NOUS41 KWBC 091918
Service Change Notice 17-67
National Weather Service Headquarters Silver Spring MD
318 PM EDT Fri Jun 9 2017
NOAA Weather Wire Service
Emergency Managers Weather Information Network
Other NWS Partners, Users and Employees
From: Dave Myrick
NWS Office of Science and Technology Integration
Subject: Global Forecast Systems (GFS) Upgrade:
Effective July 19, 2017
Effective on or about Wednesday July 19, 2017, beginning with the
1200 Coordinated Universal Time (UTC) run, the National Centers
for Environmental Prediction (NCEP) will upgrade the Global
Forecast Systems (GFS) Analysis and Forecast System as follows:
- Changes to the model components
- Changes to the data assimilation and tropical storm
- Changes to the post-processing
- Changes to output products
1) Changes to the Global Forecast System Global Spectral Model
- Implement GSM source code in NOAA Environmental Modeling System
- Upgrade to asynchronous quilting for scalable and efficient
write component in NEMS GSM. Asynchronous quilting means that the
model writes out chunks of data to disk in a non-sequential
manner. This improves I/O efficiency.
- Replace spectral history file output (sigma files) with new
nemsio binary files on model native grid. Documentation of nemsio
format including data structure, interface, how to open, read,
write, and MPI I/O support are at
http://www.emc.ncep.noaa.gov/NEMS/nemsio.php and nemsio library
- Implement Near Surface Sea Temperature (NSST) to replace Real-
Time Global SST (RTGSST) to provide more realistic ocean boundary
- Upgrade deep and shallow convection schemes with scale- and
aerosol-aware features along with convective cloudiness
- Modify Rayleigh damping to improve temperature and wind
forecasts in the upper stratosphere.
- Upgrade the land surface model to increase ground heat flux
under deep snow; and unify snow cover fraction and snow albedo.
- Use new high-resolution MODIS-based snow-free albedo, maximum
snow albedo, soil type and vegetation type.
- Upgrade surface layer parameterization scheme to modify the
roughness-length formulation and introduce a stability parameter
constraint in the Monin-Obukhov similarity theory to prevent the
land-atmosphere system from decoupling.
2) Changes to the Global Data Assimilation System (GDAS) and
Tropical Storm Relocation:
- Upgrade GDAS and Ensemble Kalman filter (EnKF) to use nemsio
- Implement Near Sea-Surface Temperature (NSST) Analysis.
- Implement CrIS full resolution data assimilation capability.
- Implement readiness for new Geostationary Operational
Environmental Satellite (GOES-16), Joint Polar Satellite System
(JPSS-2) and Constellation Observing System for Meteorology,
Ionosphere and Climate (COSMIC-2) data assimilation capability.
- Extend Regional Advanced Television Infrared Observation
Satellite (TIROS) Operational Vertical Sounder (ATOVS)
Retransmission Services (RARS) and Direct Broadcast Network
- Implement bug fix to cloud water increment in Gridpoint
Statistical Interpolation (GSI).
- Upgrade land surface type specification in Community Radiative
Transfer Model (CRTM).
- Update data monitoring for Megha-tropiques Sounder for Probing
Vertical Profiles of Humidity (SAPHIR) and Global Precipitation
Measurement (GPM) Microwave Imager (GMI) radiances.
- Assimilate Visible Infrared Imaging Radiometer Suite (VIIRS)
Atmospheric Motion Vectors (AMVs) and implement log-normal wind
quality control for AMVs.
- Assimilate Geostationary Operational Environmental Satellite
system (GOES) clear-air water vapor winds.
- Assimilate additional global navigation satellite system (GNSS)
-Radio Occultation (RO) observations.
- Modify pressure and hybrid coordinates transformation during
the storm relocation.
- Change relocation of the vorticity and divergence fields to the
relocation of u,v wind components.
- Remove bogus Tropical Storm/Hurricane data for use in Data
- Assimilate Global Hawk dropsonde data when available.
- Upgrade data assimilation monitoring package.
3) Changes to the post-processing
- Upgrade post-processing software to use new nemsio model
- Implement continuity equation to derive omega on grid space for
new nems model output only.
- Modify interpolation procedure for all categorical fields
including land mask, icing severity and precipitation types
products to use nearest neighbor interpolation.
- Change interpolation method for In-Cloud Turbulence Potential
(CTP) and CB cover (Horizontal Extent of Cumulonimbus) from
'linear' to 'nearest neighbor' to avoid averaging their own
specific negative value with normal values when doing grid
- Users are advised to screen out and not use soil moisture
values above 0.468 (the maximum porosity among all soil types) in
GFS output files. Values above 0.468 are flag values associated
with permanent deep-layer land ice. The land surface model does
not predict soil moisture at land ice points.
4) Changes to output products on web services
With this upgrade the following changes occur on either the NCEP
Or on the NWS web services:
- The 2.5km resolution pressure GRIB output files will be
discontinued. NCEP has been providing the higher resolution
products in order to provide a smooth transition period, but will
no longer maintain the resources to continue creating these
products. The discontinued output will be:
NWS web: fh.0FFF_tl.press_gr.2p50deg
NCEP web: gfs.tHHz.pgrb2.2p50.fFFF
- The following BUFR dump and prepbufr files will be renamed as
described below. There is no change to the file content.
gdas1.tCCz.*tm00.bufr_d.unblok to gdas.tCCz.*.tm00.bufr_d
gdas1.tCCz.*tm00.bufr_d.unblok.nr to gdas.tCCz.*.tm00.bufr_d.nr
gfs.tCCz.prepbufr.unblok to gfs.tCCz.prepbufr
gfs.tCCz.prepbufr.unblok.nr to gfs.tCCz.prepbufr.nr
gdas1.tCCz.prepbufr.unblok to gdas.tCCz.prepbufr
gdas1.tCCz.prepbufr.unblok.nr to gdas.tCCz.prepbufr.nr
- On the NCEP web services, the EnKF surface analysis ensemble
mean file is being discontinued. This file is simply the average
of the 80 sfcanl_mem files. Thus, users may still obtain the
sfcanl_ensmean content on their own.
NCEP web: enkf.YYYYMMDD/sfcanl_YYYYMMDDCC_ensmean
- The following files will be removed from the NWS websites and
the exact same product will instead be available from the NCEP
websites listed above. Users are encouraged to migrate to the
NCEP sites as soon as possible as all of the products are
available currently. Please see below for removals and the
associated NCEP site product names:
NWS web removal: fh.0FFF_tl.sflux(.idx)
NCEP web replacement: gfs.tHHz.sfluxgrbfFFF.grib2(.idx)
NWS web removal: fh.0FFF_tl.press_gr.1p00deg(.idx)
NCEP web replacement: gfs.tHHz.pgrb2.1p00.fFFF(.idx)
NWS web removal: fh.0FFF_tl.press_gr.0p50deg(.idx)
NCEP web replacement: gfs.tHHz.pgrb2.0p50.fFFF(.idx)
NWS web removal: PT.sndn_DF.buf/fh.afhr_bs.STN_ID
NCEP web replacement: bufr.tHHz/bufr.STN_ID.YYYYMMDDHH
Where YYYY is year, MM is month, DD is day, HH is cycle, FFF is
forecast hour, and STN_ID is the 6 digit station ID
- On the NCEP websites the number of days of GFS and GDAS
datasets available will be reduced from 14 to 10.
- On the NWS web services, the GRIB1 211, 225, FOS 21-24, and
WAFS 37-44 grids will be removed from the NWS web service
Where HHHH is the forecast hour, parm is the forecast parameter,
and octantX is the WAFS grid letter.
Users can find GRIB2 replacement of the WAFS 37-44 grids
available in the in PT.grid_DF.gr2/fh.HHHH_tl.press_ar.octantX
- Visibility field will be added to the pressure grib files for
NCEP web: gfs.tHHz.pgrb2.DDD.fFFF
Where HH is cycle, FFF is forecast hour and DDD is for all 0.25
degree (0p25), 0.5 degree (0p50), and 1.0 degree (1p00) grib2
- On the NCEP web services, the following changes will occur to
the GFS Flux files:
A. Packing has been changed to complex packing to be consistent
with packing method of GFS pressure Grib files.
B. These files will be distributed at hourly time steps instead
of every 3 hours.
C. Remove category rain (CRAIN) parameter.
D. Correct GRIB2 IDs for soil temperature from "TMP...below
ground" to "TSOIL...below ground."
E. Correct GRIB2 IDs for total column cloud fraction from "entire
atmosphere (considered as a single layer)" to "entire
F. The time label for SUNSD will be changed to instantaneous to
be consistent with time label in GFS pressure GRIB files.
NCEP web file name: gfs.tHHz.sfluxgrbfFFF.grib2
- All GDAS output on the NCEP web servers will be renamed to
remove the "1", such that:
gdas.YYYYMMDD/gdas1.tCCz* will be renamed to
- On the NCEP servers, modify the BUFR list of stations from 1919
to 2021 and correct a few errors in the original station list.
Land/water designations were added for those stations that do not
have the designations. For the full list:
- On the NCEP servers, the station bufr files are now in
unblocked format and the file names are changing:
Where YYYY is year, MM is month, DD is day, HH is cycle, and
STN_ID is station identifier.
- Replace copygb2 by WGRIB2 in downstream pressure GRIB products
and change the Grid definition template (octets 43-46)
subdivision of basic angle used to define extreme longitude and
latitude, and direction increments from 0 to 255 (missing).
NWS web: fh.0FFF_tl.press_gr.DDDdeg
NCEP web: gfs.tHHz.pgrb2.DDD.fFFF
- A second land mask (LAND) is added to GFS and GDAS pressure
GRIB files for all resolutions. The second land mask is generated
using bi-linear interpolation.
NCEP web: gfs.tCCz.pgrb2.DDD.fFFF, gdas.tCCz.pgrb2.DDD.fFFF
- New GFS pressure GRIB files use a very large value of 9.99e+20
to represent the value for the variables that do not have
sensible values at any given grid point. For example, soil
temperature at a ocean grid point will have a value of 9.99e+20.
Users may have to modify their decoding programs to handle such a
large value. Files impacted:
NWS web: fh.0FFF_tl.press_gr.DDDdeg
- With the change in nemsio output the following link contains a
list of files on the NCEP web services for the GFS, GDAS and EnKF
that will be impacted. Users are highly encouraged to download
sample data and test:
- Nemsio binary atmospheric files are approximately 2x larger
than their sigio counterparts. Nemsio atmospheric files contain
data on the native model gaussian grid while sigio files project
grid space data into wavenumber (spectral) space. The nemsio
binary surface files are approximately the same size as their
sfcio counterparts and both representations contain data on the
native model Guassian grid.
- With the change in supercomputer architecture for both this
upgrade and the following one, there may be some minor (less than
5 minutes) changes in timing of the output files. NCEP will
always attempt to deliver products end to end within the expected
window, but users are encouraged to re-baseline the output times
once we move into operations.
- On the NCEP web site the following additions will be put into
A. The surface flux GRIB2 files will be added to grib_filter.
B. The GDAS pressure GRIB forecast hours will be added to
- GFS legacy fax chart TIF images will be discontinued on the NWS
web service here:
5) The following changes will be made to NOAAPORT/SBN
- Modify the lists of stations in the GFS BUFR sounding
collectives disseminated on NOAAPORT. For the full list please
reference this page:
- Replace copygb2 by WGRIB2 and correct the resolution and
component flag from 8 to 48. This change applies to the following
GRIB2 output on NOAAPORT:
20km CONUS grid; 20km Alaska grid; 20km Puerto Rico grid and Grid
213 (National - CONUS - Double Resolution Polar Stereographic
- In 2016 NCEP solicited feedback to remove all legacy GFS grids
in favor for high resolution 20km and 1.0 deg grids. With this
upgrade we will be removing the Alaska Region, North Polar
Stereographic - 47.5km (Grid Value #160). The full list of WMO
headers can be found here:
To reference the Public Information Statement (PNS) please click
- In 2014 NCEP solicited feedback to removal of legacy FAX
charts, and at that time we were unable to move forward. So with
this upgrade the following will no longer be available on
NOAAPORT or GTS:
Winds and temperatures at various flight levels and surface
analyses for various domains with WMO headers that match this
pattern are being removed:
See the PNS for more details here:
As part of NCEP's standard 30-day parallel testing, the parallel
products will be available here:
NCEP urges all users to ensure their decoders can handle changes
in content order, changes in the scaling factor component within
the product definition section (PDS) of the GRIB files, and
volume changes. These elements may change with future NCEP model
implementations. NCEP will make every attempt to alert users to
these changes before implementation.
Any questions, comments or requests regarding this implementation
should be directed to the contacts below. We will review any
feedback and decide whether to proceed.
For questions regarding these changes, please contact:
NCEP/EMC Modeling and Data Assimilation Branch
College Park, MD
For questions regarding the data flow aspects, please contact:
NCEP/NCO Dataflow Team Lead
College Park, MD
NWS Service Change Notices are online at: