Multidecadal variability of the ENSO teleconnection to Europe in early-winter and implications for seasonal forecasting

The impacts of the El Niño-Southern Oscillation (ENSO) on the climate of the North Atlantic and Europe (NAE) are season-dependent and, in some cases, neither symmetric nor stationary. Generally, ENSO teleconnections involve different tropospheric mechanisms, depending on the ocean background state. However, the impacts and mechanisms of the ENSO teleconnection to NAE in early-winter (November-December) remain unclear. Here, the teleconnection is analysed for different sea surface temperature background states of the Pacific Ocean. Using gridded reanalysis and observational datasets, the results reveal that the teleconnection is not stationary and has changed with the Pacific Decadal Oscillation (PDO) phase, leading to distinct impacts on the surface climate in Europe. The SEAS5 dynamical seasonal prediction model from ECMWF accurately captures ENSO as a source of early-winter predictability over Europe. Moreover, the model's teleconnection and predictive capability show multi-decadal variability. This implies the emergence of windows of opportunity for seasonal forecasting, where predictability may be higher than initially expected.