Hail is a frozen form of precipitation that falls from the sky as pellets of ice, ranging from pea-size to large grapefruits. Hail is generally associated with severe thunderstorms.
When a strong convective cell forms, warm air rises up in the air and cool air sinks. If there is sufficient amount of super-cooled water present, accumulation of ice can begin in the clouds. The ice formed is suspended in the air by the strong updrafts and later falls. This process continues, adding layer upon layer to the hailstone.
Severity of the clouds are judged by strength of the up drafts but if very strong drafts are present then hails do not get enough time to grow.
In order for hail to form, a number of meteorological conditions need to be in place and these are:
• Firstly, moisture-laden clouds must build up to heights of about 50,000 feet or more.
• Secondly, the air temperature at those heights should be cold enough to freeze water droplets. Accordingly, they should remain in liquid form but below freezing in temperature.
• These super frozen droplets should come in contact with anything solid, say a nuclei in meteorological terms, and freeze immediately.
When do hailstorms occur in India?
Winter and pre-monsoon seasons are most prone to hailstorms. Southwest Monsoon season virtually sees no event of hailstorm. The atmosphere should be highly unstable for hailstorms to occur and the air mass during monsoon season is characteristically stable.
The most preferred time for hailstorms are during late afternoon and evening hours.
Which Indian states are prone to hailstorms?
The Northeastern states are very prone to hailstorms. The coastal stations and Peninsular India mostly do not receive hailstorms. To be precise, places south of Maharashtra and Telangana do not receive hailstorms. These places remain mostly hot and humid and as soon as the temperature shoots up, it starts raining, leaving hardly any time for hail formation. Therefore, Telangana, Vidarbha and Marathwada regions are most prone to hailstorm during the pre-monsoon season. Punjab, Haryana and Rajasthan also receive hailstorms during the pre-monsoon season.
Damage to crops
Hail can be extremely damaging to crops. Unseasonal downpour accompanied by hailstorms and strong winds in Maharashtra, Punjab, Haryana and Rajasthan have dashed hopes of a bumper crop this year. Over the past weekend, more than a dozen people died as unprecedented rain and hailstorm lashed parts of Rajasthan, Maharashtra and Punjab.
Almost 40% each of onion and grape crop have been damaged due to spat of hailstorms since October, in Maharashtra alone. Hailstorm in Nashik caused immense damage to onion, pomegranate and grape crop. The last spell of rain lead to a surprise bout of ravaged grape crops in the vineyards of Nashik.
Standing Rabi crops including wheat, mustard, potato and gram have been damaged in parts of Punjab, Haryana and Delhi. Rain and hailstorms have left farmers helplessly watching their flattened crops and waterlogged fields that could have given them a bumper harvest this year.