Sudden hail as big as an egg in many places in my country Big data tells you where hail has the highest occurrence
China Weather Network News yesterday (11th) from the afternoon to the evening, cold and warm air in Liaoning, Henan, Hebei, Sichuan and other places intersected intensely, and local strong convective weather such as thunderstorms, strong winds and hail occurred. Henan Xinxiang, Sichuan Anyue, and Hebei Handan The hail covered the ground, some even as large as eggs, and the car windows were smashed through in Anyue, Sichuan.
So Hail, a guy who comes and goes in a hurry and is extremely destructive, is there any pattern to follow?
China Weather Network specially studied the data from 1981 to 2010, and deeply analyzed the "mysterious and capricious" hail.
Where is the hail preference for mysterious places?
If the weather is likened to war, strong convection is fighting "guerrilla warfare". As an important member of the strong convection family, the characteristics of hail "coming and going in a hurry" are particularly obvious.
Often, the duration of a hailstorm is only about 2 minutes to 10 minutes, and the impact range is mostly about tens of meters to several kilometers. The duration of hail is short and the "locality" is also very strong.
However, China Weather Network has studied the meteorological data from 1981 to 2010 and found that there are still some laws to follow in the hailstones that are "elusive". more likely to happen.
Meteorological data show that the areas with the highest probability of hail in my country are the Qinghai-Tibet Plateau, southern Qinghai, northern Tibet, and parts of the western Sichuan Plateau. The annual average number of days is also 3-5 days; the eastern plains are relatively low, and the annual average number of days in most areas is less than 1 day.
Among the provincial capital cities, Lhasa, Hohhot, Guiyang, Xining, Harbin, Changchun, Beijing and other places are more likely to be hit by hail. The highest average annual number of hail days in Lhasa is 3.8 days. Beijing ranks 5th to 6th with an annual average of 1.7 days and 1.4 days respectively; Chengdu, Hefei, Chongqing, Shanghai and other places have an annual average of less than 0.1 days of hail, which means that these cities On average, there may be 1 hailstorm in ten years, and the probability is extremely low.
Hail "comes and goes in a hurry", preferring spring and summer "infestation"
my country has a vast territory, and hail may occur in 12 months of the year. Generally speaking, there are obvious seasonal differences. Spring and summer are the high incidence periods, and winter rarely occurs.
Due to the complicated conditions of hail formation, its high occurrence time in different regions is not the same.
From January to February, the areas with high hail incidence are mainly concentrated in the Yunnan-Guizhou Plateau and the western part of Jiangnan; in March, the hail area began to expand, and most of Jiangnan, South China, and Southwest China entered a period of high hail; In the Huaihe River Basin, hail will also appear in parts of North China and Northeast China. From May to September, most of the North and Southwest China became the main positions for hailfall. There will still be hail in most areas, but the frequency of hail is also significantly reduced.
Judging from the average situation of provincial capital cities across the country, May-September is the main hailstorm period in my country, accounting for more than 70%, especially the peak period from May-June, accounting for more than 35%; while November to the following year In January, hail is rare everywhere.
In addition, in a day, the hailstorms in various parts of our country are generally concentrated in the afternoon to the evening, about 70% of which occur at 13-19 pm, of which 14-16 pm are the most.
Hail is like a "snowball", the longer the time, the bigger the "volume"
For the description of the size of hail, a poet once described it as follows: "The capital has rained hail, the small is like a bomb, and the big is like a fist."
So, why are the hailstones different in size?
Hu Xiao, chief meteorological analyst at China Weather Network, said that the hail came from cumulonimbus clouds, and the areas below 0°C of the cumulonimbus are water droplets, and the above are supercooled water droplets, ice crystals and snowflakes.
When the raindrops in the cloud encounter the violent upward airflow and are brought to the high altitude above the 0°C layer, they quickly freeze with the supercooled water droplets and ice crystals and become hail cores; the hail cores continue to roll in the cumulonimbus cloud like a snowball The bigger the roll and the longer the time, the bigger the "size" of the hail.
When the hailstone weighs more than the updraft can hold, the hailstone falls to the ground.
Therefore, the stronger the updraft, the longer the hail will tumble in the cloud, and the larger the final hail "volume" will be.
Meteorological data show that most of the hail in our country is less than 2 cm in diameter, and hail above 5 cm is relatively rare. Generally, hail with a diameter of 2-5 cm is considered a large hail.
Relatively speaking, my country's Tibet and Qinghai have the most hail, but most of them are small hail; while in the plain area, although the probability of hail is much lower than that in the plateau area, it is easy to form large hail.
Hail "lethality" three tricks to teach you to avoid hail raids
Once the hail falls, the impact is not small.
Generally speaking, hailstones with a diameter of about 5 cm are often referred to in the news as "egg-sized hailstones" and weigh about 30 grams.
According to the law of conservation of energy, when it falls from a height of 1000 meters to the ground, its gravitational potential energy is converted into kinetic energy.
How big is this energy?
It is equivalent to dropping a 3 kg object from a height of about 10 meters, which is almost equivalent to throwing a soiled flower pot from a 3-story building and smashing it at a person or car... This is just a hailstorm. If we encounter hail outdoors, it may be It is a number of "flower pots" falling from the sky.
It should be noted that the above conversion is an estimation result without considering factors such as air resistance and updraft movement. During the descending process of hail, it will inevitably be affected by factors such as air resistance, and the lethality may be attenuated. , we still cannot take it lightly.
So once we encounter hail outdoors, how should we avoid it?
1. Quickly find obstructions
If you encounter a hailstorm suddenly, you must quickly enter the room or take shelter under a solid shelter.
If there is no suitable shelter nearby, squat down with your back to the wind, hold your head with both hands, and fully protect your head, chest and abdomen from being attacked.
If you carry bags and folders with you, you can temporarily put them on the top of your head to minimize the harm.
2. Keep away from fragile items
When evading, observe whether there are dangerous objects that are easy to fall around, and if so, move the place immediately to avoid being hit.
At the same time, keep away from glass products such as windows, because hail may smash the glass and cause bodily injury to people.
3. Beware of electric shock
When evading, keep away from lighting lines, high-voltage wires and transformers to prevent serious consequences of electric shock.
Hu Xiao reminded that the high incidence of hail has entered the period now, the public should be extra vigilant of hail weather, keep in mind various self-rescue measures, and beware of being smashed.
(Text / Zhang Hui Design / Ren Chengying Data Support / Hu Xiao Shao Peng )