Attribution of the 2022 extratropical storm Fiona

In late September 2022, the Atlantic Hurricane Fiona transitioned to an extratropical cyclone making a landfall in the Canadian Atlantic provinces and setting a new national lowest pressure record. The insured damage from the resulting windstorm and flooding is estimated to be 800 million CAD (600 million USD).

In this study, we analyze the maximum daily near-surface wind speeds in Atlantic Canada using reanalysis and CMIP6 HighResMIP data. According to our preliminary results from ERA5 reanalysis, the 2022 Fiona wind speeds were the highest in Atlantic Canada since 1950, with an estimated return period of 500 years. Additionally, using HighResMIP data from the models with a spatial resolution exceeding 56x56 km, we compare the wind speeds in the current climate with those from 1950-1969 and in 2031-2050 under the highres-future scenario, similar to RCP8.5. While currently in Atlantic Canada, there is no statistically significant increase in the maximum daily wind speeds in comparison to 1950-1969 climate, the increase in the mid-21^st century wind speeds in comparison to the 1950-1969 period is statistically significant with the 2022 event being 3.8 times more likely. We apply similar analysis to the data from CAM5 model as well as to the CMIP6 precipitation data in the region.