2 tornadoes in 2 weeks is rare - but not as rare as you might think

 nj.com  06/14/2019 17:34:33   Len Melisurgo | lmelisurgo@njadvancemedia.com

In a span of just two weeks and two days, New Jersey has been hit by two tornadoes. One twister packing 100 mph winds struck in Sussex County on May 28, and another touched down in the southwestern county of Gloucester Thursday night as a cluster of strong thunderstorms swept across the region.

Dont worry. New Jersey is not becoming a new tornado alley.

Even though the Garden State gets an average of two tornadoes per year  so we already reached our average only halfway through 2019, and just as thunderstorm season is ramping up  New Jersey has gotten hit by as many as 11 tornadoes in one year, back in 1989, according to the National Weather Services storm database.

It seemed like a wall just hit. South Jersey family describes sudden tornado that hit their home.

There were 20 places of interest to investigate for possible tornado damage between Harrison, Woolwich, Deptford and Mantua Townships.

The database shows New Jersey had nine confirmed tornadoes in 1987, eight in 1990 and 1973, and seven in 2003 and 1994.

During many of those years, and in several other years, the state was hit with multiple tornadoes on the same day. (The worst was seven on one day in 1989, during a severe tornado outbreak that wreaked havoc on the northeastern United States.)

Outbreaks like those are very rare in New Jersey, but statistically its still unusual to get two confirmed tornadoes in a two-week period, said Chad Shafer, a meteorologist at the National Weather Services regional forecast office in Mount Holly.

Thursdays tornado was not expected

The small tornado that swirled across Gloucester County Thursday night, sending debris flying through the air, was both surprising and not surprising to meteorologists.

Shafer said the U.S. Storm Prediction Center, an affiliate of the National Weather Service, had placed South Jersey under a marginal risk of getting severe thunderstorms on Thursday. And he notes that severe thunderstorms are capable of producing tornadoes, sometimes with little or no advance warning.

However, what was surprising was the atmospheric setup. Unlike the late May storm outbreak, when conditions were ideal for tornadoes to develop, the atmosphere on Thursday did not appear to be as conducive for twisters, Shafer said.

Steven DiMartino, a meteorologist who heads the private NY NJ PA Weather forecasting company, said he didnt expect so much instability in the atmosphere  one of the key ingredients for tornadic activity  but he noticed another ingredient, vertical wind shear, was pretty strong on Thursday.

That contributed to the strength of the thunderstorms that rolled through southern New Jersey at night when a strong cold front was moving through, DiMartino said, so he wasnt too surprised a funnel cloud had formed.

When you get enough spin in the atmosphere, tornadoes can form very quickly, he said.

And thats what happened Thursday night. When the thunderstorms fired up and the winds started swirling, the National Weather Service noticed rotating winds (a key tornado signature) on their radar screens, prompting them to issue three tornado warnings in South Jersey between 8:09 p.m. and 9:05 p.m.

This happened while a Tornado Warning was in effect this evening. Thank you Heather Patterson for sharing your sisters video with us! pic.twitter.com/YhdsgA0xSR

— Adam Joseph (@6abcadamjoseph) June 14, 2019

Damage survey continues

A team of meteorologists from the weather service is continuing its survey of the storm damage in Gloucester County Friday afternoon to determine if all the damage was caused by the twister that was videotaped in the Mullica Hill area of Harrison Township, or if additional tornadoes may have formed, Shafer said.

We cant rule out more than one, he said Friday morning, before the survey team arrived in Gloucester County. It could have been just one tornado. It could have been a tornado that intermittently touches the ground.

The survey team started out in the Salem and Woodstown in Salem County, where they determined the damage in those areas was caused by straight-line thunderstorm winds, not by a tornados rotating winds.

A preliminary report on the Gloucester County storm survey is expected to be issued later today.

Len Melisurgo may be reached at LMelisurgo@njadvancemedia.com. Follow him on Twitter @LensReality or like him on Facebook. Find NJ.com on Facebook.

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