Explained: The science behind hail storms
In tropical countries like India, a hailstorm is quite an incident. We don’t see snowfall in the plains. So a hailstorm is really exciting. But how do lumps of ice fall with rain? Clearly, this ice is coming from the cloud. How does it form and unlike rain, how does the ice remain frozen till it hits ground?
How do hailstones form?
A hailstone literally grows drop by drop. It begins as a small water drop that freezes to a round snow pellet in a cloud. This is a phenomenon possible only when cloud temperatures are very low. The drop collects other drops and grows in size. The strong wind inside the cloud now blows it towards meeting and teaming up with extra cold water drops towards the top of the cloud system. The super cooled droplets now fuse into a piece of ice or a hailstone. By now, the hailstone is on top of the cloud, in a calm part of the sky with no wind. So it falls back down through the cloud, getting bigger as it plummets towards earth. Hailstones have been recorded to have achieved speeds of 120 to 144 km per hour, and can travel even faster. When the hailstone hits soft soil, it buries itself, otherwise it breaks into pieces on hard surfaces.
If a hailstone is examined closely, rings can be seen in it, illustrating how it froze in rounds of drop collection. Little air bubbles are sometimes trapped inside the hailstone.
How big can a hailstone grow?
The biggest recorded hailstone in the world so far was almost 2 kilograms. It fell in Kazakhstan. In 2010, Dakota, USA was pelted by giant 8 inch hailstones. Hondo of Texas, the country of Libya, and several places in Australia last year saw hailstones measuring between 6 to 6.4 inches. Most of these large icy balls came with storms in October 2021.
Can hailstones cause damage?
Being hit by a large, hard ball of ice, travelling at the pace of a speeding car, may not be such a wonderful experience. Hough we usually enjoy hailstorms with children collecting the ice to such them, hail can cause widespread damage. It kills crops, breaks windscreen and windows, and can even kill small animals.