Martin
Thanks for your reply.

Do the difficulties you refer to also apply to predictions on a larger scale
(as in running from St Kilda in flat calm when we should have seen strong
winds?). What is the reason(s) for the model failure (If that is the right
word).

In my day job I have a fair bit to do with thermodynamics in process systems
and would have thought that the relatively stable conditions in a high
pressure system would be much easier to work with rather than the dynamic
conditions of a low pressure system?

Iain




"Martin Rowley" wrote in message
...

In article , Iain Mackay
writes
Encouraged by a forecast of "cold and clear with wall to wall sunshine"
in
the West of Scotland last Friday, I travelled from Perth (in the East of
Scotland) via Fort William to the Isle of Skye and finally up to Gairloch
in
NW Scotland.
The only thing that was 'wall to wall' was the layer of gloomy grey
cloud,
and with the exception of a tiny patch of sun at Kyle of Lochalsh, we
never
saw the sun all day.

... there are still serious problems with low-level cloud within the
atmospheric boundary layer - Stratocumulus is fiendishly difficult for the
models, even at high resolution, to capture (analyse) and forecast
properly. When you see the cloud we have outside now (Bracknell/southern
England), it's not particularly thick, and now and then a little gap
appears - how on earth a model is going to handle that is beyond belief.
Marine-based SC especially can behave differently from that formed (or
moving) overland - another variable in the mix.

Martin.


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