Weather research helps save lives
Link found between tornado activity and El Niño

A team of researchers, including Christopher Wikle, professor of Statistics, has found a link between tornadoes and two famous weather phenomena, El Niño and La Niña. Now, the National Science Foundation has awarded a $750,000 grant to Christopher Wikle and assistant professors Neil Fox, Department of Soil, Environmental and Atmospheric Sciences, and Athanasios Micheas, Department of Statistics, to study short-term storm forecasting, or "nowcasting," to develop a more precise forecasting tool that will help save lives.

Wikle, who also holds degrees in meteorology, has concluded that certain regions of the United States have a decreased chance of tornado activity if an El Niño is occurring in the Pacific Ocean. Likewise, Wikle says, there appears to be an increase in tornadoes during years when a La Niña is present. He says current indications of a mild El Niño next year could indicate fewer tornadoes in several areas of the United States that are prone to tornado activity. El Niño is characterized by unusually warm sea surface temperatures in the tropical Pacific Ocean near the equator, while La Niña is characterized by unusually cold temperatures in the same region.

Using a statistical model that combines historical data with current information, Wikle and his collaborator, Christopher J. Anderson of Iowa State University, plotted tornado report data from 1953-1995. They found that in the Midwest, including portions of Missouri, Iowa and Illinois; the Southeast, including portions of Georgia, Alabama, Mississippi, Kentucky, Tennessee and the Carolinas; and the East coast that includes portions of Maryland, Pennsylvania and New York, there is a significant decrease in tornado reports in years with an El Nino present. There is an increase in years when there is a La Nina.

"Statistically, there is a relationship between El Niño, La Niña and tornado counts. Given that we have forecast models that can predict El Niño well into the future, what’s happening in the fall this year can project next year’s activity," Wikle said.

Wikle and colleagues at The Ohio State University, Noel Cressie and Mark Berliner, have developed an El Niño forecasting model that has proven quite accurate up to seven months into the future. He says that the current picture suggests continued warmer than normal sea surface temperatures in the Pacific through March 2005, which will be a low-intensity El Niño. Although this would indicate a lower than average number of tornadoes for the areas in the Midwest, these results are statistical, and any given year could still show quite a few intense tornadoes.

Wikle and Anderson are continuing their research to better refine the number of reports of F-2 to F-5 tornadoes. Wikle said there appears to be a decrease in the overall number of tornadoes in what is termed "tornado alley" through the middle United States, but they also must consider that in previous years, tornadoes in low population areas were often not reported.

With the NSF grant, Wikle, Fox and Micheas will target the "nowcasting" of weather radar, hoping to develop a more precise method for that system to track storms by using not only prior history but current conditions.

"If you think about it, what is more important than improving the forecasting of intense storms into the immediate future?" Wikle said. "This is critical for predicting flash floods and the movement of severe weather. Our method really tries to get a handle on the uncertainty of forecasts, because when it comes to lives and property, it is important to be honest about what you know and what you don't know."

2004

Additional links:

Christopher Wilke
Department of Statistics

Neil Fox, Department of Soil, Environmental and Atmospheric Sciences
Athanasios Micheas, Department of Statistics

Noel Cressie, The Ohio State University
Mark Berliner, The Ohio State University

National Science Foundation

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