Hail is precipitation in the form of a chunk of ice that can fall from a cumulonimbus cloud. Usually associated with multicell, supercell and cold front induced squall line thunderstorms, most hail falls from the central region of a cloud in a severe storm.
Hail begins as tiny ice pellets that collide with water droplets that are still liquid above the freezing level. The optimum freezing level for the formation of hail is from 8,000 to 10,000 feet.
The water droplets attach themselves to the ice pellets and begin to freeze as an ice coating. The hailstone is suspended in the strong updraft of the thunderstorm, continuing to add ice coating. Once the hailstone grows to big to be levitated by the updraft, it falls to the ground.
Both gravity and downdraft thunderstorm winds pull the pellets down, where they encounter more droplets that attach and freeze as the pellets are thrown, once again, back up into freezing portions of the cloud.
HailstonesLarge hailstones are an indication of powerful updraft and downdraft winds within a thunderstorm. This is why large hail is associated with severe thunderstorms.
To create pea-size hail (about 1/2 inch in diameter) winds within the thunderstorm updraft will generally be around 20 miles per hour. Quarter size hail (3/4 of an inch in diameter) requires updrafts of about 40 miles per hour.
Golf ball size hail (1 3/4 inches in diameter) needs updrafts of around 55 miles per hour and softball size hail, approximately 100 miles per hour!
The heaviest hailstone ever measured in the United States fell at Coffeyville, Kansas, on September 3, 1970. It weighed 1.67 pounds and measured 17.5 inches in circumference. A larger, but slightly lighter one fell at Aurora, NE on June 22, 2003. It was seven inches in diameter.
Hail AlleyThe Great Plains states, especially northeastern Colorado and southeastern Wyoming, receive more hail yearly than any other part of the United States. Hail in this area of the country is most likely to fall late in the afternoon and evening during the months of May and June and is often responsible for extensive crop loss, property damage, and livestock deaths.
Other elements of a thunderstorm include thunder and lightning. Some of the most severe weather may occur in a microburst.
Check how thunderstorms form for more information.