The ECMWF SEAS5 Seasonal Forecast of the Hot and Dry European Summer of 2022

Oral Presentation 

The 2022 European summer was characterised by hot and dry anomalies across much of the continent, likely influenced by a northward-shifted jet stream. These general features were well predicted by the ECMWF seasonal forecast initialised on the 1st May. However, such successful predictions for European summers are relatively uncommon, particularly when it comes to atmospheric circulation. In this study a set of hindcast experiments are employed to investigate the role that initialisation of the ocean, atmosphere and land-surface played in the 2022 forecast. 

We find that the trend from external forcing was the strongest contributer to the forecast near-surface temperature anomalies, with atmospheric circulation and land-surface interactions playing a secondary role. On the other hand, atmospheric circulation made a strong contribution to precipitation anomalies. Euro-Atlantic circulation anomalies in 2022 were consistent with a La Nina-forced teleconnection from the tropical Pacific. However, a northward jet trend in the model hindcasts with increasing greenhouse gas concentrations, also contributed to the predicted circulation anomalies in 2022. This northward jet trend in the model is at odds with the observed southward shift of the summertime North Atlantic jet over recent decades and suggests that some of the predicted circulation was correct for the wrong reasons. Nevertheless, this case study demonstrates that important features of at least some European summers are predictable at the seasonal timescale.