[gradsusr] Plotting GFS_HD apcpsfc every 3 hours problems

[Jeff Chabot]

Hello GrADS Users,

I am looking for help plotting 3 hr precip using gfs_hd (from
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
http://jeffsweatherservice.com
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