Rare “Super” Derecho Slams South Jersey (And 4 Other States)

Glenn explains why the storm that slammed New Jersey this past weekend was both extremely rare and extremely unpredictable.

Derecho’s are pretty rare in this area to begin with; a “Super” Derecho is almost unheard of. And, they are even harder to forecast than tornadoes because they are so rare.

A Derecho is “a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms.” That definition comes from the Storm Prediction Center of NOAA, which is in charge of severe storm watches and outlooks. They had no severe storm outlook for the South Jersey part of our area that was hardest hit. But the strongest storms on earth are often the most predictable.

An F5 tornado like the one that wiped out Joplin, Missouri was part of a severe weather outbreak predicted days ahead. We can usually predict a major snowstorm at least a day in advance, and often several days in advance. And we can see hurricanes approaching days ahead of landfall. The forecasts and outlooks are never perfect, but at least they are not a surprise to anyone following the weather at all.


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Derecho’s are different. Here is a detailed explanation from the Storm Prediction Center.

And here is an amazing youtube video of the whole event, from its origin in Iowa to New Jersey.

The ingredients for forming a “Super Derecho” are not fully understood. There has to be a strong Jetstream and front nearby, but we see that a lot without a derecho forming. The all-time record heat in the Midwest and East was surely a factor.

On a personal note, I was at the Jersey Shore when the storm hit, awake at 1am when it started. I was in a small apartment with nothing but glass on the side the storm was coming from. There was a full hour of terror as the windows rattled and the wind howled, with nearly constant flashes of lightning. The power went out minutes after the storm hit, and gradually, the lights went out for miles around us. It was perhaps the worst storm I’ve ever experienced outside the eye wall of a Category 3 hurricane.

Even though more thunderstorms are expected this week, and some could be severe, a repeat of a “Super Derecho” is certainly not expected.

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