The Impact of El Nino Southern Oscillation on the Climatology of U.S. Winter and Early Spring Tornado Outbreaks

Abstract

In recent years, the notion of a potential seasonal tornado outbreak prediction scheme has garnered the attention of several researchers. The studies that have arisen on this topic have focused mainly on the influence of large-scale climate drivers (e.g., El Niño Southern Oscillation, North Atlantic Oscillation, Pacific Decadal Oscillation) on tornado outbreaks. Studies on these relationships, however, have yielded conflicting results regarding the roles of the climate drivers on tornado intensity and frequency.

The present study addresses the need to establish linkages between winter and early spring U.S. tornado outbreaks to ENSO. Linkages between tornado outbreaks and ENSO are established in two ways: 1) statistically by relating raw counts of tornadoes in outbreaks (six or more in a 24 hour period in the U.S. east of the Rocky Mountains) and their destruction potential to sea surface temperature anomalies in the Niño 3.4 region and 2) qualitatively by relating shifts in synoptic-scale atmospheric phenomena contributing to tornado outbreak development to ENSO. The latter method for establishing these linkages is key as they help to avoid the weaknesses present in several previous studies of neglecting physical explanations of underlying shifts in tornado activity as a function of ENSO.