Monday, April 4, 2011

What Causes it to Hail?

The solid precipitation, hail, is actually made from ice and usually forms in large thunderclouds during severe storms. Hail stones can range in size from a quarter of an inch to larger than a softball. They are created inside clouds where strong winds are present, some blowing upward so that the cooling and expansion of air occurs. The process of layering happens as freezing raindrops become ice pellets. When the wind whips those around inside the cloud, their voyage through warmer wet regions causes them to pick up an extra layer or moisture which then freezes onto the pellet in the cooler air region. More layers are formed as the hail stone continues to travel around the cloud. They eventually fall from the cloud when they become too heavy to be held up by the winds. Stronger winds inside a cloud will lead to larger hail, and larger hail usually fall at a higher speed. Hail has been known to damage automobiles, houses, and farm crops among other things.

The library has a recommended reading list on weather books for kids and also a page of water facts for adults.

Photo credit: Madison Hail by Emily Eggleston