Well thank you all for your replies, from your answers I can see that its
not as simple as I first thought, oh well back to the drawing board.

Thanks again and best regards.

Len.

"Will Hand" wrote in message
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"Col" wrote in message
...

"GKN" wrote in message
news
Hi Will.
I am not sure as to its actual thickness, but it looked at times that it
should have been pouring with rain. Lets say I have seen heavier rain
with the sun shining through thinner cloud.


For proper rain as opposed to drizzle you need upward motion and the
correct microphysics within the cloud. Either enough moisture to produce
raindrops by coalescence or (more normally in UK) the presence of ice
crystals.
Thinnish altostratus with sun visible will produce rain as the air is
ascending normally due frontal ascent and there are ice crystals allowing
rain production by the Bergeron Findeisen process, i.e. tiny water cloud
droplets evaporate and condense onto ice crystals eventually falling out
as snow then melting to give rain. In mountain terrain thinnish stratus or
stratocumulus cloud can produce copious rainfall if very moist air is
continually lifted over the high ground and the stratus clouds are seeded
with rainfall/snow from above. So I hope you can see that optical
thickness (darkness) of clouds is not always the best guide as to what
clouds will give a lot of rain, one has to understand the physics and
cloud dynamics as well!

HTH

Cheers,

Will
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