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University of Washington west-wide experimental hydrologic forecast system Andy Wood, Ted Bohn, George Thomas, Ali Akanda, Dennis P. Lettenmaier Components of Overall Real-time Forecasting Approach OBJECTIVE The forecasting system was created to evaluate the use of distributed macroscale hydrologic models for hydrologic forecasting, and provide a testbed for assessing the use of climate predictions and data assimilation in a streamflow forecasting context. Hydrologic Forecasting Simulations start of month 0 1-2 years back OVERVIEW Forecasts are made once monthly, using simulated initial conditions based on real-time observations of temperature and precipitation. Experimental hydrologic forecasts are also made using the climate forecast ensembles derived from the NCEP Climate Prediction Center Seasonal Climate Outlooks. Benchmark hydrologic forecasts are also constructed via the wellknown Extended Streamflow Prediction (ESP) method of the U.S. National Weather Service. The ESP forecasts are also categorized to provide ENSO and PDO-conditioned ensembles, which past work has shown can improve seasonal forecast accuracy. end of mon 6-12 forecast ensemble(s) model spin-up climatology ensemble Climate Forecasts Hydrologic Model (Liang et al., 1994) ESP and ESP/ENSO forecasts • VIC model resolution (1/8 degree) • use ensemble of historical 12 month daily sequences taken from 1960-99 • use subsets based on ENSO category corresponding SWE adjustment NCEP CPC Official Outlooks data sources NCDC met. station obs. up to 2-4 months from current LDAS/other real-time met. forcings for remaining spin-up climate forecast information snow state information Forecast Products streamflow soil moisture runoff snowpack derived products Current conditions nowcasts for soil moisture / SWE http://www.hydro.washington.edu/forecast/westwide/ Snow Assimilation NRCS SNOTEL / Env. Canada ASP observed SWE anomalies are merged with simulated anomalies to adjust the forecasts’ initial hydrologic state, e.g.: example obs SWE anomalies • derived from Probability of Exceedence seasonal precipitation and temperature forecasts for US climate divisions • ensembles of precipitation and temperature generated by non-parameteric resampling approach called the Schaake Shuffle Forecasts from Climate Model Output • from NCEP CFS (in re-development) Major Products of Westwide Forecasting System Forecast Web Page Univ. of Washington Current Activities Multiple Land Surface Model Ensembles We are evaluating the benefits of using three separate models to generate forecasts that can be combined via Bayesian model averaging techniques. Models: • VIC • SAC – Sacramento / SNOW17 model (NWS) • NOAH – NCEP, OSU, Army, NWS Hydrology Lab Test Case: Salmon R., ID Retrospective Comparisons Individual Models Monthly Avg Flow Collaboration with Operational and Research Groups U. Arizona / USBR forecast study, Lower Colorado basin Miscellaneous: Seattle City Light, energy traders, hydropower utilities, NOAA regional climate offices Princeton University Hydrologic Forecast System 3TIER Environmental Forecast Group NRCS National Water and Climate Center Forecast Group Monthly RMSE UW Climate Impacts Group (CIG) Annual Water Outlook meetings Spatial Forecasts for P, T, SWE, Soil Moisture, Runoff Prior evolution of water balance for drainage area of each forecast location UW Puget Sound region flow forecasts Bayesian Model Average Monthly Avg Flow NWS Hydrologic Ensemble Prediction Experiment (HEPEX) UW Hydrologic Forecast and Nowcast Systems Monthly RMSE new US Drought Monitor NOAA Climate Prediction Center’s US Drought Outlook Daily Updating Land Surface Nowcast Columbia River Intertribal Fish Commission NOAA National Centers for Environmental Prediction (NCEP) testbed activities Klamath R. Basin Bureau of Reclamation WA State Dept of Ecology & Yakima R. Basin Bureau of Reclamation UCI / California Dept of Water Resources • Now operational for current domain + Missouri R. basin • Next basins: Mexico, Arkansas-Red, Gulf Other Changes / Ongoing Work Westwide overview map of current water supply period volume forecast This map clicks through to forecast hydrographs at right, and water balance plots above re-evaluating the NASA/NOAA NLDAS 1/8 degree forcing product as a potential real-time forcing in Western U.S. automating nowcast / initial condition simulation over the US westward of the Mississippi River adopting selected experimental reservoir system forecasts as routine products comparing nowcasts with retrospective simulations now in progress extending back to 1915 Expanding the set of streamflow forecast points to the Great Basin, Missouri, and upper Rio Grande Rivers References / Acknowledgements Wood, A.W., E.P. Maurer, A. Kumar and D.P. Lettenmaier, 2002. Long Range Experimental Hydrologic Forecasting for the Eastern U.S., JGR, 107(D20). Liang, X., D. P. Lettenmaier, E. F. Wood and S. J. Burges, 1994. A Simple hydrologically Based Model of Land Surface Water and Energy Fluxes for GSMs, JGR., 99(D7). Wood, A.W. and D.P. Lettenmaier, 2006, A testbed for new seasonal hydrologic forecasting approaches in the western U.S., BAMS (accepted). The authors gratefully acknowledge the support of NOAA/OGP (now the Climate Program Office) CDEP and CPPA programs.