Since April, strong convective weather has been very frequent in many places in the south, with thunder, lightning, strong winds, and hail occurring from time to time. For example, at about 15:30 on April 27, hail the size of an egg fell in Zengcheng District, Guangzhou.
Hail is solid solid precipitation that falls from a thundercloud in the form of a hard ball, cone, or irregular shape.
When you hear the word ice, you will think of the cold winter.
What season does hail usually occur?
In fact, hail mostly occurs in late spring and early summer, and sometimes occurs during intense and long-lasting thunderstorms in the middle of summer.
Why doesn't this kind of ice lump that falls from the sky appear like snowflakes when it's cold?
This is from the principle of hail formation:
Hail is a small drop of water in a cumulonimbus cloud. Cumulonimbus clouds are very high, up to 10 kilometers in height, the higher the cloud top, the lower the temperature, the temperature at the top of the cumulonimbus cloud can generally reach below -20 °C, and the water vapor in the cloud is very abundant, and the convection up and down the cloud is strong.
The small water droplets in the cumulonimbus cloud rise rapidly with the air current, increasing in height and decreasing in temperature, and when the temperature reaches below 0°C, the water droplets condense into ice crystals. Therefore, the upper layer of the cumulonimbus cloud is ice crystals, and the lower layer is water droplets.
As the air flow rises, some of these water droplets and ice crystals collide with the surrounding ice crystals and supercooled water droplets to grow, freezing on the ice crystals into an opaque ice core, which forms the hail core.
When the hail cannot support the growing hail, the hail will fall in the updraft, and if it falls into another stronger updraft area, then the hail will rise again and grow larger again.
The rise and fall of the air flow in the cumulonimbus cloud is very drastic, and the hail is rolling up and down in the air again and again, and the pasted ice crystals and supercooled water are more and more, like a snowball, rolling bigger and bigger, once the big hail is rolled, when the updraft in the cloud is completely unable to support it, it falls from the sky, so it becomes our common hail.
Therefore, an important factor in the production of hail is to have a strong updraft, and the air is humid, and the hot and humid air rises strongly, so that it is easy to produce cumulonimbus clouds.
That's why hail often occurs in late spring and early summer, or in the middle of summer when there are strong thunderstorms, and more than 70% of them occur in the late afternoon to late afternoon.
In winter, when it is cold near the ground, there is not enough updraft, and small water droplets condense at high altitude, and directly turn into snowflakes and float down, not rolling back and forth in the high altitude, and of course, not forming hail.
According to the climate data statistics in the figure below, we can also see that hailstorms mostly occur from February to May in southern cities such as Wuhan, Changsha, Chongqing, and Guiyang. Northern hailstorms generally occur in May and June.
Hail is sometimes the size of a soybean or mung bean, but sometimes it can be as big as a chestnut or even an egg, and this hail is very powerful. When a hailstone the size of an egg falls from the sky, the power is amazing:
These hailstones are like bombs crafted by nature, which can penetrate the glass of automobiles, and have very serious hazards to agriculture, construction, communications, electricity, and transportation.
When severe convective weather is frequent, everyone must pay attention to the forecast and warning information in advance, prepare early, and minimize losses.
Source: News Network Weather Forecast
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