hydrologic outlook for the pacific northwest in water year 2008 andy wood xiaodong zeng and george...
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Hydrologic Outlook for the Pacific Northwest in Water Year 2008
Andy WoodXiaodong Zeng and George ThomasAlan Hamlet and Dennis Lettenmaier
Dept. of Civil and Environmental Engineering
for Climate and Water Resource Forecasts for the 2008 Water Year
UW Climate Impacts Group
October 17, 2007, Boise, ID
Presentation Outline
1. Introduction: UW Experimental Hydrologic
Forecasting System
2. Water Year 2007 Discussion and 2008 Outlook
Introduction
UW Seasonal Hydrologic Forecast System
www.hydro.washington.edu/forecast/westwide/
PI: Dennis Lettenmaier, UW
Current Sponsors:NOAA CPPA program, UW CSES
Experimental W. US Hydrologic Forecast System
Soil MoistureInitial
Condition
SnowpackInitial Condition
Hydrologic Model-based Forecasting
ICs*Spin-up Forecast
obs
recently observedmeteorological data
ensemble of met. datato generate forecast
hydrologicstate
IC = initial conditions
ENSO subset
196019611962……
1999
ESP
Can adjust IC by assimilatingsnow or other observations
Streamflow Forecast Results: West-wide at a Glance
Flow location maps give access to monthly hydrograph plots, and also to raw forecast data.Clicking the stream flow
forecast map also accesses current basin-averaged conditions
Applications: streamflowHydrologic Analyses
Presentation Outline
1. Introduction: UW Experimental Hydrologic Forecasting
System
2. Water Year 2007 Discussion and 2008 Outlook
Average annual water cycle
The PNW hydrologic cycle
PNW
* Where we are now on average
soil moisture near annual low
runoff near low
nearly all water year precipitation yet to come
snow season not really underway
evaporation not a factor
The PNW hydrologic cycle
Note that there is variability insoil moisture now…
current
basin averages
Recap WY2007, Jan. 1 hydrologic conditions
Soil Moisture SWE
Recap WY2007, Mar. 1 hydrologic conditions
Soil Moisture SWE
Recap WY2007, Snow Obs & Simulation
Observed SWE
Recap WY2007, Apr. 1 hydrologic conditions
Soil Moisture SWE
Winter 2006-07: seasonal volume forecast for APR-SEP
OBS
Forecasts made on 1st of Month
Apr-Sep Flow Forecast, Columbia R. (Dalles)
40
50
60
70
80
90
100
110
120
130
140
Nov
Dec Jan
Feb
Mar
Apr
May Ju
n
Jul
% o
f av
erag
e
OBS RFC WS
0.1 - % of avg 0.5 - % of avg
0.9 - % of avg enso % of avg
SlidesSince last winter:
spring & late
summer precip
was low
one heat
outbreak (in July)
soil moistures
have dropped
entering new
water year with a
deficit
Oct 1 Soil Moisture Comparison with Last Year
THIS YEAR LAST YEAR
La Nina-flavored Climate Outlook for Winter
Outlooks are probabilistic – show ‘tilting of the odds’
La Nina versus Normal conditions: Oct, Nov, Dec
oct
nov
dec
precip temperature SWE soil moist runoff
La Nina versus Normal conditions: Jan, Feb, Mar
jan
feb
mar
precip temperature SWE soil moist runoff
La Nina versus Normal conditions: Apr, May, Jun
apr
may
jun
precip temperature SWE soil moist runoff
Forecast initialized Oct 1 ‘07: Summer Volumes
Forecasts of April-September 2008 Flow
Dalles: 93 / 102
ESP ESP: La Nina
Forecast initialized Oct 1 ‘07: Summer Volumes
Forecasts of April-September 2008 Flow
ESP ESP: La Nina
Priest Rapids: 96 / 103
Forecast initialized Oct 1 ‘07: Summer Volumes
Forecasts of April-September 2008 Flow
ESP ESP: La Nina
Snake: 84 / 98
Snake: 84 / 98 low soil moisture depresses flows through June
La Nina compensates, especially in June & July
Forecast initialized Oct 1 ‘07: Summer Volumes
Forecasts of April-September 2008 Flow
ESP ESP: La Nina
Upper Snake: 88 / 100
Forecast initialized Oct 1 ‘07: Summer Volumes
Forecasts of April-September 2008 Flow
ESP ESP: La Nina
Waneta: 93 / 102
Forecast initialized Oct 1 ‘07: Summer Volumes
Forecasts of April-September 2008 Flow
ESP ESP: La Nina
Arrow: 100 / 107
Summary
current soil moisture
deficits in eastern half
of Columbia R. basin
La Nina tendencies
toward wetter and
colder climate
hydrologic outlook
Columbia R. (The Dalles): slightly above normal
about + 5% to north
about - 5% to east or southeast (Snake)
wide uncertainty ranges about these forecast
averages
early
season
forecast
thank youquestions? [email protected]