Hailstones

Hail forms on condensation nuclei such as dust, insects, or ice crystals, when supercooled water freezes on contact. Hailstones are usually from the size of a small pea to the size of a golfball. In clouds containing large numbers of supercooled water droplets, these ice nuclei grow quickly at the expense of the liquid droplets because the saturation vapor pressure over ice is slightly less than the saturation vapor pressure over water. If the hailstones grow large enough, latent heat released by further freezing may melt the outer shell of the hailstone. The growth that follows, usually called wet growth, is more efficient because the liquid outer shell allows the stone to accrete other smaller hailstones in addition to supercooled droplets. These winds hold the rain and freeze it. As the process repeats, the hail grows increasingly larger. Once a hailstone becomes too heavy to be supported by the storm's updraft it falls out of the cloud. When a hailstone is cut in half, a series of concentric rings, like that of an onion, is revealed. These rings reveal the total number of times the hailstone had traveled to the top of the storm before falling to the ground.

HILLANDGLEN