Technical Implementation Notice 11-07, Amended

National Weather Service Headquarters Washington DC

304 PM EDT Fri May 6 2011


To:         Subscribers:

            -Family of Services

            -NOAA Weather Wire Service

            -Emergency Managers Weather Information Network


            Other NWS Partners, Users and Employees


From:       Timothy McClung

            Science Plans Branch Chief

            Office of Science and Technology


Subject:    Amended: Global Forecast System (GFS) Upgrade:

            Effective May 9, 2011


Amended to change the implementation to as early as Monday, May 9 with the 1200 UTC model cycle. A determination will be made on Monday May 9. There is a high likelihood that Tuesday, May 10, will be declared a Critical Weather, preventing this GFS implementation from proceeding for indeterminate time. The NCEP Senior Duty Meteorologist will issue a NOUS42 administrative message when the implementation has taken place.


Amended to reschedule the implementation from April 26, 2011, to May 10, 2011 to allow for a full evaluation period.  Also amended to include details of a new sea level pressure field being added to select products available via the ftp servers.


Effective May 10, 2011, beginning with the 1200 Coordinated

Universal Time (UTC) run, the National Centers for Environmental

Prediction (NCEP) will upgrade the GFS. The upgrade includes:


Analysis Changes:

  --Improve Ozone Monitoring Instrument (OMI) quality control

  --Remove redundant SBUV/2 total ozone

  --Retune SBUV/2 ozone observation errors

  --Relax AMSU-A Channel 5 quality control

  --Update Community Radiative Transfer Model(CRTM) to

    version 2.0.2

  --Include field of view size/shape/power for radiative      


  --Remove down weighting of collocated radiances

  --Limit moisture >= 1.e-10 in each outer iteration and at

    end of analysis

  --Include uniform (higher resolution) thinning for satellite


  --Improve location of buoys in vertical (move from 20m

    to 10m)

  --Improve Gridpoint Statistical Interpolation (GSI) code

    with optimization and additional options

  --Recompute background errors

  --Include SBUV from NOAA-19

  --Ambiguous vector quality control for ASCAT (type 290) data


Model Changes:

  --Set new thermal roughness length

  --Set minimum moisture value in Stratosphere to 1.0x10-7

  --Reduce background diffusion in the Stratosphere


Product Changes:

  -Correct error in the 192 hr, 12-hr precipitation bucket

  -Addition of a new membrane sea level pressure (SLP) field to

   the 0.5, 1.0 and 2.5 degree pressure grib (pgrb) files only.

   This pressure is generated by first relaxing the underground

   virtual temperature and then integrating the hydrostatic

   equation downward.  The field will be subject to Spectral

   Gibsing near the coast, but this will be addressed in a future



The three model changes and the 192 hr precipitation change

listed above are designed to address shortfalls introduced

with the 27 July 2010 GFS resolution increase. The issues

being addressed are:


  --increased low level warm bias over land

  --negative temperature bias in the stratosphere

  --negative wind speed bias in the stratosphere

  --error in the calculation of the 12 hr accumulated

    precipitation at 192 hrs only.


Data Availability:


The format and content of all GFS data sets will remain

Unchanged, with the exception of the addition of the new SLP field. GFS data is currently available on NOAAPORT, the

NWS FTP server, the NCEP server and in NOMADS. The location

of the data will remain unchanged.


Product delivery timing of the GFS products is not expected

to change as a result of this implementation. More information

regarding the GFS and associated products can be found at:


A consistent parallel feed of data will become available on the

NCEP server once the model is running in parallel on the NCEP

Central Computing System by mid-March.  The parallel data will

be available via the following URLs:


NCEP encourages all users to ensure their decoders are flexible

and are able to adequately handle changes in content order,

changes in the scaling factor component within the product

definition section (PDS) of the GRIB files, and also any volume

changes which may be forthcoming. These elements may change with

future NCEP model implementations. NCEP will make every attempt

to alert users to these changes prior to any implementations.


For questions regarding these changes, please contact:


  John Derber

  NCEP/EMC, Global Climate and Weather Modeling Branch

  Camp Springs , Maryland

  301-763-8000 x 7740


  John H. Ward

  NCEP/EMC, Global Climate and Weather Modeling Branch

  Camp Springs , Maryland

  301-763-8000 x 7185


For questions regarding the dataflow aspects of these data

sets, please contact:


  Rebecca Cosgrove

  NCEP/NCO Dataflow Team

  Camp Springs , Maryland 20746

  301-763-8000 x 7198


NWS National Technical Implementation Notices are online at: