1. Andy Wood, Ted Bohn, George Thomas, Ali Akanda, Dennis P. Lettenmaier University of Washington west-wide experimental hydrologic forecast system 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. 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 well- known 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. Major Products of Westwide Forecasting System 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. Hydrologic Model (Liang et al., 1994) Hydrologic Forecasting Simulations Forecast Products streamflow soil moisture runoff snowpack derived products model spin-up forecast ensemble(s) climate forecast information climatology ensemble 1-2 years back start of month 0end of mon 6-12 NCDC met. station obs. up to 2-4 months from current LDAS/other real-time met. forcings for remaining spin-up data sources snow state information NRCS SNOTEL / Env. Canada ASP observed SWE anomalies are merged with simulated anomalies to adjust the forecasts’ initial hydrologic state, e.g.: Forecasts from Climate Model Output Current Activities  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 Other Changes / Ongoing Work Univ. of Washington Climate Forecasts 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 NCEP CPC Official Outlooks Snow Assimilation Components of Overall Real-time Forecasting Approach example obs SWE anomalies corresponding SWE adjustment Forecast Web Page http://www.hydro.washington.edu/forecast/westwide/ Prior evolution of water balance for drainage area of each forecast location Spatial Forecasts for P, T, SWE, Soil Moisture, Runoff Current conditions nowcasts for soil moisture / SWE 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 from NCEP CFS (in re-development) Westwide overview map of current water supply period volume forecast This map clicks through to forecast hydrographs at right, and water balance plots above Collaboration with Operational and Research Groups Daily Updating Land Surface Nowcast Now operational for current domain + Missouri R. basin Next basins: Mexico, Arkansas-Red, Gulf 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 Bayesian Model Average Multiple Land Surface Model Ensembles Monthly Avg Flow Monthly RMSE Monthly Avg Flow Monthly RMSE U. Arizona / USBR forecast study, Lower Colorado basin NWS Hydrologic Ensemble Prediction Experiment (HEPEX) 3TIER Environmental Forecast Group NRCS National Water and Climate Center Forecast Group NOAA Climate Prediction Center’s US Drought Outlook Miscellaneous: Seattle City Light, energy traders, hydropower utilities, NOAA regional climate offices UW Puget Sound region flow forecasts UW Climate Impacts Group (CIG) Annual Water Outlook meetings NOAA National Centers for Environmental Prediction (NCEP) testbed activities Columbia River Inter- tribal Fish Commission Klamath R. Basin Bureau of Reclamation UCI / California Dept of Water Resources WA State Dept of Ecology & Yakima R. Basin Bureau of Reclamation new US Drought Monitor Princeton University Hydrologic Forecast System UW Hydrologic Forecast and Nowcast Systems