Fierce storm that tore through N.J. was a rare derecho

NJ weather - storm damage 6-3-20

Large trees damaged a house in Laurel Springs in Camden County when a powerful storm swept through New Jersey on Wednesday, June 3. Weather experts say the storm was a rare weather event called a derecho.Jessica Beym | NJ Advance Media for NJ.com

The powerful cluster of thunderstorms that tore through eastern Pennsylvania and parts of New Jersey Wednesday afternoon, toppling trees and knocking out power to tens of thousands of homes, was part of a rare weather phenomenon known as a derecho.

Officials from the U.S. Storm Prediction Center and the National Weather Service say the violent storm system that generated wind gusts as strong as 89 mph in Ocean County and 70 to 80 mph in other parts of New Jersey on Wednesday met the criteria of a derecho.

UPDATE: Strong derecho that hit N.J. packed winds as strong as 93 mph

A derecho — pronounced deh-REY-cho — is a “widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms,” according to the National Weather Service. “Although a derecho can produce destruction similar to the strength 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.”

Under the weather service’s definition, a derecho occurs if the swath of wind damage extends more than 240 miles and includes wind gusts of at least 58 mph or greater along most of its length.

Those criteria appeared to be met on Wednesday, according to New Jersey State Climatologist David Robinson, whose office at Rutgers University oversees the Rutgers NJ Weather Network.

“I think what we saw this morning into early afternoon was indeed a derecho,” Robinson said.

“I haven’t followed the line back to its origin, but it crossed into northwestern Pennsylvania at about 8 this morning and was off the New Jersey coast by shortly after 1 p.m. That is 350 miles in 5.5 hours, or a 65 mph speed to this uber squall line.”

“Given its wind strength, speed and longevity, I think it deserves the derecho designation,” Robinson said.

One of the strongest derechos in recent years in New Jersey occurred in June 2012, causing widespread damage in South Jersey. That derecho started in Chicago and essentially grew stronger as it moved east and across New Jersey, exploding into a violent line of thunderstorms.

UPDATE: Power still out for 100K in N.J. from rare derecho storm. Live power outage tracker.

New thunderstorm watch issued in N.J.

Earlier on Wednesday, 14 counties in New Jersey were under a severe thunderstorm watch, which later turned into warnings in many places. After the storms began to weaken, the warnings and watches were canceled.

However, a new severe thunderstorm watch was issued shortly before 4 p.m. Wednesday for the southern half of New Jersey and southeastern Pennsylvania , effective until 10 p.m., because another round of thunderstorms will be moving through the region.

A watch means conditions are favorable for severe thunderstorms to develop, with some winds gusting as high as 60 to 70 mph. The weather service says an isolated tornado cannot be ruled out.

With temperatures soaring high Wednesday, a daily record was set at Atlantic City International Airport in Pomona, where the mercury hit 92 degrees. The National Weather Service said that broke the old June 3 record high of 91 degrees, set in 2010.

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