Introduction to the squall line

Squall line (English: Squall line), sometimes also called line squall. It refers to a medium to small-scale strong convective weather consisting of a band-shaped thunderstorm group with sudden changes in wind direction and wind speed. It usually accompanies or precedes the appearance of a cold front. It is very destructive. The occurrence of squall lines is mostly due to the cold air traveling to warm and humid areas, resulting in a pattern of cold at the top and warm at the bottom, which makes the thermal structure of the upper and lower troposphere different, resulting in high-intensity severe convective weather. Thunderstorms on squall lines are usually composed of several thunderstorm cells, so they can produce dramatic weather changes. In the early 20th century, squall lines were often used as a synonym for cold fronts. Typical phenomena when a squall line passes through are sudden changes in wind direction, rapid increase in wind speed, sudden rise in air pressure, and rapid changes in temperature. During the peak stage, the average wind force is above level 10, and the gust exceeds level 12. It may also be accompanied by thunderstorms, heavy rain, hail, strong straight-line winds, tornadoes and sea tornadoes. Squall lines usually have a characteristic bow-like shape and are accompanied by strong straight-line winds. Tornadoes may exist along wavy linear echoes when mesoscale low-pressure areas exist. In the summer, bow echoes may develop into extremely severe convective storms and pass through large areas at extremely high speeds. The rear edge of the rain shield is usually accompanied by a well-developed squall line, with wake low pressure and sometimes even a thermal burst. The horizontal range of squall lines is very small, usually only 150 to 300 kilometers in length, only half a kilometer to dozens of kilometers in width, and only about 3 kilometers in height. Its maintenance time is generally 4 to 10 hours.