Abstract
Abstract. Around 26 000 severe convective storm tracks between 2005 and 2014 have been estimated from 2D radar reflectivity for parts of Europe, including Germany, France, Belgium, and Luxembourg. This event set was further combined with eyewitness reports, environmental conditions, and synoptic-scale fronts based on the ERA-Interim (ECMWF Reanalysis) reanalysis. Our analyses reveal that on average about a quarter of all severe thunderstorms in the investigation area were associated with a front. Over complex terrains, such as in southern Germany, the proportion of frontal convective storms is around 10 %–15 %, while over flat terrain half of the events require a front to trigger convection. Frontal storm tracks associated with hail on average produce larger hailstones and have a longer track. These events usually develop in a high-shear environment. Using composites of environmental conditions centered around the hailstorm tracks, we found that dynamical proxies such as deep-layer shear or storm-relative helicity become important when separating hail diameters and, in particular, their lengths; 0–3 km helicity as a dynamical proxy performs better compared to wind shear for the separation. In contrast, thermodynamical proxies such as the lifted index or lapse rate show only small differences between the different intensity classes.
Highlights
Severe convective storms (SCSs) are responsible for almost one-third of the total damage by natural hazards in Germany and central Europe (MunichRe, 2020)
Using composites of environmental conditions centered around the hailstorm tracks, we found that dynamical proxies such as deeplayer shear or storm-relative helicity become important when separating hail diameters and, in particular, their lengths; 0– 3 km helicity as a dynamical proxy performs better compared to wind shear for the separation
By combining hailstorm tracks determined from radar data over Switzerland between 2002 and 2013 with front detections (Schemm et al, 2015) based on the Consortium for Small-Scale Modeling (COSMO) analysis, Schemm et al (2016) found that up to 45 % of storms in northeastern and southern Switzerland were associated with a cold front
Summary
Severe convective storms (SCSs) are responsible for almost one-third of the total damage by natural hazards in Germany and central Europe (MunichRe, 2020). By combining hailstorm tracks determined from radar data over Switzerland between 2002 and 2013 with front detections (Schemm et al, 2015) based on the Consortium for Small-Scale Modeling (COSMO) analysis, Schemm et al (2016) found that up to 45 % of storms in northeastern and southern Switzerland were associated with a cold front They concluded that mainly wind-sheared environments created by the fronts provide favorable conditions for hailstorms in the absence of topographic forcing. Reporting is selective and biased towards population density and available spotters, these reports provide valuable information about the intensity of the various convective phenomena associated with SCSs such as maximum hail diameter The combination of these reports with storm tracks estimated from radar observations allows us to reconstruct entire footprints of SCSs and/or hailstorms.
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