Knowra Hail Hail Hail is precipitation made of balls or irregular lumps of ice formed when strong thunderstorm updrafts carry water droplets into freezing layers of the atmosphere.
Thunderstorm : A storm with lightning and thunder, produced by a cumulonimbus cloud. Hail forms inside strong thunderstorms, whose turbulent air carries droplets through freezing layers.
Cumulonimbus : A towering cloud associated with thunderstorms, heavy rain, lightning, and sometimes hail. Its deep vertical structure provides the turbulent, freezing environment where hail develops.
Hailpad : A soft panel used to record hailstone impacts and estimate their size and number. Hailpads provide ground measurements for checking storm reports and radar-based estimates.
Giant hail : Exceptionally large hailstones, commonly defined in the United States as at least four inches in diameter. Giant hail shows how sustained storm growth can produce stones far larger than ordinary hail.
Updraft : An upward-moving current of air in the atmosphere. An updraft suspends hailstones and carries them through regions where they gain ice.
Riming : The growth of an ice particle as supercooled water droplets freeze onto its surface. Riming describes the freezing-on process that adds ice to a growing hailstone.
Hailstorm : A storm that produces hail at the ground. Hailstorms are the events forecasters track and communities prepare for.
Vivian, South Dakota hailstone : A hailstone that fell near Vivian, South Dakota, on July 23, 2010, and holds the United States records for diameter and weight. This measured specimen illustrates the extreme size hail can reach.
Supercooled water : Liquid water that remains unfrozen below its normal freezing point. Supercooled droplets freeze onto hailstones when they collide with them.
Ice crystal : A solid particle of water with a crystalline ice structure. Ice crystals can serve as embryos around which hail accretes frozen droplets.
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