MSW Wind Swell and Dominant Swell

[surfnoob]

OK, I have been wasting my time turning up to the break only to find unsurfable tiny mush when MSW is saying 5ft swells and the local buoy swell is giving 7ft.

Then i noticed the swell breakdown option on MSW and it tells me that wind swells makes up most of the total swell with a dominant swell of only 1ft or so.

How does the wind swell calculation work - does this tend to give really variable wave height results if this is dominant? Should I be concentrating mainly on what the dominant swell?

Any tips on reading the forecast a little better would be much appreciated - it will reduce my carbon footprint by half

[PapaW]

Hey,

Right so. Firs things first. The buoy swells and main figures on MSW are the open sea swells. IE the peeks and troughs of uninterrupted swell at sea. So with that in mind when it reaches sections of coast (and in our case in the UK it has to travel over 200-400miles of continental shelf as well). This saps a fair amount of energy out of the swell and each location it reaches the coast as will also be different.

So wind swell is local swell generated by local winds.
Ground swell is swell generated by winds well out at sea... it travels and, for want of a better description, 'sorts itself out' giving is a higher period ground swell.

When you have a ground swell running it can be interrupted and messed up by a local wind swell. In most cases wind swells will be dominant over ground swells if its particularly windy.

There are various explanations on MSW about how best to use the data provided. The best results will come from practice and knowing what makes your breaks work.

Don't forget about swell direction too!

[surfnoob]

Many thanks for that. The thing that has me confused is that the Pembroke buoy is only a few miles off the coast from my local breaks.

I'm gonna keep an eye on the swell make-up and see if over time I can apply this to some sort of method in determining whether its worth a trip in the car.

Thanks for your post - much appreciated - explains a lot.