Penzance - Strongest gust of the Winter so far .

[Graham Easterling]

. . which isn't saying much. A recent gust of 43mph.

The remarkable thing isn't the strength of the gust (which in current media fore comprises a 'gale force gust') but the fact it proves what an quite exceptionally quiet winter it has been. The last stronger gust 45mph on 27/11/21. Even Lands End has struggled, todays strongest gust just 56mph even out there.

The have been 501 days with stronger gusts since 1992, 131 days in January alone!! Never been a winter like it in my 70 years (50 in west Cornwall). Doesn't stop the local news blaming any damage on global warming. It's just become a ready excuse for incompetence or inaction.

For the whole of this century, I get the impression depressions have tended to get stuck in mid Atlantic much more. (O in this winter, take a very northerly track. )That's certainly the case with the exceptionally deep one to be close to SW Iceland shortly. (The models did a good job of picking that up well in advance).

Anyway, with that depression & relatively light wind's over Cornwall, some superb surfable waves coming up. Next Wednesday at Sennen

The interesting thing here is that as the swell's come a long way, the period is an impressive 17sec. There's also a smaller 18 sec period wave. When these 2 swells are in synch there could be some impressive sets, some time apart.

Graham

Penzance

[jack.h...@gmail.com]

Now I often watch the swells on the Moray Firth and certainly the old adage that every seventh wave is a big one has some validity.  Not always the seventh but the larger ones do seem to have some periodicity.

I am embarrassed to say that I had never thought of two swells of different frequency coming together to make that biggie.  

At my regular viewpoint just off the harbour at Nairn,  matters are usually confused by waves reflected off the harbour wall.

It's all very complex and maybe some time lapse would help understand.

Jack

[Graham Easterling]

Wave's have interested me all my life, ever since as a mere child I used to sit on the beach and be intrigued by them. I've read so many books on surf science swell generation and the rest. There are loads of complex equations, but when it come's to wave sets, nothing to really help predict but a bit of common sense & looking at the Atlantic synoptic charts. You can greatly simplify some of the equations and get a broad idea. So doubling the swell period increases the energy by roughly the same as quadrupling the wave height. So short period, local wind generated swells, have little real energy. Though an onshore gale can strip away a beach due to the undertow, rather than wave energy.

Nobody has come up with a way to accurately predict the frequency of sets, every storm creates it's own pattern, or the number of waves in a set. I think your 'seventh wave' is a pretty good guide. There are so many things to affect it. 2 out of synch long period swells are a guarantee of some good sets, often several big waves in the set. The waves move at a slower speed to the 'set' .

This wave group, sometimes called 'surf beat' has the effect of actually raising sea level for a period of 2-3 minutes typically. It has a typical period of 1-3 minutes & is a swell in it's own right . This is called a wave setup surge when it hits the coast and can act like a tsunami, raising sea level 2-5 meters (more under extreme conditions, 5 metres has been recorded. It amuses me when the EA gives a warning about a 0.5m storm surge, when we regularly have wave setup surges far greater (which are ignored) and swells 10 times that height.

Surfing a wave setup surge up the river at Bude .

https://www.youtube.com/watch?v=fClnkia61Zk

I'll stop, before I write a book!

Graham

[Len]

It's the melting Arctic ice through glabal warming that has weakened the westerly winds Graham.

:-()

The latest press release from UKMO explains.

I don't think 3000 simulations from 16 different models was really necessary when a reduced N-S temp. gradient is an obvious result,

but there you go. We've got the super computers so let's use them.

It's not quite so simple though. It appears the storm tracks have shifted north.

Witness storm Malik and storm Corrie.

https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2022/arctic-sea-ice-impacts-on-british-winters

Len

Wembury