Inhabitants of the Midwest and Mid-Atlantic regions of the United States have been learning some Spanish this weekend. Specifically, we have learned the term derecho (“straight”), which a NOAA (National Oceanic and Atmospheric Administration) website describes in this manner:
A derecho . . . 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.
According to reports from the Washington Post and the New York Times (and as can be verified by most of the Dewey editorial team), Friday afternoon and evening saw a derecho, which formed outside of Chicago at midday, sweep across to the Atlantic Ocean by day’s end—traveling 700 miles (1125 kilometers) in 10 hours. The associated 60-80 mph (95-125 kph) winds downed many trees, killing more than two dozen people and leaving over 3 million people without power. Power restoration efforts are estimated to take a week or more. Meanwhile, the weather is forecast to be hot and humid through the week. (We are loving our jobs more than usual this week, since at work we have power, Internet access, phone service, and blessed air conditioning.)
A post on the Washington Post Capital Weather Gang blog gives further explanation on the meteorological facts about derechos in general and about this derecho in particular.
Derechos are classed in 551.554 Thermal convective storms, where thunderstorms are in the class-here note. Fortunately, they are rare enough events not to have produced a monographic literature of their own. They belong to the kinds of storms described in Severe convective storms, which is classed in that number. The first chapter of this resource is found here.