[gradsusr] Plotting GFS_HD apcpsfc every 3 hours problems

[Jeff Chabot]

Hello Wesley,

Thanks for your explanation of the 3 hour versus 6 hour accumulation problem
with gfs_hd.

I tried your workaround, but it failed pretty quickly for me.  I have never
used wgrib or wgrib2 and I searched on the internet for some documentation,
but I couldn't find much.

This is where if failed for me:

>sh
>[ -f IN.grb ] && rm IN.grb
>for f in (list of file from f03 to fNN)
sh: syntax error near unexpected token `('

Also, I believe that you would need to open the data file first, but I
couldn't get that to work either:

>wgrib
http://nomads.ncep.noaa.gov:9090/dods/gfs_hd/gfs_hd20101202/gfs_hd_00z
could not open file:
http://nomads.ncep.noaa.gov:9090/dods/gfs_hd/gfs_hd20101202/gfs_hd_00z

So, I am not sure how to use this workaround.  Any further help would be
greatly appreciated.

Sincerely,


Jeff



Message: 4
> Date: Wed, 01 Dec 2010 09:21:02 -0500
> From: Wesley Ebisuzaki <Wesley.Ebisuzaki at noaa.gov>
> Subject: Re: [gradsusr] Plotting GFS_HD apcpsfc every 3 hours problems
> To: GrADS Users Forum <gradsusr at gradsusr.org>
> Message-ID: <4CF659CE.3050106 at noaa.gov>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Jeff,
>
>   The "Joys of Compatibility" strikes again (old code expects 6 hour
> accumulations).
> Anyways there is a function in wgrib2 to make all the accumulations into
> 3 hour chunks.
>
> 1) put all the APCP records into one file (IN.grb) in order (f03 to
> fNN).  Here is how to do it in sh.
>
>     [ -f IN.grb ] && rm IN.grb
>     for f in (list of file from f03 to fNN)
>     do
>        wgrib2 f -match ":APCP:" -append -grib IN.grb
>     done
>
>    IN.grb should contain the APCP from one forecast run starting from 3
> hour forecast to N hour forecast.
>
> 2) Run wgrib2 to normalize the records.
>
>    wgrib2 IN.grb -match ":APCP:" -set_grib_type c1 -ncep_norm precip.grb
>
>            Wesley Ebisuzaki
>
>
> Jeff Chabot wrote:
> > Hello GrADS Users,
> >
> > I am looking for help plotting 3 hr precip using gfs_hd (from
> > nomads.ncep.noaa.gov <http://nomads.ncep.noaa.gov>) every three
> > hours.  I have it working fine using nam and gens.  However, when I
> > plot apcpsfc using gfs or gfs_hd, every other hour it seems like it is
> > plotting 3 hour precip, then 6 hour precip, and back to 3 hour, then 6
> > hour precip all the way through the 65 points.  This makes the precip
> > appear to pulsate, every other frame.  I have attached two images to
> > illustrate the problem.  Does anyone have a work around for this
> > issue?  The problem is isolated to just gfs data (both gfs_hd and
> > gfs), but doesn't happen with GFS Ensembles.
> >
> > Versions:
> > Grid Analysis and Display System (GrADS) Version 2.0.a9
> > Fedora-13-x86_64
> >
> > Data source example:
> >
> > sdfopen:
> > http://nomads.ncep.noaa.gov:9090/dods/gfs_hd/gfs_hd20101130/gfs_hd_12z
> >
> > Attached files:
> > precip_US_6.png (appears to show 3 hours of precip)
> > precip_US_7.png (appears to show 6 hours of precip)
> >
> > Here is my attempt to work around the issue for just gfs_hd / gfs,
> > though it doesn't solve the problem:
> > (Note: This is the section of my .gs file related to my work around
> > attempt):
> >
> > *grads code
> >
> > t = 1
> > t0 = 0
> > alt = -1
> > while ( t <= 65 )
> >
> > 'set t 't
> > 'define precip = apcpsfc/25.4'
> > if alt > 0 then
> >  'define product = precip(t='t')'
> >  'define over4= precip(t='t')'
> > endif
> > if alt < 0 then
> >  'define product = (precip(t=t) - precip(t=t0))'
> >  'define over4   = (precip(t=t) - precip(t=t0))'
> > endif
> >
> > *more grads code
> >
> > t = t+1
> > say ' = 't
> > t0 = t0+1
> > say ' = 't0
> > alt = alt * -1
> > endwhile
> >
> > Any help here would be greatly appreciated.  Thanks again.
> >
> > Sincerely,
> >
> >
> > Jeff Chabot
> > jsc219 at gmail.com <mailto:jsc219 at gmail.com>
> > http://jeffsweatherservice.com
>
>
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