Robust responses of tropical and post-tropical cyclones to climate warming in WRF and CAM storyline ensembles

Tropical and post-tropical cyclones (TCs and PTCs) can produce severe hazards, making it critical to robustly assess how their characteristics may change under future climate warming. This study examines ten 2022–2024 North Atlantic storms using storyline ensemble simulations with the variable-resolution Community Atmosphere Model (CAM) at 14 km and 28 km, and the Advanced Research Weather Research and Forecasting (WRF) model at 14 km resolution over the North Atlantic. Future warming scenarios of +2 K, +3 K, and +4 K in global mean surface temperature relative to preindustrial levels are considered. Across all model configurations, climate warming leads to a robust increase in storm intensity and inner-core rainfall, along with a consistent delay in extratropical transition completion. Differences in mean and extreme inner-core 3-hourly rainfall rates among model configurations are statistically not significant, suggesting that the projected changes are robust across models with different resolutions and physical designs. When treating the experiments using different configurations as a multi-model ensemble, the mean inner-core 3-hourly rainfall rate increases by 3.8 ± 1.0% K⁻¹, and the 95th, 99th, and 99.9th percentiles of rainfall rate increase by 3.2 ± 1.1% K⁻¹, 6.1 ± 0.9% K⁻¹, and 7.8 ± 0.7% K⁻¹, respectively, relative to present-day conditions. During the post-tropical phase, the mean and extreme rainfall increase at a higher rate than when calculated across both TC and PTC phases, underscoring the importance of assessing future PTC hazards under a warming climate.