Hydrologic forecasting for the NAMS region – extension of the University of Washington westwide forecast system Dennis P. Lettenmaier Chunmei Zhu Andrew W. Wood Department of Civil and Environmental Engineering University of Washington for presentation at Monsoon Region Climate Applications Workshop ITSON Guaymas, Sonora, Mexico May 10, 2006

Forecast system objectives Demonstrate/evaluate the utility of a regional approach to seasonal streamflow forecasting Evaluate the potential to integrate climate forecasts into seasonal (two week to one year) lead streamflow forecasts over the western U.S. Evaluate the potential to integrate research advances (including alternative data sources, e.g., remote sensing, and data assimilation) into operational seasonal streamflow forecasting

Forecast System Overview Objective: To create a model-based testbed for evaluating potential sources of improvement in seasonal forecasts since inception of regression/ESP methods operational seasonal climate forecasts (model-based and otherwise) greater real-time availability of station data computing advances new satellite-based products (primarily snow cover) distributed, physical hydrologic modeling for macroscale regions

Forecast System Schematic NCDC met. station obs. up to 2-4 months from current local scale (1/8 degree) weather inputs soil moisture snowpack Hydrologic model spin up SNOTEL Update streamflow, soil moisture, snow water equivalent, runoff 25th Day, Month 0 1-2 years back LDAS/other real-time met. forcings for spin-up gap Hydrologic forecast simulation Month 6 - 12 INITIAL STATE SNOTEL / MODIS* Update ensemble forecasts ESP traces (40) CPC-based outlook (13) NCEP GSM ensemble (20) NSIPP-1 ensemble (9) * experimental, not yet in real-time product

Modeling Framework Snowpack Initial Condition Soil Moisture

Forecast points and sample streamflow forecasts monthly hydrographs targeted statistics e.g., runoff volumes

Westwide Forecast System – climate forecast drivers ESP ENSO/PDO ENSO CPC Official Outlooks Seasonal Forecast Model (SFM) CAS OCN SMLR CCA CA NSIPP-1 dynamical model VIC Hydrology Model NOAA NASA UW

Climate forecast bias correction scheme from COOP observations from GSM climatological runs raw GSM forecast scenario bias-corrected forecast scenario month m

VIC initial condition estimation: SNOTEL assimilation Problem sparse station spin-up period incurs some systematic errors, but snow state estimation is critical Solution use SWE anomaly observations (from the 600+ station USDA/NRCS SNOTEL network and a dozen ASP stations in BC, Canada) to adjust snow state at the forecast start date

Expansion to multiple-model framework Multiple Hydrologic Models CCA NOAA CAS OCN CPC Official Outlooks NWS HL-RMS SMLR CA Seasonal Forecast Model (SFM) VIC Hydrology Model NASA NSIPP-1 dynamical model others ESP weightings calibrated via retrospective analysis ENSO UW ENSO/PDO

May 1, 2006 forecasts

Ongoing work Improved data assimilation (snow cover extent, SNOTEL) 2-week forecasts Multi-model ensemble (hydrology and climate) Forecast domain expansion Augmented forecast products (e.g. nowcasts in real-time)

Surface Water Monitor Produces nowcasts of drought conditions across CONUS (domain to be extended to include Mexico) directly related to retrospective drought reconstruction Andreadis et al. (“Twentieth Century drought in the conterminous U.S., JHM, Dec. 2005) and westwide forecast system enabled by recent NCDC extension of digital data archives back to 1915 (places current droughts in historic context) forecasts that can be used in drought outlook type analysis

SW Monitor Information Flow Index Station Method Gridded Forcing Creation SW Monitor Information Flow NOAA ACIS Prcp Tmax Tmin Coop Stations 1930s 1955+ VIC Retrospective Simulation Daily, 1915 to Near Current Hydrologic State VIC Real-time Simulation (~1 month long) Hydrologic State (-1 Day) Hydrologic values, anom’s, %-iles w.r.t. retrospective PDF climatology (PDF) of hydrologic values w.r.t. defined period vals, anoms %-iles w.r.t. PDF

Monitor Webpage daily updates 1-2 day lag soil moisture & SWE percentiles ½ degree resolution archive from 1915-current uses ~2130 index stns

Scheme for drought recovery/persistence analysis (planned) Drought recovery probability described by soil moisture percentiles: (a) Current drought area (based on August 1933); and for different lead times, maps showing the probability (in each grid cell experiencing drought) that soil moisture percentiles will recover. (b) The grid cell-specific recovery probabilities are derived from real-time soil moisture simulations up to the current date, after which simulations are driven by ensemble climate forecasts based on a variety of sources -- e.g., ESP, climate index-conditioned ESP, and the CPC seasonal climate outlooks

Spatial Domain for Expanded West-wide Seasonal Hydrologic Forecast System Old w_fcst Expanded

Strategy for extension of forecast system over Mexico Real-time precipitation from SMN (linked to index stations for climatology as in western U.S.) Real-time surface air temperature and surface wind from EDAS (NOAA Eta Data Assimilation System) Other downward fluxes (solar, longwave) and surface variables (vapor pressure deficit) derived from Tmin, Tmax Surface air temperature climatology from NARR (North American Regional Reanalysis)

Retrospective precipitation data set (Zhu et al, 2006)

Climatology (1925-2004): Gridded Long-Term Land Surface Data Set Surface forcing data: Daily precipitation, maximum and minimum temperatures SMN daily precipitation, surface air temperature data (pre-1940 – 2003 ) produced by SMN (Servicio MeterorolÓgico Nacional), over 5000 stations. SMN daily precipitation data (1995 – near realtime) provided courtesy of Miguel Cortez Vázquez of SMN, around 1,000 stations. NW Mexico NAME Event Raingage Network (NERN) precipitation daily data ( 2002 - ) provided courtesy of David Gochis, 86 station cross Sierra Madre Occidental

Pan-Mexican index river basins

First focus area: Rio Yaqui basin

Availability of forecasts and data Open access, via UW hydro group web site (www.hydro.washington.edu/forecasts) Westwide forecasts through MOU with NRCS National Water and Climate Center Surface Water Monitor results used in U.S. Drought Monitor New users welcome!