Evaluation and Application of Conditional Symmetric Instability, Equivalent Potential Vorticity, and Frontogenetic Forcing in an Operational Forecast Environment

Abstract

Abstract The related fields of equivalent potential temperature (θe), geostrophic momentum (Mg), equivalent potential vorticity (EPV), and frontogenetic forcing were computed, analyzed, and evaluated for two mid-Atlantic states snowstorms in which conditional symmetric instability (CSI) is believed to have been present. Observed data as well as model gridded data were used with the National Weather Service PC-based Gridded Information Display and Diagnostic System in evaluating the event, thereby providing both initial and model forecast fields. A brief physical and historical review of CSI is provided as a basis for better understanding and increased proper application of this technique into operational forecasting. The implications of CSI for the operational forecaster are then demonstrated through a diagnosis of events occurring in Maryland and Virginia on 26 February 1993 and 30 January 1995, in which precipitation banding related to frontogenetic forcing and CSI are believed to have occurred. The int...