Demonstration of a HRRR-National Water Model Hydrometeorological Ensemble Prototype for Flash Flood Forecasting

The state of the art of real-time National Weather Service (NWS) hydrological forecast operations requires the integration of precipitation and land surface monitoring, forecasting of precipitation and surface runoff, and delivery of flood and water supply forecasts to emergency response and water system managers. A USWRP-Hydrometeorology Testbed (HMT) project has been supported to extend on-going research and development efforts within the NOAA Earth Systems Research Lab, NCAR, and the new NWS National Water Center to explore probabilistic flash flood guidance through a combination of atmospheric and hydrologic perturbations. Initial work is exploring the use of developmental probabilistic QPF information from high-resolution, convection-allowing forecasts generated by the operational and research versions of the High Resolution Rapid Refresh (HRRR) model, and incorporating these QPFs into a physics-based, distributed hydrologic modeling ensemble framework (WRF-Hydro/National Water Model).

Modeling efforts to date have utilized a retrospective, case study-based approach. Results will be presented which use time-lagged precipitation ensembles from the HRRR model in the generation of probabilistic hydrometeorological forecasts for the 1 – 6 October 2015 South Carolina flood event. Experimental hydrometeorological ensemble outputs are explored toward effective communication of both probabilistic QPF information and probabilistic hydrologic response information. Operational forecaster feedback is also guiding the development of both the hydrometeorological ensemble design, as well as the optimal outputs to best address critical forecaster needs and challenges.