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

• To: David Ovens <ovens@xxxxxxxxxxxxxxxxxxxx>
• Subject: Re: [gembud] problems with NAM 104/255 CONDUIT files
• From: Steve Chiswell <chiz@xxxxxxxxxxxxxxxx>
• 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 <chiz@xxxxxxxxxxxxxxxx>
Unidata

• References:
  • [gembud] problems with NAM 104/255 CONDUIT files
    • From: David Ovens