North America temperature response to convectively persistent eastward propagating tropical convection associated with the Madden-Julian Oscillation

Periodic active tropical convection associated with the Madden-Julian Oscillation (MJO) is a known contributor to subseasonal variability in the large-scale flow over the extratropics. The characteristic response in the large-scale flow, for example in terms of temperatures over North America, is typically determined instantaneously or time-lagged from composite analyses during the different phases and amplitudes of the MJO. This presentation investigates characteristic responses in temperatures over North America during December-February from an evolutionary-MJO perspective by considering convectively persistent eastward propagating MJO events. The objective of this research is to identify MJO characteristics that strongly influence extreme temperature events which drive volatility in wintertime natural gas markets.

Time-lagged composite analyses of convectively persistent eastward propagating MJO events indicate that incorporating an evolutionary aspect to investigations of the influence of the MJO on the extratropical flow can sharpen the relationship between temperatures over North America and MJO phase. For example, convectively persistent eastward propagating MJO events centered over the Maritime Continent are associated with an approximately 20% increase in the probability of extreme temperatures over the subsequent 7 to 14 days over the central and eastern U.S. as compared to instantaneously determined MJO events located over the Maritime Continent. This presentation will further emphasize how incorporating an evolutionary aspect to investigations of the influence of the MJO on the extratropical flow may help identify events truly associated with the MJO versus events in which large-scale flow patterns may project onto the MJO-filtered time series.