You must have seen, along with the drops of rain, many times suddenly small pieces of ice begin to fall or small pellets of ice start falling from the sky. They are also called Hail Storm.
Hail Storm hit without warning mainly during the summer or spring months in the temperate zones. It batters the roofs of houses, shatters the windows, destroys entire crops etc. Do you know they develop during thunderstorms and in very humid weather means when winds are strong enough to hold up the hailstones that form the clouds?
Let us study through this article how hails are formed, why they are oval or round in shape, why suddenly they fall from the sky.
How Hails are formed?
We all know that ice is a state of water that is formed by the solidification of water. Whenever the temperature of the water falls below zero degrees Celsius or less then it becomes ice.
As we get higher and higher than the sea level, the temperature gradually decreases. That is why there is cold on the mountains or the temperature is low. But in Ladakh, it is so cold that there is always water in the form of ice, because it is located at a high altitude.
Do you know about the process of transpiration? Due to this process, the water of rivers, ponds, seas, etc. becomes steam; generate clouds of rain in the sky and these clouds causes rain.
But when the temperature in the sky decreases by several degrees below zero, then the air gets accumulated in the form of small drops of water.
Water is accumulated on these frozen droplets and gradually they form the shape of ice crystals which are known as hail.
Therefore, we can say that when small currents of rising air that is updrafts carries droplets of water high enough that they freeze then hails are formed. The stronger the updraft, the larger will be the hail.
Let's now study what causes hail to fall from the sky?
When these pellets of ice become overweight then they start falling on the ground from the sky. When they are falling from the sky then they collide with the warm air, starts melting convert into the droplets which fall down in the form of rain. But when the pieces of ice are big enough they are not able to melt and fall on the earth as the pellets of ice with a speed of 90mph, taking around a minute and a half to reach the land. These ice crystals are known as Hail.
You must have noticed that when the hail falls, thunderstorms and lightning occurs in the clouds.
Do you know why there is a thunder in the clouds? Thunder occurs in the clouds when the day is hot and the air has enough humidity. We know that the hot air rises above the humid air. As it rises up, it becomes cold and the water gets condensed in the form of particles and takes the shape of the crystals of ice.
What are the atmospheric conditions that support hail?
- To keep suspended hailstorms in the air strong updraft is required.
- If there will be no updraft then ice crystals will melt and fall into the form of raindrops.
- It helps if the freezing level is low in the atmosphere.
- A cool pool aloft is required. It is an area or pool of cold air that exists in the mid-upper levels of the atmosphere. This will occupy the same area as warm air at the surface, generated by heating from the sun.
- In the Northeast and upper Midwest cold pools are very helpful for the development of hail.
Note: All the ice that falls from the sky is not hail. Only chunks or crystals of ice that fall during thunderstorm from the sky is hail. When small crystals of ice fall from the sky during winter storms are known as sleet.