The Real-time National Severe Storms Laboratory 4-km WRF Model Ensemble
Beginning in 2007, with support from the NOAA Collaborative Science, Technology, and Applied Research (CSTAR) Program, CAPS began providing experimental convection-allowing ensembles for testing during annual NOAA/HWT Spring Forecasting Experiments. Once again, results from these tests were very positive as the ensembles provided much needed additional information on forecast uncertainty, and several new ensemble visualization strategies and forecast diagnostics were developed. Because of the large computational expense required to integrate a convection-allowing ensemble, the year-round NSSL-WRF system has remained deterministic, with the ensemble experiments led by CAPS limited to the 5-week long Spring Forecasting Experiments during May and June. However, very recently (early 2014), NSSL was granted an increase in computing allocation on the Jet HPC cluster, which is being used to run a year-round, real-time, nine-member convection-allowing ensemble. This ensemble, which is known as the NSSL-WRF ensemble uses the NSSL-WRF as a control member (ICs/LBC from the NAM), with the other eight members using NCEP's SREF system for ICs and LBCs. The ensemble system will serve as permanent ensemble framework to provide guidance to SPC forecasters and serve as a testing ground for developing an optimal ensemble configuration and useful storm-scale ensemble diagnostics. The ensemble began running in March 2014 and was tested and evaluated in the 2014 NOAA/HWT Spring Forecasting Experiment. Also, a new public website has been developed for displaying the real-time forecasts. This talk will provide further details on the ensemble configuration, and present initial subjective and objective results obtained during the 2014 NOAA/HWT Spring Forecasting Experiment.