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Severe Weather Safety Week: How severe thunderstorms work

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Severe thunderstorms can be just as destructive as tornadoes. A Severe Thunderstorm is defined as having 58+ mph wind gusts and/or 1"+ hail. Today's topic will focus a bit more on straight line wind gusts.

For one thing, severe thunderstorms are much more common than tornadoes are and can still contain wind speeds just as strong as tornadoes. Also, these straight line wind events affect a larger area.

While tornadoes can hit wind gust speeds of over 200 mph, most are in the 65-100 mph range. Most severe thunderstorms contain wind speeds near or in this range as well, but affect a much larger area.

Straight line wind gusts come in two forms- microbursts and macrobursts. The schematic above is of a microburst, but a macroburst works exactly the same way, just on a larger scale. Usually that's on the leading edge of a bow echo on a squall line.

As raindrops get lifted higher into a tall thunderstorm cloud's updraft, some evaporate as they lift into drier air. This causes the air around the drops to cool.

That cool air starts to fall since the air around it is much warmer. As it falls into even warmer air, it speeds up. Air hits the ground at high speed and is forced outward in straight lines.

Knowledge of this is how NWS meteorologists determine if damage is caused by this process or a tornado in which the air moves inward and in circular motions. Straight line wind damage tends to be spread out with debris and downed trees either pointing the same way or pointing out from a center point in the case of a microburst.

Tornadoes tend to produce more chaotic damage, but the trend is for damage to be pointing towards the center or in spiral swaths pointing slightly into the spiral as opposed to outward.

Tornadoes and severe thunderstorm wind gusts and hail are not mutually exclusive, however. Most storms that produce tornadoes also have straight line wind gusts and large hail in different parts of the storm, so a lot of times there will be damage from both in close proximity to each other.

Matt Schaefer

Matt Schaefer was promoted to Chief Meteorologist in July of 2019 and has been our evening meteorologist for News 18 since June of 2016. Prior to that, he was our Saturday meteorologist starting in September 2014.

Matt was born and raised in Sheboygan, Wisconsin. He enjoys all the extremes that mother nature throws at the Badger State: from severe thunderstorms to blizzards to subzero temperatures.

Matt studied meteorology in the Midwest as well, earning his Bachelor’s of Science in Meteorology at Valparaiso University in Indiana. There, Matt was heavily involved in VUTV Weather, the Valpo student chapter of AMS/NWA, and VUSIT (Valparaiso University Storm Intercept Team). He’s logged more than 20,000 miles chasing and studying severe storms all across the country and witnessed nine tornadoes including six in one day!

Matt describes himself as a Wisconsin boy at heart and enjoys cheering for the Packers, Brewers, Badgers, and Admirals just to name a few. He loves simply being outdoors and enjoys the Wisconsin wilderness especially in fall, and whitetail deer season!

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