Graham Easterling wrote:

There looks like being some very intense depressions in the mid/west
north Atlantic in the coming few days, but not too close to the UK. As
a result the swell generated will have a good chance of cleaning up
nicely by the time it reaches Cornwall, with the long period swells
well out away from the mush.

A generally 10'-15' swell forecast for the end of the week, with a
period in the mid teens.

Looks perfect for the week end http://magicseaweed.com/Sennen-Surf-Report/4/
Shame it's not 10C warmer!

I was interested to read recently that the highest average ocean
swell, over a month, anywhere in the world, is in an area of the
Atlantic just NW of Ireland in January. Not in the southern ocean in
July, as you might expect. (Over the a year the story's very
different)

Graham
Penzance

The reason is that swell travels on great circle tracks. A westerly gale in the
Southern Ocean at, say 50 deg S doesn't produce a swell that runs round 50 deg
S. It very quickly propagates to lower latitudes. If you ever get the
opportunity, have a look at some oceanic charts on a gnomic projection. Great
circle tracks are straight lines on these charts and are quite revealing. For
example, a SW gale off the mid-atlantic coast of the USA will produce a swell
that reaches Cornwall from WNW.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.