Comparison of severe weather guidance derived from single and double moment configurations of a microphysical parameterization in daily forecasts with the WRF model

Every night during the 2010 Hazardous Weather Testbed (HWT) Spring Forecasting Experiment the University of Oklahoma Center for Analysis and Prediction of Storms (CAPS) ran a 26 member ensemble of high-resolution WRF-model configurations covering the entire CONUS. Two members of this ensemble used identical initial conditions and WRF-ARW configurations, except their microphysical parameterizations differed. In particular, one member used the WRF single-moment, 6 category microphysical parameterization (WSM6) while the other used the WRF double-moment, 6 category scheme (WDM6).

These forecasts were generated at least 5 days per week (M-F) from about May 1 through June 18. A wide range of meteorological scenarios developed and evolved during this period, producing tornadoes, large hail, high winds, flooding, and aviation hazards, among other disruptive impacts. Model output was examined briefly as part of daily Spring Experiment activities and some differences in performance characteristics WSM6 and WDM6 have already been noted. A more detailed comparison of archived output is expected to reveal unique information about the relative performance of the WSM6 and WDM6 schemes under a variety of conditions. This information will be used to assess the potential benefits of double-moment vs. single-moment microphysical parameterizations in generating numerical guidance for severe weather forecasters. Results from this investigation will be presented at the conference.