21 Apr 2022
21 Apr 2022
Status: a revised version of this preprint is currently under review for the journal WCD.

Predictability of a tornado environment index from ENSO and the Arctic Oscillation

Michael K. Tippett1, Chiara Lepore2, and Michelle L. L'Heureux3 Michael K. Tippett et al.
  • 1Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York
  • 2Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York
  • 3NOAA/NWS/NCEP/Climate Prediction Center, College Park, Maryland

Abstract. ENSO modulates severe thunderstorm activity in the U.S., 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.

Michael K. Tippett et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2022-25', Todd Moore, 25 Apr 2022
  • RC2: 'Comment on wcd-2022-25', Anonymous Referee #2, 17 May 2022
  • AC1: 'Comment on wcd-2022-25', Michael Tippett, 01 Jun 2022
  • EC1: 'Comment on wcd-2022-25', Johannes Dahl, 01 Jun 2022

Michael K. Tippett et al.

Michael K. Tippett et al.


Total article views: 442 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
340 88 14 442 24 2 2
  • HTML: 340
  • PDF: 88
  • XML: 14
  • Total: 442
  • Supplement: 24
  • BibTeX: 2
  • EndNote: 2
Views and downloads (calculated since 21 Apr 2022)
Cumulative views and downloads (calculated since 21 Apr 2022)

Viewed (geographical distribution)

Total article views: 409 (including HTML, PDF, and XML) Thereof 409 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 26 Jun 2022
Short summary
The El Nino-Southern Oscillation (ENSO) and Arctic Oscillation (AO) are phenomena that affect the weather and climate of North America. Although ENSO harkens from the tropical Pacific and the AO high above the North Pole–the spatial patterns of their influence on a North American tornado environment index are remarkably similar in computer models. We find that when ENSO and the AO act in concert, their impact is large, and when they oppose each other their impact is small.