1. Recap of Water Year 2007 Hydrologic Forecast and Forecasts for Water Year 2008 Alan F. Hamlet Andrew W. Wood Dennis P. Lettenmaier JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering University of Washington

2. Recap of WY 2007

3. http://www.ecmwf.int/products/forecasts/d/charts/seasonal/forecast/plumes/ Obs.

5. Modified Flow (cfs) Ensemble Streamflow Forecast for the Columbia River at The Dalles for WY 2007. (Nino3.4 anomalies between 0.7 and 1.5) Black = Climatological Extremes Gray = Forecast Ensemble Members Red = LTM from 1950-1999 Blue = Ensemble Mean

6. Validation of 2007 Forecast Modified Flow (cfs)

7. ColSim Reservoir System Storage Forecast All Years from 1960-1999 for which J. Nino3.4 Anom. >= 0.7 AND <= 1.5 2007 Obs Storage Sept 30, 2007 45.86 MAF

8. WY 2008 Forecast

9. http://www.ecmwf.int/products/forecasts/d/charts/seasonal/forecast/seasonal_range_fo recast/nino_plumes_public_s3!3.4!200709!/

10. 1916-2002 April-September Naturalized Flow for the Columbia River at The Dalles, OR from Historic Water Years vs January Nino 3.4 Anomalies.

11. Based on Dalles Climatology 1901-2003 Natural Streamflow (cfs)

12. Based on Dalles Climatology 1901-2003

13. Natural Streamflow (cfs) [ -1.4 to -0.6 ] Based on Dalles Climatology 1901-2003

14. West-Wide Hydrologic Forecast

15. Modified Streamflow (cfs) Bias Adjusted West Wide Forecast (1961-2000)

16. Modified Streamflow (cfs) Bias Adjusted West Wide Forecast (1961-2000)

17. Modified Streamflow (cfs) Bias Adjusted West Wide Forecast (1961-2000) [ -1.4 to -0.6 ]

18. ColSim Storage Forecast (cool ENSO composite 1961-2000)

19. Conclusions: The WY 2007 ESP forecast predicted increased likelihood of drought. Observed summer flows in 2007 were below average and were close to the ensemble forecast mean (skillful forecast). A moderate to strong cool ENSO event is expected for the winter of 2007-2008, which historically is associated with increased likelihood of above average Apr-Sep flow at The Dalles. Dry initial soil conditions in the basin are projected to systematically reduce natural flows from Jan-July for water year 2008 by about 8 percent. The combined forecast is for near normal conditions, because the cool ENSO signal and soil moisture signal are roughly equal and in opposite directions.

20. WY 2007WY 2008 Potential Implications of ENSO Transition States

21. 19041.47 19071.00 19211.00 19250.49 19320.39 19430.88 19650.90 19711.55 19742.22 19840.58 1989-0.40 19960.93 19990.89 Historic Dalles Apr-Sept streamflow anomalies for water years with previous winter warm ENSO, current winter cool ENSO Stats: 12 of 13 above 0.39 11 of 13 above 0.49 9 of 13 above 0.88

22. Natural Streamflow (cfs) Based on Dalles Climatology 1901-2003