Alternative approaches to current nowcasting schemes

This work examines alternate usage strategies for both the Warning Decision Support System – Integrated Information (WDSS-II) K-means pseudo-radar nowcast product developed by the National Severe Storms Lab (NSSL) and the Spectral Prognosis (S-Prog) nowcaster developed by the Bureau of Meteorology Research Centre (BMRC). First, the WDSS-II K-means nowcaster has been run in an ensemble-type format by selecting different options in the command to run the segmotion product, including the reflectivity threshold on which the storm motion is calculated. Once motion is calculated based on different combinations of thresholds an ensemble mean can be calculated and a comparison based on skill scores can be accomplished. Secondly, S-Prog was run without altering the code; however, the resulting nowcasts were altered by canceling out the smoothing factor inherent to the system. This has the effect of yielding more of a worse case scenario for flash flood applications. In each case one is provided with a simple ensemble that illustrates the range of possible nowcast outcomes. Examples of both products will be presented taken from a variety of test cases including both convective and stratiform events.