1. 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

2. 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

3. 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

4. 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
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

5. Modeling Framework Snowpack Initial Condition Soil Moisture

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

7. 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

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

9. 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

10. 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

11. May 1, 2006 forecasts

12. 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)

13. 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

14. 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

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

17. 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

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

19. 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)

20. Retrospective precipitation data set (Zhu et al, 2006)

21. 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 ( ) provided courtesy of David Gochis, 86 station cross Sierra Madre Occidental

22. Pan-Mexican index river basins

23. First focus area: Rio Yaqui basin

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