Severe Weather Awareness Week: Thunderstorms and Lightning
LINCOLN, Neb. (KOLN) - This week is Severe Weather Awareness Week in Nebraska. Each day the 10/11 Weather Team is covering a topic to get you ready and prepared for the upcoming severe weather season. Today’s topic is thunderstorms and lightning.
In order for a thunderstorm to develop, there has to be moisture, instability and lift. Shear is needed in order for a tornado to form in a thunderstorm. There can be wind shear or speed shear. Wind shear is the of changing of wind direction with height. Speed shear is the changing of wind speed with height. A thunderstorm is considered severe when hail is one inch or larger (size of a quarter or larger), wind speeds are 58 mph or greater or there is a tornado.
There are approximately 100,000 thunderstorms each year in the United States with tornadoes occurring in about 1,000 of them. Hail can also happen with any thunderstorm. It is an opaque or white ball of ice that forms through the convective process in thunderstorms. Hail can range from the size of a pea to a grapefruit in most cases. There have been some instances of hail larger than a grapefruit. In Nebraska, the largest hailstone ever recorded was 7″ in diameter in Aurora on June 22, 2003. The largest hailstone ever recorded in the United States was 8″ in diameter in Vivian, South Dakota on July 23, 2010. That is around the size of a volleyball.
Lightning is a threat with any thunderstorm and is a giant spark of electricity in the atmosphere. When opposing charges build enough during a thunderstorm they overcome the insulating nature of the air and form lightning. Thunder can’t happen without lightning. It is caused by the energy from lightning rapidly heating and expanding the air it passes through creating a sound wave that we hear.
When thunder roars, go indoors! Lightning can typically strike up to 10 miles away from the parent thunderstorm, but in extreme cases it can strike as far as 25 miles away from the parent thunderstorm. Once inside when you have heard thunder, stay away from windows and avoid anything that conducts electricity (landline telephones, water in showers or sinks for example). Stay inside for at least 30 minutes after the last sound of thunder.
Severe Weather Awareness Week continues Thursday with the topic of Flooding and Flood Safety.
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