Aug 6, 2014

The increasing efficiency of tornado days in the United States

by
James B. Elsner, Svetoslava C. Elsner, Thomas H. Jagger
,
Climate Dynamics
  • Analyzes the historical record of tornado reports in the United States and finds evidence for changes in tornado climatology possibly related to global warming
  • Examines the annual number of days with many tornadoes and the ratio of these days to days with at least one tornado and by examining the annual proportion of tornadoes occurring on days with many tornadoes
  • Presents additional evidence of a changing tornado climate by considering tornadoes in geographic clusters and by analyzing the density of tornadoes within the clusters
  • Finds a consistent decrease in the number of days with at least one tornado at the same time as an increase in the number of days with many tornadoes
  • Interprets these changes to mean there is an increasing proportion of tornadoes occurring on days with many tornadoes
  • Finds that increases in tornado density as defined by the number of tornadoes per area are coincident with these temporal changes
  • Finds that trends are insensitive to the beginning year of the analysis
  • Results indicate that the risk of big tornado days featuring densely concentrated tornado outbreaks is on the rise, a finding that is broadly consistent with numerical modeling studies that project increases in convective energy within the tornado environment