Cross-Pacific forcing of the boreal winter hydrological extremes over western North America

Large-scale circulation anomalies over the western Pacific and the Far East can modulate the likelihood of the occurrence of boreal winter hydrological extremes (e.g., drought and floods) over western North America by affecting the distribution of synoptic-scale disturbances over the North Pacific. To understand this, we investigate the modulation of the North pacific storm track and its downstream impact by tropical convection on intraseasonal timescales and by East Asian winter monsoon on interannual timescales. In both cases, the total precipitable water and surface precipitation along the west coast of North America exhibits coherent patterns consistent with the anomalous storm track forcing over the eastern Pacific. The spatial structure and temporal evolution of these patterns are discussed in the context of forced intraseasonal to interannual variability in coastal cyclonic activity.