Update on the Northwest
Regional Modeling System 2013
Cliff Mass and David Ovens
University of Washington
http://www.atmos.washington.edu/mm5rt/
NW High Resolution Regional
Prediction
• Supported by NW Modeling Consortium-a
collection of local, state, and Federal Agencies
AND the private sector (King-5)
• Currently runs with 36, 12, 4, and 1.3 km grid
spacing using the WRF (Weather Research and
Forecasting) ARW model twice a day at 0000
and 1200 UTC (5 AM and 5 PM PDT)
• One of the highest resolution numerical
weather prediction efforts in the U.S.
36 km
12
km
4 km
1.33 km
Who is looking?
New Mode of Distribution: TV!
King-5 is getting our model grids and creating on-air graphics.
Verification: Does Resolution
Help? Yes!
Lots of Upgrades Over the Past
Year
Upgrades
• Moved to the latest version of the WRF model
(3.1.1 to 3.4.1). 3.1.1 was about two years
old.
• Pushed the upper boundary of the model way
up! 100 hPa to 50 hPa (16 to 21 km)
• Installed a radiation condition that stopped
unphysical reflections off the top.
Shading is vertical velocity.
New Cumulus Parameterization
• We were getting wacky cloud and
precipitation lines over the ocean when the air
was less stable.
• To fix this we moved from the old Kain-Fritsch
scheme to the same one used by the National
Weather Service in the global GFS model
(Simplified Arakawa Schubert-SAS).
Old Kain-Fritsch
SAS
Also partially solved a major
summer problem we had: lack of
convection over the Cascades and
downstream over western
Washington and Oregon
Old
New
New
Two Major Proposed Improvements
for Next Few Months
• Better radiation scheme-RRTMG
• Adding Land Surface Model (LSM)-RUC LSM
RRTMG much more sophisticated
Some 2-m Temperature Results at
4 PM in Winter (all stations)
Red (original), Green (with RRTMG)
Mean Error or Bias
Summer
Land Surface Model (LSM)
• Land Surface Models provide much more
sophisticated descriptions of surface
properties and how they evolve.
• Generally also provides much better dew
point forecasts
• Snow distribution can change in time.
• We had been using the NOAH LSM but found
unacceptable cold biases over the interior.
• But things (and the model) have changed.
Land Surface Model Schematic
Testing LSMs
• Old NOAH LSM (had cold bias)
• New NOAH MP (had stability issue)
• RUC LSM (tested comprehensively)
RUC LSM with RRTMG Radiation
• As expected dew point is much improved in
summer.
Winter Temp: Improvement
Snow Can Change in Time During a
Forecast with LSM
Finally, we are continuing
development and operational
availability of our local data
assimilation and forecasting system
Regional Data Assimilation and
Forecasting
The Long Term Future of the UW
Modeling Effort
• Based on a large (64 member) ensemble of
forecasts at 36 and 4 km grid spacing. WRF
model and DART Ensemble Kalman Filter (EnKF)
System
• Every three hours assimilate a wide range of
observations to create 64 different analyses.
• Then we forecast forward for 3 hours and then
assimilate new observations.
• Thus, we have a continuous cycle of probabilistic
analyses.
EnKF Ensemble Forecasting System
• We can run ensemble of forecasts forward to
give us probabilistic forecasts for any period
we want. Now doing 24h ahead, four times a
day.
• Planning to go to a 1-hr cycle and to use more
observations (e.g., more surface pressure
obs).
• More next year.
Improvement in short-term
forecast using our local
assimilation system
WRF 4 km at same time
NWS NAM
Major New Enhancement
• The use of high density, bias-corrected surface
pressure observations…more next year….
• Including the use of pressures from
smartphones!
The End