Graham Easterling wrote:

On Tuesday, December 9, 2014 6:09:21 PM UTC, Togless wrote:
"Malcolm" wrote (quoting the Daily Express, I think):

"The deepest and most powerful low pressure system for A CENTURY
is currently hurtling towards the west coast where mammoth 50-ft
waves threaten mayhem."

Are they claiming that it's already the deepest and most powerful low
pressure system for a century (which should be easy enough to verify or
refute), or just that they expect it to be?

It certainly looks quite lively out there in the Atlantic...

Whilst 50' waves are very large, they occur in the north Atlantic every
winter. In fact 60' waves have been surfed in Ireland & Portugal.


It depends, of course, on whether we're talking about significant wave height
(which is the usual way to describe the sea state) or the maximum wave height.

Down the more exposed parts of the west coast of the British Isles the once in
50 year extreme significant wave height is around 16 metres (about 52 feet) so
this would be a rare occurrence . West Cornwall is a little lower with 14
metres (about 46 feet). However, with a significant wave height of 16 metres
the highest occasional individual waves would be 27-30 metres (around 90-100
feet).

So, if we are talking about 50 feet as a significant wave height around the
west coast of the British Isles this would be a rare and very notable
occurrence but if we are talking about a maximum wave height then it would not
be a notable occurrence.


--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org