Reconstruction of violent tornado environments in Europe: High-resolution dynamical downscaling of ERA5

Abstract

<p>Around 2–3 violent tornadoes hit Europe per decade. Although they are less frequent compared to the Great Plains of the United States, Europe has a population density higher by the order of the magnitude, thus extreme convective events typically produce large societal impacts and considerable damage to infrastructure. As operational prediction of such events is of high priority to emergency managers and forecasters, in this study we reconstruct environmental conditions for selected 12 violent tornadoes from the period between 1950 and 2021. Because numerical modeling of severe weather events requires convection-permitting resolutions, we used the Weather Research and Forecasting model for dynamical downscaling of ERA5 reanalysis. Results show that out of 12 high-resolution simulations (3 km), in 10 cases the modelled updraft helicity (UH) tracks cross the neighborhood of tornado reports, however, in 2 cases the timing of convection was more than 3 hours away from the time of the reports. Analysis of vertical profiles show that all simulations represented favorable tornado environments with cyclonically curved hodographs, comparable to significant tornadoes on the Great Plains of the United States. The combination of UH tracks with convective environments offers promising results for operational forecasting in Europe, and should be explored in future studies.</p>