Convective activity behaviour on tropical cyclones impacting Europe in a warmer world

Tropical transition (TT) events represent a complex interaction between baroclinic and tropical processes in cyclones, often leading to high-impact tropical cyclones in the mid-latitudes. The cyclones start as extratropical cyclones and then surface enthalpy fluxes and convective activity are able to transform the structure of the cyclone. As the climate warms, changes in atmospheric thermodynamics may alter the structure and convective behavior of these special systems.

In this work, we analyze how convective activity evolves during the TT of cyclones in a warmer climate context. Using high-resolution meteorological simulations with the HARMONIE-AROME model, operational at AEMET, from both historical and future climate conditions, we examine an archetypal TT case (Tropical Storm Delta, 2005) in the North Atlantic, which led an extraordinary impact in the Canary Islands (Spain). We perform the pseudo-global technique and analyze convective activity using the cloud tracking TOBAC. Particular attention is paid to behavior, organization, intensity, and spatial distribution of convection during the transition phase and how it then alters cyclone dynamics. We also assess how warming-related factors affect convective development. Our results aim to improve the conceptual understanding of TTs under climate change and open a line of support for adapting future forecasting strategies for these potentially hazardous system.