Flow dependence of wintertime subseasonal prediction skill over Europe

Abstract. Issuing skillful forecasts beyond the typical horizon of weather predictability remains a challenge actively addressed by scientific community. This study evaluates winter subseasonal reforecasts delivered CNRM and ECMWF dynamical systems identifies that level skill for predicting temperature in Europe varies fairly consistently both systems. In particular, initialized during positive North Atlantic Oscillation (NAO) phases tend to be more over at week 3 Composite analyses performed an atmospheric reanalysis, long-term climate simulation forecast unveil very similar sea-level pressure patterns weeks after NAO conditions. Furthermore, regressing these fields onto 3-weeks-prior index reanalysis shows consistent but also other regions Northern Hemisphere extratropics, thereby suggesting lagged teleconnection, related either persistence or recurrence negative NAO. conditioned intensity initial phase, is well captured As result, it key mechanism determining priori confidence wintertime as parts Hemisphere.