Extending the Lead Time for European Winterstorm Activity Predictions

The most dangerous and costly meteorological hazards in Europe are extreme extra-tropical cyclones and associated windstorms (EUWS) in winter. Recent studies have shown that seasonal prediction systems can skilfully predict the seasonal frequency of EUWS with a one-month lead time using November initialisations. Given that many seasonal prediction systems produce seasonal forecasts at the start of each month, this raises the question whether pre-November initialised seasonal forecasts could provide usable information in predicting seasonal activity of EUWS.

In this study, we will present preliminary results of an approach aimed at extending the predictive horizon of seasonal EUWS activity. While the direct outputs of the pre-November initialised seasonal predictions of EUWS do not have the sufficient skill, skilful predictions of seasonal EUWS activity can be obtained by an approach that utilises the information of the upper ocean mean potential temperature from seasonal prediction systems. Based on our approach, skilful predictions of seasonal EUWS activity becomes possible as early as October.