[gembud] GEMPAK GRIB Bug?

[Arthur A. Person]

On Thu, 15 May 2008, Robert Mullenax wrote:

> Ditto.  I am sure there are many here that remember back to the 80's 
> like me or earlier where such cooperation would have never happened. 
> It is a credit to NWS/NCEP and Unidata that we have this great 
> cooperation.
>

Ditto Ditto. :)  The oversight could have just as easily been introduced 
at Unidata as NCEP.  Unidata makes a number of modifications to the NCEP 
package... it doesn't matter how it happened... it's great we can all work 
together to solve problems like this so quickly!

                                Art


> -----Original Message-----
> From: gembud-bounces at unidata.ucar.edu on behalf of David Knight
> Sent: Thu 5/15/2008 5:35 PM
> To: jhuddleston at hughes.net
> Cc: bshaw at wdtinc.com; support-gempak at unidata.ucar.edu; gembud at unidata.ucar.edu; Scott.Jacobs at noaa.gov
> Subject: Re: [gembud] GEMPAK GRIB Bug?
>
> That is not what I read. What I read is that NCEP fixed
> a bug that somehow did not get into the Unidata release.
> I do not see anybody trying to blame anybody else. I see
> two groups working cooperatively to fix a bug in
> the code. This is a GOOD thing. Thanks NCEP and Unidata.
> All code of this complexity has bugs - thanks Scott
> for tracking down where the bug was and making the fix
> available to all. And thanks Brent for pointing out
> and documenting the bug.
>
> David
>
>> 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
>>
>>
>>
>> Weather <http://www.wdtinc.com/>  Decision Technologies Inc.
>>
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>>
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>>
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>>
>>
>>
>>
>>
>>
>>
>>   _____
>>
>>
>>
>>
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Arthur A. Person
Research Assistant, System Administrator
Penn State Department of Meteorology
email:  person at meteo.psu.edu, phone:  814-863-1563