Biggest swell of the stormiest Atlantic winter for years is about to hit – What is going on?

פורסם: 7 בפבר׳ 2014, 10:59 על ידי: Sustainability Org   [ עודכן 7 בפבר׳ 2014, 10:59 ]
Posted on February 6, 2014 by David

Posted on February 6, 2014 by David

What’s that coming over the hill…Yes that’s a monster!

There is no doubt we are witnessing a historic weather event this winter. Here at Carve we’ve been watching charts to forecast surf for 35 years or so and we’ve never seen as many lows, so deep and consistently bombing to 940 or below; or as many 20+ foot swells. But this weekend could be the cherry on the cake.

To give you some idea why consider this: Hercules resulted in a swell that was 28 feet at 21 seconds from a long fetch. This Saturday’s swell could peak in excess of 35 feet at 19 seconds with high winds. The only consolation is that neap tides will help protect coastal property. However so much damage has already been done this swell is sure to exasperate already desperate situations.

What does it mean for surfers? Well if you know what you are doing, run for cover and go exploring the little nooks and crannies. If you are a beginner, probably best to just watch the show. The majority of the swell is heading for southern Ireland and Wales but due to the propagation of the storm the swell is going to wrap right up from the south west of England and up the south coast.

So what is happening and why is all this so extraordinary? To some extent we’ve probably been softened up by lots of winters of small swell and a relatively quiet Atlantic, especially over the last five years or so, with long periods of blocking highs (how many surfs did you have at open beaches over those winters?). But this year has been unusually active. In Autumn we started with a trail of consistent lows and some great surf, followed by “Phase One” as an unusually strong jet stream kicked in firing low pressures at us and intensifying their strength right off Britain and Ireland’s western approaches. This meant that the sand, which normally helps protect the land from the sea, was already mobile before the powerful storms started stripping it from foreshores. Then the combination of high spring tides, storm surges, wind and mega swells reached new levels and the damage was really done.

Storm surges have been a major factor in the flooding and high tide damage. They occur when strong winds push water up against a coastline. The larger the fetch across the Atlantic (like Hercules) the larger the surge. Add in record low atmospheric pressures as the fast moving systems pass which allow the sea level to rise even further, and throw in rogue sets … you can see where this is going. Up the beach and into car parks, roads and cafes!

Interestingly a storm surge on the Jan 3 2014 in the Irish Sea (similar to the one on the December 5 2013) raised the sea surface above the tide level by 0.75 metres to 1 metre over a large area. In the case of Hercules we have saw huge waves with long periods, add to surge of over half a metre in the south west. Combine this with large spring tides (7.7m) so you can see why there was so much coastal damage. Now, in Phase Two, the jet stream is again whipping up lows and the softened defences are down so the continued battering of swell is really taking its toll.

Other points of interest are that this is probably more a ‘weather event’ than a ‘climate event’ as it isn’t part of any long term trend (more a one off). On the surf side some beaches have been stripped of sand while others have had massive amounts piled up. This is providing some with good banks, some with no banks. There is no rule of thumb as to which beaches are benefiting and which aren’t. Some beaches that had too much sand are now working better after stripping. Some have lots of new sand and are great. Some have no sand or too much sand and are crap!  The sheer volume of sand that has shifted around the coast however is amazing.

All in all it has been a pretty productive winter and lots of mythical spots have been lighting up. In between swell peaks there have also been a lot of variable winds opening up lots of spots around the UK. Pretty much every region from Thurso to Kent has had a days of days, and even the east coast has been benefitting. And there are no signs of it slowing down. As to this weekend … Well let’s wait and see! Just be careful out there.