Big, high energy wave about to hit west Cornwall

[Graham Easterling]

There's a very big swell on the way, it's been building for ages in the mid Atlantic under the influence of a persistent low pressure.

The significant wave height is forecast to reach 5m around Lands End by Friday evening, the largest sets are typically around 50% bigger. That height is not exceptional, but it's only just half the story. The swell has been building well to the west, so it'll be long period when it gets here. As a result the wave energy in the SW approaches will be higher than anywhere else in the world by Friday night A wave energy forecast map. (These are very accurate at this timescale, as the swell has already largely formed)

It's interesting, that in January, the highest significant wave height anywhere in the world is just to the west of Ireland. This is due to swells following great circle routes, and if you use a piece of string you find the longest great circle route (fetch) from Cornwall or Ireland aligns nicely with typical Atlantic storm tracks, so the swell builds, and gets longer period, all the way. Hence the phenomenal surf Portugal can get in light winds & sunshine.

As a result no sailings to Scilly tomorrow!

Graham

Penzance

[Graham Easterling]

A vast amount of sand removed by last nights swell. The beach now, well -the bit that's left.

 

Very recently the sand was right up to the top of the fairly steep path looking down to the beach. The sand level is now around 12' lower!

This photo taken at the beginning of the month, looking back up the path.

Incredible the power of that swell, even though it wasn't particularly high.

Next time you sea the EA with a digger moving the odd bucketful of sand for the benefit of appearing to do something for the media . . .

It'll all come back. It's all dumped in sandbars just below the low tide mark. Porthminster (St Ives) is a good place to visit after a NE gale, 1 tide can cut into the beach leaving a sheer cliff in the sand. (Photos on request!)

Graham

Penzance

[Nick Gardner]

Similar happens at Nanjizal Beach which is mostly boulders and cobbles but occasionally sand moves in transforming the whole beach. Quite remarkable to see it but it is rare and the few times I've witnessed it, I didn't have a camera with me. It is also where I've seen the green flash just after sunset, I've seen it twice there.

From a sopping, mild, dank, showery Devon. Will it ever dry up!

Nick

Otter valley, Devon.

[Graham Easterling]

Google Earth shows the amount of sand near & below the low tide mark at Nanjizal, which accumulates at the top of the beach in an offshore wind.

During my younger days (1970s!) I swam into the cave at Nanjizal and in the darkness with every stroke you got the glow of  bioluminescent plankton. The only time I've ever seen it. Sennen in August 2020, shows the surf up!  

Graham

Penzance

[Len]

According to Surfline the swell is due to be at its max today.

[Graham Easterling]

Just checked swell height at Sevenstones, it's around 12' (Ties in with current Surfline forecast for Sennen)

It peaked the night before last (Sevenstones) at 16' with a swell period of 16secs. The current forecast period (you can't use wave buoys for period) is a short 11secs. The equation to calculate energy is not at my fingertips, but certainly the current swell energy is well <20% of what it was the night before last. 

Graham

Penzance

[Graham Easterling]

Wave energy at noon today. Nothing of note really. 

Compare to Friday evening in my first post (peak was near midnight), which was quite something.

Graham

Penzance