By National Weather Service Des Moines
Governor Terry Branstad, the Iowa Homeland Security and Emergency Management Division, and the National Weather Service have designated the week of March 24 to March 28 as severe weather awareness week in Iowa. Each morning this week, the National Weather Service in Des Moines will issue a Public Information Statement focusing on a different item each day. Topics this year includes the following:
- Monday: Flash Flooding
- Tuesday: Warning Reception
- Wednesday: Tornadoes
- Thursday: Severe Thunderstorms
- Friday: Family Preparedness
Today’s Topic: Severe Thunderstorms
Thunderstorms are a common occurrence each spring and summer across the Midwest and Iowa is not immune. Each year, Iowa see hundreds of severe thunderstorms and thousands of non-severe thunderstorms. Thunderstorms can be extremely dangerous storms which may bring deadly tornadoes and lightning, damaging winds, and hail and can lead to flash flooding.
The National Weather Service issues severe thunderstorm warnings for thunderstorms that are producing, or capable of producing winds of at least 58 MPH and/or hail at least 1 inch in diameter. Often times, severe thunderstorms may be much stronger than the minimum criteria.
One of the dangers of thunderstorms is lightning. Lightning causes an average of between 55-60 fatalities each year. Lightning can strike from as far as ten miles away from an area of rain, which is about the distance you can hear thunder, so it is important to remember that if you can hear thunder, you are susceptible to the dangers of lightning. When thunder roars, go indoors. Other thunderstorm threats include large hail and wind. Hail causes more than 1 billion dollars in damage to property and crops each year across the United State. Large hail stones can fall at speeds faster than 100 MPH. Straight-line winds can cause damage equivalent to a strong tornado. Straight-line winds can exceed 125 MPH, which can be as strong as a category 3 hurricane.
Before a thunderstorms threatens, know the county in which you live and the names of nearby major cities, since severe thunderstorms are issued by county. Check the weather forecast before leaving to be outdoors for extended periods. Keep a NOAA Weather Radio or AM/FM radio with a battery backup with you.
To stay safe when a thunderstorm approaches, move to a study building or car. Do not take shelter in a small shed, under isolated trees, or in convertible automobiles. If lightning is occurring and a sturdy shelter is not available, get inside a hard top automobile and keep the windows up. Get out of boats and away from water. Do not take baths or showers and stay away from windows.