Climate Prediction Applications Science WorkshopDes Moines, IA – March 3, 2011

Andy WoodNWS Colorado Basin River Forecast Center

Also:

John Schaake, John Lhotak, Kevin Werner, Michelle Schmidt

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Incorporating weather and climate predictions from NCEP GFS and CFS into operational water

supply forecasts for the Western U.S. 

Outline

Motivation – applications of probabilistic prediction

ESP overview and new developments

CFS-based water supply forecast example

Applications of Probabilistic Flow Forecasts

Western water supply Water Utilities, Mgmt Districts: Denver, S. Calif. USBR 24-month study BOR Midterm

Probabilistic Model

Others Pacificorps operation on Bear River (UT and ID) BPA and USACE operation on Columbia River INFORMS in CA

Western Water Supply Forecasts

Forecasts for spring runoff amounts from snow melt dominated basins in western US

Routinely produced at 6 RFCs and coordinated with other agencies

NWS forecast program began in 1940s

Primary forecast tools:– Ensemble Streamflow Prediction– Multivariate Linear Regression

Applications of Probabilistic Flow Forecasts

Denver Water:

•Long history of using ensemble forecasts for risk management

•Download CBRFC ensemble forecasts into reservoir operations spreadsheet (right)

•Optimize reservoir operations by minimizing negative impacts

LAKE POWELLFORECAST PROBABILITY DISTRIBUTION

OBSERVED INFLOW VOLUMEWATER YEAR 2010

6789

1011121314

AUG-71%

SEP-65%

OCT-55%

NOV-50%

DEC-36%

JAN-21%

FEB-25%

MAR-19%

CHANCE OF EQUALIZATION

MA

F

6.007.008.009.0010.0011.0012.0013.0014.00

required volume

30% exc volume

70% exc volume

50% exc volume

Southern CA MWD:

•Requested forecast for probability of equalization releases from Lake Powell

•USBR determines inflow volume required to trigger equalization from 24 month study

•CBRFC uses regulated ESP forecast to determine probability of reaching the required volume

Applications of Probabilistic Flow Forecasts

4,035 cfs

Mar 15 Forecast570 KAF

Applications of Probabilistic Flow ForecastsUpper Colorado Reservoir Management

Lake Powell & Lake Mead Operational Diagrams for 2010

11.41/1/10

Projection3,6351/1/10

Projection

15.41/1/010Proj

ection1,0981/1/10

Projection

Major releases depend on CBRFC April 1 Forecasts

Applications of Probabilistic Flow ForecastsUpper Colorado Reservoir Management

Note discontinuous decision rules – ill-suited to deterministic forecasts

CBRFC – BOR Cooperation

Thepast

Thefuture

Efforts in parallel --

CBRFC working to improve probabilistic flow forecasts

BOR working to implement probabilistic water management model

Current forecast framework

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Target, multi-forecast framework

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Current forecast performance CBRFC/NRCS official forecasts have plenty of skill at

times, but…

Applications of Probabilistic Flow Forecasts

…little of that skill comes from traditional climate forecasts, currently

(JFM Precip correlation with Nino 3.4)

1970 1980 1990 2000

ESP first used at California-Nevada River Forecast Center

NWS/HRL begins ESP development

ESP first presented at the Western Snow Conference

ESP used for drought assessment

ESP used for water supply forecasts

ESP released with NWSRFS

ESP Analysis and Display Program (ESPADP) development started

ESPADP deployed to the field

Water Resources Forecasting Services (WARFS) quantifies

value of ESP

Climate Prediction Center (CPC) forecast pre-adjustment developed for use in ESP

Historic development of ESP

Medium to long-range ESP short-medium-long range ESP

Experimental Ensemble Forecast System (XEFS) work begins

Western Snow Conference paper, 1977

Work to incorporate climate forecasts

©The COMET Program

An ESP Upgrade: The NWS Hydrologic Ensemble Forecast Service (HEFS)

Pre-processor

Weather Input Ensembles

Ensemble Streamflow Prediction

System

Hydrologic Model Output

Statistics processor

Verification system

Post processed

Hindcaster/ reforecaster

Input flow data

Streamflow

Operational Forecast System

Product generation

system

Verification products

Ensemble products

“Raw”

Post processor

flow ensembles

HEFS climate forecast calibration

15Limin Wu, Generation of Precipitation Ensemble Forecasts from Single-ValueQPF via Mixed-Type Meta-Gaussian Model, AGU Fall Meeting 2010

Key Point

GFS & CFS ensemble forecast means are used to generate calibrated, seamless ensemble time-series of RFC model inputs (P, T), 6-hourly!

The HEFS WSF Input

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Example: CFS climate forecasts, late 2010

November

Water Supply Forecast Results (Dec 1, 2010)

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Average contribution to Lake Powell Apr-Jul inflow:

Green River 34%Colorado River50%San Juan River13%

Returning to the framework

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The water supply forecast approach may become ‘messier’, but also, we hope: more transparent better informed by climate forecasting

We are still evaluating approaches, but making real progress

Lastly … GapsSkillful climate forecasts in Upper Colorado

– 2 weeks to 2 years (medium range to interannual)

– Need to go “beyond ENSO”, given weak ENSO-index skill in upper Colorado

– CBRFC & BOR organizing an SI-to-Year2 Climate/Flow Forecasting workshop/testbed later this month

Improved land surface analysis (snow, soil moisture)– A critical part of every forecast (initial conditions)

– Can collaborative efforts improve this information?

Connect decision frameworks with forecast characteristics– Ensembles enable risk-based analysis

– Forecast skill varies in space and time: decisions should account for this property

Thank You!

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Lake Powell Inflow forecast with GFS and CFS based inputs

Daily updating, experimental

Contact: Andy.Wood@noaa.gov