Greetings,

The purpose of this message is to announce the routine availability of parallel data at the NWS ftp server and to describe some changes to data locations described in the earlier message on this subject.

Public data availability -
NCEP Central Operations is now making output from the parallel global ensemble processing available on the NWS FTP server located at:
tgftp.nws.noaa.gov/SL.us008001/ST.opnt/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/
These data are in the same format that will be implemented on May 30, 2006 for the 12 UTC model cycle.  Users of NCEP global ensemble products should use these parallel data sets to modify their transfer routines to use these data.  These data will be continually updated at this location up to the implementation date.  After the May 30, 2006 implementation date the global ensemble data will only be available at:
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/

MAJOR PRODUCT CHANGES TO NCEP GLOBAL ENSEMBLE OUTPUT -- PLEASE READ CAREFULLY

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 (ftpprd.ncep.noaa.gov/pub/data/) and the NWS ftp server (tgftp.nws.noaa.gov/SL.us008001/ST.opnl/).  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 -
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.
On the NWS ftp server (tgftp.nws.noaa.gov) the directories will change as follows:

Current - tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/

New - tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/
        - tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.low/

where CC = 00 or 12 and YYYYMMDD is the current date.  The exact location of the parameters you may need is given in item 3 below.

2.  Six hourly output -
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) -
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 5 below) at one degree resolution out to 180 hours and 2.5 degree resolution from 186 to 384 hours.  These are being termed the A files and this is an increase in their resolution for the 90 to 180 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 NWS ftp server, the files will change as follows:

Current - tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.0024_pa.membrp01_tl.press_gr.onedeg and
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.0384_pa.membrp01_tl.press_gr.2p5deg

- For the "A" files:       

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.0024_pa.membrp01_tl.press_gr.onedeg and
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.0024_pa.membrp01_tl.press_gr.2p5deg

- For the "B" files:

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.low/fh.0024_pa.membrp01_tl.press_gr.onedeg and
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.low/fh.0384_pa.membrp01_tl.press_gr.2p5deg

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:

http://www.nco.ncep.noaa.gov/pmb/changes/gefs_20060530_Alist   and
http://www.nco.ncep.noaa.gov/pmb/changes/gefs_20060530_Blist

4.  File Names Changing due to new ensemble transform mechanism -
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 http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/ENS_IMP.html]  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 NWS ftp server the names will change as follows: 

Current - tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.0024_pa.membrn01_tl.press_gr.onedeg

New - For the "A" files:       

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.0024_pa.membrp01_tl.press_gr.onedeg

          - For the "B" files

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{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.membrp01.* to fh.{FFFF}_pa.membrp{NN}.*, where NN is the number of ensemble members.  The control run for all cycles will be named as fh.{FFFF}_pa.memberc00.*.

5.    Removal of enspost Data Files -

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) 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 NWS ftp server at:

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.{FFFF}_pa.membr{NNN}_tl.press_gr.onedeg

(where NNN is the member name, c00, p01-p10) and on the NWS ftp server at:

Even though these new "A" grids contain the same information as the enspost (fh.xxxx.* files at NWS ftp) 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.

6.  Corrected ensemble extensions in GRIB1 PDS -
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:

http://www.nco.ncep.noaa.gov/pmb/docs/on388/appendixc.html

7.  Removal of all GRIB index files -
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 on the NWS ftp server:

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{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:

http://www.nco.ncep.noaa.gov/pmb/codes/nwprod/util/sorc/grbindex.fd/

8.  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:

tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.high/fh.{FFFF}_pa.membrc00_tl.press_gr.2p5deg and
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ensg_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1_RE.low/fh.{FFFF}_pa.membrc00_tl.press_gr.2p5deg and

9.  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. 

Information on how these changes affect data on the NCEP ftp server can be found at:

http://www.nco.ncep.noaa.gov/pmb/changes/


Please direct any questions on these changes to:

NCEP.List.PMB-PCSP@noaa.gov

Sincerely,

NCEP Central Operations.



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