US Summer Precipitation and Temperature Patterns Following the Peak Phase of El Nino

Evidence for spatially coherent, but different, U.S. summer precipitation and surface air temperature anomalies during the evolving phase and during the summers following the peak phase of the winter El Nino is presented. The spatial patterns during the decaying phase of El Nino are distinctive from patterns in the preceding summer when El Nino is in its evolving phase, that is, the traditional simultaneous composite patterns associated with El Nino. The analysis of a multimodel ensemble of global atmospheric models forced by observed sea surface temperature further confirms that the differences in the U.S. summer precipitation and surface temperature anomalies between the developing and decaying phases of El Nino are a result of the atmospheric response to tropical warm SST anomalies that are shifted eastward and are confined east of 120 W during the decaying phase of El Nino. Given the distinctive pattern, and relatively large amplitude of these anomalies during the decaying phase of El Nino, the results may have implications for the seasonal prediction of U.S. summer precipitation and temperature following winter El Ninos.