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[GEMPAK #ADX-952588]: dcgrib2 unable to decode GEFS grid

Hi,

re:
> Thank you.

No worries.

re:
> I had made some progress, actually with help from Russ Schumacher.
> 
> /home/gempak/GEMPAK7/os/linux64/bin/dcgrib2 -m 20000 -v 1 -d
> dcgrib2_gefs.log -e GEMTBL=/home/gempak/GEMPAK7/gempak/tables -e ENSEXT=0
> ./gefs_2020102000_gep01 < gefs_gep01_2020102000.grib2

Excellent!  An expert GEMPAK user is the appropriate person to ask!!  The
other resource to remember/take advantage of is the address@hidden
email list as subscribers to that list are, or have been, active GEMPAK
users.  I see that you are already subscribed to the 'gembud' list, so
you wouldn't have to do anything before posting.

re:
> Notice the ENSTEXT? Now I also have an input file that has all the forecast
> hours for one member, by just 'cat' all forcesthours to one

OK.  I have no familiarity with the ENSTEXT setting.  Did Russ explain it to
you?  If yes, can you share what he said so that it will be part of this 
inquiry?

re:
> grib file to run dcgrib on it.
> 
> 
> Now I have output that has something in it that could be right, but still
> this one error remains:
> 
> [29241] 201020/0937[DC 2]  Number of bulletins read and processed: 312
> [29241] 201020/0937[DC 6]  Shutting down.
> [29242] 201020/0937[DCINIT 3] Version 7.5.1
> [29242] 201020/0937[GB 1]  No GEMPAK parameter name defined for this grid.
> [29242] 201020/0937[DECODE_GRIB2 -34] Could not determine parameter name 10 2 
> 1 1 [0]
> [29242] 201020/0937[GB 1]  No GEMPAK parameter name defined for this grid.
> [29242] 201020/0937[DECODE_GRIB2 -34] Could not determine parameter name 10 2 
> 1 1 [0]
> [29242] 201020/0937[GB 1]  No GEMPAK parameter name defined for this grid.
> [29242] 201020/0937[DECODE_GRIB2 -34] Could not determine parameter name 10 2 
> 1 1 [0]
> [29242] 201020/0937[GB 1]  No GEMPAK parameter name defined for this grid.
> [29242] 201020/0937[DECODE_GRIB2 -34] Could not determine parameter name 10 2 
> 1 1 [0]
> [29242] 201020/0937[DCGRIB -9] End of Data
> 
> And the parameter is indeed not in the
> /home/gempak/NAWIPS/gempak/tables/grid/*g2v*crdwmo2.tbl table.
> 
> There is 10,2,1,0 and it is Ice Thickness.

Right.  I traced this down using NOAA's online GRIB2 tables:

https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/

  GRIB2 - Table 0.0
  https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table0-0.shtml

    Code Figure 10 - Oceanographic Products (see Table 4.1)
    
https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table4-1.shtml#10

      Category (octet 10) 2 - Ice (see Table 4.2-10-2)
      
https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table4-2-10-2.shtml

re:
> Maybe the missing parameter is not even important for what I need just to
> do a spaghetti plot of 500mb height.
> 
> If you could find what this one missing parameter is that would be great
> just for the sake of completness, and me learning.

I think that the line needed to be added to the GEMPAK NCEP GRIB2 table
(g2varsncep.tbl) is:

010 002 001 001 Ice Thickness                    m                    ICETK     
       0  -9999.00

This should be added in the section whose informational lines read:

!
! Category 2 - Ice
!D# CT# ID# PD# NAME                             UNITS                GNAM      
   SCALE   MISSING
!23|123|123|123|12345678901234567890123456789012|12345678901234567890|123456789012|12345|123456.89

With the the line addition above, the snippet in the copy of the table I am
looking at would read:

!
! Category 2 - Ice
!D# CT# ID# PD# NAME                             UNITS                GNAM      
   SCALE   MISSING
!23|123|123|123|12345678901234567890123456789012|12345678901234567890|123456789012|12345|123456.89
010 002 000 000 Ice Cover                        Proportion           ICEC      
       0  -9999.00
010 002 001 001 Ice Thickness                    m                    ICETK     
       0  -9999.00
010 002 006 000 Ice Growth Rate                  m s**-1              ICEG      
       0  -9999.00

re:
> How do you look those grib2 parameters up?

Working through the URLs above should give you a feeling for the procedure
needed to find definitions that are missing from the GEMPAK GRIB2 table(s).

Please note:

There are several 'g2vars...' tables in the GEMPAK distribution.  Here is
the set that is included with LDM distributions for NOAAPort ingest
purposes:

-rw-r--r--. 1 ldm Users  56505 Oct 21 09:57 g2varsncep.tbl
-rw-r--r--. 1 ldm Users  89920 Oct  9 15:56 g2varswmo.tbl
-rw-r--r--. 1 ldm Users  13061 Oct  9 15:56 g2varsnssl.tbl

Standard parameter definitions should be found in g2varswmo.tbl.  Parameters
that are defined at modeling centers will be found in a center-specific
table.  For instance, g2varsncep.tbl for NCEP defined parameters.

Also, format of the GEMPAK GRIB2 tables is fixed: fields are separated
by spaces (NOT tabs!) and value definitions MUST be in the correct
columns.  The easiest way to add a new entry is to copy an existing one
and modify the values in the copy making sure that the columnization
stays fixed.

What I would do is:

- make a copy of the GRIB2 table to be modified

  Just in case the edit has typos

- add the new entry making sure to preserve columinization

- run the 'dcgrib2' decoding invocation and see if the new
  entry is correctly being used

  If not, go back and correct the entry or add needed new ones,
  then retry the 'dcgrib2' invocation.

re:
> Thank you,

No worries.  Please let us know about your progress...

Cheers,

Tom
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Ticket Details
===================
Ticket ID: ADX-952588
Department: Support GEMPAK
Priority: Normal
Status: Closed
===================
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