CCTV News: On May 16, Beijing also issued an orange lightning warning, a yellow wind warning, and a yellow hail warning. It is clear that the sky is clear, and thunderstorms and hail begin to occur from evening to night. Why do strong convective weather such as hail, thunderstorms, and strong winds "combine"? Why do hail always come at night?
Why do hail, thunderstorms and strong winds hit Beijing in groups?
Meteorological analyst Hu Xiao introduced that this is closely related to the characteristics of strong convective weather. Strong convective weather belongs to a weather system of small and medium-sized scales, with rapid development and many changes. This is also an important branch of weather forecasts. Usually, hail, thunderstorms, strong winds, short-term heavy rainfall, and even tornadoes and downstorms are collectively called strong convective weather. Sometimes they appear in combination, or these are different manifestations of strong convective weather. Of course, strong convective weather requires unstable atmospheric ganglia, warm and wet in the lower layer, dry and cold in the upper layer, which we often call "cold on top and warm on the lower layer" vertical structure; there is also a certain water vapor and lifting trigger mechanism: such as cold air, terrain lifting, etc. Thunderstorms, strong winds and hail are actually when the water vapor conditions on the bottom layer are not sufficient, and sometimes they will appear together. May and June are the dry and hot seasons that include Beijing in the North China region, so they will be relatively frequent.
Why does hail always come at night?
Hu Xiao said that when it comes to hail, this is closely related to the daily changes in convective weather. During the day, the increase in solar radiation caused the surface to heat up, and the air near the ground rose after being heated. After nightfall, the high-rise atmosphere cools down very quickly, which will form an unstable layering of cold top and warm bottom. This vertical temperature difference will aggravate the upward airflow, which will make the upward airflow develop more vigorously, and will also help hail appear at night.
