We all know that April showers bring May flowers but some of those showers could be strong enough to bring damage along with the nourishing rain. The three criteria for a thunderstorm to be considered a severe thunderstorms are hail that is at least 1 inch in diameter or larger, and/or wind gusts of 58 mph or greater, and/or a tornado. Today I would like to focus on the hail component of thunderstorms, both severe and not severe.
Hail is produced by thunderstorms where updrafts are strong enough to carry water droplets well above the freezing level. Hail may begin as a lonely snowflake at an elevation where the temperatures are well below freezing and where super-cooled water droplets hang out.
Snowflakes encounter liquid water that freezes on contact and makes ice pellets to get things started. These pellets succumb to gravity and fall earthward only to be redirected up into the storm by powerful updrafts. Back above the freezing level, these ice pellets gain more ice and grow larger. These pellets may do many cycles like this adding more ice to what quickly becomes hail stone. Finally, the hailstone becomes too heavy to be supported by the updraft, it falls out of the cloud toward the surface.
Hail can do widespread damage to crops, buildings, cars and can even be life threatening to people and animals.
One of the costliest hail events on record impacted me personally in July of 1990. This day, a supercell thunderstorm dropped golf ball to baseball sized hail from Estes Park to near Colorado Springs, Colorado.
I witnessed the damage to some of the hardest hit areas in Boulder, Arvada, Wheat Ridge, and Westminster, Colorado and in today’s dollars this storm would have caused over 1 billion in damage. The hail damaged houses, cars, and injured around 50 people.
Nebraska, Colorado, and Wyoming normally have the most hail producing storms annually. This area of the country especially where these states meet is referred to as part of “hail alley,”. Hail alley gets so much hail because the freezing levels (the area of the atmosphere at 32 degrees or less) in the high plains are much closer to the ground than they are at sea level. At lower elevations hail has more time to melt before reaching the ground.
For Weather Nation: Meteorologist Mike Morrison