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September 4, 2003

Scientists Ask: Is The Weather Weirder Now?

By Stan Finger - The Wichita Eagle

The most tornadoes in a seven-day span in recorded history. A June hailstorm that dropped a record-setting cantaloupe of ice on Nebraska. A tornado two days later in South Dakota that produced a drop in barometric pressure far greater than weather experts believed possible.

Winds of 120 mph, equaling a powerful hurricane, that slammed Wichita's McConnell Air Force Base in late August. Even in Kansas, where the wind is part of the state's personality, that turned heads.

What the heck is going on?

The answer depends on who's talking. Some experts have suggested for a while now that, because of global warming, severe storms are going to become more frequent and more violent. Others say the only thing that has really changed is our enhanced ability to notice and understand what Mother Nature can do.

"You have to keep things in perspective," said Dan McCarthy, director of the National Oceanic and Atmospheric Administration's (NOAA) Storm Prediction Center in Norman, Oklahoma

"Whenever we hear someone say, 'We're seeing things that we've never seen before,' " McCarthy said, the thing to ask is, "Relative to what?" Just because people are seeing something for the first time doesn't mean it has never happened before. It just means those people haven't seen it. Many records now being kept go back only a few decades, offering a limited
base from which to draw comparisons.

Sometimes the surprises can be linked to new technology. Scientists have been trying for years to put small sensors in the path of a tornado, hoping the sensors would get sucked up and provide data on what goes on inside the storm.

That is just what happened on June 24 in South Dakota.

"They measured over a 100-millibar pressure drop" in the atmosphere, said Jon Davies, a research meteorologist based in Wichita. "That's larger than what had been previously thought possible or previously recorded."

Drops in barometric pressure have long been associated with tornadoes, but the June 24 drop was almost twice the accepted norm. Of all the eye-catching severe weather this summer, the Aug. 23 straight-line winds at McConnell are likely the easiest to explain, said Mike Kreyenhagen, a meteorologist with the National Weather Service's Wichita office.

A layer of cool, moist air was sandwiched between two layers of very hot air. Temperatures in Wichita had reached or exceeded 100 degrees for the eighth straight day. Cool air naturally sinks, Kreyenhagen said. Because the air beneath it that night was so hot, offering a strong contrast, "once the cool air breaks through, it just howls down," he said.

The winds destroyed a pole barn, uprooted several trees and damaged roofs at McConnell.

Explanations are proving tougher to come by for what happened June 22 in Nebraska just north of the Kansas state line. Two powerful thunderstorms erupted 50 miles from each other and pretty much set anchor, said Todd Holsten, a meteorologist in the National Weather Service office in Hastings, Neb.

One cell produced a foot of rain, hailstones as large as 2.5 inches in diameter and eight tornadoes -- including one that killed a person in Deshler, Neb. The other cell, farther north, hit Aurora with hailstones as large as cantaloupes but produced not a single tornado.

"I don't know why the Aurora storm didn't produce a big, honking tornado," said Davies, who tracked the storm cell but avoided its center because he could tell from the radar that "if we punch the core, we're probably going to lose a windshield on this one."

He was right.

One hailstone from the Aurora storm measured 7 inches in diameter and 18.75 inches in circumference, seemingly earning the title of largest hailstone ever recorded in the United States, displacing a stone that fell in Coffeyville in 1970. But McCarthy said a search of storm data at the Storm Prediction Center unearthed a report of a hailstone nearly 10 inches in diameter that fell in
Indiana on May 6, 1961. That's bigger than a basketball.

Davis said only a half-dozen storms in a database of 550 storms he has accumulated from the past 11 years had as much instability as the Deshler storm. Instability typically translates into severe weather of some kind, such as hail or tornadoes.

The Deshler storm had twice as much instability, Davies said, as the supercells that produced the F-5 tornado that struck Andover in 1991, or the F-4 that hammered Hoisington in 2001. Yet, the Deshler tornado only rated an F-2. "There'll be a lot of future research papers that come out of those two storms" in Nebraska, Holsten said. "There's a lot of oddities on that day."

As radar has improved, meteorologists can look inside a storm to see activity at different levels, allowing them to monitor structure, development and areas of rotation. But for every answer, said Dick Elder, chief meteorologist at the Wichita
office of the National Weather Service, more questions arise. "It's just like opening one door to see all the wonderful things, but
understanding there's still another door to be opened," he said.

At the National Weather Association conference in Oklahoma City three years ago, Elder heard a presentation on the effect of global warming on weather patterns. Thanks to fossil fuels, climatologists say, we have put more carbon into the atmosphere in the past 50 years than in the previous million years.

"Is that carbon going to do anything?" Elder asked. "Everyone says 'yes.' "

While one climatologist used computer-generated models to suggest that summer heat indexes would often reach 150 in Washington, D.C., by the year 2050, another offered an explanation that makes more sense to Elder. "Mother Nature is a very resilient old gal," Elder said, recalling the presentation. "She's going to do everything she possibly can to keep our planet as much as we perceive it now."

The extra carbon in the atmosphere traps more heat and more moisture, which translates into more energy. The most efficient way for the atmosphere to maintain equilibrium is to generate storms. With more energy and instability on hand, there's more fuel for the storms that fire up. That means they can be bigger and nastier.

"We're going to see more of those" giant storms, Elder said.

The week of May 4-10 set an all-time record for most tornadoes in one seven- day period. By an unofficial count, 386 tornadoes touched down in 19 states, killing more than 40 people, including seven in Kansas. The one-week total more than doubles the previous record, set in 1999. But tornado records only go back to 1950.

Davies isn't ready to pin this year's spate of eye-popping storms on global warming. In fact, he's not sure they can be attributed to any particular phenomenon, such as El Nino. But they're definitely worth a good look, he said.

"Mother Nature isn't slowing down any," he said, "and maybe she's picking her step up."


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