The 200-Member West-WRF Near Real-Time Forecast Ensemble

The Center for Western Weather and Water Extremes (CW3E) has developed a customized version of the Weather Research and Forecasting model (WRF), named West-WRF, that is run in near-real-time (NRT) forecast mode in support of decision making and scientific research of extreme weather events over the Western U.S. The West-WRF NRT framework is used to generate a 200-member ensemble that provides gridded model forecasts tailored for the representation of atmospheric rivers and Western U.S. precipitation. It is run daily from October through March with a 0000 UTC initialization out to 7 day forecast lead time. A single 9-km domain covers much of Western North America and the Northeastern Pacific, and the 60 vertical levels use a configuration customized for optimal resolution of atmospheric river processes. A combination of initial and lateral boundary conditions from the Global Ensemble Forecast System (GEFS) and European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble are used to initialize the ensemble. Additional ensemble perturbations are introduced through multi-physics (100 unique combinations) and stochastic kinetic energy backscatter (SKEB). Performance of the 200-member West-WRF NRT ensemble forecast products during the 2022-2023 season, across a range of metrics and meteorological features, will be discussed. CW3E has also developed novel deep learning-based post-processing methods for the 200-member West-WRF NRT ensemble, for which results show promising applications towards improving predictability of precipitation across the Western U.S.