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Starting with the 12 UTC cycle on 30 May 2006 NCEP Central Operations will implement changes to the global ensemble processing that will result in drastic changes to its products.  These changes are necessary to allow us to:

  1. Streamline our ensemble processing
  2. Provide additional ensemble members at higher resolutions on public servers
  3. Eliminate redundant global ensemble products on these servers.

These changes will impact products available on both the NCEP ftp server ( and the NWS ftp server (  Users of these products will need to modify their automated retrieval and processing routines so that they can continue to receive and use these data.

The nature of these changes are as follows:

  1. Directory Structure - [Affects both the NCEP and NWS ftp servers]

    The directory tree of global ensemble data will be drastically changed to allow for better system performance on the NCEP Central Computer System (CCS).  This change is being brought to the NCEP and NWS ftp servers as it will help with both access times and directory listings.

    1A. On the NCEP ftp server the directories will change as follows:

    Current -{YYYYMMDD}


    where YYYYMMDD is the current date, CC is the cycle time (00, 06, 12, or 18), and FILE_TYPE is a descriptor for the type of data files contained in the subdirectory.  Examples of FILE_TYPE that will be on the NCEP ftp server include: pgrba, pgrbb, ensstat, and wafs.

    Users who use the standard pressure GRIB files (ens*.pgrbf*) files on the NCEP ftp server will be able to access these data from one of the following locations:{YYYYMMDD}/{CC}/pgrba/  or{YYYYMMDD}/{CC}/pgrbb/

    The exact location of the parameters you may need is given in item 3 below.

    Users of the ensemble data on WAFS grids will be able to access these at:{YYYYMMDD}/{CC}/wafs/

    1B.  On the NWS ftp server ( the directories will change as follows:

    Current -{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/

    New -{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/

    The exact location of the parameters you may need is given in item 3 below.

  2. Six hourly output - [Affects both the NCEP and NWS ftp servers]

    The global ensemble data sets will begin to be available in 6-hour increments out through 384 hours.  Currently 6-hour increment data are only available to 84 hours, then data are available in 12-hour increments to 384 hours.

  3. Break Up of Pressure GRIB data sets (pgrb files) - [Affects both the NCEP and NWS ftp servers]

    To facilitate the removal of redundant data sets the individual member ensemble files are being broken up into two files per time step.  The first file will contain all of the parameters currently contained in the enspost format files (see Item 6 below) at one degree resolution out to 384 hours.  These are being termed the A files and this is an increase in their resolution for the 90 to 384 hour time period.  The second set (the B files) will contain the rest of the parameters at one degree resolution to 84 hours and 2.5 degree resolution from 90 to 384 hours.  This is the same resolution that these parameters are currently made available.

    On the NCEP ftp server, files will change as follows:

    Current -{YYYYMMDD}/ensp1.t{CC}z.pgrbf24

    New -{YYYYMMDD}/{CC}/pgrba/gep01.t{CC}z.pgrbaf24   and
             -{YYYYMMDD}/{CC}/pgrbb /gep01.t{CC}z.pgrbbf24

    On the NWS ftp server, the files will change as follows:

    Current -{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.0024_pa.membrp01_tl.press_gr.onedeg

    New - For the "A" files:{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high /fh.0024_pa.membrp01_tl.press_gr.onedeg

              - For the "B" files:{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.low/fh.0024_pa.membrp01_tl.press_gr.onedeg

    This change will allow for a subset of higher resolution (one degree) data to be available out to 180 hours, whereas today it is only available to 84 hours.  Parameter lists for the "A" and "B" files are located at:   and

  4. File Names Changing due to new ensemble transform mechanism - [Affects both the NCEP and NWS ftp servers]

    When this change is implemented, NCEP will be creating perturbations in its ensemble members via a ensemble transform breeding method.  [For specific information about this change, please see]  Under this method, there will no longer be positive and negative pairs of ensemble members.  NCEP will therefore cease identifying its members as either positive or negative and instead use positive numbers for member identification.  For example, on the NCEP ftp server:

    Current -{YYYYMMDD}/ensn1.t{CC}z.pgrbf24

    New -{YYYYMMDD}/{CC}/pgrba/gep01.t{CC}z.pgrbaf24   and/or

    The names of these files will range from gep01 to gep{NN}, where NN is the number of ensemble members.  A low resolution control run will be added for all cycles and will be named as gec00.t{CC}z.*.

    On the NWS ftp server, the names will change as follows: 

    Current -{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.0024_pa.membrn01_tl.press_gr.onedeg

    New - For the "A" files:   {CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.0024_pa.membrp01_tl.press_gr.onedeg

              - For the "B" files{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.low/fh.0024_pa.membrp01_tl.press_gr.onedeg

    The names of these new files will range from fh.{FFFF}_pa.memberp01.* to fh.{FFFF}_pa.memberp{NN}.*, where NN is the number of ensemble members.  The control run for all cycles will be named as fh.{FFFF}_pa.memberc00.*.

  5. Renaming and restructuring Ensemble mean files (enstat.*) - [Affects NCEP ftp server only]

    The ensstat.* files on the NCEP ftp server will no longer be available.  These grids contain ensemble mean and spread information for a single parameter for all ensemble members and all forecast hours.  They will instead be replaced by files that contain multiple parameters for a single ensemble member and a single forecast hour.  With this configuration the creation of these data will be made while the ensemble members are running on the NCEP CCS.  Currently these are not available until the end of the ensemble run which creates a large amount of data to download at once.

    The current data sets are named as follows:{YYYYMMDD}/ensstat.t{CC}z.{Parameter-name}

    The new data sets will be named as follows:{YYYYMMDD}/{CC}/pgrba/geavg.t{CC}z.pgrbaf{FFF}  and{YYYYMMDD}/{CC}/pgrba/gespr.t{CC}z.pgrbaf{FFF}

  6. Removal of enspost, and ensemble Data Files - [Affects both the NCEP and NWS ftp servers]

    To reduce product redundancy and to allow for the additional data sets outlined in items number 2 and 3 above, the enspost.* (fh.xxxx.* files at NWS ftp) and ensemble.* data sets will no longer be produced.  These data sets contain redundant information that is already available in the pressure GRIB data sets.  They are being removed and users should instead use the "A" files located on the NCEP ftp server at:{YYYYMMDD}/{CC}/pgrba/ge{NNN}.t{CC}z.pgrbaf{FFF}

    (where NNN is the member name, c00, p01-p10) and on the NWS ftp server at:{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.{FFFF}_pa.membr{NNN}_tl.press_gr.onedeg

    Even though these new "A" grids contain the same information as the enspost.* (fh.xxxx.* files at NWS ftp) and ensemble.* data sets, they are organized differently.  The existing files are created at the end of the ensemble processing and each file contains information for a single parameter for all ensemble members and all forecast hours.  The new "A" files will be made available throughout the production time of the ensemble processing on the NCEP CCS and they will each contain multiple parameters for a single ensemble member and a single forecast hour.

    There is one exception to this change.  The 24-hour bias corrected ensemble products created at 00 UTC and available only the NCEP ftp server, will continue to be made available in the following new location:{YYYYMMDD}/{CC}/ensstat/ensstat.pqpf_24h and ensstat.pqpf_24hbc

  7. Corrected ensemble extensions in GRIB1 PDS - [Affects both the NCEP and NWS ftp servers]

    The current global ensemble data sets do not properly use the extended Product Definition Section (PDS) of GRIB1.  When this change is implemented the GRIB1 data will be correctly labeled as ensemble data sets.  This information is given in PDS octets 41 and higher.  A description of NCEP's use of these octets is given at:

  8. Removal of all GRIB index files - [Affects both the NCEP and NWS ftp servers]

    The GRIB index files are no longer required by NCEP production and are being removed from the ftp servers.  These files are currently named as follows:

    NCEP -{YYYYMMDD}/ens{NN}.t{CC}z.pgrbif24

    NWS -{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.{FFFF}i_pa.membr{NNN}_tl.press_gr.{XXX}deg

    If users still need GRIB index files, they can be created with NCEP software located at:

  9. Removal of the 12 UTC "e2" Member -- Addition of Low Resolution Control Run for all Four Cycles

    With this implementation all four cycles per day will have a low resolution control run.  The need for the "e2" member at 12 UTC will go away at that time.  The NCEP CCS resources that were used to run the "e2" member will be used for the low resolution control member.  The low resolution control member data will be found at:{YYYYMMDD}/{CC}/pgrba/gec00.t{CC}z.pgrbaf{FFF}  and{YYYYMMDD}/{CC}/pgrbb/gec00.t{CC}z.pgrbbf{FFF}

  10. 6-hour Accumulations for Precipitation and Maximum and Minimum Temperature

    In the current global ensemble system accumulation variables alternate between 6-hour and 12-hour amounts depending upon the forecast hour.  With this upgrade all accumulation amounts will be based on a 6-hour period. 


    At this time we are not able to provide parallel global ensemble data sets for user to compare the old versus new.  We are however able to provide a static data set.  These data can be viewed at:

    note that these static data are located under /pub/data1 not /pub/data.

    It is anticipated that we will be able to establish a real time feed of the parallel data sets by the end of March 2006.  Once this parallel feed of the new ensemble data sets is available, a new message will be sent out via this mechanism.

    Please direct any questions on these changes to:


    NCEP Central Operations.

Page last modified: 18 June 2024.