In the Philly region’s tornado outbreak, it was the sun that helped light the fuse

The rains had shut off, and the sun that has been gaining power daily emerged to bestow a splendid April afternoon on the Philadelphia region. Temperatures had warmed to 70 degrees by 5 p.m.

But the meteorologists on duty were aware that the sun’s appearance meant trouble. It was lighting a fuse, its energy supplying fuel to a tremendously volatile atmosphere.

What followed was one of the wildest 90 minutes in the region’s weather history. “It was quite an impressive setup,” said Ray Martin, a lead meteorologist at the National Weather Service Office in Mount Holly. “Once we got the sun, it was game on.”

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By 6 p.m. Saturday, ominous cloud masses were advancing from the west, foreshadowing what would be a brief but violent rain of terror wrought by a potent squall line with embedded supercell thunderstorms.

They would spin off nine verified tornadoes from Bucks County to South Jersey to Delaware, where an EF-3 on the Enhanced Fujita scale, with winds up to 140 mph, one of the strongest on record in the Diamond State, was verified. It produced only the second recorded tornado fatality in Delaware.

Once again, we learned that weather is like so much of life. It can turn bad in a hurry.

The region has experienced quite a harvest of tornadoes since 2020, with more than 30 confirmed within about a 60-mile radius of the city.

Is this the future of climate around here?

“You can’t connect the dots and say ‘yes,’” said Bill Bunting, the chief of Forecast Operations Operations Branch Storm Prediction Center, which had posted a tornado watch for the region Saturday afternoon.

A major barrier to drawing conclusions about a climate-change role, say Bunting and other tornado experts, is the database. Since the weather service modernization in the 1990s and the use of Doppler radar, tornado detection has improved immensely.

Plus, these days, with social media and most folks armed with cell phones, it’s becoming ever harder for a tornado to spin unnoticed, he said.

From 1950 to 2022 period, Philadelphia and its four Pennsylvania counties recorded an average of fewer than two tornadoes annually, with only three in all of New Jersey, according to government data.

However, the database has experienced enormous increases in weaker tornadoes in recent years, and that, in all likelihood, is about improved detection.

“It’s not an apples-to-apples comparison,” Bunting said.

Bunting added, however, that the lack of those drying, air-cleansing, wintry cold fronts that were so absent in the non-winter that recently ended would give storms “ready access” to warm and moist air. He said it was possible that favorable conditions could be occurring more frequently.

“It’s just hard to say.”

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Tornadoes, say those who study and try to forecast them, are at least as enigmatic and strange as they are ferocious.

What happened around here Saturday was related to the storm that had resulted in so much death and destruction in the South and Midwest late last week. As the cyclone moved northeast toward the St. Lawrence Valley, a trailing cold front and an associated squall line approached the Philadelphia region with embedded “supercell” thunderstorms.

Bunting said the atmosphere was primed for a spell of riot. About 2,000 to 3,000 feet above the surface, the winds were changing direction, or “veering.” More ominously, the upper atmosphere was dramatically unstable, with temperatures at the 10,000- to 20,000-foot level dropping 13 and 14 degrees for every 3,000 feet.

“That’s a very important signature,” he said. “It’s a sign that this is a day to take seriously.” Thunderstorms are launched by warm air rising over cooler air, causing moisture to condense. In this case, the air was rocketing upward.

Then along came the sun to add heat energy.

“Once we realized there was going be ample daytime heating, the only question was how bad is it going to be.”

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The answers began coming shortly after 6 p.m. with the first of seven tornado warnings issued by the Mount Holly office. That one announced the deadliest and most-powerful one of the local outbreak with winds peaking at 140 mph, the EF3 in Sussex County’s Bridgeville-Ellendale area, caused a two-story home to collapse after it slid off its foundation.

The weather service said that for peak winds it rivaled the one that stuck New Castle on April 28, 1961, although Martin pointed out that it’s difficult to say precisely how strongly the wind was blowing. The speeds are inferred from structural damages, and the quality of construction of buildings can vary considerably.

In any event, it was one powerful tornado and one impressive outbreak, considering how far the region is removed from nation’s busiest tornado zones.

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Said Bunting, “Maybe this isn’t traditional tornado alley, but they do occur. It’s that time of year.”

Martin pointed out that one of New Jersey’s worst outbreaks actually occurred in November, in 1989, followed a week later by a Thanksgiving snowstorm.

“The weather will do what it wants to do,” he said.

Inquirer staff writer Frank Kummer contributed to this article.