The Effects of El Niño on Tornado Behavior in the Great Lakes Region

Abstract

The Southern Oscillation and its teleconnections have been shown in previous research to change weather patterns across the United States. These changes, which have been caused by either El Niño or La Niña, could affect the way a tornado behaves. Forty counties in Illinois, Indiana, and Wisconsin over a period of 30 years from 1978 to 2008 were studied. The behaviors that were studied were: 1) the number of tornadoes, 2) the magnitude of the tornadoes, 3) Length of the tornado path, 4) Width of the tornado, and 5) the length of the tornado season. The data was analyzed both statistically and spatially. Little difference was found in the strength of the tornadoes, the length of the tornado season, the width of the tornado, and the length of the tornado path. There were 60 more tornadoes that occurred during El Niño years. However, when looking at a strong El Niño year and a strong La Niña year the magnitude of the tornadoes was stronger during the La Niña year. By looking at the data spatially it was determined where the tornadoes occurred which was all over the study area. It was also determined that the mean centers ended up being close together. The tornadoes are clustered for both El Niño years and non-El Niño years. Tornadoes were denser during El Niño years. Tornadoes did not behave differently during El Niño in the Great Lakes region. In future studies it is recommended that the study area be larger and only stronger tornadoes be looked at.