[gradsusr] Plotting GFS_HD apcpsfc every 3 hours problems

[Wesley Ebisuzaki]

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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