Prediction of atmospheric rivers over the North Pacific and its connection to ENSO in the North American multi-model ensemble (NMME)

Prediction skills of the wintertime atmospheric rivers (ARs) and moisture flux over the Northeast Pacific in response to El Niño Southern Oscillation (ENSO) forcing are evaluated from the North American Multi-Model Ensemble (NMME) hindcasts (CFSv2, CCSM4, CanCM3, CanCM4, GEOS5, and GFDL CM2.1). The skill is estimated for the active AR season, December–February (DJF) with initial conditions around early November. Models underestimate the climatological moisture flux to different extents corresponding with various climatological biases in predictions of sea surface temperature (SST) and large-scale atmospheric circulation fields. The anomalous moisture flux and AR frequency over the Northeast Pacific are predicted in the models but in weaker amplitude than the reanalysis. Significant regional biases are shown in the anomalous landfalling AR frequency corresponding with ENSO, underlining the challenge in regional precipitation forecasts.