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Re: [gembud] problems with NAM 104/255 CONDUIT files

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  • Subject: Re: [gembud] problems with NAM 104/255 CONDUIT files
  • Date: Tue, 06 Nov 2007 15:01:18 -0700
David,

I produce the plot from the grib2 NAM 104 (using GAREA=USLCC)which
appears correct as shown here:
http://www.unidata.ucar.edu/staff/chiz/gifs/nam104_pmsl.gif

When zooming out to the GAREA=NAM, the data missing values (-100) appear
which result in your auto selected contour value probably having an
interval of 200
leading to the ring around the data area. That is, there are grid points
in the model grid
domain that have "-100" assigned to them, rather than "-9999.00" which
should occur if the data points are noted as missing value in the GRIB2
file (as if
the -9999.00 is still being scaled be 10**-2 before storage). I'll look
into
the missing value storage of dcgrib2 and nagrib2.

Steve Chiswell
Unidata User Support




On Tue, 2007-11-06 at 13:18 -0800, David Ovens wrote:
> CONDUIT users and Gembuds,
> 
> As you know, the CONDUIT data feed recently dropped the NAM 104 grids
> in GRIB1 format.  We are receiving the 90-km NAM grids in GRIB2 format
> under the following pqact entry:
> 
>  CONDUIT        /nam\.t(..)z\.grbgrd.*grib2
> 
> Most everything looks fine; however, when I convert these files to
> GEMPAK using dcgrib2 from 5.9.4, 5.10.3, or 5.10.4, the PMSL field is
> all fouled up.  The following URL shows what I get for a 'CINT=0' setting: 
>   http://www.atmos.washington.edu/~ovens/2007110600_badpmsl.gif
> 
> Here's how I decoded the file:
> 
>  $GEMEXE/dcgrib2 -d - 2007110600_nam104.gem < \
>  /home/disk/data/conduit/nam.20071106/nam.t00z.grbgrd00.tm00.grib2
> 
> I suspect this is a problem with the GRIB2 file (my first guess) or
> the way GEMPAK is decoding the sea-level pressure field.
> 
> Does anyone have a fix for this yet?
> 
> Thanks,
> 
> David
-- 
Steve Chiswell <address@hidden>
Unidata