The severe thunderstorms that inundated Philadelphia and parts of neighboring counties on both sides of the river with soaking rains early Thursday spawned a tornado in Gloucester Township, Camden County, the National Weather Service said.
The weather service office in Mount Holly said that it was an EF-1 on the Enhanced Fujita scale, with top winds of 90 mph, and that winds took down multiple trees and large limbs in the vicinity of Deer Park Circle, with at least one tree landing on a house, a weather service survey team reported.
By tornado standards it was a short-timer, lasting all of two minutes, from 4:59 to 5:01 a.m., and traveling just over a quarter-mile. On average tornadoes last about five minutes, according to the National Severe Storms Laboratory, surviving for about 1.5 miles before they spin out.
No injuries were reported as a result of a twister that came as a surprise.
No tornado watches or warnings had been issued. “We had the thunderstorms moving in from the west and there was a warm front lifting north,” said Ray Martin, a lead meteorologist at the Mount Holly office. Conditions happened to be ideal “to get the spin going,” he said, “and one just happened to spin up.”
Severe weather wasn’t widespread, Martin said, but a 54-mph wind gust was reported at Philadelphia International Airport, where the 1.97 inches of rain exceeded the total that had fallen there in the previous 12 days. At the I-95 Pennsylvania welcome center near the Delaware border, 2.58 inches was measured.
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The downpours prompted flood warnings around 4:30 a.m. for Philly, Delaware County, parts of adjacent South Jersey, and northern Delaware.
But not every place got a dousing, nor was there a widespread storm outbreak. “It was pretty sporadic,” said Martin, and the tornado “isolated.”
This was the second time this year a survey team had verified a tornado in the region, the other occurring March 31 in Upper Bucks County. That one had top winds of 100 mph and lifted debris so high into the air — up to 4,000 feet — that it was captured by radar.
Straight-line winds can be as damaging as those that blow in circles, but weather service officials say the tornado storm surveys are important for scientific and future-forecasting purposes and checking the reliability of radar.
The survey crews almost certainly can take a day off Friday as the region is in for another exquisite June day with sun and a high around 80. But shower chances return for both Saturday and Sunday.