Storm clustering in the North Atlantic and Europe: a window of opportunity for sub-seasonal prediction?

Serial clustering of extratropical cyclones has been linked to large cumulative losses within Europe in recent years. Serial clustering describes the passing of multiple cyclones over a fixed region within a short time period. These successive events bring strong winds and heavy precipitation, causing extensive economic losses and leading to impact on society. Serial clustering is found to be largest within the storm track over the North Atlantic, setting especially North-Western Europe under risk. Consequently, predicting extratropical storms and particularly serial clustering is of high interest. However, the predictability of these events on sub-seasonal to seasonal timescale and their role in forecast uncertainty remains unresolved.

Here, we investigate the predictability of extratropical cyclones clustering over North-Western Europe on sub-seasonal timescales. Successive cyclones can form on the cold front behind a predeceasing cyclone. Thus, storm clustering events can potentially provide a window of opportunity for enhanced forecast skill for the following cyclones. Using ECMWF ERA-5 reanalysis data and reforecasts from the Sub-seasonal to Seasonal (S2S) Prediction Project database, we examine case studies of storm clusters over Europe, including February 2020 and 2022, which were associated with considerable impact on surface weather over the United Kingdom. Furthermore, we investigate which drivers influence the occurrence of serial clustering in this region and what the relative roles of local versus remote drivers, such as the stratospheric polar vortex, are. Gaining more insights into the precursors of such extratropical cyclone clustering can in turn lead to better predictability of these events and their associated surface impacts, including wind and flood damage.