The Promise and Challenge of Explicit Convective Forecasting with the WRF Model

Convective weather remains a significant challenge for numerical weather prediction systems, and is recognized as a major contributor to poor warm season quantitative precipitation forecasting (QPF). During the recent Bow Echo and MCV Experiment (BAMEX), 36h realtime forecasts were conducted daily with WRF using a 4 km horizontal grid resolution and explicit convection over the central US (2000x2000 km). These 4 km forecasts were then compared to equivalent 10 km WRF forecasts as well as to other operational models, which all employed convective parameterization. We found that the 4km simulations did a surprisingly good job at forecasting timing, location, and number of significant convective systems, and did a much better job at predicting convective system mode and propagational characteristics, as compared to the coarser resolution simulations. These improvements in convective forecast guidance were found to be extremely useful for operations planning each day, and were also highly praised by NWS forecasters, who used the WRF output for their daily severe weather outlooks. Challenges remain, however, as the 4 km simulations did not show corresponding improvements in overall QPF. Based on last year's experience and success, we are again running explicit convective forecasts this spring and summer in collaboration with the Storm Prediction Center, CAPS, and NWS forecasters, using an updated version of the WRF code, and covering even a larger region of the US. Results from last year and preliminary results from this year's forecast experiment will be discussed.