NOUS41 KWBC 031408



Technical Implementation Notice 15-43

National Weather Service Headquarters Washington DC

1010 AM EDT Thu Sep 3 2015


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Timothy McClung

           Chief Operating Officer

           NWS Office of Science and Technology Integration


Subject:   Global Ensemble Forecast System (GEFS) Changes

           Effective October 13, 2015


On or about Tuesday, October 13, 2015, beginning with the 1200

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

Environmental Protection's (NCEP) Global Ensemble Forecast System

(GEFS) will be updated.


The upgrade in the GEFS production suite includes:


1. Running the latest Global Forecast System (GFS) model with

Semi-Lagrangian dynamic scheme and improved physics scheme, GSM

v12.1.0, to replace the currently used GFS v9.1.0.


2. Increasing the horizontal resolution from T254 (about 55km) to

TL574 (about 33km) for the first 192 hours (8 days) of model

integration, and from T190 (about 70km)to TL382 (about 55km)

between 192 hours and 384 hours of model integration.


3. Increasing vertical resolution from 42 levels to 64 levels for

0-384 hours (0-16 days) forecasts.


4. Modifying the ensemble initialization method by replacing the

Bred Vector with Ensemble Transform and Rescaling (BV-ETR) scheme

with Ensemble Kalman Filter (EnKF) scheme. The 6-hour forecasts

of the 80 EnKF ensemble members of the Hybrid Data Assimilation

system, from the previous cycle, are used to initialize the

ensemble perturbations.


5. Improving the Stochastic Total Tendency Perturbation (STTP)

scheme by (1) turning off perturbations in the surface pressure,

(2) increasing the perturbation amplitude of other model state

variables around the time of model truncation (192 hours), and

(3) adjusting its parameters to match the Semi-Lagrangian scheme,

the increased model resolution and improved model physics.


There will be several changes in the 1 degree GEFS product data

files (affects files with names pgrb2a/pgrb2b).  The GEFS

products disseminated over NOAAPORT will not change in format or

content.  The GEFS products disseminated via the NWS and NCEP

servers will have some changes in content.  A significant

increase in the GRIB product data volumes is expected due to

these changes.  These products are available at the following






NWS server:



Note that all YYYYMMDD strings represent the Year, Month, Day

value and CC is the model cycle.


Specific sub-directories and file names on these servers will be

given for each product change below.


Replacing GRIB Products


In order to make best use of resources, the 2.5 degree grids will

be replaced by the 0.5 degree grids.  The 1 degree grids will

continue to be available.


The 2.5 degree GRIB2 datasets on the NCEP FTP, NOMADS, and tgftp

servers, will not be available after this upgrade. Below are the

affected servers and directories:

D/CC/pgrb2alr and pgrb2blr

MMDD/CC/pgrb2alr and pgrb2blr






Note that HHHH is the forecast hour and ??? is the ensemble



The new 0.5 degree product files will be written to the new sub-

directories pgrb2ap5 and pgrb2bp5. The file names will be

ge???.tHHz.pgrb2a.0p50.anl, ge???.tHHz.pgrb2a.0p50.fhhh,

ge???.tHHz.pgrb2b.0p50.anl, and ge???.tHHz.pgrb2b.0p50.fhhh.


When these two (pgrb2ap5 and pgrb2bp5) sub-directories are

combined, these files will have the same content as the 1 degree

products but at higher frequency (every 3 hours) for the first

192 hours (8 days) of model integration. However, the division of

variables between the two sub-directories is different from that

between pgrb2a/pgrb2alr and pgrb2b/pgrb2blr. While most of the

variables are in the pgrb2bp5 files, the pgrb2ap5 files include

the following 43 variables:


HGT: 1000, 925, 850, 700 mb, surface (000h and 204h only)  (5)

TMP: 1000, 925, 850 mb and 2m above the surface  (4)

RH: 1000, 925, 850 mb and 2m above the surface   (4)

UGRD: 1000, 925, 850, 700, 500 400 300 mb and 10m above surface


VGRD: 1000, 925, 850, 700, 500 400 300 mb and 10m above surface


PRES: surface, mean sea level                    (2)

APCP, CSNOW, CICEP, CFRZR, CRAIN                 (5)

PWAT, TCDC, CAPE, CIN                            (4)

TMAX, TMIN                                       (2)

VVEL, 850 mb                                     (1)


Product Additions


In pgrb2b and pgrb2blr, 166 new variables will be added. A list

of these new products is available on line:


Product Removals


The following 3 variables in pgrb2b/pgrb2blr will be removed:

GPA: 500 mb, 1000 mb (anomaly)

5WAVA: 500 mb (HGT filtered, anomaly)


The following 4 variables will be moved from pgrb2b/pgrb2blr to


UGRD: 300, 400mb

VGRD: 300, 400mb


Product Changes


The four products of soil temperature (for 0-0.1, 0.1-0.4, 0.4-1,

1-2 m below ground) will be re-named TSOIL (currently TMP). The

corresponding Product Definition Section (PDS) for this parameter

will also change to accurately represent the product as TSOIL. 


GRIB2 Packing Changes


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,

including UGRD and VGRD wind components being packed into two

different records instead of one. Users are encouraged to test

with the parallel datasets and upgrade their software to handle

the encoding changes. Please see the links below for upgraded



Changes in the ensstat directory


The bias corrected 24-hour accumulated precipitation, in the file

enspost.t00z.prcp_24hbc.grib2, will be changed: Perturbed members

of ENS=+15, +16, +17, +18, +19, +20 will be added, resulting in

an increase of 6x31=186 records in the file. Meanwhile, the 16

records for the intervals from 180-204h to 15-16 day (360-384h)

from the hi-res control forecast will be removed to be consistent

with the original design.


New tropical cyclone track and genesis forecast products:


For the first time, tropical cyclone track forecasts and genesis

probability forecasts will be disseminated as text files in the

sub-directories tctrack and genesis, respectively.


tctrack: storm positions for individual perturbed members (ap01-

20), low resolution control member (ac00) and high resolution

control member (gfsx), and the ensemble mean (aemn) are available

in the following files:







genesis: probability for each potential storm XX in each Northern

Hemisphere Basin, HC, AL, EP, and WP, is presented in the

following files:


Similar tropical storm track and genesis forecasts, from

Environmental Canada Global Ensemble (CMC) and Fleet Numerical

Global Ensemble (FNMOC) systems, will also be available at the

following locations:





MMDD/xx/genesis or tctrack



MMDD/xx/genesis or tctrack



MMDD/xx/genesis or tctrack


The ensemble identifier in the tctrack file names for the

perturbed members, low and high resolution control, and the

ensemble mean for the cmce (CMC)directories are cp??, c00, cmc

and cemn, respectively. For the fens directory (FNMOC), they are

fp??, fc00, ngx and femn. The identifiers cemn and femn are also

used to name the corresponding genesis files.


Retrospective forecasts for the period of May 2013 to April 2015

(00Z only) were conducted using the GEFS upgrade package. The

data set is available at:



The retrospective data are the pgrb2a files at 1.0 degree



Certain components of the current GEFS production package will

continue to run for a limited time, with a name GEFS_LEGACY, so

that users can transition to the new GEFS. It will run the BV-ETR

based ensemble initialization cycling every 6 hours and provide

the 00Z cycle forecast. A limited set of output products will be

accessible at:


A consistent parallel feed of data from the new GEFS will become

available on the NCEP server once the model is running in

parallel on the NCEP Weather and Climate Operational

Supercomputing System (WCOSS) by late August. The parallel data

will be available via the following URL:


Test data are also available at:


Specific information regarding the scientific implementation can

be found at:


Disclaimer:  NCEP would encourage all users to ensure their

decoders are flexible and are able to adequately handle changes

in content order, parameter fields changing 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 implementation.


For questions regarding these changes, please contact:


    Dingchen Hou

    NCEP/EMC Global Modeling Branch

    College Park, Maryland

    Phone: 301-683-3707


For questions regarding the dataflow aspects of this dataset,

please contact:


    Justin Cooke

    NCEP/NCO Dataflow Team

    College Park, Maryland



National Technical Implementation Notices are online at: