Hurricane Ophelia: A case study of dynamically downscaled model analysis under alternate climate scenarios

Abstract

Tropical cyclones are both deadly and costly disasters, though their impact on Europe is infrequently studied due to relatively few occurrences. However, recent studies suggest the number and impact of tropical-origin storms affecting Europe is likely to increase with future warming.

We present a case study of one recent Europe-impacting storm, 2017's Hurricane Ophelia, examining its representation in analysis datasets (ERA5, GFS, and the ECMWF Operational) as well as in simulations of these datasets downscaled with the regional model RACMO. The ECMWF-based models do not accurately simulate Ophelia, especially in the tropical phase where Ophelia's central pressure is overestimated by more than 30 hPa.

Applying a uniform temperature forcing ranging between -2 to +4 $^\circ{}$C to the GFS-driven RACMO simulations allows us to model alternative climates. In warmer climates the storm grows larger and stronger than in the present-day scenario, moving faster and further from land. Despite this, the wind speeds experienced on the Irish Coast are higher than when it impacts the coast directly in the present-day scenarios. Additionally, its extratropical transition proceeds differently: in the warmest scenarios Ophelia does not complete extratropical transition, but continues to resemble a warm-core tropical cyclone.