23STUDENT ENSO Impacts on Monthly Tornado Climatology Within the United States and Oklahoma

Understanding of ENSO’s relationship to tornado count is critical to producing accurate long-range seasonal tornado forecasts. Statistical analysis proved that tornado count is enhanced during autumn, winter, and early spring by La Niña due to climatologically stronger upper and low-level jet streams and enhanced instability due to stronger moisture advection and a stronger elevated mixed layer. The biggest surprise of the research was that El Niño leads to enhanced tornado count for May both nationwide and in Oklahoma, the exact physics behind this relationship flip are unknown, although high temperature-dewpoint spreads and convective inhibition could play a factor. During June and July, the main tornado zone shifts northward, the low-level jet relationship flips, with the low-level jet being stronger in the summer during El Niño, and El Niño enhances tornado count during these months. Finally, La Niña appears to slightly enhance tornado count during August and September, but this relationship is less defined.