[gembud] GEMPAK GRIB Bug?

[Brent L Shaw]

I originally found the problem in 5.10.2, but I have also tried 5.11.1 and observed the same issue.

Thanks to both NCEP and Unidata for looking into this!  I appreciate the effort of both organizations.

Best regards,
Brent

-----Original Message-----
From: Don Murray [mailto:dmurray at unidata.ucar.edu]
Sent: Friday, May 16, 2008 8:16 AM
To: jhuddleston at hughes.net
Cc: 'Scott Jacobs'; Brent L Shaw; gembud at unidata.ucar.edu; support-gempak at unidata.ucar.edu
Subject: Re: [gembud] GEMPAK GRIB Bug?

Unidata made one change and NCEP made a different one to the routine
to handle the constant grids.  There is no blame here - Scott showed
me the message before he sent it (I've been at NCEP all week) and
I approved what he said.  We will get the Unidata distribution fixed,
but might wait until the 5.11.3 release.

Brent, which version of GEMPAK were you using for your tests?
I didn't see that in your e-mail. (You can answer offline if you want).

Don


John Huddleston wrote:
> So basically NCEP made a mistake and is blaming it on Unidata.
>
>
>
>   _____
>
> From: gembud-bounces at unidata.ucar.edu
> [mailto:gembud-bounces at unidata.ucar.edu] On Behalf Of Scott Jacobs
> Sent: Thursday, May 15, 2008 1:26 PM
> To: Brent L Shaw
> Cc: gembud at unidata.ucar.edu; support-gempak at unidata.ucar.edu
> Subject: Re: [gembud] GEMPAK GRIB Bug?
>
>
>
> Brent, et al.,
>
> We fixed this problem with constant grids in 5.11.1. However, looking at the
> Unidata release of 5.11.1, there is a discrepancy with the function that we
> modified. We will work with the Unidata team to get this fixed in their copy
> of NAWIPS/GEMPAK so that it can be made available to the entire community.
>
> Scott Jacobs
> NCEP NAWIPS Development Team
>
>
> Brent L Shaw wrote:
>
> I have searched the GEMBUD and GEMPAK support lists and have not found this
> reported by anyone else, but it seems that NAWIPS/GEMPAK has an issue with
> GRIB records where the decoded values should be an entire grid of zeros (as
> sometimes happens with precipitation and hydrometeor fields in limited area
> mesoscale models).  I have found this problem using a Linux build of
> NAWIPS/GEMPAK that I have built from source using g77 and gcc.  I have found
> it to be a problem on both 32-bit Linux and 64-bit Linux (RedHat in both
> cases).  Here is a detailed description of what I did and observed:
>
>
>
> 1.    GRIB edition 1 files (created by the NCEP-developed WRF
> post-processor) are decoded with dcgrib2 as follows:  dcgrib2 myfile.gem <
> myfile.grb
> 2.    Rendered the total precipitation forecast from the resulting GEMPAK
> file and find a corrupted, noisy image that changes patterns each time I hit
> reload.  Additionally, the rendering generates the following error in the
> Error status window:
>
> [DG2] Too many maxs found -- increase radius or reduce range
>
> 3.    Ran the GEMPAK file through "gdlist" to see min/max values actually
> contained in the GEMPAK file.  It reports a combination of zeros, 10.0s,
> 20.0s, and 30.0s.
> 4.    Ran the original GRIB file through wgrib and IDV and verified the
> original GRIB field is encoded correctly and that all grid points actually
> are 0.
>
>
>
> The attached tar ball has the original GRIB record, the resulting GEMPAK
> file created from dcgrib2, and the sample NAWIPS image demonstrating the
> problem.
>
>
>
> Thanks for your help in advance!  Please let me know if you need anything
> else from me.
>
>
>
> Best regards,
>
>
>
> Brent
>
>
>
> Brent Shaw
>
> Senior Meteorologist and Project Manager
>
>
>
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>   _____
>
>
>
>
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--
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray at unidata.ucar.edu                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
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