What the Hell Is a Derecho?

Storm blowing over Chicago, June 29, 2012. Photo by Ben Richmond

Batten the hatches, upper Midwest, there’s a storm a-brewing. This storm’s so big the warning spans from Cedar Rapids all the way to Baltimore with the black-heart of the beast right over Chicago. The experts are saying the conditions are ripe for the fearsome and semi-rare derecho.

Derecho zone, June 12, 2013. Map via NOAA

A derecho, from the Spanish for “direct,” is a long-lived windstorm, which usually has swiftly-moving severe thunderstorms. To be a proper derecho, the storm has to cover a swath of at least 240 miles, with winds above 57 miles per hour for most of the way. Meteorologists compare derechos and the damage left in their wake to something like a straight tornado.

They move quickly, usually striking during the summer months, and have cruelly ruined a good number of 4th of July barbecues, toppled many mobile homes and endangered and killed those caught in their path unaware.

The kick-ass name makes derechos seem exotic and rare, when actually they blow through the South almost annually. If another derecho forms tonight and makes it all the way to the D.C. and the coast that would make for a somewhat unusual second year in a row.

Residents from Ohio to our nation’s capital might remember last year’s derecho that hit at the end of June. It was an especially miserable storm because it knocked out electricity and was followed by a severe heat wave, that people had to deal with without air conditioning or popsicles.

Time-elapsed satellite of the June 29, 2012 derecho. Map via NWS

Weather hipsters, if they exist, probably all have their own favorite, more obscure, derechos from the past. The “More Trees Down” derecho, which ambled across the country from Omaha to Washington D.C on July 4 and 5 in 1980, is an impressively sustained storm. 

The “More Trees Down” Derecho, 1980. The purple lines indicate the storm’s front, three hours apart. The red numbers indicate windspeed. Via NOAA.

In July 1995, a heat wave in the Upper Midwest fed four derechos over as many nights. The longest and most vicious-looking was July 11’s “Right Turn” derecho which spanned 1,400 miles, killed seven people and did millions of dollars worth of damage.

The appropriately-named “Right Turn” Derecho from the marathon in July 1995. Via NOAA

As with any specific meteorological event, linking derechos to climate change is a dubious proposition—derechos aren’t new; they happen. Still, Harold Brooks, a researcher at NOAA’s National Severe Storms Laboratory, told the Washington Post last year that given the correlation between severe windstorms and hot weather, an undiscovered link between the two might be there.

In any case, even if they aren’t derechos, severe storms should be breaking over northern Illinois shortly, so take down the volleyball net, and go inside. If you take any compelling pictures or videos, feel free to Tweet ’em over.

@a_ben_richmond