UPDATE, Wednesday August 19: As forecasted, the low is now a double-centred system west of the Celtic Sea, slow-moving over the next 36 hours or so, and deepening rapidly as the two centres merge. It is expected just south west of Ireland by early Friday.
An area of gale-force winds on its southern flank is already developing and will move eastwards and intensify, generating a pulse of large swell for mid areas. Late Friday and into Saturday, the system will begin to move off north-eastwards and weaken.
Forecast confidence levels are now high, with probabilities getting near 100 per cent for most spots on Friday when the swell is due to hit.
In south west England, Wales and Ireland, the windfield arrives at the same time as the swell, producing very woolly conditions. Wave heights are well over six feet at exposed spots, and winds are gale-force, mostly south-westerlies. Wave heights drop on Saturday and conditions don’t really improve.
In northwest Spain, things are much better, with a more lined-up swell and light south to moderate southwest winds, depending on where you are. Wave heights are expected to reach six or eight feet at exposed spots on Friday, ramping down over the weekend, with good wind conditions and some good surf at the right spots.
Further south into Portugal, the swell arrives fairly clean and lined up, but apart from a short window on Friday morning, the northerly trades will be a major feature at most places.
Live cam: Supertubos
Looking further ahead, there is a chance that the low will re-animate itself after passing north of Scotland late in the weekend. A northerly airstream on its western flank could produce a pulse of swell for the far north. This is obviously still a long way ahead, but worth keeping an eye out.
Keep an eye on your local forecasts for more updates.
EARLIER, Monday August 17: A summer swell alert for Europe isn't too common, but given the tame season, this could be a welcome one for people seeking some chunkier conditions. Later this week, the Old Continent could be in for a surprising couple of days and a decent prelude to autumn.
Across Europe, there's been a bit of a heatwave recently, but towards the weekend we may see some decent surf for the west of the continent, thanks to a mid-Atlantic cut-off low developing right now.
Tip: Bookmark your favourite surf spots to keep an eye on the conditions.
“The North Atlantic has been pretty dormant lately,” says MSW forecaster Tony Butt. “Which is nothing unusual for summer. The upper airstream has been weak and broken up, with the surface flow containing the occasional cut-off low drifting north of the Azores. This week, however, one of these lows is forecast to strengthen a bit more than usual, sending an unusual pulse surf to westerly exposures.
“The system is already gradually taking shape east of Greenland, and is expected to gradually deepen as it moves eastwards over the next few days. On Wednesday it becomes a double-centred system west of Ireland, and continues to intensify through Thursday and into Friday. A short-but intense fetch with west and southwest winds develops on its southern flank, together with a longer northerly fetch on its northwest quarter.
“From Friday onwards, expect some largish, average-quality swell to hit mid areas such as southwest Ireland, southwest England and Wales, and northwest France, and some smaller but cleaner swell to arrive further south. At exposed spots in Cornwall, for example, current forecasts for Friday are showing wave heights around six feet with strong perhaps gale-force southwest winds. In northwest Spain, wave heights are expected to hit around five or six feet at exposed spots, with light variable winds at less exposed spots but moderate south-westerlies in the far west.
For the North Atlantic, keep an eye on our swell chart HERE
“Even though wave heights are forecast to reach autumn or winter-like values, this swell is not the same as a winter one. Due to dispersion (see HERE), a typical summer low – relatively weak but close to the coast – can show just as large wave heights as a much stronger, winter system that sends swell from further away. The big difference is that a long-travelled winter swell will be more lined-up, more solid and longer lasting.
“Also, systems like the current one can be quite volatile, and things could still change quite a lot between now and Friday.”
We'll bring you updates as they play out – but this is certainly one to keep an eye on. Stay tuned.
Cover shot of Natxo Gonzalez, in a silky Mundaka robe, by Manu Miguelez.