The Madden-Julian Oscillation and its relation to tornado outbreaks in the central and eastern United States

Abstract

The Madden-Julian Oscillation (MJO) is the leading mode of tropical intraseasonal variability and has known links to modification of extratropical patterns. Spatial and temporal scale differences between the MJO and US tornadoes makes connecting the two difficult, but using tornado outbreaks (TO) that are typically synoptically evident helps close this gap. An assessment of TO probability was conducted for each of the eight Realtime Multivariate MJO index phases for each month. In addition, clusters of TOs were used to identify how the MJO’s extratropical response influences patterns that lead to outbreaks in the US. It was found, and in part, consistent with previous research, that the shifts in the jet stream and wave breaking over the Pacific that occur in response to the current location of the MJO convection and circulation anomalies contribute to changes in the mid-latitude flow that can produce TOs in the central and eastern US.