Summer surprise…Thunderstorm Downburst

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Take a look at the slide show of images above. No, these were not taken during the April or May tornadoes. They were taken in Danville (Yell County) on Saturday evening by Chief of Police Rick Padgett. What happened you ask? It had to be a tornado! That’s one of the most common things we hear in the weather center: If trees are down, “….it had to be a tornado.” Nope. Not at all. Here’s what the radar looked like over Danville at 6:30pm on Saturday June 4, 2011:

That is a t-storm. It’s not very big. About 3-5mi. wide when it was at its largest. It developed right where you see it and died out in the same spot. It didn’t rotate and had little lightning. What was the cause of all the damage? WIND!

It wasn’t just any wind however. Summer time pop-up storms are very different than regular storms.

Thunderstorms develop when an area of air near the ground begins rising quickly. In the summer this is cause by heating at the surface. Many of our severe storms encounter strong wind several thousand feet up. As the air rises it gets pushed in the direction of the wind, causing the t-storm to tilt in the direction of the upper level winds and move. In the summer, these strong upper-level winds may not be present. The air rises up and pretty much travels vertically without being diverted to the side by winds. As it rises it begins to cool, condense and eventually produces rain. The rain evaporates into the air around it cooling the air further. Suddenly, the air that was warm and light is now cold and much heavier than the air around it. It begins to drop, quickly. This dropping air can attain speeds of over 70mph. The air hits the surface like a water balloon. Crashing into the ground and spreading outward from the area that it hits (like a water balloon splashing everyone around the area it bursts in). These winds down trees and power lines in a large circular area around where the “balloon of cold air” crashed into the ground. The amount of downed trees and power lines may seem like damage done by a tornado. Because the wind spreads out from a central location, trees WILL NOT all be facing in the same direction. In fact, they’ll all be facing in different locations pointing away from where the air first made contact with the ground and broke its fall. This type of wind event is called a “downburst” or “microburst” if it happens in a very small area. This is what happened in Danville on Saturday evening.

Storms again popped up over the state Sunday. One such storm produced similar wind damage in the area of Hot Springs. Winds knocked down trees and power lines. One tree fell on car killing one person.

A tree falls on a car on hwy 7 between Hot Springs & Fountain Lake killing one person. Photo by: Mike Gonzales

Downburst winds roll a trailer over in Camden. No one was inside at the time. Photo by Amber Lynn Green

The Hot Springs fatality could actually mean that more people so far this year have died due to winds in Arkansas than tornadoes. Surprised? Don’t ever take a severe thunderstorm warning lightly. They can be just as dangerous as tornadoes.

Greg “Weather Dork” Dee


About Weather-Dork-Dee

I'm a meteorologist at KARK-TV in Little Rock, Arkansas.
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One Response to Summer surprise…Thunderstorm Downburst

  1. Pingback: Oh hail no! | The Weather Geek Nation

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