Hurricane swells are notoriously complex. If that gigantic storm moves just a mile, it can throw just about everything off-kilter. Major hurricane Fiona has already caused widespread destruction in Puerto Rico, is delivering waves for the US east coast (more on this soon!) and is about to send a long period swell over the North Atlantic straight into Europe.
And that's a lot of info to process. Mostly, it's likely a swell that will be marred with strong onshore wind up in the UK and Ireland, but could be better down into Europe. That wind will still hang around in France. The full forecast is HERE, and as we say there, keep your expectations low. Unless you're in Morocco...
Anyway, we set up a ittle Q&A over on our Instagram account to understand what you, dear reader, wanted to know about this hurricane. Then we pitched them straight over to forecaster Jamie Bateman, who got into it.
Will25james: “Why do some long period intervals result in closeouts?”
A good question, will25james and we're glad you asked. Long-travelled swells, particularly from a single source, tend to have a small directional spread, which results in less interference between wave-fronts arriving from different angles, so the swell arrives in long, parallel lines. Closer-generated swells have a larger directional spread, so the wave fronts interfere with each other and produce peaks, even on a beach with little or insignificant bathymetric features. The other feature of long-travelled swells is that they are more radially dispersed and (as long as the swell generated in the storm centre contained long periods in the first place) the long periods will arrive first, separated out from the rest.
If there is a significant bathymetric feature like a sandbar, reef or point, the long, straight lines of a long-travelled swell can produce much cleaner, walled-up waves than a more closely-generated peaky swell. The fact that the same swells tend to have longer periods, so the waves feel the bottom earlier, in deeper water, making local bathymetric focusing more intense, can exagerate the effect of the bathymetry, making the breaking waves bigger and more powerful.
IG handle: IG: martijnsint “Will it reach the Netherlands?”
Not this one, but there will be swell from a North Atlantic storm reaching Netherlands in the same timeframe. So what is on the chart isn't Hurricane Fiona, but something else entirely.
Jowiebj: “When’s it going to arrive in Central Morocco?”
Super long-period forerunners will be showing Monday Sept 26,, the peak of the swell will be on Tuesday though. Keep an eye on your local forecast or check the live cam up at Anchor Point.
Chimpy4: “Can I have the day off when it hits?”
You'll have to ask your boss but we'd say; keep an eye on your local forecast right now and make a call over the weekend. That wind could be problematic, depending on where you are. But yes, you can have the day off. Offshoreitis is a very serious condition.
nimrod_mordechay: “Do you think this swell effects the Med?”
Long-period energy from Fiona will find its way through the Gibraltar Straight but the swell height will be so small that any surf will pass by largely unnoticed. Sorry Med! Hopefully something for you soon.
Mauriciocgarcia: “Any tips for France?”
Find shelter. That wind is coming in strong from the WNW, so anywhere out of it would be your best bet.
erik_with_the_a_k: “Will it reach Lofoten?”
Yes, swell from Fiona will reach well into the Arctic Circle but bigger surf from a powerful North Atlantic storm will mean the longer-period energy will mostly come through unnoticed. That's the same storm impacting the Netherlands too.
joe_el_duarte: “Early start for Nazare?”
Think we all want to see Nazare go off for the first time this season. Conditions will be cleaner in the morning along Portugal's west coast and then the north wind will blow through in the afternoon. Don't expect those XXL tee-pees just yet though.
Danilozano: “How about the Canary Islands?”
Super long-period forerunners will be showing Monday Sept 26th, the peak of the swell will be Tuesday. Keep a close eye on the forecast over the next few days for where to go.
william_erwood: “Is Bantham about to go off?”
Well, swell from Fiona will be a little too WNW for the South Coast of England to really see the brunt of that long-period energy. Whatever surf makes it through will be inconsistent and mostly wind affected by breezy WNW/NW wind. But keep a close eye on late next week, something could be brewing.
Oiinoah: “How hard do you think it’s going to hit Cornwall, specifically, Fistral?”
UK's surfing Mecca! The north coast of Cornwall is probably best placed in the south west of the country to receive the long-period energy from Fiona but, unfortunately, locally strong NW wind (onshore) looks like it will mostly spoil conditions and bring with it fairly chunky, shorter-period, WNW wind-swell, which will mask the hurricane swell. Goose chase, anyone?!