[gradsusr] DEW POINT GRAPH

[Chorley Weather]

Hi all, 

I'm trying to plot t2m, t850 and dew points in a line graph. The temp
and 850's work fine but for some reason the dew point just flat lines,
is there any reason for this? Ive attched an image to show and also here
is the section of script for the dew point. 

'set display color white'
 'clear'
 'set mpdset hires'
 'set grads off' 

'set t 1 65'
 'set csmooth on'
'set cmark 0'
 'set lat 53';'set lon -2.23'
 'set vrange -30 30'
'define dew = const((dewpt(tmp2m,rh2m)-273.16),0,-u)'
 'set gxout line'
 'set ccolor 2'
 'set cthick 20'
 'd dew' 

I'm rather perplexed as to why the line is flat and clearly there is no
value there but the Dew point script works fine when I produce charts. 

Regards, 

Stuart. 
-- 

Stuart Markham 

 
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