"Iain Mackay" no_one@here wrote in message
...
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).

.... You would need to consider each situation individually, but the
current generation of mesoscale models (on which coastal forecasts would
be based), whilst not perfect, would not explain why you experienced
calm when strong winds are expected. Within the Minches for example, I
can think of examples where, with some wind directions, you might get
much lighter winds than 'generally' forecast, but not on a voyage
to/from St. Kilda which it much more 'open'.

Even several years ago, the model output was pretty good for such
situations - the only problem I can think of offhand is that St. Kilda
is part of 'Hebrides' sea area (in the Shipping Forecast), and a F6/7
*might* have been forecast for the far west and the peculiar spike
between Bailey and Faeroes, but would not be applicable to the rest of
Hebrides. This was/is a common problem with the larger sea areas -
sometimes the forecaster runs out of words to split the area
sufficiently and has to concentrate on the 'worst-case' scenario. When
writing the Shipping Forecast, by the time you get to Malin, Hebrides
etc., you find you're rapidly running out of words (strictly limited)
and have to lump areas together with no leeway to sub-divide. It's only
a guess, but I've known it happen.

Can you remember the dates? It is possible to look at archive mslp
charts now online and get an idea what sort of situation was in place.

Martin.


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