NOUS41 KWBC 091918



Service Change Notice 17-67

National Weather Service Headquarters Silver Spring MD

318 PM EDT Fri Jun 9 2017


To:       Subscribers:

          ­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

relocation components

  - Changes to the post-processing

  - Changes to output products


1) Changes to the Global Forecast System Global Spectral Model

(GSM) components:


- Implement GSM source code in NOAA Environmental Modeling System

(NEMS) framework.

- 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 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

binary files.

- 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

(DBNet) capability.

- 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

web services:

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.* to gdas.tCCz.*

gdas1.tCCz.sfcshp.tm00.bufr_d.unblok to

gfs.tCCz.prepbufr.unblok to gfs.tCCz.prepbufr to

gdas1.tCCz.prepbufr.unblok to gdas.tCCz.prepbufr to


- 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

all resolutions

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:

bufr.tHHz/bufr3.STN_ID.YYYYMMDDHH to


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

NCEP web:gfs.tHHz.pgrb2.DDD.fFFF


- 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


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:


Vijay Tallapragada

NCEP/EMC Modeling and Data Assimilation Branch

College Park, MD



For questions regarding the data flow aspects, please contact:


Carissa Klemmer

NCEP/NCO Dataflow Team Lead

College Park, MD



NWS Service Change Notices are online at: