Future Redistribution of North Atlantic Tropical Cyclone Risk in Two Contrasting CMIP6 Scenarios

Ratnaksha Lele, Adam H. Sobel, Chia-Ying Lee, Suzana Camargo, Michael K. Tippett, Patrick Kelly, Ted Amdur, Radovan Drinka

We analyze North Atlantic Tropical Cyclone (TC) activity using the Columbia HAZard (CHAZ) model to downscale 12 models from CMIP6 under the SSP1-2.6 and SSP5-8.5 scenarios --- representing low and high radiative forcing, respectively. Despite greater warming under SSP5-8.5, basin-wide North Atlantic TC frequency is not consistently higher than under SSP1-2.6, contrasting the global-mean response. Landfalling TC frequency increases along the Southeastern U.S. and declines along the Gulf under both SSPs, a contrast that persists throughout the 21st century. Both TC genesis and steering flow changes contribute to this contrast, and appear consistent with projected El Niño-like shifts in the tropical Pacific mean state, influencing both Atlantic potential intensity and vertical wind shear variability. These results emphasize the sensitivity of regional TC activity to the spatial pattern of surface warming over its global-mean change, and the significance of the contention around projected trends in the tropical Pacific, in particular.