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Re: 19990302: AVN Thin Grids

> 
> >From: Brett Newkirk <address@hidden>
> >Organization: .
> >Keywords: 199903022256.PAA28160
> 
> >Hi-
> >     I have a concern about the AVN Thin grids which we receieve from
> >our ldm. Since about Feb 19, some of these grids have incorrect times
> >stored in the GEMPAK headers. For example, todays case (99030212); if I
> >want to plot using GDPLOT the surface pressure and use GDATTIM=first, it
> >worked fine. However, if I use GDATTIM=f00, I get the error message that
> >990302/1232F000 is an invalid time. The 1232 appeared in today's 12Z run
> >instead of 1200. I have a series of programs that use GD_RDAT to read
> >various grids and noticed that this was the time being read into the
> >variable GDATTM(1) and consequently, GD_RDAT will not work. If you could
> >please look into this problem with your copy of the AVN Thin grids it
> >would be greatly appreciated.
> >     Here at the University of Washington, we use dcgrib to decode the
> >data and perhaps there is a problem with the grib file?
> >Thank you for your help --
> >Sincerely,
> >Brett Newkirk
>
> Brett,
> 
> I don't find any grids such as you mention above.
> I posted our raw grib files for avn thin files at:
> ftp.unidata.ucar.edu under /pub/chiz/
> 
> Can you try decoding the data in those files locally and
> see if the same problem occurs?
> 
> If you don't have any problem with our files, then you probably
> need to check your pqact.conf file entry to make sure only one
> copy of dcgrib is writing out to the thin.gem files. Also
> send me your pqact.conf entry so I can see if the pattern
> we are using is more restrictive and filtering out bad grids.
>
> NCEP has been doing alot of Y2K mods on the AVN, but I can't say I
> see any effects here at this time.
> 
> Steve Chiswell

Steve,

I ran our pqact.conf entry of dcgrib on the grib files you provided
and they worked fine.  I also re-ran dcgrib on our avn-x grib file and
got the corrupted time again.  

 GEMPAK-GDPLOT>gdattim=all
 GEMPAK-GDPLOT>r

 PARAMETERS FOR GDPLOT: 

 Grid file: 99030212_ourthin.gem                                                
    
 TIMES:    990302/1200F000                     
           990302/1200F006                     
           990302/1200F012                     
           990302/1200F018                     
           990302/1200F024                     
           990302/1200F030                     
           990302/1200F036                     
           990302/1200F042                     
           990302/1200F048                     
           990302/1200F060                     
           990302/1200F072                     
           990302/1232F024                     

Somehow we got corrupted grib data.  I am willing to bet that the
problem was on our end, since I heard Harry and David Warren talking
about recent troubles with grayskies including yesterday and a few
days ago.  Also, today's avn-x gempak files look fine.

Thanks for looking into this.

David
-- 

David Ovens             e-mail: address@hidden
(206) 685-8108
Dept of Atmospheric Sciences, Box 351640
University of Washington 
Seattle, WA  98195