GFS Is Messed Up

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Bob Hartig
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Location: Grand Rapids, MI

GFS Is Messed Up

Post by Bob Hartig » Mon May 09, 2011 7:52 pm

Andy, something is really screwy with the GFS. I've tried a number of maps and none of them has worked properly, or even at all. NAM is okay. I haven't tried RUC.
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Andrew Revering
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Post by Andrew Revering » Mon May 09, 2011 8:36 pm

It appears NCEP made some changes for us. It looks like its affecting only the surface maps. I'll have to go in and figure out how the changes are done in the GRIB files and correct my decoders. Here's the statement announcing the upgrade:
NOUS41 KWBC 061904

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

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:
Andrew Revering
Bob Hartig
Heavy User
Posts: 147
Joined: Wed May 16, 2007 3:57 pm
Location: Grand Rapids, MI

Post by Bob Hartig » Tue May 10, 2011 8:17 am

Looks like the GFS is back in business. Thanks!
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