What do large hail, tornado, and severe thunderstorm wind environments have in common across continents?

Abstract

Abstract

Abstract Studies evaluating convective storm environments have historically focused on single continents. Here, we considered severe weather reports (hail, tornadoes, severe convective winds), lightning detection data and ERA5 reanalysis across four parts of the world: Europe, Australia, South America, and the United States. We analyzed convective parameters and vertical profiles of atmospheric quantities for severe and non-severe thunderstorms to better understand which environmental features share similarities among continents. Thermodynamic parameters are the most useful proxies of hail and warm-season severe winds, whereas kinematic parameters are the most robust predictors of storm severity, especially tornadoes, whose environments feature a large contribution of low-level streamwise vorticity. For hail, the strongest, and the most skillful depth of bulk wind shear is located around 1–4 km above ground level, unlike tornadoes and cold-season severe winds, which have the largest shear near ground. Larger hail and stronger tornadoes can be expected with increasing low-level storm-relative winds, and their perpendicular component in mid-troposphere. Extending a hodograph to its origin while calculating storm-relative helicity and streamwise vorticity improves tornado prediction, especially considering the lowest few hundreds of meters above ground level. Lifted parcel buoyancy in the hail growth layer (-10°C to -40°C), especially its peak value, is important for assessing the likelihood of hail. We also note that some parameters are geographically dependent (e.g. lapse rates, mixing ratio), and that parameters which are good predictors for the occurrence of convective hazards may not be the best parameters to infer their intensity, and vice-versa.