| Summary: | The UK and western Europe experienced periods of intense and disruptive storminess in February 2020 and 2022. In February 2020, named storms Ciara, Dennis and Jorge caused widespread damage from strong winds and heavy precipitation. In February 2022, storms Dudley, Eunice and Franklin arrived in quick succession, with Eunice setting a new UK wind gust record of 122 mph. In both months, the stratospheric polar vortex was amongst the strongest on record. Here, we analyse multi-model seasonal hindcast simulations to examine the association between the strong polar vortex conditions in February 2020 and 2022 and the characteristics of North Atlantic cyclones. We show that the presence of a strong polar vortex induced a northward shift in the tracks of North Atlantic cyclones, increased the peak intensity of cyclones, and increased the monthly total rainfall and average maximum 10m wind gusts over the UK and Scandinavia. The likelihood of occurrence of the most intense North Atlantic cyclone observed in February 2022 was increased by a factor 16 due to the presence of a very strong polar vortex. The results demonstrate an important role for intense stratospheric polar vortex conditions in increasing extreme northern European storminess.
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