The effective bulk shear (EBS) and most-unstable convective available potential energy (MUCAPE) are used as predictors in the statistical model. New RAP forecast and analysis data are available approximately every hour. Once new RAP data are available, the EBS and MUCAPE fields are computed for every gridpoint for the analysis grid, as well as the 1-, 2-, and 3-hour forecasts.
Next, for each grid point, the maximum EBS (or MUCAPE) is taken over the previous hour analysis (computed previously), the current analysis, and the 1-, 2-, and 3-hour forecasts (just computed). This "off-centered" approach is implemented since RAP data have about a one hour latency. Thus, the 1-hour forecast is approximately valid at the time the data are delivered. After the temporal compositing is complete, a spatial filter is applied, which has a Gaussian kernel. The temporal compositing and spatial smoothing of the RAP data is performed in an effort to mitigate placement and phasing errors inherent in NWP data.
