Environmental Characteristics Associated with the Tropical Transition of Mediterranean Cyclones

Using tracks from a reference dataset (Flaounas et al., 2023), cyclones in the Mediterranean Sea have been classified based on thermal winds (Hart, 2003). This classification allowed us to explore the major differences between extra-tropical cyclones with a cold inner core and tropical-like cyclones with a
deep inner warm core. For that purpose, the time evolution along the cyclones’ lifetime of different environmental characteristics taken from the ERA5 reanalysis has been studied. Warm-core cyclones are characterized by higher surface wind speeds, larger air-sea fluxes, and more intense precipitations. In comparison to cold-core cyclones, their development is favored by low wind shear and high moisture levels in the mid-troposphere. Different proxies also attest the major importance of the convective process in the establishment of the warm core. Finally, their dissipation seems to be driven by an abrupt decrease in the mid-level moisture content. This decrease is possibly related to the occlusion phase of the cyclone, and not to a limitation of moisture supply at the surface due to landfall.