What is a ‘super derecho’?

AccuWeather.com reports a “super derecho” of violent thunderstorms left a more than 700-mile trail of destruction across the Midwest and mid-Atlantic on Friday, cutting power to millions and killing thirteen people.

More than 600 damaging wind reports were received by NOAA’s Storm Prediction Center (SPC) as the derecho took roughly 12 hours to race from northern Indiana to the southern mid-Atlantic coast.

A derecho is defined as a widespread and long-lived wind storm that accompanies rapidly moving showers or thunderstorms. The most severe derechos are given the adjective “super.”

Winds gusted to 91 mph (equal to that of a category 1 hurricane) at the Fort Wayne International Airport, Ind., Friday afternoon.

As the derecho maintained its violent nature, an 81 mph gust was then measured at Tuckerton, on the southern New Jersey coast, early Saturday morning.

Downed trees dominated the damaging wind reports and led to the deaths of 13 people, according to Fox News.

One of the multiple trees that crashed into homes in Springfield, Va., killed a 90-year-old woman as she was sleeping in her bed, according to the Associated Press.

A few hours earlier, a falling tree outside of North Middletown, Ky., (located east-northeast of Lexington) killed a man who was attempting to clear some tree limbs off a road.

Two boys died by a pine tree fell onto a tent at Parvin State Park, N.J.

Damage on Friday was not confined to downed trees. Power poles were also snapped, while some structures sustained damage. At least four semi-trucks were blown over by the winds on I-75 between Findlay and Bluffton, Ohio.

States of emergencies have been declared in Virginia, West Virginia and Ohio. With 2.5 million in the dark, Virginia Gov. Bob McDonnell stated that his state experienced its largest non-hurricane power outage in history.

Friday’s super derecho was triggered by a ripple in the jet stream and fueled by the intense heat that caused Washington, D.C., to set a June record high and Columbia, S.C., to break its all-time record on Friday.

Derechos typically strike the lower Midwest states once every year, according to the SPC. The occurrence of derechos, however, are quite rare across the mid-Atlantic, south of Philadelphia. On average, this region endures a derecho once every four years.

One of the most recent significant derechos to slam the United States occurred on May 8, 2009. This weather phenomena traveled more than a thousand miles in 24 hours from southeastern Kansas to the southern spine of the Appalachian Mountains.

Destruction from the May 2009 derecho totaled millions of dollars with numerous injuries and several deaths reported.

One main difference between the May 2009 derecho and Friday’s is the number of tornadoes spawned. Forty-five tornadoes were sighted in May 2009, while there was only one unconfirmed report of a tornado on the ground in Newcomerstown, Ohio, Friday afternoon.

Winds in the strongest derechos can top 100 mph. The derecho that tore through Wisconsin and Lower Michigan on May 31, 1998, produced a 128 mph wind gust in eastern Wisconsin.

Additional severe thunderstorms will threaten parts of the Midwest and mid-Atlantic later today, but a repeat of Friday’s widespread destruction is not expected.