In the early morning of today (April 19),
The squall line swept quickly across Hunan from west to east,
Successively in Huaihua, Loudi, Shaoyang,
Yongzhou, Hengyang, Zhuzhou, Chenzhou and other places,
Thunderstorms and gales were almost everywhere they went.
Severe convective weather such as short-term heavy precipitation and hail.
According to the real-time monitoring, from 11 o'clock on April 18 to 11 o'clock on the 19th, the cumulative rainfall in 14 townships (towns) in 10 counties (cities and districts) including Xiangxi Prefecture (Fenghuang, Liaojiaqiao Town, Tuojiang Town), Changsha (Liuyang, Daweishan Town), and Zhuzhou (Liling and Pukou Town) exceeded 50 mm, with the largest being 67.7 mm in Yizhang Meitian Town. During the process, a total of 124 townships (towns) in 45 counties (cities, districts) had a maximum hourly rainfall intensity of more than 20 mm, and the maximum was 38.8 mm in Huayanxi Town, Dingcheng District (from 05:00 to 06:00 on the 19th). The maximum wind speed at 129 stations in 30 counties (cities and districts) in 9 cities and prefectures south of central Hunan exceeded level 8, and the maximum was 35.1 m/s (level 12) at Leiyang Changping Station. Hail occurred in Chenzhou (Jiahe).
so
What is the squall line that has been frequently swiping the screen recently?
Liu Hongwu, chief forecaster of the Hunan Provincial Meteorological Observatory
Let's give you a popular science
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What kind of line is a squall line?
The squall line is a group of thunderstorms arranged in a line (band), or it can be regarded as an "aircraft carrier" in severe convective weather, and each convective single thunderstorm is like a fighter jet on an "aircraft carrier". The squall line is characterized by short duration, severe weather, and extremely destructive. The squall line is maintained for a few hours to more than a dozen hours. From the radar chart, the squall line is a vivid line or banded echo.
What kind of weather can be caused by the squall line?
As an "aircraft carrier" of severe convective weather, the squall line carries a huge amount of energy, and the severe convective weather that may be caused is also very diverse, there may be thunderstorms and strong winds, short-term heavy rainfall, hail, and even sometimes tornadoes, these strong convective weather may occur alone or in combination.
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. Due to the short life history of the squall line, it is destined not to leave much advance in forecast. The area where the squall line is located should not only be protected from rain, but also from wind and lightning, and must stay in a safe place to avoid danger, away from dangerous areas such as glass doors and windows, balconies, and billboards.
Source: Hunan Provincial Meteorological Observatory
Editor/First Instance: Sun Jiao
Second trial: Zeng Yanyan, Zhang Qian
Third trial: Liang Xiao