Forecast-based attribution for midlatitude cyclones

The widespread destruction incurred by midlatitude storms every year makes it an imperative to study how storms change with climate. The impact of climate change on midlatitude windstorms, however, is hard to evaluate due to the small signals in variables such as wind speed, as well as the high interannual variability in Atlantic storms. Here, we compare multiple severe midlatitude cyclones with both wind and precipitation impacts using forecast-based event attribution. We use a recent version of the ECMWF IFS ensemble prediction system which is demonstrably able to predict the storms, significantly increasing our confidence in its ability to model the key physical processes and their response to climate change. The comparably high resolution of our simulations, and the focus on individual case studies are particularly useful for dynamically driven events like storms. Our approach is able to combine a dynamical analysis of the storm in question with an analysis of past and future changes. Our results confirm trends of increased severity in storm impacts found in climate projections but add reliability to the forecasted structure and impacts of the storm. This indicates that forecast-based attribution is viable for reliable and fast attribution systems.