Monday, February 20, 2012

Severe weather awareness week: HAIL

Today starts severe weather awareness week in the state of Texas. Each day we will write a brief story on one type of severe weather to educate you on how this severe weather phenomenon occurs so you can take precautions to protect life and property. Today’s discussion will cover hail.

Hail can be a very dangerous and damaging form of severe weather. Here in East Texas we are hit every year with many hailstorms, some of which have produced a substantial amount of damage. Yours truly has replaced the roof on my home twice in 4 years and had a car totaled by hail. In fact, nearly 40 percent of all home insurance claims in the state of Texas are from hail damage.

So how does hail form and why are some stones much bigger than other stones? Hail forms when small ice particles are held above the freezing level by strong thunderstorm updrafts allowing for super cooled water droplets to freeze on these ice particles causing the hail stone to grow. As long as the updraft is strong enough, the hail stone will continue to grow. At times the hail stone will fall out of the main draft falling towards the ground only to be picked back up by the updraft before hitting the ground. This will cause the stone to take a roller coaster ride up and down inside the storm collecting more water droplets that will refreeze causing the stone to become even large. So the stronger the updraft, the larger the hail stone. Hail the size of peas will be supported by updraft speeds of 24 mph where as softball size hail need an updraft speed of 104 mph! The largest hailstone to hit the United State fell in Vivian, SD July 23 2010. This hailstone measured 8” in diameter and weighed nearly 2 pounds. A stone this size can reach downward speeds of over 120 mph! So it is easy to see how hail can be very deadly and damaging during severe thunderstorms.

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