Proximity soundings for severe convection for Europe and the United States from reanalysis data

Abstract

Proximity soundings from reanalysis data have been created for significant severe thunderstorms in the United States and Europe, along with corresponding soundings not associated with severe thunderstorms. The probability of a combination of convective available potential energy (CAPE) and deep tropospheric wind shear being associated with significant severe thunderstorms has been calculated for both areas. Probabilities of significant severe storms are higher for high CAPE and shear in Europe, but those large scale environmental conditions are experienced much more frequently in the US, so that the overall number of events is much higher in the US. Probabilities of significant storms are approximately constant for constant values of CAPE⁎Shear for each of the datasets. High values of 0–1 km wind shear and low lifted condensation levels are associated with higher probabilities that significant severe thunderstorms will be associated with significant tornadoes. A subset of the US data, taken from the southeastern US in the cool season, produces probabilities that are much closer to the European values than the overall US data. The environments also are closer to European values with relatively low CAPE and low lifted condensation levels. From the southeastern US data, it is shown that the probability of severe convection occurring with moderate values of CAPE⁎Shear is much higher in the cool season than in the warm season. It is suggested that the higher probabilities result from stronger synoptic forcing and stronger and more frequent boundaries to initiate convection.