Recap of WY 2006

ENSO is typically very stable from Oct-Jan

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

WY 2003

WY 2004 WY 2005

Used range: Jan3.4 >= -0.4Jan3.4 <= 0.6

Evaluation of Aug 1 ECMWF Nino3.4 Forecast for WY 2006

Nino3.4 -0.4 to 0.6

Ensemble Streamflow Forecast for the Columbia River at The Dalles for WY 2006. (Nino3.4 anomalies between -0.4 and 0.6)

Nat

ural

ized

Flo

w (

cfs)

Black = Climatological ExtremesGray = Forecast Ensemble MembersRed = ObservedBlue = Ensemble Mean

Used range: Jan3.4 >= 0.0Jan3.4 <= 0.6

Evaluation of Sept 1 ECMWF Nino3.4 Forecast for WY 2006

Nino3.4 0.0 to 0.6

Ensemble Streamflow Forecast for the Columbia River at The Dalles for WY 2006. (Nino3.4 anomalies between 0.0 and 0.6)

Nat

ural

ized

Flo

w (

cfs)

Black = Climatological ExtremesGray = Forecast Ensemble MembersRed = ObservedBlue = Ensemble Mean

ColSim Reservoir System Storage ForecastAll Years from 1916-2003 for which J. Nino3.4 Anom. >= -0.4 AND <= 0.6

Obs. SystemStorage Sept 28, 2006

WY 2007 Forecast

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

150000

200000

250000

300000

350000

400000

450000

-3 -2 -1 0 1 2 3 4

NINO3.4 Index Anomaly

Ap

ril-

Se

pte

mb

er

Av

era

ge

S

tre

am

flo

w

1916-2002

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

Mod

ified

Flo

w (

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 ExtremesGray = Forecast Ensemble MembersRed = LTM from 1950-1999Blue = Ensemble Mean

ColSim Reservoir System Storage ForecastAll Years from 1960-1999 for which J. Nino3.4 Anom. >= 0.7 AND <= 1.5

2007

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) : 333-341

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): 1076-1090

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 2006-2007. ESP traces from 1960-1999 associated with a forecasted range of Nino3.4 anomalies from 0.7-1.5 suggest elevated drought risks for WY 2007.