Our surf rating is calculated in thre parts. First we have a look at the swell height and period. Predominantly it's the period which tells us whether a swell looks surfable, but we also make sure there is enough size to the swell for it to make it to the beach. This gives us a rating of zero to five which is then adjusted based on the angle of the swell to the beach.
We then check out the winds. If they are looking good (light or offshore) we do nothing to the rating but if we spot some onshore or strong crossshore conditions we'll deduct stars from the rating. Please bear in mind that this is all done automatically by a computer. The software is good (it's taken us four years to write it and we still constantly improve it) but the computer isn't a surfer - it's not going to tell you exactly when the waves are great - its going to tell you when the swell looks like it *might* produce great waves.
We display the swell rating as the total number of stars, with any stars removed for bad winds turned grey. So, for example:
No Stars
No Swell - Flat
Very Weak Swell - Probably no surf.
Poor Swell - Poor surf possible.
Some Swell - Average surf possible.
Good Swell - Good surf likely.
Classic Swell - Classic surf likely.
Then taking into account wind, for example the three star forecast above might look like this:
Some Swell - Average surf possible and decent local winds.
Some Swell - Average surf possible but with less than perfect local winds.
Some Swell - Poor surf with bad local winds (on/crossshore).
Some Swell - Poor surf with howling onshore winds.
If you're clued up and know of a beach in the area sheltered from poor winds you can just use the total number of stars, if you're looking to surf the main beach listed you'll probably be best just using the total number of dark blue stars.
What about the surf size?
As explained here predicting accurately the local surf height from the swell information is not simple. Our principle is that a solid clean 2ft swell and a soild clean 6ft swell are both worth the journey, but size doesn't save a poor day from being a wash out. So we'll never give a decent rating to a poor swell just because it's large. If you spot a swell with a decent rating check out the swell size and you can quickly make a decent estimate for your local beach from that. Also bear in mind that long period swells generally feature flatter waves (less height) as the approach the shore but that they have more energy (and hence create bigger surf) than low period waves. Eg. 5ft@13seconds will ALWAYS be better than 10ft@7seconds.
How accurate is it?
The rating is designed ONLY to highlight conditions that looks as though they *might* be worth checking out further. This is not a 'go / don't go' forecast. It's based on our experience of what turns on the average beach on the average day. As you get experience of it with your local beach you'll get a better idea of what kind of rating you need for a decent sesh'. The rating does nothing you can't do yourself by checking the wind and swell data in the table. Please please please check with a webcam, surf shop or mate before driving a long distance and getting pissed off with us!
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