Short-range forecasting and nowcasting, using a simple, isentropic prediction model

A numerical advection model which can be run on a local computer in a real-time forecast environment is described. This isentropic forecast model provides the local forecast office with easy access to temporally and spatially detailed estimates of atmospheric temperature, moisture, and wind field changes between 12-h rawinsonde observations. Case studies are presented based on the use of the model to predict the preconvective environment in spring and summer situations. Short-term forecasts of midtropospheric static stability patterns and stability index changes are traced for several severe storm events with and without the inclusion of surface data observed during the day. Forecast images of VAS low- and midlevel moisture fields and vertical moisture gradients are compared with the observations to determine the utility of the combined model/VAS imagery as a nowcasting guide.