Research Thunderstorm Formation Thunder and Lightning Severe Thunderstorms Hail 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.
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 strong updraft winds toss the pellets and droplets back up into the colder regions of the upper levels of the cloud. As the attached droplets freeze, the pellets become larger. Both gravity and downdraft thunderstorm winds pull the pellets back down, where they encounter more droplets that attach and freeze as the pellets are thrown, once again, back up through the cloud. The more times a hailstone is tossed up and down through the cloud, the larger the hailstone will be.