Forecast Products Based on the 200-Member West-WRF Ensemble: A CW3E and NWS Western Region Collaborative Effort

The Center for Western Weather and Water Extremes (CW3E) and the National Weather Service Western Region (NWS WR) have collaborated on the development of NWS-tailored forecast products since Fall 2021. These products leverage the CW3E 200-member West-WRF ensemble, which produces 3-hourly output (15-min for key 2D variables) at 9-km horizontal grid spacing and 168-h lead time over the Northeastern Pacific and Western U.S. from October through March. The primary outcome is a probabilistic suite of forecast products for surface fields across the Western U.S. These products include forecast percentiles (e.g., 10th, 50th, 90th), probabilities of exceedance, and meteograms with stacked probability charts. NWS forecasters across WR have been briefed on these products and use them to augment their forecasts and messaging. This presentation will highlight examples from the Dec 2022 – Jan 2023 storm sequence that brought widespread damage, and loss of life, across California. Additional collaborative efforts focused around debris flow hazards and ensemble-member clustering will also be described, as well as future work focused on increasing the customization and interactivity of these tools. The West-WRF ensemble configuration will be briefly described.