Thursday, May 2, 2013

A possible link between solar activity and tornado activity?

A paper published today in Geophysical Research Letters finds tornado activity in the central US is related to phases of the natural Madden-Julian Oscillation (MJO). Prior research has suggested the Madden-Julian Oscillation is modulated by the 11-year solar cycle. ENSO and the Pacific Decadal Oscillation have also been linked to both tornado activity and solar activity. This begs the question, are changes in solar activity a factor in explaining changes in tornado activity?

Variability of central U.S. April–May tornado day likelihood by phase of the Madden-Julian Oscillation


April–May tornado day likelihood from 1990–2011 was calculated for the central U.S. for phases of the Madden-Julian Oscillation (MJO). An April tornado day was found more likely during MJO phases 6 and 8 and less likely during phases 3, 4, and 7. A May tornado day was found more likely during phases 5 and 8 and less likely in phases 2 and 3. During phases with above-normal tornado day likelihoods, positive anomalies of convective available potential energy, bulk vertical wind shear, and storm-relative helicity were found in the central U.S. Negative anomalies were found during phases with below-normal tornado day likelihoods. Anomalies of such environmental parameters were connected to the MJO via variability in tropospheric circulation. These results provide an important starting point for extended-range prediction of U.S. tornado activity.

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