Reading Swells

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Reading Swells

Postby atwsurf » Sun Mar 25, 2012 2:19 pm

I have recently picked up surfing and still cannot figure out how to predict the wave size and break. In terms of predicting a good day for surf what are the most important factors? It seems like there are so many variables- swell direction, swell height, wind direction, wind speed, period ect. In terms of getting good sized waves what should I look at? I surf mostly in massachussets, cape cod, and Rhode Island so there have been many times when I thought it was going to be great surf and it ended up completely flat or too choppy. Any suggestions?

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Joined: Sun Mar 25, 2012 2:12 pm

Re: Reading Swells

Postby Jim Birtwisle » Mon Mar 26, 2012 9:32 am

Whole essays can be written on this subject so I'll try and keep it brief...

Generally speaking winds want to be light and offshore. However depending on how well sheltered from whatever direction a break might be, you might find it can work with cross shore winds. The thing you don't want is on shore. A swell is usually squashed flat, or made completely unsurfable by on shore winds. Although I'm sure there are some exceptions.

Swell direction. Again this will depend on the geography of the shoreline, the direction the beach faces, the angle of sand bars, points, reefs etc. In most cases swell coming toward the beach from any direction should make for a wave, but again, where it is not coming directly on shore it will depend on whether the break is sheltered from any direction as to whether you'll get waves.

Swell period. The longer the better. Up to 6-7 seconds usually means it will be wind swell or some ground swell with wind swell making a mess of it. 10+ seconds and you're in for a good time surfing some solid ground swell, even if small it should be punchy.

Swell height. This does not always indicate how high a wave will be. It depends on the factors above. My local break can predict a 1ft swell but if it is light winds and a 12 second period I can be hopeful of something at least waist height. I've even seen that there is no incoming swell predicted and it's been chest high. I am reticent to quote wave height in feet as everone measures differently. Different breaks handle swell differently so one beach might be overwhelmed by an 8ft swell but you may find a more sheltered spot nearby putting on some good, surfable waves.

There is an absolute ton of stuff on the net relating to this topic, I'm only scratching the surface here. Best advice really is take your stuff to the beach and go have a look, otherwise try find a webcam.

In a perfect world your forecast will be direct on shore swell, no wind (or light off shore), swell height around 4-6ft at 12-14 seconds.
Jim Birtwisle
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Joined: Fri Nov 19, 2010 9:57 pm

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