94 An objective technique for evaluating forecast radar reflectivity from an NWP model

Monday, 24 January 2011
Edward Colón, NOAA/NWS/NCEP and I.M. Systems Group, Camp Springs, MD; and B. Zhou, B. S. Ferrier, S. Liu, M. Pyle, and G. DiMego

3D radar reflectivities produced by NCEP with coverage over the CONUS domain will be used to provide an objective means of verifying simulated radar reflectivity forecasts produced from the NOAA Environment Modeling System / Nonhydrostatic Multiscale Model on the B grid (NEMS/NMMB). Recent programs conducted by the DTC, SPC, HPC, and other organizations have found that forecast radar reflectivities were useful in formulating short-range forecasts. They allow forecasters to determine the mode, evolution, and structure of mesoscale convective systems predicted from the models, and to compare them against high-resolution, real-time radar observations. While determining these higher-order aspects of forecast reflectivities is beyond the scope of this paper, we instead are utilizing objective verification methods as one of several factors to assess model performance and to determine whether or not changes in the model and/or post processing lead to improved forecasts of simulated equivalent radar reflectivity factor, in addition to subjective assessments currently being used by model developers. The objective verification is accomplished by the use of the NCEP Grid-to-Grid (g2g) Verification System, which expands upon the capabilities that exist in the NCEP Grid-to-Obs (g2o) Verification system. This verification approach may serve as a useful tool for assessing the impact of forecast model changes on simulated radar reflectivities with the goal of improving operational NWP forecast skill at regional scales. Depending on the progress made in this research, the g2g verification may also be used in conjunction with various satellite-based cloud analyses, the Real-Time Mesoscale Analyses (RTMA), and in the future three-dimensional products from the Analysis of Record (AOR).
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