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Hail is a form of solid precipitation. [1] It is distinct from ice pellets (American English "sleet"), though the two are often confused. [2] It consists of balls or irregular lumps of ice, each of which is called a hailstone. [3] Ice pellets generally fall in cold weather, while hail growth is greatly inhibited during low surface temperatures.
A large hailstone, about 6 cm (2.4 in) in diameter. Hail forms in storm clouds when supercooled water droplets freeze on contact with condensation nuclei, such as dust or dirt. The storm's updraft blows the hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted up again.
As the hailstone ascends it passes into areas of the cloud where the concentration of humidity and supercooled water droplets varies. The hailstone's growth rate changes depending on the variation in humidity and supercooled water droplets that it encounters. The accretion rate of these water droplets is another factor in the hailstone's growth.
A hailstone grows larger when other drops freeze onto its surface while it is inside an updraft, creating growth layers and the knobby appearance that big stones get as they spin and tumble in the ...
The hailstone then may undergo 'wet growth', where the liquid outer shell collects other smaller hailstones. [41] The hailstone gains an ice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud. [42]
the cloud IR emissivity, with values between 0 and 1, with a global average around 0.7; the effective cloud amount, the cloud amount weighted by the cloud IR emissivity, with a global average of 0.5; the cloud (visible) optical depth varies within a range of 4 and 10. the cloud water path for the liquid and solid (ice) phases of the cloud particles
A hailstone that fell in Vivian, South Dakota, on July 23, 2010, holds the United States record for the largest size with a diameter of 8 inches and heaviest weight at 1.94 pounds.
Storm trackers in the Texas Panhandle recovered a massive hail stone that researchers say is likely to be a new state record. Val and Amy Castor, veteran storm chasers with Oklahoma City ...