The Extratropical Transition of North Atlantic Tropical Cyclones in a Changing Climate

Chunyong Jung, University of Illinois at Urbana-Champaign
a Category 5 hurricane simulated by the CESM at 13 km resolution

Description: Tropical cyclones undergoing extratropical transition (ET) can produce adverse societal impacts in areas that rarely experience direct TC impacts. This, in conjunction with projected environmental changes in climatological ET regions, motivates the investigation of possible future changes in North Atlantic ET characteristics. Here, we have conducted composite-based, quasi-idealized simulations drawing from numerous past North Atlantic ET cases, utilizing pseudo-global warming method. Future simulations show greater intensity, heavier precipitation, and stronger downstream Rossby wave train development. Specifically, the future ET is substantially stronger before ET completion, though the system undergoes less reintensification after ET completion. In addition, the future ET accompanies larger eddy kinetic energy, leading to stronger amplification of downstream energy maxima via intensified ageostrophic geopotential flux convergence and divergence. These results suggest future ET events could have great potential to cause high-impact weather in areas such as northeast U.S. and western Europe through both direct and remote processes.

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