Using short-range ensemble forecasts for predicting severe weather events

An ensemble of mesoscale model simulations of the most severe tornadic outb reak of the modern period, 24-15 June 1967, is examined. Results indicate t hat the fields of convective available potential energy (CAPE), storm-relat ive environmental helicity (SREH), and bulk Richardson number shear (BRNSHR ), are able to provide useful guidance on the region of tornadic supercell thunderstorms for this outbreak. CARE is used to define the region in which convection is possible, SREH is used to define the region in which thunder storms are likely to be supercells, and BRNSHR is used to define the region in which low-level mesocyclogenesis is more likely. These results highligh t the potential value of analyzing various severe weather parameters in for ecasting tornadic thunderstorms, and the value of mesoscale ensemble foreca sts for predicting severe, life threatening weather events ill Europe. The ensemble also clearly shows the sensitivity and uncertainty of the mode l simulations to the physical process schemes used. Variations in all three severe weather parameters are significant near regions of convection, whic h unfortunately are where forecasters need these parameter values to he mos t reliable. These sensitivities highlight the value of an ensemble system f or short-range weather forecasting, since it is clear that if a single mode l forecast of convective activity goes awry, then it provides little guidan ce to forecasters concerned with threats to life and property from severe w eather. Published by Elsevier Science B.V.