Response of Extreme North Atlantic Midlatitude Cyclones to a Warmer Climate in the GFDL X-SHiELD Kilometer-Scale Global Storm-Resolving Model

Using the novel kilometer-scale global storm-resolving model Geophysical Fluid Dynamics Laboratory eXperimental System for High-resolution prediction on Earth-to-Local Domains (X-SHiELD), we investigate the impact of a 4 K increase in sea surface temperatures on Northern Hemisphere midlatitude cyclones, during the January 2020–January 2022 period. X-SHiELD simulations reveal a poleward shift in cyclone tracks under warming, consistent with CMIP projections. However, X-SHiELD's high resolution and explicit deep convection allowed for a detailed analysis of the warm and cold sectors, which are instead typically underrepresented in traditional CMIP models. Instead, compositing the 100 most intense midlatitude cyclones in the North Atlantic, we find that the warm sector exhibits statistically significant increases in wind speed and precipitation of up to 15% locally per degree of warming, while changes in the cold sector are less pronounced. This study demonstrates X-SHiELD's potential to provide a realistic-looking perspective into the evolving risks posed by midlatitude cyclones in a warming climate.