours, but it often leaves traces with its huge destructive power.
Meteorological monitoring shows that several squall line systems hundreds of kilometers long from north to south have appeared in the Guangdong and Guangxi regions, bringing with them short-term heavy rainfall and thunderstorms and strong winds, sweeping from west to east. Central and southern Hunan, Jiangxi and other places also experienced local thunderstorm winds of magnitude 8 to 10, with local levels reaching magnitude 11 to 12. Large hail occurred locally in western and southern Guangxi.
Relevant experts from the China Meteorological Administration said that the formation of severe convective weather is the result of the synergy of a variety of meteorological conditions. Abundant water vapor conditions are its "material basis", unstable atmospheric structure is the "key prerequisite" for its formation, and strong upward motion is the "power engine" triggered by it. In addition, the blessing of terrain will also help its formation and development.
"The strongest convection in this weather process is mainly in the warm area. Driven by high- and low-altitude jet streams, multiple squall line convections are repeatedly generated, causing strong winds and rains. This is the strongest convection process this year." Zhang Tao said.
Zhang Tao said that the weather development of this round of strong convection is very complex, and it is sudden and local. Although it has been predicted in advance that most areas from the eastern part of Southwest China to the south of the Yangtze River have the possibility of severe convective weather, there is great uncertainty about which place will be affected.
At present, this round of severe convective weather in the south is still continuing. The Central Meteorological Observatory issued a blue warning for heavy rain and a yellow warning for severe convective weather at 18:00 on the 30th. It is expected that from 20:00 on the 30th to 20:00 on the 31st, there will be thunderstorms and strong winds above level 10 in some areas in southern Jiangxi, northern Guangxi, and northern Guangdong, with the maximum wind force reaching level 11 or above. Some areas in southern Jiangxi, northern Guangxi, central and northern Guangdong and other places have short-term heavy precipitation weather with hourly rainfall greater than 50 mm, and the maximum can reach more than 60 mm.
According to the forecast, in the next ten days, the southern region will face multiple rounds of rainfall and frequent severe convective weather. It is necessary to pay attention to the impact of local heavy rainfall and wind and hail on transportation, spring plowing and sowing, urban operations, etc., and to prevent secondary disasters such as local flash floods, geological disasters, and farmland waterlogging.
Zhang Tao reminded that in terms of short-term heavy rainfall, the main thing is to prevent short-term waterlogging in urban and rural areas. In mountainous areas, we must be highly vigilant about secondary disasters such as flash floods, landslides, and debris flows. In terms of thunderstorms and strong winds, be wary of falling objects from high-rise buildings and avoid narrow passages where the "narrow tube effect" may occur, where the wind force will increase instantly. At the same time, we must prevent secondary injuries caused by the collapse of large trees and billboards.
