On April 30th, according to reports from multiple domestic media outlets, a squall line swept through Fujian this morning, affecting the Xiamen area with thunderstorms, strong winds, and short-term heavy rainfall. The daytime turned into night as the sky was covered by thick dark clouds, leaving only a thin line of sky visible.
Information indicates that a squall line, also known as an unstable line or a surge line of air pressure, is a discontinuous line of small range and short lifespan of air pressure and wind.
Meteorologically, a squall line refers to a narrow and intense convective weather zone with small range, short lifespan, sudden changes in air pressure and wind. When it arrives, there may be sudden changes in wind direction, rapid increase in wind force, sharp rise in air pressure, abrupt drop in temperature, and other severe weather phenomena.
From the weather radar images, a squall line looks like a string of candied haws, threading through a cluster of thunderstorms or cumulonimbus clouds. Near the squall line, apart from the drastic changes in wind, air pressure, and temperature, there may also be accompanying severe weather processes such as thunder and lightning, heavy rain, hail, and tornadoes.
Squall lines often occur in the warm regions before the cold front during the transition from spring to summer, and are also common in the presence of typhoons, mostly from March to September.
