NOUS41 KWBC 101854



Technical Implementation Notice 14-46

National Weather Service Headquarters Washington DC

150 PM EST Mon Nov 10 2014


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Timothy McClung

           Chief, Science Plans Branch

           Office of Science and Technology


Subject:   Global Forecast Systems (GFS) Update: Effective

           December 17, 2014


Effective on or about December 17, 2014, beginning with the 1200

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

Environmental Prediction (NCEP) will upgrade the GFS Analysis and

Forecast System which includes:


  - Changing model components

  - Increasing horizontal resolution

  - Adding 0.25 degree gridded output

  - Adding new product fields

  - Changing product naming convention

  - Changing product timeliness

  - Generating downstream model impacts


1) Model changes to the GFS Global Spectral Model:


- Increase horizontal resolution of the first segment of the

forecast from Eulerian T574 (~27 km) to Semi-Lagrangian T1534

(~13 km), and extend the length of forecast from 192 hours to 240


- Increase horizontal resolution of the second segment of the

forecast from Eulerian T192 (~84 km) to semi-Lagrangian T574 (~35

km), and set forecast time from 240 hours to 384 hours  

- Change from Eulerian dynamics to Semi-Lagrangian dynamics,

which uses Hermite interpolation in both vertical and horizontal


- Use 5 minute daily Real-Time Global (RTG) Sea Surface

Temperature (SST) to replace 1.0 degree Reynolds 7 day SST


- Initialize ice at small inland lakes in the northern hemisphere

with 4 km Interactive Multi-sensor Snow and Ice Mapping System

(IMS) ice analysis data from the National Ice Center.  For large

water bodies, use 5 minute NCEP/MMAB ice analysis data to replace

30 minute ice data

- Use 1982-2012 5 minute SST climatology (replacing 1982-2001 1

degree SST climatology).

- Use 1982-2012 30 minute sea ice concentration climatology

(replacing 1982-2001 1 degree climatology).

- Replace update of model snow depth by direct insertion of AFWA

depth data with a blend of the model first guess depth and the

AFWA depth.

- Use X-number to prepare spectral transform base functions.

X-number is a numerical technique. It uses paired numbers to

represent real number to avoid computational underflow or

overflow that can occur in spectral truncation for wave number

larger than T1000.

- Use divergence damping in the stratosphere to reduce noise

- Add a tracer fixer for maintaining global column ozone mass

- Use the Monte-Carlo Independent Column Approximation (McICA)

for Rapid Radiative Transfer Model (RRTM) Radiation

- Reduce drag coefficient at high wind speeds

- Use Hybrid Eddy-Diffusivity Mass-Flux Planetary Boundary Layer

(EDMF PBL) scheme and Turbulent Kinetic Energy (TKE) dissipative


- Retune ice and water cloud conversion rates, orographic

gravity-wave forcing and mountain block; and reduce background

diffusion of momentum

- Add stationary convective gravity wave drag

- Modify initialization of forecast state variables to reduce a

sharp decrease in cloud water in the first model time step

- Correct a bug in the condensation calculation after the digital

filter is applied

- Replace 1.0 degree bucket soil moisture climatology with

CFS/Global Land Data Assimilation System (GLDAS) climatology at

T574 (~27 km)

- Replace 1.0 degree momentum roughness length climatology by

using a look-up table based on vegetation type

- Add a dependence of the ratio of the thermal and momentum

roughness on vegetation type


2) Model changes to the GDAS/GFS Hybrid 3D-VAR Ensemble Kalman

Filter (EnKF) Data Assimilation:

- Increase EnKF resolution from T254L64 to T574L64

- Assimilate hourly GOES and EUMETSAT atmospheric motion vectors

- Update radiance assimilation: 

- Assimilate SSM/IS UPP LAS and Metop-B IASI radiances

- Use enhanced radiance bias correction scheme

- Update to version 2.1.3 of the Community Radiative Transfer

Model (CRTM).  CRTM v2.1.3 improves specification of microwave

sea surface emissivities. This, in turn, improves the analysis of

near surface temperature over water, especially in the southern


- Use stochastic physics in EnKF ensemble forecasts

- The dump window for GOES Satellite Wind (satwnd) data will

change from 1 hour to 6 hours. Subtypes will be added for

(NOAA/METOP AVHRR SATWIND) infrared cloud motion vector and

(NESDIS/GOES 3.9 micron channel) derived cloud motion vector


3) Output product changes


All filenames given below are on the NCEP ftp server, the NCEP

http server, NOMADS or the NWS ftp server respectively via

the following URLs (YYYYMMDD is the year, month, and day; CC is

the cycle):


Product to be Removed:


With this upgrade NCEP is removing output files that are obsolete

and not widely used. Please reference the link below for

explanations and possible replacement products:


- The following files will be removed

















- The following variables from GFS and GDAS pressure GRIB files

(*pgrb*) will be removed:

  - Geopotential Height Anomaly (GPA)

  - 5-Wave Geopotential Height Anomaly (5WAVA)


Current Product Changes:


- The naming convention will change to include the grid and 

3 digit forecast hours:


On the NCEP server:

     GFS FH = "anl" or "f000-f384"

     GDAS FH = "anl" or "f000-f009"

      gfs.tCCz.pgrb2.fFFF -> gfs.tCCz.pgrb2.0p50.FH

      gfs.tCCz.pgrb2b.fFFF -> gfs.tCCz.pgrb2b.0p50.FH

      gfs.tCCz.pgrb.fFFF.grib2 -> gfs.tCCz.pgrb2.1p00.FH

      gfs.tCCz.pgrb2b.fFFF -> gfs.tCCz.pgrb2b.1p00.FH

      gfs.tCCz.pgrb.2p5deg.fFFF.grib2 -> gfs.tCCz.pgrb2.2p50.FH

      gfs.tCCz.pgrb.fFFF.grib2 -> gfs.tCCz.pgrb2.2p50.FH

      gfs.tCCz.goessimpgrb2fFFF.1p0deg ->  


      gfs.tCCz.goessimpgrb2fFFF.grd221 ->


      master/gfs.tCCz.mastergrb2fFFF ->


      gdas1.tCCz.pgrbfFF.grib2 -> gdas1.tCCz.pgrb2.1p00.FH


     On the NWS server:

     GFS FH = 000-384

      fh.0FH_tl.press_gr.0p5deg -> fh.0FH_tl.press_gr.0p50deg

      fh.0FH_tl.press_gr.1p0deg -> fh.0FH_tl.press_gr.1p00deg

      fh.0FH_tl.press_gr.2p5deg -> fh.0FH_tl.press_gr.2p50deg


- The following files will have decreased forecast hour


      gfs.YYYYMMDDCC/gfs.tCCz.bfFF hourly output from 00-12

      gfs.YYYYMMDDCC/gfs.tCCz.sfFF hourly output from 00-12


- There are numerous changes to the operational NOMADS files. For

all of the details please reference this page:


- The packing for GRIB2 will be switched to second order complex

packing. The changes will result in much faster IO time compared

with the existing JPEG packing. The second order packing provides

good accuracy, although files will be slightly larger than JPEG



- The changes involve modifying the list of stations for which

BUFR data is generated for the GFS.  The changes will also modify

the lists of stations in the GFS BUFR sounding collectives

disseminated on NOAAPORT. For the full list please reference this



- Use of the enhanced radiance bias correction scheme will change

the abias file. The format of the file is being changed to

incorporate information from the satang file.



- The GFS cyclone tracker file code has changed from "NA" to "AA"

for storms in the Arabian Sea.



- Change variables averaged or accumulated over time, such as

precipitation accumulation, will go from 12 hourly to 6 hourly

between forecast hours 180 to 240.


- Modify fields to both GFS and GDAS:

  - Add Frozen Precipitation Fraction (CPOFP)

  - Add Ozone (O3MR) at 150, 200, 250, 300, 350, and 400 mb

  - Add Dew Point (DPT) at 2 meters

  - Add Apparent Temperature (APTMP)

  - Add instantaneous precipitation type (CICEP, CFRZR, CRAIN,


  - Add Membrane SLP in GDAS pressure grib files

  - Rename TMP at 0-0.1 m, 0.1-0.4 m, 0.4-1.0 m, and 1-2 m to the

more accurate name of Soil Temperature (TSOIL)

  - Modify the precision of Relative Humidity (RH) grids

  - Modify GRIB encoding level of Total Cloud Cover (TCDC),

removing "considered as a single layer"

  - Modify GRIB encoding level of Precipitable Water (PWAT)

removing "considered as a single layer"


New Products:


- Produce GRIB2 output at the highest resolution on 0.25 degree

latitude-longitude grid 193 (1440x721)

      gfs.YYYYMMDDCC/ gfs.tCCz.pgrb2.0p25.FH



Product Timeliness:


GFS product delivery timing on NOMADS, the ftp server and

NOAAPORT will be delayed for numerous products. Pressure GRIB

(*pgrb*) files will be as much as 20 minutes delayed. Please

reference this page for a full list of delays:


NOAAPORT/SBN product changes:


- Additional forecast hours 186, 198, 210, 222, and 234 will be

added for the following GRIB2 grids only. There are no new

headers to add as these grids use existing headers:

201 - 381km Northern Hemisphere

212 - 40km CONUS

213 - 95km CONUS

160 - 47.5km Alaska

161 - 0.5 degree lat/lon for Puerto Rico

254 - 40km Pacific Region


- Variables averaged or accumulated over time, such as

precipitation, will now be valid over a 6 hour period for

forecast hours 180 through 240, rather than a 12 hour period.

There are no new headers to add as these new grids use existing



4) Downstream model impacts


There are impacts to downstream GFS models and their product

output. Please reference this page for more information on the



- GFS-based Model Output Statistics (MOS) products

- Global Ensemble Forecast System variable change

- Numerous downstream model output timeliness changes. These

changes impact both NOAAPORT/SBN and the NCEP/NWS servers.


5) Parallel data available


Due to system constraints the parallel GFS will run on the backup

supercomputer. This will cause impact to output availability on

at least 3 days due to mandatory maintenance. We will notify

users when a cycle will not be available through this user list:


Starting in late October all parallel data sets will be available

on the following servers:


NCEP has a full list of products that will be available for

download from both the NCEP and NWS servers as well as NOMADS.

You can find the file names and their inventory through the

following http page:


For more information on this GFS upgrade, please see EMC real-

time and retrospective parallels and verification pages:


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.


For questions regarding these changes, please contact:


     Mark Iredell

     NCEP/Global Climate and Weather Modeling Branch

     College Park, MD



For questions regarding the data flow aspects of these data sets,

please contact:


     Carissa Klemmer

     NCEP/NCO Dataflow Team

     College Park, MD



National Technical Implementation Notices are online at: