Hail Storms in The United States

Although hail storms may occur throughout the U. S. there is one geophysical area that has the dubious honor to be called “Hail Alley”. It is a name given to the region called”The Great Plains” which includes the following states:

Colorado Wyoming Texas
New Mexico Montana Oklahoma
Nebraska South Dakota Kansas


What Is Hail And How Does It Form?

Hail is defined as a precipitation in the form of balls or lumps usually called hailstones. With summer come thunderstorms. Tornadoes, flash floods, and hail are dramatic by-products of thunderstorms. Of the different types of inclement weather that summer can bring the most devastating though not the most dramatic is hail which results in an estimated 1- 2 billion dollars worth of damage per year.

Cumulonimbus clouds commonly known as thunderheads are where hail stones form. The ground is heated during the day by the sun and the air close to the ground is heated as well. Hot air is less dense and therefore lighter than cold air, therefore it rises and cools. As it cools, it loses the capacity to hold moisture. Water vapor then condenses, forming loose clouds reminiscent of cotton balls. This condensing moisture releases heat of its own into the surrounding air, causing the air to rise faster and release still more moisture. Cummulonimbus clouds contain vast amounts of energy in the form of updrafts and downdrafts. Hail grows in the storm cloud's main updraft, where most of the cloud is in the form of "supercooled" water. The term supercooled is a reference to the fact that this part of the cloud is composed of water that remains liquid although its temperature is at or below 0 degrees Celsius. A supercooled water drop needs something on which to freeze, or it remains liquid. Ice crystals, frozen raindrops, dust, and salt from the ocean are also present in the cloud. On collision, supercooled water will freeze onto any of these hosts, creating new hailstones or enlarging those that already exist.

Cross sections of hailstones often reveal layers, caused by the different rates of accumulation and freezing of supercooled water, as the hailstone forms. The more supercooled water a hailstone makes contact with, the larger and heavier the stone is likely to become. When the hailstone becomes so heavy that the updraft can no longer support it, it falls from the sky.

Hail Storm Damage

Hail falls along paths called hail swaths. These vary from a few square acres to large belts reaching sizes as large as 10 miles wide and 100 miles long. Swaths can leave hail piled so deep it has to be removed with a snow plow. Hail does a great deal of damage to crops. U.S. costs run into hundreds of millions of dollars annually. While hailstones have been found weighing as much as 0.75 kilograms (1.67 pounds), even much smaller hail can destroy crops, slicing corn and other plants to ribbons in a matter of minutes. Farmers cope with the hail hazard by purchasing insurance. Illinois farmers lead the United States in crop-hail insurance, spending more than $600 million annually.