Aug 4, 2016

Spatial Redistribution of U.S. Tornado Activity between 1954 and 2013

by
Ernest Agee, Jennifer Larson, Samuel Childs, and Alexandra Marmo
,
American Meteorological Society
  • Undertakes a preliminary investigation into the possible effects of global warming on the climatological behavior of US tornadoes for the domain bounded by 30°–50°N and 80°–105°W
  • Divides the modern tornado record into a cold “Period I” from 1954 to 1983 and a subsequent 30-year warm “Period II” from 1984 to 2013
  • Finds that tornado counts and days indicate a general decrease in tornado activity from Period I to Period II concentrated in Texas/Oklahoma and increases concentrated in Tennessee/Alabama
  • Finds that these changes show a new geographical distribution of tornado activity for Period II when compared with Period I
  • Statistical analysis that is based on field significance testing and the bootstrapping method provides proof for the observed decrease in annual tornado activity in the traditional “Tornado Alley” and the emergence of a new maximum center of tornado activity
  • Seasonal analyses of both counts and days for tornadoes and significant tornadoes show similar results in the spring, summer, and winter seasons, with a substantial decrease in the central plains during summer
  • The autumn season displays substantial increases in both tornado counts and significant-tornado counts in the region stretching from Mississippi into Indiana
  • Finds similar results from the seasonal analysis of both tornado days and significant-tornado days
  • Results indicate that this temporal change of spatial patterns in tornado activity for successive cold and warm periods may be suggestive of climate change effects yet warrants the climatological study of meteorological parameters responsible for tornado formation