Storm Frequency and Intensity in the Faroe Islands Between 1940 and 2024: a Method for Establishing a Storm Record Based on the ERA5 Reanalysis Data

This comprehensive study establishes a detailed storm record for the Faroe Islands from 1940 to 2024 using ERA5 and NORA3 reanalysis data, as well as in situ observations. Over these 85 years, the Faroe Islands experienced 396 storms, averaging 4.8 yearly. The data revealed that storm events occur most years, with notable periods of heightened activity. The majority of storms were classified as stormy weather (20.8–24.4 m/s), with fewer (1.4 yearly) but significant occurrences of severe storms (≥ 24.5 m/s), with a higher number of severe storms in specific areas. Predominant wind directions from the southwest and west highlight the influence of Atlantic weather systems, with storms mainly occurring in the winter months. Comparing wind observations from Tórshavn with ERA5 data calibrated with the high-resolution NORA3 reanalysis highlighted the accuracy and limitations of ERA5 in capturing storm events. While the calibrated ERA5 data provided reliable estimates of average wind speeds, it tended to smooth out fluctuations, underrepresenting the variability and intensity of extreme wind conditions. Applying a gust factor, derived from detailed observations, adjusted ERA5 wind speeds to reflect true conditions better. The study also demonstrated the utility of geostrophic wind speed records derived from pressure measurements to construct a long-term storm activity index. A trend analysis reveals almost no discernible long-term trend in frequency and intensity, indicating minimal change over time. Overall, this study emphasises the need for continued monitoring and refinement in storm identification and classification methods to improve the accuracy of storm event representations, crucial for the mitigation of severe storm impacts in the region.