Pentad evolution of wintertime impacts of the Madden-Julian Oscillation on the contiguous United States

Lagged pentad composites of surface air temperature and precipitation are analyzed for the winter season (DJF) to assess the influence of the Madden-Julian Oscillation (MJO) on the contiguous United States. Significant positive temperature anomalies develop in the eastern United States 5-20 days following Wheeler and Hendon MJO Phase 3, which corresponds to enhanced convection centered in the eastern Indian Ocean. At the same lag, positive precipitation anomalies are observed from the Southern Plains to the Great Lakes region. Negative temperature anomalies appear in the central and eastern US 10-20 days following MJO Phase 7. Also at this lag, a precipitation anomaly dipole is observed in the western US. These impacts are supported by an analysis of the evolution of 200-hPa geopotential height and zonal wind anomalies.

Furthermore, impacts are assessed by analyzing composites based on a velocity potential index of the MJO. This analysis suggests that MJO-related velocity potential anomalies produce a climate response in the contiguous US even when the Wheeler and Hendon index does indicate an MJO phase.

Finally, anomaly correlations based on a simple reconstruction of 200-hPa geopotential height and surface air temperature using RMM 1 and RMM 2 are presented to assess objective prediction skill.