A pan-European analysis of large-scale drivers of severe convective outbreaks

Abstract

Severe convective outbreaks have been an important driver of weather-related damages in Europe in recent years. Regional convection affecting thousands of square kilometres is driven by large-scale conditions that establish convectively favourable conditions. Systematically analysing the large-scale drivers of severe convective outbreaks helps link synoptic-scale predictability to convective-scale hazards, addressing persistent challenges in forecasting and impact assessment. We analyse the continental-scale atmospheric and land-surface conditions in the days leading up to widespread severe convective outbreaks in Europe with reanalysis data. We split Europe into regions that often experience severe convective outbreaks on the same day. Each region shows distinct dynamical and thermodynamic patterns leading up to an outbreak. Colder regions north of the Alps are associated with synoptic-scale upper-level wave patterns, accompanied by strong temperature anomalies, as they can be considered to be temperature limited. Severe convection in drier regions of eastern Europe is associated with greater moisture anomalies. Severe convection in regions bordering the Mediterranean is associated with weak upper-level flow anomalies. These regions have a climate that is favourable for convection, and convection is more frequent. The required additional contribution from the upper level is thus weaker.