Mar 12, 2018

Cold-season Tornadoes: Climatological and Meteorological Insights

by
Samuel J. Childs, Russ S. Schumacher, and John T. Allen
,
Weather and Forecasting
  • States that tornadoes that occur during the cold season, defined here as November – February (NDJF), pose many societal risks, yet less attention has been given to their climatological trends and variability than their warm-season counterparts
  • Develops a climatology of all (E)F1-(E)F5 NDJF tornadoes from 1953–2015 across a domain of (25-42.5°N, 75-100°W)
  • Finds:
    • An increasing trend in cold-season tornado occurrence across much of the southeastern U.S., with a bullseye in western Tennessee, and a decreasing trend across eastern Oklahoma
    • A cyclic pattern of enhanced NDJF counts every 3-7 years, coincident with the period of ENSO
    • That La Niña episodes favor enhanced NDJF counts, but a stronger relationship was found with the Arctic Oscillation (AO)
    • Most-tornadic cold seasons are characterized by warm and moist conditions across the Southeast, with an anomalous mean trough across the western U.S.