What is a "Derecho" Anyway?

"The Line Storm," by John Steuart Curry, 1897-1946

Lately there have been several lines of devastating storms moving through the Ohio Valley, and meteorologists have been referring to them as a "derecho." I've lived in the U.S. all my life and never heard that term, even though we routinely get straight-line winds and severe weather here in the Southeast. They never mentioned it last year on the day of the April tornadoes, although that line of storms lasted for hundreds of miles, which makes me think that tornadoes trump derechos. Officially, the terrible line of storms that passed over the Northeast last week were not part of a derecho:

Pitch black now but 10 mins ago @twcbreaking @NewYorkology #derecho #NYC twitter.com/davidbrunonyc/…
— david bruno (@davidbrunonyc) July 26, 2012

LA Times Story

Joey Picca , a meteorologist with the National Weather Service, said in a telephone interview with the Los Angeles Times from his office in Upton N.Y. on Long Island. “What we saw yesterday wasn’t a derecho in the traditional sense because it wasn’t widespread enough. Although we did see a large line of thunderstorms, it was lacking the true intensity you would like to see in a derecho.”
A derecho is defined as an event that has wind gusts of at least 58 mph and leaves a swath of damage for a minimum of 240 miles, according to the U.S. Storm Prediction Center.

So the phenomenon is actually rare, but with global warming raising the mercury it it could certainly happen again, so let's get educated by going directly to NOAA for the definition:

Definition of a derecho
A derecho (pronounced similar to "deh-REY-cho" in English, or pronounced phonetically as "") is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to that of tornadoes, the damage typically is directed in one direction along a relatively straight swath. As a result, the term "straight-line wind damage" sometimes is used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho.

Origin of the term "derecho"
The word "derecho" was coined by Dr. Gustavus Hinrichs, a physics professor at the University of Iowa, in a paper published in the American Meteorological Journal in 1888. A defining excerpt from the paper can be seen in this figure showing a derecho crossing Iowa on July 31, 1877. Hinrichs chose this terminology for thunderstorm-induced straight-line winds as an analog to the word tornado.

"Derecho" is a Spanish word that can be defined as "direct" or "straight ahead." (Click here to hear a pronounciation of the word "derecho"). In contrast, the word "tornado" is thought by some, including Hinrichs, to have been derived from the Spanish word "tornar," which means "to turn." Because derecho is a Spanish word, the plural term is "derechos;" there is no letter "e" after the letter "o."

A web page about Gustavus Hinrichs has been created by Ray Wolf of the Davenport, Iowa National Weather Service Forecast Office. The page provides information on Hinrichs' background, and on his development of the term "derecho" in the late 1800s. Wolf's page also briefly discusses how the term "derecho" has come into more common use in recent years.