Is Europe Under UNSEEN Risk of Cyclones of Tropical Origin?

Abstract The impacts and potential multidecadal variability of cyclones of tropical origin (CTOs) remain poorly understood, particularly when these events make landfall or pass near Europe (named CTO‐Es) or cause measurable impacts in Europe (named CTO‐EIs). Following the UNprecedented Simulation of Extremes using Ensembles (UNSEEN) approach, we generate CTO event sets from twentieth‐century hindcasts. The UNSEEN sets produce similar CTO‐Es spatial patterns to ERA‐20C but provide 45–69 times more events, enabling robust hazard assessment. Our results indicate that CTO‐EIs pose a greater risk to the British Isles than to continental Europe. While CTO‐E activity reflects multidecadal variability, the CTO‐EI to CTO‐E ratio is insensitive to the Pacific Decadal Oscillation or Atlantic Multidecadal Oscillation, suggesting largely stochastic occurrences under favorable conditions. The return period of historical CTO‐EIs such as Hurricane Lili (1996) is estimated at 21.2–32.9 years, with doubled‐severity events at 47.8–91.5 years.