What is a “derecho”?

What is a “derecho”? - NWS


Essentially, a “derecho” is a long-lived, rapidly moving line of intense thunderstorms that produces widespread damaging winds in a nearly continuous swath.

By definition (according Johns and Hirt, 1987), the term “derecho” applies to a complex line of thunderstorms that travels a minimum distance of 240 miles (~400 km) or more, and produces a nearly continuous and widespread swath of damaging winds over that distance, with concentrated areas of wind speeds over 58 mph (93 km/hr). Surface wind gusts accompanying a derecho can often approach or exceed 100 mph.

The term “derecho” was originally coined over a century ago by a physics professor at the University of Iowa, named Dr. Gustavus Hinrichs, in a paper he published in the American Meteorological Journal in 1888. The term “derecho” is Spanish and means “straight ahead”, an attribute Dr. Hinrichs applied to the storm’s ability to produce damage from essentially straight-line winds. (Note: a fascinating description on how this term was developed by Dr. Hinrichs, and how it recently was revived can be found here:https://www.crh.noaa.gov/images/dvn/hinrichs/JohnsDerechoStory.pdf).


Derecho in Spanish means straight. It also means rights, like legal rights, but I’d assume it’s derived from Spanish here.

The intent was to distinguish a derecho from a tornado which may come from tornar - to turn.

The link in the OP evidently doesn’t work.


The word “derecho” was coined in 1888 by Dr. Gustavus Hinrichs, a professor of physics at the University of Iowa. Hinrichs used the term in a paper published by the American Meteorological Journal to distinguish thunderstorm-induced straight-line winds from the damaging, rotary winds of tornadoes. “Derecho” is a Spanish word meaning “right,” “direct,” or “straight ahead.” (Click here to hear a pronunciation of the word “derecho”). In contrast, the word “tornado” is thought to have been derived from the Spanish word “tornar,” which means "to turn." Because “derecho” is of Spanish origin, the plural form is spelled “derechos;” i.e., the letter “e” is not added after the letter “o.”

Here is a link to the 1888 paper by Hinrichs: Tornadoes and Derechos - it’s a scanned paper, you have to scroll down half a page to get the beginning

Just one more reason we need to build that wall!

And it can be easily confused with “derecha” which means the direction right. A few years ago in Spain the hotel we were staying in had an off-premises parking garage, someone form the hotel got in the car with me to direct me to it. As we approached an intersection he said “derecho” but I heard “derecha” tuned right and began an extended diversion on narrow one-way streets.

Haha yep. It takes a few times getting lost before it sticks, at least there is no misunderstanding with izquierda or left.


View of the ‘People Chaser’ derecho storm system near Fort Supply, OK. Photo by Douglas Berry.

Notable Derechos - NWS

May 8, 2009 Super Derecho

This was one of the most intense and unusual derechos ever observed. The wind storm produced significant and often continuous damage over a broad swath from the high plains of western Kansas to the foothills of the Appalachians in eastern Kentucky.

Multiple wind gusts in excess of 70 mph (113 km/h) and a few gusts over 90 mph (145 km/h) were measured along its path. In addition, flash flooding was widespread on the northern edge of the system, especially in Missouri.

But what made the event most unique was the appearance of an unusually strong, long-lived, larger-scale circulation known as a mesoscale convective vortex.

This feature was accompanied by a band of intense surface winds and tornadoes that occurred independent of the severe weather directly associated with the large-scale bow. (May 8, 2009 Super derecho details)

It appears that you are describing what in most of the world is known as a “Line Squall”:

In Singapore this is also known as a “Sumatra”, since the phenomena usually develop over Sumatra and move east from there.
Most common during the SW Monsoon, but can occure during the transition period between the SW and NE Monsoons.

It is a major problem when doing difficult Marine operations in Singapore waters, since they come suddenly and can be very intense.

Line Squalls occurs in sub-tropical climates as well. (Well known in the North Sea)
Passing of the “line” is easily detected by the sudden drop in temperature and change of wind direction.

Here is a link to the 1888 paper by Hinrichs:Tornadoes and Derechos

Hinrichs explains why he uses the term derecho.

From the linked paper:

  1. It may be objected that the term squall might answer, and that a new term is superfluous. In that case the term tornado should also be discarded, and the more general term of “cyclone” used for all allied phenomena, from a waterspout and a dust- whirl raising withered leaves into the air, to the grand circula tory motions traversing the seas and continents. Such looseness in the use of terms is but the outgrowth of superficiality in thought and knowledge. Nothing is more necessary in science than the recognition of specific forms of phenomena and the application of specific terms to the same. Upon further study, generic relations of, these specific forms may properly be indicated by more general terms. The derecho is as thoroughly marked a specific atmospheric disturbance as is the tornado.

Here is “The Boundary Waters - Canadian Derecho” that hit Maine in 1999.

Figure 1. Area affected by the July 4-5, 1999 derecho event (outlined in blue). Curved purple lines represent the approximate locations of the gust front at three-hourly intervals. “+” symbols indicate the locations of wind damage or estimated wind gusts above severe limits (58 mph or greater). The other symbols are described in the text below.


This is from the NWS ABOUT DERECHOS

In the lower drawing the red line is the gust front, cold air descending from the storm. It acts similar to a cold front. In a dercho the gust front forces warm moist air upward which in the right conditions will cause new storms to develop. The gust front is the source of the strong straight line winds associated with a derecho.

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