RFC Climate Requirements 2 nd NOAA Climate NWS Dialogue Meeting

1. RFC Climate Requirements2nd NOAA Climate NWS Dialogue Meeting January 4, 2006 Kevin Werner

2. Outline • RFC overview • Water supply forecasting • Other possible climate – hydrology intersections • Case Study

3. 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.

4. 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

5. 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).

6. 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.

7. 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

8. Ensemble Streamflow Prediction • Daily RFC Forecasts: • Precipitation • Temperature • Model Updating Climate Forecast Adjustments • Current Conditions: • Soil • Reservoirs • Streamflow Historical Time Series All Years Basin Mean Areal Time Series Forecast Meteorological Time Series (single value or ensemble) NWSRFS Hydrologic Models

9. 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)

10. 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.

11. 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

12. 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