What Is A Derecho Storm? How Is It Different From A ‘Regular’ Wind Storm Or Tornado?

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Derecho — the word sounds kind of like ‘tornado,’ and for good reason. Like tornadoes, derechos refer to strong winds.

However, unlike tornadoes, derechos are a type of straight-line wind. Tornado winds, on the other hand, swirl around.

This is a derecho storm in Laporte, Indiana (2012).
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The word derecho derives from the Spanish language.

While a straight-line wind can mean any wind coming from one direction and going in the opposite direction, derechos most commonly refer to very strong straight-line winds.

Derecho storm damage aftermath.
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In fact, wind damage from a derecho storm is sometimes mistaken to be tornado damage.

What Is A Derecho Storm?

So far, you know derechos refer to strong, straight-line winds. But they’re really much more than just that.

Let’s look at the minimal attributes that must exist in order to be a true derecho:

  • The storm’s winds are at least 58 miles per hour. (Winds in some derechos can gust well over 100 mph.)
  • A derecho storm has a lifespan of at least 6 hours.
  • Derechos form in a ‘family of downburst clusters’.
  • The line of storms producing microbursts and downbursts are long — often 250 miles or even longer.

Some general facts about derecho storms:

Derechos come from very strong storms that cover a wide area and travel a long way. In fact, some of the most damaging derecho storms have marched hundreds of miles across the country.

Derechos are most commonly found in squall lines. A squall line is a line or row of storms — often fierce — which can extend hundreds of miles long. Despite their length, most squall lines are relatively narrow.

Derechos form in bow-shaped storms called bow echos. In fact, it’s often the case that the strongest area of thunderstorms is in the areas where the storm bulges outward.

Derecho storm bow echo
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You can easily ‘see’ these bow-shaped areas of these storms when satellite or radar images are superimposed on a weather map.

3 Kinds Of Derecho Storms

Derechos are classified in 3 different ways:

  • Serial Derecho Storms are found in long squall lines and can involve the formation of many bow echos. Serial derechos form as a result of what meteorologists call migrating areas of low pressure.
  • Progressive Derecho Storms occur in rather short squall line systems (under 250 miles long) and are associated with stationary fronts. A progressive derecho can involve either one or several bow echos.
  • Hybrid Derecho Storms involve general characteristics of both serial derechos and progressive derechos.

Historic Derecho Events

Straight line winds from a derecho storm caused downed power lines.
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Like tornadoes, hurricanes, and other severe wind events, some derechos have reached historic proportions.

Here’s a brief overview of some of the most serious derecho storms in United States history:

  • In 1993, a strong derecho occurred during the Storm of the Century. This derecho produced highly damaging winds that affected Florida and Cuba.
  • A very severe derecho affected much of the northern Midwest in 1983 during an event since dubbed the I-94 Derecho. It formed in Montana and moved through North Dakota, Minnesota, and Wisconsin, Illinois, and Indiana.
  • The More Trees Down derecho cut a large swath across the country on July 4-5, 1980. The derecho formed near Omaha Nebraska and finally dying out over Maryland, Delaware, and Virginia. 6 people were killed in this derecho.
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