Spate of twisters nothing unusual, forecasters say

Recent recurring pattern in weather apparently ideal for severe storms

May 14, 2002|By Michael Stroh | Michael Stroh,SUN STAFF

Is Maryland experiencing an epidemic of twisters?

Yesterday made the fourth time in the past 16 days that tornadoes were either spotted on radar or on the ground. It's hard not to wonder whether all this twisting is normal.

"There's nothing strange about it. It's just the way the weather's been working," said Heidi Sonen, a meteorologist at Penn State University. Maryland has been experiencing a recurring weather pattern that's "perfect for severe storms," said Sonen.

But what is clear is that in the past decade, more tornadoes have rolled through the state than at any other time since meteorologists began keeping records, said Barbara McNaught Watson of the National Weather Service's Baltimore-Washington forecast office.

That doesn't mean the state's nickname should be changed to Tornado Alley East, however. Watson said there's no evidence that the increase is permanent.

"It's just a cyclical kind of thing," Watson said. "Just like you go through periods of more winter storms." Tornado trends are tough to determine because historical records on Maryland tornadoes are rough at best, said Russell R. Dickerson, acting chairman of the meteorology department at the University of Maryland.

Since the 1950s, when the National Weather Service first began to keep comprehensive tornado logs, Maryland recorded an average of four tornadoes a year (although given the difficulty of getting accurate counts, experts, as a rule of thumb, typically multiply this number by three.)

In the past decade, the annual tornado record has been broken three times, Watson noted. The busiest tornado season in Maryland history occurred in 1995, when 24 twisters whipped through the state.

Surprised you never noticed? Watson isn't.

Most of the tornadoes that hit the state are not the stuff of Weather Channel highlight films. Many probably don't even make the local papers.

Maryland has never had an F5 twister - the worst on the Fujita tornado damage scale - in which winds can hit 318 m.p.h. Only three F4 tornadoes have been recorded in the state. One of them pummeled La Plata on April 28.

Most of Maryland's twisters are small, F2 or less, Watson said. They blow shingles off the roof, maybe knock down a tree or two. Unless you're among the one or two unlucky people whose house or car gets clobbered, you're unlikely to know a tornado was in your town.

There have been blips before: Tornadoes picked up in the 1920s, Watson said. La Plata got socked by its first F4 on Nov. 26, 1926.

There could be other factors at work. The introduction of Doppler radar and other technology has made it possible to spot tornadoes not visible from the ground. Demographics play a role, too. As Marylanders have built homes in previously rural parts of the state, there are more people around to witness tornadoes and report them to the weather service.

Whether this year will break records remains to be seen. The tornado season - which in Maryland can last well into the fall - has just begun. Forecasters are tracking more storm systems that may roll into the area at the end of the week.

The way things are going this season, "don't be surprised if by the end of the week you have another," Sonen said.

Staff writer Frank Roylance contributed to this article.

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