RFC Climate Requirements

2nd NOAA Climate NWS Dialogue Meeting

January 4, 2006

Kevin Werner

Outline

• RFC overview

• Water supply forecasting

• Other possible climate – hydrology intersections

• Case Study

RFC Overview• NWS Hydrology Mission:

– Provide river and flood forecasts and warnings for the protection of lives and property.

– Provide basic hydrologic forecast information for the nation’s environmental and economic well being.

• River Forecast Center Functions:– Continuous hydrometeorological

data assimilation, river basin modeling, and hydrologic forecast preparation.

– Technical support and interaction with supported and supporting NWS offices.

– Technical support and interaction with outside water management agencies and users.

– Applied research, development, and technological implementation to facilitate and support the above functions.

Water Supply Forecasts• Water Supply Forecasts issued

jointly by RFCs and NRCS for western US basins.

• Water Supply Forecasts may directly apply climate forecasts

• Existing procedure for incorporating climate forecasts into ESP was developed largely by OHD

• Little effort by NOAA climate community to apply climate forecasts to water supply forecasts

Historical Synopsis of Climate In Water Resources Forecasting

(credit: Dave Brandon)

– 1917–Church,J.E. The first documented application to forecasting using correlation of snowpack to water level in Lake Tahoe

– 1943-USWB. Created bi-monthly 30-day weather– Internal outlooks, and went public in 1953.– 1947-USWB/SCS. Started publishing seasonal water supply

outlooks. – 1955-CBIAC Report. Evaluated use of 30-day outlooks in– forecasting Columbia Streamflow…potential could be great– but there was little/no skill.– 1958-USWB. Created seasonal 90-day internal outlooks– and went public in 1974 (temp) and 1978 (precip).

• 1964-CBIAC. Follow-up Report Forecast skill improving• but hard to apply broad forecasts to specific basins.• 1974-NWS. Seasonal 90-day temperature forecasts release to the public followed by

precipitation forecasts in 1978.• 1976-Marron(NRCS). Began using SOI in forecasts for Lake Tahoe• 1977-Schaake, J. (NWS). Used 30-day precipitation outlook to remove a series

of anti-analogs in ESP.• 1987-Croley/Hartmann. Used climate outlooks subjectively to• alter ESP traces in forecasting Great Lake Levels.• 1995-Rundquist, L. Developed ESP post weighting scheme.• 1988-Perkins, T.(NRCS). Began using SOI as predictor in lower• Colorado.• 1989-Cayan/Peterson. Investigated El Nino and western streamflow• 1994-Hartman, (NWS) Investigated using SOIs at CBRFC• 1995-CPC. Begins issuing new climate format, with tercile• probability anomalies for 13 overlapping months.• 1997-Mantua et al. Development of PDO• 1997/1998-El Nino spurred variety of research• 1998-Brandon, D. (NWS). Began using SOIs in preliminary • Outlooks issued in the fall.• 2000-Perica, S. (NWS). Developed CPC pre-adjustment • technique to be used in NWSRFC ESP.

Water Supply Forecasts

• Two major tools:– Statistical Water Supply (SWS)

• Regression based approach• Based on snow observations, antecedent

conditions, climate conditions (e.g. ENSO), etc.

– Ensemble Streamflow Prediction (ESP)• Based on continuous calibrated hydrologic model• Calibration requires long record of streamflow,

precipitation, and temperature

Ensemble Streamflow Prediction

Climate Forecast

Adjustments

Daily RFC Forecasts:

•Precipitation•Temperature

•Model Updating

NWSRFS Hydrologic

Models

Basin Mean Areal Time

Series

Forecast Meteorological

Time Series

(single value or ensemble)

Historical Time Series

All Years

Current Conditions:•Soil

•Reservoirs•Streamflow

Climate Requirements

• Increased skill in medium to long range precipitation forecasts - Castuccio et al (1981) estimated that a 6 percent improvement in forecasting accuracy would produce $36.5 million in annual benefits to agriculture and hydropower in the west

• New methods for incorporating climate forecasts– Must be based on data that is available when forecasts are

made• New methods for incorporating and assimilating data into

hydrologic forecasts.• Improving forecast verification to validate impact of

climate forecasts• Expanding and improving use of water supply forecasts

(including ensemble based decision support systems)

Climate Requirements (con’t)

• Longer term forecasts (e.g. 2 year and beyond) – RFCs are increasingly being asked to produce water supply outlooks for 2 years, sometimes even longer.

• Data – High quality, long duration, high frequency records of precipitation, streamflow, and temperature are necessary for calibration and real-time operation.

A (partially) Successful Collaboration

• 2002-2004 CBRFC/CIRES/CDC partnership to improve medium range forecasts– Incorporated probabilistic

meteorological model output into ESP

– Documented improvements in medium range streamflow forecasts (Werner et al, 2005)

– Implemented in CBRFC operations

– No direct national implementation although concepts have helped drive national software development

Elements of Successful Collaboration

• Focus on mutually interesting problem:– Directly address operational requirement(s).– Also address relevant research question(s).

• Early and active NWS involvement: Must include both RFC or WFO and OHD as active participants

• Proposed solutions must be possible in real-time NWS forecasting environment