Supercell thunderstorms in Europe – insights from km-scale climate simulations

Supercell thunderstorms are among the most damaging and hazardous weather phenomena. Due to heterogeneous observation networks, no comprehensive and homogeneous observation-based supercell climatology exists for Europe. Utilizing a km-scale 11-year current climate simulation, we derive a climatology for supercell thunderstorms in Europe, applying tracking to rotating updrafts in convection. Supercells cluster around mountain regions, with an absolute maximum in Northern Italy, and local maxima surrounding the entire Alps, the Massif Central, Pyrenees, and Dinaric Alps. With the same tracking in a +3°C global warming scenario, an 11% increase in supercell frequency is detected, accompanied by a spatial shift towards the northeast and higher altitudes. These patterns are also reflected in changes in instability, convective inhibition, and deep layer shear. Fundamentally, a drying of southwestern Europe is responsible for reductions in instability, causing a supercell frequency decrease. Using storm-centered composites, the pre-storm environment is analyzed. Overall, supercells occur in higher instability and shear, however the lower bound of the distribution remains approximately stable. Pre-storm environments are correlated with the intensity of convective hazards, such as hail size, lightning potential index, precipitation intensity, and wind gusts. These simulations provide the first pan-European supercell climatology from convection-resolving climate data, offering crucial insights into current and future hazard distributions.