1. Recap of Water Year 2006 Hydrologic Forecast and Forecasts for Water Year 2007
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 2006

3. ENSO is typically very stable from Oct-Jan

4. Evaluation of Sept 1 ECMWF Nino3.4 Forecast for WY 2003-2005

5. Evaluation of Aug 1 ECMWF Nino3.4 Forecast for WY 2006
Used range:
Jan3.4 >= -0.4
Jan3.4 <= 0.6

6. Naturalized Flow (cfs)
Ensemble Streamflow Forecast for the Columbia River at The Dalles for WY (Nino3.4 anomalies between -0.4 and 0.6)
Black = Climatological Extremes
Gray = Forecast Ensemble Members
Red = Observed
Blue = Ensemble Mean
Naturalized Flow (cfs)
Nino to 0.6

7. Evaluation of Sept 1 ECMWF Nino3.4 Forecast for WY 2006
Used range:
Jan3.4 >= 0.0
Jan3.4 <= 0.6

8. Naturalized Flow (cfs)
Ensemble Streamflow Forecast for the Columbia River at The Dalles for WY (Nino3.4 anomalies between 0.0 and 0.6)
Black = Climatological Extremes
Gray = Forecast Ensemble Members
Red = Observed
Blue = Ensemble Mean
Naturalized Flow (cfs)
Nino to 0.6

9. ColSim Reservoir System Storage Forecast
All Years from for which J. Nino3.4 Anom. >= AND <= 0.6
Obs. System
Storage Sept 28, 2006

10. WY 2007 Forecast

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

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

14. ColSim Reservoir System Storage Forecast
All Years from for which J. Nino3.4 Anom. >= 0.7 AND <= 1.5
2007

15. Selected References on Compositing Techniques:
Hamlet, A.F., Lettenmaier, D.P., 1999: Columbia River Streamflow Forecasting Based on ENSO and PDO Climate Signals, ASCE J. of Water Res. Planning and Mgmt., 125 (6) :
Werner K, Brandon D, Clark M, et al., 2004: Climate index weighting schemes for NWS ESP-based seasonal volume forecasts, J. of Hydrometeorology, 5 (6):

16. Conclusions:
The WY 2006 ESP forecast predicted a range of flows centered around near normal conditions. Actual flows in 2006 were towards the upper range of this forecast, probably due in part to an unusually large ENSO forecast error.
A moderate warm ENSO event is expected for the winter of ESP traces from associated with a forecasted range of Nino3.4 anomalies from suggest elevated drought risks for WY 2007.