I think most people are familiar with tornadoes, hurricanes, and blizzards, all storms associated with ferocious winds. But there is another menacing monster out there in the clouds, beyond these familiar storms, called a derecho.
The term comes from the Spanish word for “straight” or “direct.” Unlike the swirling winds of a tornado, a derecho produces radial or straight-line gusts. A tornado is also a localized portion of a thunderstorm, though they can, of course, be very large. A derecho, on the other hand, is actually a broad system of storms.
Technically, derechos are widespread, long-lasting, straight-line storms. They tend to look like squalls and can be hundreds of miles long. They bring these straight-line winds for hours at a time, at hurricane-force levels, moving extremely quickly across large swaths of land. Where a tornado might affect a neighborhood, city, or county, derechos can ravage entire regions of a country.
According to the National Weather Service, a derecho is the result of families of downburst clusters. Many people might be familiar with microbursts, which are the sudden spurts of wind from thunderstorms that rush downward toward the earth. Essentially, derechos are giant conglomerations of these downbursts. When the wind hits the ground from above, it radiates in a straight line in all directions, including ahead of the storm.
The storms form what is known as bow echoes, a band of storms that resembles a curved line or a C-shaped squall.
In the National Weather Service graphic above, you can see the formation of a derecho from small outburst to full-fledged, bow-echo beast.
Most derechos happen during the summer months of June, July, and August, but they can occur during any month of the year. As with many severe thunderstorms, they also tend to happen more often in the United States than in other parts of the world. Derechos have been documented elsewhere, but the vast majority occur in the Great Plains, the Ohio Valley, and the Southeast.
If you’ve never heard about these storms before, don’t hate on your attention levels. Derechos are relatively rare. Typically, the United States will see one or two per year.
That rarity is a blessing, as these storms can produce continent-wide destruction. While many supercell storms form and dissipate relatively quickly and tornado touchdowns average only five minutes, derechos can go on and on, sometimes for more than a day.
The following image is a composite radar visual from a derecho that raged in 2012 from Iowa all the way to the Atlantic Ocean. The tempest claimed 22 lives and caused $2.9 billion in damages thanks to peak wind speeds of 91 miles per hour.
Meteorologists warned today of a derecho heading toward the Chicago area. Hopefully, the damage is minimal.
Those of us in Ohio might remember the 2012 storm. If you didn’t experience it, check out this incredible footage from a security camera in Ohio as the derecho moved to the area. This video captures the straight-line winds fantastically!
Further Reading and Exploration
Derechos – National Weather Service
Midwest Derecho Has Raced Eastward Bringing Widespread Damaging Winds – Article on today’s derecho
“The Ohio Valley / Mid-Atlantic Derecho of June 2012” – NOAA
List of derecho events – Wikipedia