Numerical Forecasting Experiments Based on the Conservation of Potential Vorticity on Isentropic Surfaces

Abstract

In a few selected cases of explosive cyclogenesis, a ?coarse-mesh? nine-level isentropic prediction model conserving potential geostrophic vorticity is shown to yield dependable 36-hr forecasts of developing cyclones. Stagnant cyclones in adjacent areas are handled with the same degree of accuracy, indicating that numerical instability in the model is not a likely cause of the spontaneous cyclonic development. Tentative conclusions are drawn about the advantages of isentropic, as opposed to isobaric, objective analysis.