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Kay Fike Jones
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El Nino may weaken some spring tornadoes
STARKVILLE, Miss.--El Nino, the weather phenomenon blamed for Florida's killer tornadoes, actually may benefit the Lower Plains and the Midsouth during the coming spring tornado season.
After studying 40 years of accumulated weather data, Mississippi State University graduate student William Monfredo is predicting a decrease in the frequency of strong and violent 1998 season tornadoes--those rated 2-5 on the Fujita scale--for the central United States.
"El Nino won't worsen our tornado season," Monfredo said. "In fact, it may even make it milder."
The national tornado season is February-July, which usually peaks in the spring. A fall season typically peaks in November in the South. Monfredo's research concerns only the spring pattern.
Monfredo obtained much of his data from weather balloon recordings. After analyzing the information with a statistical model, he determined that wind speed and direction were inconsequential factors. "Cap strength" is another matter, however.
The cap is the layer of air that forms between the warm, moist air nearest the earth and the very warm and dry air above the layer. Its strength and thickness are determined by the air above and below. In completing the research, Monfredo said he came to appreciate that "cap strength" is the key to the milder El Nino tornadoes.
"The stronger the cap, the longer it takes for building clouds to break through into the upper atmosphere," he explained. "The resulting storms and tornadoes traditionally are more violent than usual."
Monfredo said he believes El Nino--the periodic warming of Pacific Ocean waters --will cause this spring's cap to be "weaker and less frequent." This is good news for the Southern Low Plains [Northeast Texas, Arkansas, Missouri, and most of Oklahoma and Kansas] and Midsouth [Kentucky, Tennessee and the northern halves of Alabama and Mississippi].
"While the Southern Low Plains should see fewer strong and violent tornadoes, the Midsouth region, the area most strongly affected by the results of El Nino, should benefit the most," he said.
But, be alert, South Mississippi.
Monfredo said Mississippi's climate from Jackson southward is very different from the north and cannot be included among the areas seeing fewer of the strong storms. Other regions of the country, such as the Northern Plains, also will not feel El Nino's effect on any tornadic activity.
"William has done an excellent job in analyzing such a vast amount of data," said David Arnold, assistant professor in the geosciences department and director of the department's climatology laboratory. "He is the first to discover this link between cap strength and El Nino."
Monfredo, a Pittsburgh, Pa. resident, received his bachelor's degree in speech/communication from Penn State. He is scheduled to complete his master's in geoscience from MSU in May.
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For additional comments, Monfredo may be reached at (601) 320-9394; Dr. Arnold may be called at (601) 325-2906.
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