It's a scary thought: Nebraska may have a mini Tornado Alley.
Although the theory is unproven, University of Nebraska-Lincoln climatologist Ken Dewey is among those who have become convinced.
“When we moved here in the 1970s and were told the phenomenon existed, I did not believe it,” Dewey said. “But I'm a storm chaser, and I've witnessed it.”
Tornado statistics point to several mini Tornado Alleys, areas within the larger Tornado Alley of the United States where even higher concentrations of tornadoes have been reported.
A $12 million study under way this spring on the cause of tornadoes may shed more light on the issue. A team of more than 100 of the nation's leading tornado researchers is crisscrossing the Plains in search of tornadic storms so that team members can deploy a fleet of sensors in the path of, and around, tornadoes.
While the idea of a mini Tornado Alley is intriguing, these researchers are chasing the larger question: What happens within a storm to birth a tornado?
The answer is important because tornadoes pack nature's most violent winds and strike with little warning. The National Weather Service has significantly improved its tornado warnings, but still overwarns in general and misses about a fourth of tornadoes. According to weather service statistics, warnings are issued for about 75 percent of tornadoes, but about 75 percent of warnings turn out to be false.
“If we can figure out some of the things that seem to be important, we can look for those in storms and hopefully that will lead to lower false alarms, longer lead times and saving lives,” said Don Burgess, a retired federal meteorologist who is helping to lead the study, dubbed VORTEX2 for Verification of Rotation in Tornadoes Experiment.
What Dewey found in a limited analysis of Nebraska's tornado numbers was a concentration of tornado reports in central Nebraska.
A more extensive, nationwide study of tornado data by the Storm Prediction Center in Norman, Okla., also found a spike in numbers in southern Nebraska and smaller pockets of increased tornado reports in central Iowa and northeast Nebraska.
The report noted that northeast Kansas and central Oklahoma were two areas of the Great Plains with significant-sized mini alleys.
The difference between the studies has to do with which tornadoes were included: Dewey's study included all tornadoes reported in Nebraska. The national Storm Prediction Center study examined only F3 and larger tornadoes, which would be more rigorously accurate because lesser tornadoes can sometimes be erroneously reported in one area and missed in another.
Nonetheless, both studies produced somewhat similar results.
Dewey said the theory of a mini alley in Nebraska makes sense based on the little scientists know about what causes tornadoes.
Central Nebraska has two of the key ingredients needed to foment atmospheric instability, he said: relatively dry air from the semi-arid Sand Hills bumping against relatively moist air from crop land to the south and east.
Dry air is denser than moist air, so as the two interact, the dry air pushes under the moist air, creating turbulence and instability.
In looking at the clusters of tornadoes in Nebraska and Iowa, the Storm Prediction Center's study noted that hills and higher elevation were the common features.
Adam Houston, a meteorologist and UNL assistant professor, said research has shown that topography can affect storms. However, he said, too little is known to attach too much importance to these numbers for now.
“We do know that there are micro-scale effects of topography, and we do have evidence of such effects that translate into patterns in storm formation,” said Houston, who is among the researchers participating in the VORTEX study.
“At this stage, all it is, is tantalizing,” Houston said. “That doesn't mean they aren't (right). It just means the jury is still out.”
Dewey agrees that his findings have their limitations.
“These are not research results,” he said. “This is an observation made by looking at data as a climatologist and surmising what might be the explanation for it.”
This kind of research is like peeling an onion, Burgess said. “Each layer that you peel back you think, ‘This is the core.' But no, there's a new layer.”
Contact the writer:
444-1102, nancy.gaarder@owh.com
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