A Diagnostic Case Study of the Synoptic Scale Vertical Motion and its Contribution to Mid-Tropospheric Development

Abstract

The quasi-geostrophic omega equation is employed to perform a diagnostic case study of the baroclinic structure of a developing system. The model employs height data at ten pressure levels to obtain the vertical motion along with the divergence and twisting terms at four pressure levels all evaluated in a fairly objective manner. Results are presented for one synoptic time prior to the development of a cut-off low of the Nevada type. These clearly show the scale and magnitude of the baroclinic features and the relative importance of the twisting and divergence terms for producing vorticity changes on a moving parcel. These results suggest a possible sequence of events leading to the cut-off low and the type of detail that filtered prediction models should employ to allow us to evaluate completely the ability of filtered models to handle mid-tropospheric development.