What Is a Derecho? A Meteorologist Explains

Earlier this month, a large, intense storm system known as a derecho devastated large swaths of the U.S. Midwest with winds reaching an estimated 140 miles per hour.

The damage was so widespread that NASA shared side-by-side satellite images of Iowa soybean and corn crops before and after the storm to illustrate the vast extent of the destruction. Agricultural economists have estimated the damage at somewhere around $4 billion. More than 1 million people lost power and some even lost their lives. 

I asked meteorologist Vince Condella to tell us exactly what a derecho is, how they form, how common they are, and why they're so destructive. As Chief Meteorologist for a Milwaukee, Wisconsin TV station for over 34 years, Vince is intimately familiar with the volatile weather patterns of the Upper Midwest. He grew up in the Chicago suburbs and was inspired to pursue meteorology thanks to what he calls "the dynamic Midwest weather." He has degrees in atmospheric science and meteorology from Purdue University and the University of Wisconsin-Madison.

What is a derecho and where does the name come from?

So, what is a derecho? 140 mph winds sound like "hurricane-force" winds to me. Are derechos and hurricanes at all the same? What about tornadoes?

"It's really a totally different phenomenon than a hurricane," said Vince, "but nonetheless, it represents some amazing destruction over a large swath of area, which is exactly what happens in a hurricane, as well. But a hurricane is a tropical system and derechos develop from a cluster of thunderstorms.

Derecho is taken from a Spanish word, meaning direct or straight ahead.

"['Derecho' is] taken from a Spanish word, meaning 'direct' or 'straight ahead,' which is very descriptive of the type of winds in a derecho. They are straight-line winds. Now, as best as can be found, the term was originated back in the late 1800s by a professor at the University of Iowa, Dr. Gustavus Hinrichs. He was writing about an event in Iowa, and he used that word 'derecho' ... because he wanted to differentiate [this straight-line wind damage] from wind damage from tornadoes. Tornadoes spin, but derechos are straight-ahead winds. And so that...

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