On the morning of April 18
"Clusters" of severe convective weather
Squall (biāo) line effect
Foshan, Qingyuan, Guangzhou and other places in Guangdong
On the morning of April 18, an ultra-long squall line about 600 kilometers long quickly swept across the whole of Guangdong Image source: Sina Weibo @GuangdongWeather
The sky instantly darkened in many places
"One Second into the Night"
And accompanied by instantaneous gales
Short-term heavy precipitation, hail, etc
Severe convective weather
Image source: Sina Weibo @广州weather
Early this morning (19th).
One is about 500 to 600 kilometers long from north to south
Extra-long "bow" squall line echo
Quickly swept Hunan from west to east
Be affected by it
Appeared in many places in Hunan
Severe convective weather such as thunderstorms, high winds, and short-term heavy precipitation
so
Recently, I have frequently swiped the screen
What is a squall line?
Xiangxiang will give you a popular science
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What kind of line is a squall line?
According to Hanyu Pinyin, the relatively rare character "飑" is pronounced "biāo" in Mandarin. The squall line is a type of severe convective weather, which can be understood as a group of thunderstorms arranged in a line or band, along which violent weather phenomena such as thunderstorms, heavy rain, strong winds, hail, and tornadoes can occur. From the radar chart, the squall line is a vivid line or banded echo.
Among the many severe convective weather, the squall line is known for its violent temper, which is characterized by short duration, severe weather, and extremely destructive. Thunderstorms on the "squall line" are usually composed of several thunderstorm cells, ranging from four or five to a dozen or dozens at most. Therefore, the squall line is much more drastic than the weather changes brought about by a single thunderstorm, and the squall line can cause serious disasters when it crosses with strong winds, hail, lightning, and sometimes even tornadoes.
How is the squall line formed?
Like many severe convective weather, the squall line originates from unstable atmospheric environments and is affected by topography. When the lower troposphere is occupied by warm and moist air currents, and the upper layer is occupied by cold air, forming a structure that is cold at the top and warm at the bottom, the unstable structure of the atmosphere will be formed, and a large amount of unstable energy will accumulate in the atmosphere, and when a suitable trigger mechanism exists, the unstable energy will be released, and the squall line weather will be generated.
The conditions under which the squall line occurs
In addition, the occurrence of the squall line is also closely related to the upper-air wind field, when there is a large wind speed area in the upper atmosphere, that is, the jet stream, the wind direction and wind speed difference between the upper and lower layers is large, that is, the existence of strong vertical wind shear is very important for the formation and maintenance of the squall line. Finally, topography not only affects the squall line at the beginning, but also plays an important role in maintaining the squall line, which is more likely to occur in the Great Plains than in mountainous areas, where there are large frictions and blocking.
The squall line is located at the leading edge of the cold air sinking in the thunderstorm cloud, and the spatial structure is similar to the cold front, and the transit is accompanied by a sharp change in wind direction, a sudden increase in wind strength, a drop in temperature, and an increase in air pressure, and it often appears near a cold front, so it is easy to confuse it with a cold front. Although there are many similarities between the squall line and the cold front, there are also significant differences, so the squall line is often referred to as a "pseudo-cold front" or "false cold front".
The squall line is so scary, how can we prevent it?
From appearance to disappearance, the typical life history of the squall line is only 6 to 12 hours, but it often leaves traces with its enormous destructive power. Therefore, in weather forecasting, the squall line is an unavoidable problem. Usually, forecasters mainly mention the effects of wind and rain on the squall line in their conclusions, but in their analysis of the weather, they consider the creation of the squall line and its effects. Due to the short life history of the squall line, it is destined not to leave much advance in forecast.
For example, in the previous day's analysis, forecasters can only judge the possibility of forming a squall line in a certain place and pay close attention. When the squall line is approaching or at the beginning of its development, it is possible to see obvious traces on the radar echoes. In other words, only short-term nowcasting can capture the movement of the squall line.
In the season when the squall line is prone to occur, the meteorological department will issue forecasts and warnings in advance, and the public needs to pay more attention to short-term nowcasting and related warnings, and be fully mentally prepared for the changeable weather. It is important to know that severe convective weather, including the squall line, can be sunny until a few hours before it occurs, and then turn into hot and humid, stormy and even dark and torrential rain in a short period of time. After that, the sky was clear and warm again.
When encountering strong convective weather such as thunderstorms, strong winds, hail, etc., stay away from trees, billboards, and dilapidated houses that are prone to breakage.
Finally, a reminder to everyone
Recently, Jiangnan, South China and other places
There is still strong convective weather
Under the influence of strong convection
It's best not to go out!
Students outside
Evacuate to the safety of your room!
Source: China Meteorological Administration