Northwest River Forecast Center Seasonal Volume Forecasts Using Ensemble Streamflow Prediction for the 2011 Water Year Steve King, Hydrologist [email protected].

Northwest River Forecast Center

Seasonal Volume ForecastsUsing Ensemble Streamflow Prediction

for the 2011 Water Year

Steve King, [email protected]

Topics for Presentation

Overview of Water Supply Models used at the NWRFC

Recap of WY 2010

2011 Volumetric Streamflow Outlook

Direction of NWRFC Water Supply Program

NWRFC Water Supply Models

Statistical Water Supply Seasonal Volumetric Forecasts

• Statistical Regression techniques (Legacy, SWS)• Based primarily on observation (Runoff, Snow, Precip)• NWS Driver for ‘Official’ Federal Coordinated

Forecasts

Ensemble Streamflow Prediction Many types of forecasts including

Seasonal Volumetric Forecasts• Probabilistic (ESP) technique built on top of real-time

hydrologic modeling system• Combines updated model states with QPF and

weather scenarios (typically based on climatology).

Seasonal Volume Forecasts (2010 Example)http://www.nwrfc.noaa.gov/water_supply/ws_fcst.cgi

http://www.nwrfc.noaa.gov/espws/espws.cgi

Statistical Water Supply ESP Volume Forecasts

Water Supply Release Schedulehttp://www.nwrfc.noaa.gov/water_supply/ws_fcst.cgi

WY 2010 Seasonal Precipitation

Above Grand Coulee ~ 92%Above Lower Granite ~ 95%Above The Dalles ~ 96%

OCT 09 NOV 09 DEC 09

JAN 10 FEB 10 MAR 10

APR 10 MAY 10 JUN 10

JUL 10 AUG 10 SEP 10

OCT 09 NOV 09 DEC 09

JAN 10 FEB 10 MAR 10

APR 10 MAY 10 JUN 10

JUL 10 AUG 10 SEP 10

WY 2010 Runoff Recaphttp://www.nwrfc.noaa.gov/runoff/runoff.cgi

Snake/Lower Granite

75%

Columbia/The Dalles

79%

Columbia/Grand Coulee

77%

Westside = Apr-SepEastside= Jan-Jul

PalisadesInflow

75%

Boise River

80%

OwyheeInflow

77%

Dworshak Inflow

73%

Jackson Lake Inflow

75%

Salmon River

98%

Verification of Fall Outlook (WY 2010)

Snake/Lower Granite

75%Columbia/The Dalles

79%

Columbia/Grand Coulee

77%

2010 Observed Runoff

Snake RLower Granite

96% 90%ColumbiaThe Dalles 95% 91%

Columbia RGrand Coulee

96% 91%

ESP Outlook w/o ENSOESP Outlook w/ ENSO

2010 Forecast Verificationhttp://www.nwrfc.noaa.gov/water_supply/ws_verif.cgi

2010 Forecast Verificationhttp://www.nwrfc.noaa.gov/water_supply/ws_verif.cgi

Spring 2011 Outlook

Ensemble Streamflow Prediction (ESP)

Driven by: Antecedent Snow/Soil Moisture

10 day Precip and Temp forecast

Precip and Temp climatology (1948-2002)

Published forecasts updated weekly

Capability of including climate forecasts/signals(unpublished)

Forecast input to ESP: Precipitation, Min and Max Temperature, Freezing Levels

6hr QPFavailable for day 1-3

24 hr Quantitative Precipitation Forecast for days 1-10

http://www.nwrfc.noaa.gov/weather/10_day.cgi

2011 Outlook* (ESP Forecasts)ttp://www.nwrfc.noaa.gov/water_supply/ws_fcst.cgi

50% Ex. Prob = 29 MAF97% of 30 yr Norm (30 MAF)

50% Ex. Prob = 103 MAF96% of Normal (107 MAF)

* Reflects current model states (antecendent conditions),10 day QPF, and climatology

2011 ESP Outlook*

Snake R/Lower Granite

89%

Columbia R/The Dalles

93%

Columbia R/Grand Coulee

96%

Jan-JulMedian Ensemble VolumePercent of ESP Normal

* Reflects 10/26/10 model states,10 day QPF, and ESP climatology

PalisadesInflow

102%

Boise River

102%

Dworshak Inflow

96%

Salmon River

110%

SST Predictions (Oct 2010)

SST observation and forecasts indicate that we are in a strong La Ninaclimate pattern that is expected to persist through the first half of 2011.

CPC Seasonal Winter OutlookDec-Jan-Feb

WY 2010 Outlook (issued last fall) WY 2011 Outlook (current)

CPC Seasonal Winter OutlookDec-Jan-Feb

WY 2010 Outlook (issued last fall) WY 2011 Outlook (current)

2011 ESP OutlookUsing La Nina Climatology

Snake RLower Granite

89% 97%

ColumbiaThe Dalles

93% 96%

Columbia RGrand Coulee

96% 102%

ESP for ALL yearsESP for La Nina yearsMedian Ensemble VolumePercent of ESP Normal

La Nina ClimatologyDJF ENSO ONI <= -1.0

11 cases in ESP record (1948-2002)

WY19511955195619651971197419761985198919992000

PalisadesInflow

102% 114%

Boise River

102% 109%

Dworshak Inflow

96% 110%

Salmon River

110% 125%

v

v

http://wateroutlook.nwrfc.noaa.gov

NWS Western Region / NWRFC Water Supply Directions

No operational changes for WY 2011

Examine potential for ESP as primary forecast tool.

Replace Legacy Raw model with SWS as supplementary forecast tool.

WS Model Verification Study2009-2010

• SWS similar to and often better performing than other models

• ESP stronger than others for late season forecasts

NWS Western Region / NWRFC Water Supply Directions

Work with users to determine forecast locations and forecast periods that are providing the most value for users.

Expand use of QPS in ESP

Investigate conversion of regulated forecasts to unregulated (natural) streamflow forecasts.

Northwest River Forecast Center

www.nwrfc.noaa.gov