Choosing a universal mean wind for supercell motion prediction

Abstract

The 06-km AGL mean wind has been used widely in operations to predict supercell motion. However, when a supercell is low-topped or elevated, its motion may be poorly predicted with this default mean wind— which itself could be height-based or pressure-weighted. This information suggests that a single, fixed layer is inappropriate for some situations, and thus various mean-wind parameters are explored herein. A dataset of 583 observed and 829 Rapid Update Cycle supercell soundings was assembled. When the mean wind is computed using pressure weighting for an effective inflow-layer as the base, and 65% of the most-unstable equilibrium level height as the top, the result is that better supercell motion predictions can be obtained for low-topped and elevated supercells. Such a mean-wind modification would come at the cost of only a minor increase in mean absolute error for the entire sample of supercell cases considered.