Missing grid fields in plot

[Stefan Gofferje]

Hi all,

I am trying to plot the SWEAT index for the Nordic countries but
strangely, there are lots of grid fields just missing.

E.g. see
http://www.saakeskus.fi/index.php?function=showpic&chart=NORDIC-sweatindex&number=114

This is the math:

'define tc850mb = tmp850mb-273.16'
'define tc500mb = tmp500mb-273.16'
'define ttindex = tc850mb+dewp850mb-(2*tc500mb)'
'set lev 850'
'define f850mb = mag(ugrdprs,vgrdprs)*0.514'
'define dir850mb = ugrdprs'
'set lev 500mb'
'define f500mb = mag(ugrdprs,vgrdprs)*0.514'
'define dir500mb = ugrdprs'
'define sweatindex =
(12*dewp850mb)+(20*(ttindex-49))+(2*f850mb)+f500mb+(125*(sin(dir500mb-dir850mb)+
0.2))'

Does anybody have an idea why there are those fields just missing?
There are no error or warning messages in gradsc... (using opengrads 1.9RC1)

Greetings from Finland,
Stefan Gofferje

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