Martin Rowley wrote:

"Will Hand" wrote...
snip


Hi Martin, another thought, do you remember Von Karman vortices?
They are sometimes seen where the Azores interrupts a stable flow.


... thanks for that Will - yes, that was something that did cross my
mind, but without more data can't really say: must dig out more info
on same to see if I can pin it down - I'm sure that the mechanism
must be of that ilk: what impressed me was that 'effect' as of a ship
ploughing a wake through a calm ocean - or perhaps a submarine's
conning tower doing the same thing to keep the scale correct. It must
have made a dramatic difference to those folk downwind as between OVC
SC (ST) & -DZ and bright sunshine.

I'm sure we had a small element of it here - we stayed resolutely OVC
until 15Z, with morning drizzle, but not too far away in north
Dorset, there seemed to be better breaks between the elements of the
Sc len.

Martin.

The following is an impressive satpic showing what you are describing,
Martin. It shows the Crozet Islands in the Indian Ocean under a layer
of Sc. The island on the left does not penetrate through the top of the
Sc and is producing a ship-type wake. The island on the right is
protruding above the top of the Sc and is producing von Karman vortices
downstream.

http://www.weather-consultancy.com/s...rozet-ship.jpe


Quite striking.


Norman
--
Norman Lynagh
Chalfont St Giles, Buckinghamshire
85m a.s.l.
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