Diagnotic calculations of motions of vertical velocity and low-level vertical vorticity maxima in radar data and numerically simulated supercell thunderstorms

An attempt was made to forecast the motion of vertical velocity and low-level vertical vorticity maxima in supercells using nonlinear propagation equations developed by the second author. In the first set of experiments, the equations were applied to objectively analyzed Doppler radar velocity data collected in both tornadic and non-tornadic supercells. In the second set of experiments, the same equations were applied to a numerically simulated tornadic supercell. In both cases, the forecast errors of the diagnosed motions were not significantly different from those obtained by simply using as a predictor ambient velocity at the location of the maximum. It is believed that the reasons for this observation are that (i) supercell thunderstorms are non-form-preserving, (ii) the vertical velocity and vorticity maxima are not approximately elliptical as required by the equations, even within one or two grid spaces of the maximum, and (iii) in the first set of experiments, the objectively analyzed radar data contained noise.