Evaluation of QPF from NCAR's 5.5 and 8.5 Day Convection-Allowing Ensembles Against WPC and Operational Guidance

The Weather Prediction Center (WPC), located in College Park, MD, serves as the nation’s premier center for forecasting rain storms, winter storms, extreme temperatures, and relaying the big-picture weather story. Specifically, two of WPC’s primary functions are issuing quantitative precipitation forecasts (QPF) and medium range forecasting. The WPC produces QPF forecasts out to 168 hours. In shorter range forecasts out to 36-60 hours, forecasters have multiple, operational convection allowing models (High-Resolution Rapid Refresh (HRRR) model, nested North American Mesoscale Forecast System (NAM Nest), etc.) and a convection allowing ensemble (High Resolution Ensemble Forecast (HREF)). Extending into the medium range, there are far fewer operational guidance options and no high resolution convection allowing ensembles. Currently, forecasters primarily rely on medium range forecasts from the Global Forecast System (GFS) and associated Global Ensemble Forecast System (GEFS), the European Centre for Medium-Range Weather Forecasts (ECMWF) and associated ECMWF Ensemble Prediction System (ECENS), the North American Ensemble Forecast System (NAEFS), and others.

During NOAA’s Hazardous Weather Testbed (HWT) Spring Forecast Experiment, the National Center for Atmospheric Research (NCAR) ran two different convection allowing ensembles that extended into the medium range. The first ensemble used the Model for Prediction Across Scales (MPAS) model and consisted of five members running out to 132 hours (5.5 days) over a variable-resolution global model configuration with ~3-km horizontal cell spacing over the CONUS. The second ensemble was run in collaboration with Geophysical Fluid Dynamics Laboratory (GFDL) and used ten FV3-based members running out to 204 hours (8.5 days) in a global model configuration with a 3-km nest over the CONUS. This presentation will evaluate the QPF from the members of each ensemble as well as mean QPF output from the ensembles. The QPF will be evaluated against WPC QPF as well as other operational models and ensembles that WPC normally evaluates monthly with a special focus on the medium range time period beyond 72 hours. These results will help judge the utility of running convection allowing ensembles beyond the current short-range time period.