Is Europe under UNSEEN risk of cyclones of tropical origin?

This study investigates the climatological characteristics and long-term variability of cyclones of tropical origin (CTOs) that reach Europe and those that cause measurable impacts in Europe. Using the UNprecedented Simulation of Extremes using Ensembles (UNSEEN) approach, the authors generated large CTO event sets from twentieth-century seasonal and sub-decadal hindcasts, producing 45 to 69 times more events than available in the historical record. The study assessed potential wind and rainfall impacts using storm-tracking algorithms and examined the influence of large-scale climate variability, including the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation.

This study finds that CTOs pose a greater risk to the British Isles than to continental Europe, with Ireland and the United Kingdom the most likely to experience potential wind and rainfall impacts. The authors show that the ratio of Europe-impacting CTOs relative to Europe-reaching CTOs is largely insensitive to multidecadal climate variability and that historical high-impact events such as Hurricane Lili (1996) are less rare than would be expected from observations alone. The return period of Lili-like wind impacts is estimated at 21.2 to 32.9 years, while more severe events are also plausible. The authors conclude that UNSEEN event sets can be used for robust hazard assessment of rare CTOs and highlight the importance of considering their potential impacts from a long-term planning perspective.