Andy Wood, Ted Bohn, George Thomas, Ali Akanda, Dennis P. Lettenmaier

1
University of Washington west-wide
experimental hydrologic forecast system
Andy Wood, Ted Bohn, George Thomas, Ali Akanda,
Dennis P. Lettenmaier
Univ. of Washington
Components of Overall Real-time Forecasting
Approach

• OBJECTIVE
• The forecasting system was created to evaluate
  the use of distributed macroscale hydrologic
  models for hydrologic forecasting, and provide a
  testbed for assessing the use of climate
  predictions and data assimilation in a streamflow
  forecasting context.
• OVERVIEW
• Forecasts are made once monthly, using simulated
  initial conditions based on real-time
  observations of temperature and precipitation.
• Experimental hydrologic forecasts are also made
  using the climate forecast ensembles derived from
  the NCEP Climate Prediction Center Seasonal
  Climate Outlooks.
• Benchmark hydrologic forecasts are also
  constructed via the well-known Extended
  Streamflow Prediction (ESP) method of the U.S.
  National Weather Service. The ESP forecasts are
  also categorized to provide ENSO and
  PDO-conditioned ensembles, which past work has
  shown can improve seasonal forecast accuracy.

Climate Forecasts
Hydrologic Model (Liang et al., 1994)
Snow Assimilation
ESP and ESP/ENSO forecasts
NRCS SNOTEL / Env. Canada ASP observed SWE
anomalies are merged with simulated anomalies to
adjust the forecasts initial hydrologic state,
e.g.

• VIC model resolution (1/8 degree)
• use ensemble of historical 12 month daily
  sequences taken from 1960-99
• use subsets based on ENSO category

corresponding SWE adjustment
example obs SWE anomalies
NCEP CPC Official Outlooks

• derived from Probability of Exceedence seasonal
  precipitation and temperature forecasts for US
  climate divisions
• ensembles of precipitation and temperature
  generated by non-parameteric resampling approach
  called the Schaake Shuffle

Forecasts from Climate Model Output

• from NCEP CFS (in re-development)

Major Products of Westwide Forecasting System
Current Activities
Multiple Land Surface Model Ensembles
Collaboration with Operational and Research Groups
Forecast Web Page
Current conditions nowcasts for soil moisture /
SWE

• We are evaluating the benefits of using three
  separate models to generate forecasts that can be
  combined via Bayesian model averaging techniques.
• Models
• VIC
• SAC Sacramento /
• SNOW17 model (NWS)
• NOAH NCEP, OSU,
• Army, NWS Hydrology Lab
• Test Case Salmon R., ID
• Retrospective Comparisons
• Individual Models

http//www.hydro.washington.edu/forecast/westwide/
NWS Hydrologic Ensemble Prediction
Experiment (HEPEX)
U. Arizona / USBR forecast study, Lower Colorado
basin
Princeton University Hydrologic Forecast System
Miscellaneous Seattle City Light, energy
traders, hydropower utilities, NOAA regional
climate offices
3TIER Environmental Forecast Group
NRCS National Water and Climate Center Forecast
Group
Monthly Avg Flow
Monthly RMSE
UW Climate Impacts Group (CIG) Annual Water
Outlook meetings
NOAA National Centers for Environmental
Prediction (NCEP) testbed activities
UW Hydrologic Forecast and Nowcast Systems
Spatial Forecasts for P, T, SWE, Soil Moisture,
Runoff
Prior evolution of water balance for drainage
area of each forecast location
Klamath R. Basin Bureau of Reclamation
UW Puget Sound region flow forecasts
Monthly Avg Flow
Monthly RMSE
new
US Drought Monitor
WA State Dept of Ecology Yakima R. Basin Bureau
of Reclamation
NOAA Climate Prediction Centers US Drought
Outlook
Columbia River Inter-tribal Fish Commission
UCI / California Dept of Water Resources
Daily Updating Land Surface Nowcast

• Now operational for current domain Missouri R.
  basin
• Next basins Mexico, Arkansas-Red, Gulf

Other Changes / Ongoing Work

• re-evaluating the NASA/NOAA NLDAS 1/8 degree
  forcing product as a potential real-time forcing
  in Western U.S.
• automating nowcast / initial condition simulation
  over the US westward of the Mississippi River
• adopting selected experimental reservoir system
  forecasts as routine products
• comparing nowcasts with retrospective simulations
  now in progress extending back to 1915
• Expanding the set of streamflow forecast points
  to the Great Basin, Missouri, and upper Rio
  Grande Rivers

Westwide overview map of current water supply
period volume forecast
References / Acknowledgements
Wood, A.W., E.P. Maurer, A. Kumar and D.P.
Lettenmaier, 2002. Long Range Experimental
Hydrologic Forecasting for the Eastern U.S.,
JGR, 107(D20). Liang, X., D. P. Lettenmaier, E.
F. Wood and S. J. Burges, 1994. A Simple
hydrologically Based Model of Land Surface Water
and Energy Fluxes for GSMs, JGR., 99(D7). Wood,
A.W. and D.P. Lettenmaier, 2006, A testbed for
new seasonal hydrologic forecasting approaches in
the western U.S., BAMS (accepted). The authors
gratefully acknowledge the support of NOAA/OGP
(now the Climate Program Office) CDEP and CPPA
programs.
This map clicks through to forecast hydrographs
at right, and water balance plots above