5.6 National Water Model Forecast Evaluation of Extreme Hydrometeorological Events over the Western United States

Tuesday, 9 January 2018: 11:45 AM
Room 18B (ACC) (Austin, Texas)
Francesca Viterbo, NOAA, Boulder, CO; and A. R. Thorstensen, R. Cifelli, M. Hughes, L. E. Johnson, D. J. Gochis, A. W. Wood, K. Nowak, and K. Dahm

The NOAA National Water Model (NWM) became operational in August 2016, providing the first ever, real-time distributed high-resolution forecasts for the continental United States. A collaborative project between the Bureau of Reclamation, NOAA, and NCAR is targeted to assess the NWM performance for reservoir inflow forecasting needs and water management operations. In this study, short and medium real-time forecasts and retrospective historical runs forced by North American Land Data Assimilation System (NLDAS) are evaluated in order to assess the NWM skills over key headwaters regions in the western U.S. The operational model version V1.1 is compared with the upcoming version of the model (V1.2) with a particular focus on the capability of the different model versions to predict extreme events. The relative importance of parameter calibration and the quality of the meteorological forcing as input to the model runs is also considered in the overall evaluation of the forecast performance. Finally, the advantages of using a fully distributed forecast model system are explored, comparing the NWM predictions with the available River Forecast Center local forecasts.

The results highlight the overall NWM’s ability to provide high-resolution forecast information in Western United States. In terms of stream flow, the performance is best in regions that are dominated by natural flows and where the model has benefited from efforts toward parameter calibration. In highly regulated basins, the water management operations result in NWM overestimation of the peak flows and simulates the recession portion of the hydrograph that is generally steeper than observed. As a future project goal, some reforecasts will be run on target locations, ingesting water management information into the NWM and comparing the new results with the actual operational forecast.

- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner