1. Recap of Water Year 2008 Hydrologic Forecast

2. Conclusions:
The WY 2007 ESP forecast predicted increased likelihood of drought. Observed summer flows at Milner in 2007 were strongly below average (~55% of normal for April-Sept) and were towards the bottom of the ensemble.
A moderate to strong cool ENSO event is expected for the winter of , which historically is associated with increased likelihood of above average Apr-Sep flow at Milner.
Dry initial soil conditions in the basin are projected to systematically reduce natural flows at Milner from April-Sept for water year However even with dry soils, the forecast at Milner shows increased chance of high flows. Snakesim model simulations suggest increases in carry over storage in the upper Snake in Sept 2008 above about 1.0 MAF.

3. Validation Plot for the ECMWF Nino3.4 Forecast

4. Natural Flows at Milner 1928-1989

5. Milner Simulated Natural Flow at Milner (ESP all years)
Red = long term mean
Blue = ensemble mean
Gray = ensemble members
Black = range of observations
Natural Flow (KAF)
Milner

6. Milner Simulated Natural Flow at Milner (ESP cool ENSO)
Red = long term mean
Blue = ensemble mean
Gray = ensemble members
Black = range of observations
Natural Flow (KAF)
Milner

7. SnakeSim Storage Forecast (cool ENSO composite)
Full
Obs. Oct 10, 2008
Upper Snake Storage (KAF)

8. Historic Milner Apr-Sept streamflow anomalies for water years with previous winter warm ENSO, current winter cool ENSO WY
Std Ann.
1932
-0.235
1943
1.137
1965
1.238
1971
2.170
1974
1.686
1984
1.883
1989
-0.080
Stats:
5 of 7 above 1.1
3 of 7 above 1.7

9. Based on Milner ESP 1961-2000 Natural Flow (KAF) Natural Flow (KAF)
enso_2008
enso_trans_2008
Natural Flow (KAF)
Natural Flow (KAF)