[GEMPAK #HAT-279589]: Decoding GRIB to GEMPAK

Quang,

Your error message:
"The table grib3.tbl cannot be opened"
Means that it did not find the center #136 entry in $GEMTBL/grid/cntrgrib1.tbl
(such as the line I had shown to define VNC as the center), so that it would
compose the local table string vncgrib3.tbl (eg, the string name is empy at the 
moment).

However, since your parameter for wind speed and direction are defined in the 
wmo parameter range,
you are able to decode and create the gempak grid file.

You should have SPED and DRCT grids on vertical coordinate NONE and glevel 0
as I see from your output log. You can verify this using the GDINFO program
to list out the contents of your grid file:
http://www.unidata.ucar.edu/software/gempak/tutorial/gdinfo.html

You can add this to the data sets to plot in NMAP2 as described at the bottom 
of the web page:
http://www.unidata.ucar.edu/software/gempak/tutorial/importingdata_gui.html

Assuming you name your files such as (I'll use $MODEL here, but you can place 
them elsewhere as you wish)
$MODEL/qsct/YYYYMMDDHH_qsct.gem,

1) Create a data alias in $GEMTBL/config/datatype.tbl for your gridded qsct 
data such as:

GRIDQSCT        $MODEL/qsct      YYYYMMDDHH_qsct.gem       CAT_GRD  SCAT_ANL   
10   2880   60   OFF/0/0      4

(in the above, maintain the correct column spacing such as the entr for SFCA).

The SCAT_ANL means that these grids are analysis grids, rather than forecast 
grids so that
you would most likely want to look through all the "F000" times, rather than 
all the Ffff times for a single 
initial time.

2) Create a $NMAP_RESTORE directory entry for the plot you want.
This will be the file you will reference with the entry in 
$GEMTBL/nmap/mod_res.tbl!

Since your file is SPED and DRCT (instead of UREL and VREL), you can compose 
the north relative 
components with:
UN = mul(mul(sped,-1),sin(mul(drct,DTR)))
VN = mul(mul(sped,-1),cos(mul(drct,DTR)))

The Vectors can be plotted in GDPLOT2 and NMAP from a 
$NMAP_RESTORE/misc/qsct_winds
restore file. Use one of the other files as a template. I suggest not having
a GDFILE line in your restore file as NMAP2 will set that for you. The vector 
plot
can use the parameters:
TYPE = b
GDPFUN = 
VECN(mul(mul(sped,-1),sin(mul(drct,DTR))),mul(mul(sped,-1),cos(mul(drct,DTR))))

Your mod_res.tbl line could look something like:
QSCAT_WINDS    $NMAP_RESTORE/misc/qsct_winds    QSCT   gridqsct

The 4th field on the line above (eg gridqsct) tells nmap to use the file alias 
of gridqsct
from the datatype.tbl file to find the available data files. 

Once you have created these lines, restart nmap2 to load these new table 
entries.

The above sounds complicated, but most can be copied from another entry or 
restore
file that is similar.

Steve Chiswell
Unidata User Support





> Dear Dr. Steve,
> 
> >
> > You may have a problem with your model center 100
> > not being defined in the GEMPAK grid files.
> > Your parameter listed below is #32, which is in the
> > WMO defined range, so the decoder knows
> > what to call that parameter, but we should add a
> > center number to
> > $GEMTBL/grid/cntrgrib1.tbl
> > for the identifier you are using below.
> >
> > Looking at:
> >
> http://www.nco.ncep.noaa.gov/pmb/docs/on388/table0.html
> > I see center 100 is Brazzaville. I would have
> > expected you to be using number 136,
> > but in either case, add a line such as:
> > 100 Brazzaville, Republic of Congo
> >                 BRAZ
> > 136 Socialist Republic of Viet Nam (NMC)
> >                 VNC
> >
> 
> This problem has been done well. You could see in the
> log file which is attached one.
> 
> > Your table version for that grid is version 3, so
> > create a file (for BRAZ center 100)
> > $GEMTBL/grid/brazgrib3.tbl, or (136 VNC)
> > $GEMTBL/grid/vncgrib3.tbl:
> > Use the single "255 missing" line such as in
> > $GEMTBL/grid/fnocgrib2.tbl.
> 
> Resolved too.
> 
> >
> > For GRIB decoding, parameters with numbers less than
> > 128 are defined in the WMO
> > tables $GEMTBL/grid/wmogrib#.tbl (where # is the
> > table version number).
> > For parameters 128-255, the model center defines its
> > own locat parameters, and the
> > cntrgrib1.tbl file will be used to determine the
> > string to use for the model center
> > as specified by the number in the GRIB PDS block, eg
> > brazgrib#.tbl for center 100.
> >
> > At startup of dcgrib2, you should see log messages
> > for opening 4 tables:
> > cntrgrib1.tbl, the wmo and center specific tables,
> > and the vertical coordinate table
> > $GEMTBL/grid/vcrdgrib1.tbl. Verify that all are
> > being found.
> >
> > You should be able to decode your grid with:
> >
> > cat gribfile | dcgrib2 -d - output_file.gem
> >
> > If that is what you are doing, try adding verbose
> > logging such as:
> > cat gribfile | dcgrib2 -v 4 -d - output_file.gem
> >
> > and/or send me a sample of the grib message if you
> > still have problems.
> 
> It says that "The table grib3.tbl cannot be opened".
> However the *gem file has been created.
> 
> In fact, we would like to display this *gem file in
> NAWIPS operational system. Actually, this style of
> *gem file is *daily* quickscat data that I've changed
> from another source. How can I display this *gem files
> in NAWIPS? Now we can treat this gem files as a model
> grid and we'd like to rename this gem files as
> YYYYMMDDHH_qsct.gem. How to do this, step by step?
> 
> Anyway, You could check an example grib file. This
> contains wind speed only.
> I look forward to hearing from you soon.
> 
> Nguyen Dang Quang
> Dept. of Research and Application
> Vietnam National Center for Hydrometeorological Forecast
> 4 Dang Thai Than, Hanoi, VIETNAM
> Tel.:84-4-9330942
> 
> __________________________________________________
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> 


Ticket Details
===================
Ticket ID: HAT-279589
Department: Support GEMPAK
Priority: Low
Status: Closed