NWS ~ NorthWest River Forecast Center Seasonal Volume Forecasts Using Ensemble Streamflow Prediction for the 2006 Water Year Kevin Berghoff, Hydrologist Northwest River Forecast Center October 13, 2005

NWS ~ NorthWest River Forecast Center Topics for Presentation  Northwest River Forecast Center:  Overview  NWRFC Forecasting Models and Products  NWS River Forecast System (NWSRFS)  Statistical Water Supply Forecasts  Use of the Ensemble Streamflow Prediction (ESP) model to Produce Longterm Forecasts  2006 Volumetric Outlook  Incorporation of Climate Forecasts into ESP (experimental)

NWS ~ NorthWest River Forecast Center Northwest River Forecast Center Total Area: 315,795 Grand Coulee Dam The Willamette at Salem The Dalles Dam Lower Granite Dam Columbia and Snake River Basins Coastal Drainages of Oregon and Washington 6 States & CANADA Support for 9 NWS Field Offices (WFOs)

NWS ~ NorthWest River Forecast Center NWRFC Forecasting Models  NWS River Forecast System  Short, Medium, and Longterm capabilities  Generate output in deterministic AND probabilistic (ESP) formats  2 Outputs for ESP  Match Regression based Water Supply (147 points)  Natural ESP (all 302 fx points)  Statistical Water Supply  Seasonal Forecasts  Regression techniques

NWS ~ NorthWest River Forecast Center Hydrologic Forecasting: Time Domains Time Flow

NWS ~ NorthWest River Forecast Center NWSRFS: Ensemble Streamflow Prediction (ESP) Precipitation Temperature Model Operations Model States Model Parameters Observed Inputs Ensemble Forecast Inputs (10 day QPF + historical record) Ensemble Forecast Outputs (traces) Probabilistic Products

NWS ~ NorthWest River Forecast Center 1987 ESP Output Trace Ensemble Plot Day QPF

NWS ~ NorthWest River Forecast Center

NWS ~ NorthWest River Forecast Center Sensitivity of Initial Conditions: September Soil Moisture NWSRFS has a memory for soil moisture that extends many weeks into the future This memory can be exploited for the purpose of producing spring outlooks

NWS ~ NorthWest River Forecast Center Historically used to generate Volume Forecasts  Products:  Final  Final (Coordinated with NRCS)  Early Bird  Mid-Month  Contingency (future precip 50%, 75%, 125% of normal)  Forecasts:  147 Forecast Points - 45 above Grand Coulee Dam - 63 in the Snake Basin - 63 in the Snake Basin - 39 in the Lower Columbia - 39 in the Lower Columbia Regression Based Water Supply Forecasts

NWS ~ NorthWest River Forecast Center Regression Water Supply and Observed Runoff Jan-Jul Volume 2005 Forecast Jan-Jul Volume 30 yr Normal 2005 Jan-Jul Cumulative Observed Volume MAF – 76%

NWS ~ NorthWest River Forecast Center Regression Water Supply/ESP Volume Forecast 2005 Regression Water Supply Forecast % Exceedance ESP Water Supply Forecast % Exceedance ESP Water Supply Forecast

NWS ~ NorthWest River Forecast Center 2006 Spring Outlook  Ensemble Streamflow Prediction (ESP)  Official Statistical Water Supply Points  Natural ESP Volume Forecast for all Points  Eastside and Westside  Updated weekly  Driven by Antecedent Snow/Soil Moisture, 10 day Precip and Temperature Forecast  Soon to incorporate climate forecasts

NWS ~ NorthWest River Forecast Center Climate Discussions  CPC ENSO Discussion – Oct 6, 2005  …ENSO neutral conditions expected during the next 3-6 months…  UW Climate Impacts Group – Aug 19, 2005  …increased odds of above avg air temps for the next 3 to 6 months…no indication of a shift in odds for above or below normal precip…  International Research Institute for Climate Prediction – Sept 14, 2005  … 90-95% likely that neutral conditions will prevail through the end of 2005

NWS ~ NorthWest River Forecast Center The Dalles vs SOI

NWS ~ NorthWest River Forecast Center 2006 Spring Outlook 50% Exceedance Volume - MAF 63.8 MAF – 101% 26.7 MAF – 89% 98.5 MAF – 92 %

NWS ~ NorthWest River Forecast Center 2005 Forecast Comparison 75% 30% 109% 101% 150% 141% 65% 80%

NWS ~ NorthWest River Forecast Center Effects of Current Model States and QPF Input

NWS ~ NorthWest River Forecast Center Using Climate Forecasts with ESP Temperature and Precip Seasonal Outlooks

NWS ~ NorthWest River Forecast Center Taking Advantage of Climate Forecasts: ESP Pre-Adjustment Technique Climate Forecast Probabilities used to skew the distribution of ESP inputs (historical temp/precip record)

NWS ~ NorthWest River Forecast Center  Yearly Weights applied to ESP traces  Weights are based on the similarity of a historical year to the current year  Can be used to exclude historical years Taking Advantage of Climate Forecasts: ESP Post-Adjustment Technique

NWS ~ NorthWest River Forecast Center Water Forecasts: Days Days Water Supply Peak Flow AHPS Watch & Warnings Flood Outlook Discussion Past Floods River Photos Dambreak Hydrologic Cycle Weather Snow Observations Forecasts Exp Forecasts Temp & Precip Forecasts

Water Forecasts: Days Days Water Supply Peak Flow AHPS Watch & Warnings Flood Outlook Discussion Past Floods River Photos Dambreak Hydrologic Cycle Weather Snow Observations Forecasts Exp Forecasts Temp & Precip Forecasts

Climate Climate Forecasts Drought Assessment Hazard Assessment Indexes Monthly Means Return Periods NWRFC Office Information Internal Web SDM Schedule Staff Employment Projects Papers Presentations Contact Us Links River Centers Weather Offices NWS Offices

NWS ~ NorthWest River Forecast Center NWRFC: Website 5241 NE 122nd Avenue Portland, OR (co-located with Portland Weather Forecast Office)