Hail storms

Convective storm clouds can provide the conditions for growth of hailstones, although the larger hailstones grow only inside the largest and severest storms where the core winds have very high upward velocities. Hail storms cause considerable damage to crops and property since the stones range in size from 5mm in diameter to 50 mm or more. The degree of damage is determined by whether the hail is accompanied by rain or wind.

Hail storms mainly occur in temperate climates. The air is seldom unstable enough in the polar regions and the freezing level is too high in the tropics. In the USA it is estimated that annual crop losses from hail storms are $200-300 million (greater than that caused by tornadoes).