A twister poses big challenge for meteorologists

By Stephanie Ebbert
Globe Staff / June 3, 2011

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The extreme weather that roared through New England Wednesday had been forecast for days. But the tornado that touched down in Springfield descended stealthily and suddenly, forming over the Connecticut River as horrified commuters sat in rush hour traffic on nearby Memorial Bridge.

“They’re the worst kinds of storms, always have been, always will be,’’ said Harvey Leonard, Channel 5’s chief meteorologist. “There’s only so much you can do with actual warnings of a tornado.’’

The storms’ wrath highlights the imprecision of a forecasting system that is stunning in its ability to predict and track storms, but unable to pinpoint precisely where or when a tornado will touch down.

“Until a tornado drops from the clouds, it’s a thunderstorm,’’ said Peter Judge, spokesman for the Massachusetts Emergency Management Agency. “If you watch this stuff on TV, it’s amazing how technology has grown to the point where they are able to predict, once it’s established itself, which direction, what speed, what communities are in harm’s way. But the problem is for that first community that it drops down on.’’

Although meteorologists are still assessing the damage to confirm the path and strength of the tornadoes that struck Western and Central Massachusetts, the preliminary investigation suggests that a tornado first touched down in Westfield about 4:15 p.m., said Robert Thompson, the National Weather Service meteorologist in charge of the investigation. The tornado then touched down in Springfield, Monson and Sturbridge. A second and possibly a third then struck Westfield and Springfield and Sturbridge again.

“This was not a surprise by any means that we were getting heavy-duty weather,’’ said Bill Babcock, a meteorologist with the National Weather Service in Taunton. A tornado watch had been issued for most of the state by 1 p.m.

By 4:18 p.m., a severe thunderstorm warning posed the possibility of a tornado in Springfield and Chicopee.

But the tornado warning did not come for Springfield until 4:30 p.m., just two minutes before it touched down there.

“My warning was looking out the window and seeing it coming to our building,’’ said Tom Walsh, the communications director for Springfield’s mayor, Domenic J. Sarno, who watched the funnel cloud forming from a City Hall window where aides were monitoring the news. “The minute I saw the debris, I immediately recognized what it was and ran through City Hall to get down into the basement.’’

On Fox25 News, chief meteorologist Kevin Lemanowicz had just done a cut-in about 4:26 p.m. noting the storm could bring a tornado. “We could see it in Doppler radar before there was a tornado warning,’’ he said.

But the tornado warnings are issued by the National Weather Service’s Storm Prediction Center and are not issued until a tornado can be confirmed.

“It’s a ‘nowcast situation,’ rather than a forecast situation,’’ Lemanowicz said. “All you can do is watch everything develop and warn people in the path of the storms that do come up.’’

Meteorologists say they are limited in their ability to precisely predict tornadoes, even with today’s sophisticated radar systems. They say their radar capability from Eastern Massachusetts is somewhat limited as far out as Springfield.

“Springfield is far enough away that the lowest the radar sees is about 5,000 feet above the ground,’’ said Babcock, noting that meteorologists lose some detail on storms closer to the ground.

“That is a limitation that you’re not going to get with a radar in Eastern Massachusetts because radar essentially goes in a straight line, but the earth’s surface is curved,’’ he added.

Regardless, specialists said, tornado warnings are not issued much farther in advance than the 10 minutes’ notice that Governor Deval Patrick said Springfield got.

“Ten minutes is actually a pretty good warning,’’ said Channel 5 staff meteorologist Mike Wankum. “The national average is 11 minutes’ warning time. The goal is to try to get it to 20 minutes.’’

The warnings are not aimed at giving homeowners time to go inside and save their treasures. “Sometimes people get a tornado warning and run back upstairs when they should be down in the basement,’’ Wankum said. “We’re giving you enough warning to save your life.’’

The warnings can give other towns in the path of a tornado up to an hour of advance warning, Leonard said.

Leonard weighed in on the region’s unusually powerful tornadoes from his vacation in Israel, where he finds himself explaining to other travelers that tornadoes are not unknown in Massachusetts.

The Bay State actually averages three tornadoes a year, and the Worcester tornado of 1953 was one of the 20 deadliest tornadoes in the United States, he said.

Stephanie Ebbert can be reached at Follow her on Twitter @StephanieEbbert.

Correction: Because of a reporting error, this story about how much notice communities had before last week’s tornadoes misstated how tornado warnings are issued. The warnings, which are issued by the National Weather Service’s local offices, go out as soon as a tornado is spotted on radar.