# Precipitation 3/6 h

James Burn j.burn at GEOS.COM
Tue Feb 3 06:10:42 EST 2009

```Hi Fil

When looping (with _count) to plot a set of GFS 3hrly precip charts I use:

if (math_fmod(_count,2))
'define APCPsfc6hr=APCPsfc'
'set t '_count-1
'define APCPsfcnew=APCPsfc6hr-APCPsfc'

'd APCPsfcnew'
'set t '_count
else
'd APCPsfc'
endif

Which works nicely. I've not sorted the 3 hourly precip in a meteogram yet,
but I imagine something similar would work.

Good luck
James

On Fri, 23 Jan 2009 15:00:06 +0100, Fil <fil at METEOPT.COM> wrote:

>Hi everyone,
>
>I'm trying to plot a precipitation meteogram from GFS 3h data but, for
>example, +33h timestep has precipitation from +30h to +33h but +36h
timestep
>also has precipitation from +30h to +33h and +33h to +36h. So what I wanted
>to know is how can I subtract precipitation like 30h = 30h - 27h, 36h = 36h
>- 33h, 42h = 42h - 39h, etc, so that +30h/+36h/+42h/etc timestep doesn't
>include precipitation from +27h/+33h/+39h/etc timestep.
>
>Also how can I sum precipitation from +3h to 180h? I'm trying to draw the
>total precipitation above the bars graph and I tried something like:
>
>totalprec=sum(APCPsfc,t=2,t=180)
>'draw string x y 'totalprec
>
>But it doesn't work at all.
>
>Hope someone can help me.
>
>Cheers.

```