NOUS41 KWBC 231555 CCA



Technical Implementation Notice 14-46 Corrected

National Weather Service Headquarters Washington DC

1055 AM EDT Tue Dec 23 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:   Corrected: Global Forecast Systems (GFS) Update:

           Effective January 14, 2015


Corrected to:


-Notify users that on February 3, 2015, beginning with the 12 UTC

run, the decimal precision within two fields will be fixed

-Specify which files will be available for downloading

-Remove a variable from forecast hour 00.


Effective on or about January 14, 2015, beginning with the 1200

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

Environmental Prediction (NCEP) will upgrade the GFS Analysis and

Forecast System as follows:


  - Changes to the model components

  - Increases in horizontal resolution

  - Addition of 0.25 degree gridded output

  - Addition of new product fields

  - Change to product naming convention

  - Changes in product timeliness

  - Changes to 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 hours

- 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


- Change from Eulerian dynamics to Semi-Lagrangian dynamics,

which uses Hermite interpolation in both vertical and

horizontal directions.

- 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 that 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


- 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 heating

- Re-tune 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


- 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

- Change the dump window for GOES Satellite Wind (satwnd)

data 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 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 obsolete or little used output

files. Please reference this html for explanations and possible

replacement products:


- The following files will be removed

















- Remove variables from GFS and GDAS pressure GRIB files


- Geopotential Height Anomaly (GPA)

- 5-Wave Geopotential Height Anomaly (5WAVA)

- Total Cloud Cover (TCDC) from forecast hour 00


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

availability to now only:

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

      gfs.YYYYMMDDCC/gfs.tCCz.sfFF hourly from 00-12, 3hly to 24


- 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 benefits for users will be 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 packing.


- With this upgrade output files are being written directly

to GRIB2 instead of first being written out to GRIB1 and

converted to GRIB2. Users may see some differences with the

encoding and are encouraged to upgrade their software to

handle this. Please see the links below for upgraded code:


- Modify 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 page:



- Use of the enhanced radiance bias correction scheme will

be changing 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.



- The clear sky UV radiation reaching the surface (CDUVB)

and the cloudy sky UV radiation reaching the surface (DUVB)

are being outputted as integer values. On Feb 3, 2015 with

the 12 UTC cycle these variables will be fixed to have real

values with 0.1 precision.


- Change variables averaged or accumulated over time, such

as precipitation accumulation, to 6 hourly up to forecast

hour 240 for all products (some had been 12 hourly after

forecast hour 180 and some had been 12 hourly after forecast

hour 192).


- 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 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"

- Move Snow Depth (SNOD) from the *pgrb2b* files into the

*pgrb2* files


New Products:


- Produce GRIB2 output at the highest resolution on 0.25

degree latitude-longitude grid 193 (1440x721)




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 headers.


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



NWS National Technical Implementation Notices are online at: