Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation

Abstract

Abstract. El Niño–Southern Oscillation (ENSO) modulates severe thunderstorm activity in the US, with increased activity expected during La Niña conditions. There is also evidence that severe thunderstorm activity is influenced by the Arctic Oscillation (AO), with the positive phase being associated with enhanced activity. The combined ENSO–AO impact is relevant for situations such as in early 2021, when persistent, strong positive and negative AO events occurred during La Niña conditions. Here we examine the relation of a spatially resolved tornado environment index (TEI) with ENSO and the AO in climate model forecasts of February, March, and April conditions over North America. Bivariate composites on Niño 3.4 and AO indices show that TEI predictability is high (strong signals and probability shifts) when the ENSO and AO signals reinforce each other and low when they cancel each other. The largest increase in the expected value and variance of TEI occurs when Niño 3.4 is negative, and the AO is positive. Signal-to-noise ratios are higher during El Niño–negative AO than during La Niña–positive AO, but probability shifts are comparable.

Multi-timescale exploration of teleconnection/tornado activity relationships in the Southeastern United States

“…The ENSO:AO interaction shown in Fig. 3B), with the greatest probability of an active season occurring when ENSO and AO are in opposite phases, is similar to the joint ENSO and AO effect reported by Tippett et al (2022) but also suggests that the ENSO:AO interaction may occur in other seasons and is not con ned to February, March, and April.…”

“…That said, not all interactions are characterized by these environments. Additional study is necessary to tease out the complex ways in which climate patterns work both independently and interactively to modulate tornado activity (Brown and Nowotarski 2020;Tippett et al 2022).…”

Assessing the Impact of Stratospheric Aerosol Injection on US Convective Weather Environments

“…associated with the Madden Julian Oscillation (Baggett et al, 2018;Thompson & Roundy, 2013) or the ENSO phenomenon. For instance, J. T. Allen et al (2018) examined the role of ENSO in modulating the annual cycle of tornadoes over the US, while Tippett et al (2022) studied how ENSO and the phase of the Arctic Oscillation impacted the predictability of the tornado environment index. What has not been often considered, however, is the potential role that lower frequency (e.g., decadal) internal climate variability could play in future projections of severe weather.…”

Assessing the impact of stratospheric aerosol injection on U.S. convective weather environments

“…However, they have tended to focus on sub-seasonal-to-interannual variations, such as those associated with the Madden Julian Oscillation (Baggett et al, 2018;Thompson & Roundy, 2013) or the El Niño Southern Oscillation (ENSO) phenomenon. For instance, J. T. Allen et al (2018) examined the role of ENSO in modulating the annual cycle of tornadoes over the U.S., while Tippett et al (2022) studied how ENSO and the phase of the Arctic Oscillation (AO) impacted the predictability of the tornado environment index. What has not been often considered, however, is the potential role that lower frequency (e.g., decadal) internal climate -17-manuscript submitted to Earth's Future variability could play in future projections of severe weather.…”