If you ever needed more proof that nature is determined to destroy everything you know and love, consider that a small cluster of thunderstorms that formed in Minnesota on Sunday night grew into a powerful derecho that lasted for 30 hours, traveling nearly 1,200 miles before croaking in North Carolina.
Above is a (large—4.27 MB) animation of the derecho from the time it formed at 7:00 PM CDT Sunday in Minnesota until 2:00 AM EDT Tuesday when it dissipated in central North Carolina. The system was a classic example of a much-feared and much-hyped derecho, which is a persistent complex of thunderstorms (known as a “mesoscale convective system,” or MCS) that produces widespread wind damage over a path at least 240 miles long. The strongest derechos can pack wind gusts of more than 100 MPH and travel thousands of miles, often forming in the central Plains and racing east well into the Atlantic Ocean.
Most people became familiar with the term after the derecho on June 29, 2012, which killed more than two dozen people on its path from Indiana to New Jersey, knocking out power to millions of people during an ugly, triple-digit heat wave. Derechos happen a couple of times every year, and they can be as compact as a couple of counties or as enormous as the entire longitudinal length of the United States. Most of them, though, are about the size of the one we saw this week.
We usually see these systems during the warmer months, especially when there’s a heat wave in the southern United States like the one we’re seeing right now. A ridge of high pressure over the southern half of the country (seen above) can focus instability, moisture, and wind shear along the edge of that ridge, creating a feature known as a ring of fire. These systems—not always achieving derecho status—tend to ride around the edge of the ridge, so they often form in the northern Plains and cycle toward the Mid-Atlantic or Northeast.
This scenario played out during this storm, with the cluster of storms in Minnesota taking advantage of the favorable atmosphere to organize and sustain themselves for 30 hours before petering out.
We saw more than 500 reports of destructive winds or wind damage once the derecho finally fell apart in eastern North Carolina early on Tuesday morning; the majority of the damage occurred around eastern Kentucky as the line restrengthened as it ran into an unstable atmosphere on Monday afternoon. Trees and power lines sustained most of the damage, but there were quite a few reports of structural damage as a result of the 60-70+ MPH winds. Reports of homes damaged by falling trees or winds tearing away shingles or siding weren’t uncommon—the rescue squad in Eden, North Carolina, reported that the storms ripped siding and gutters off of their building as the squall came through.
We’ll probably see a few more systems like this before the summer is out. The majority of them unfold during the nighttime hours, so make sure you have a way to receive severe weather alerts while you’re asleep, either by buying a weather radio or setting up alerts on your smartphone. You don’t want to be woken up by the sound of your roof peeling away.