Progress in storm-scale ensemble forecast system design at NCAR

Forecasting convective precipitation remains a considerable challenge for the weather community, but recent progress in storm-scale ensemble forecast system design has enabled recent progress. The approach at NCAR includes developing appropriate ensemble initial conditions with the Data Assimilation Research Testbed (DART) toolkit, using a continuously cycled ensemble analysis to identify optimal physics options for a given model and observing network, as well as lateral boundary condition and stochastic model error representation to maintain reliable predictions. We have also explored probabilistic approaches for forecast verification to interpret both forecast skill and reliability, with a recent emphasis on verification of high impact weather events (e.g. storm reports). This collective knowledge will be exhibited in a yearlong daily ensemble forecast demonstration. Beginning in Spring 2015, NCAR will run a real-time, continuously cycling, 50-member ensemble analysis system (DART) to initialize a 10-member, full CONUS, convection-permitting (3-km horizontal grid spacing) 48 h ensemble forecast (WRF) from 00 UTC daily. At the conference, we will give a brief description of the ensemble design, highlight select forecast events from the Spring 2015 season, provide information on how to access real-time forecast products, and a brief overview of other areas of storm-scale ensemble design that we are actively investigating, including higher resolution ensembles (1-km horizontal grid spacing) and more frequent (hourly) cycling of the ensemble analysis.