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  1. #11
    Join Date
    Jun 2006
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    I'm going to take a stab at this one...(micah, if this is wrong please correct me) but i believe it has to do with the depth of the ocean off of the east coast. Long period waves tend to reach deeper into the ocean and therefore the continental shelf will have a more profound impact on the wave height that on our typical short period swells. Friction causes the wave to lose energy and thus lose it's height

    If you look at our friends in Cali, they have little to no continental shelf off the coast (blacks for example has a giant canyon) so when they get a long period swell the bottom will not cause the waves to shrink significantly.

    Generally speaking, depending how wide and how long the fetch is that generates these waves you can expect the energy to dissipate as it moves away from the storm.

    Also worth mentioning is that the sand on the east coast tends to be setup better for short period swells and can't handle the amount of energy a long period swell brings to the coast. Of course you also need to account for how the wave refracts off of inlets, piers, etc...but i think you get the idea.

    There is a good basic book out there called Surf Science by Tony Butt. It covers how to forecast waves in easily understandable terms. I read it every time i take a crap...haha.
    Last edited by beaner; Aug 10, 2007 at 03:02 PM.

  2. #12
    Join Date
    May 2006
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    Lewes, DE
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    sure thing... Here's a simplified answer:

    This is what I call CS syndrome or continental shelf syndrome.

    On the east coast, the continental shelf extends far off the coastline, as compared to the west coast or the island chains (which don't have a shelf).

    The longer the period of the swell, the deeper the swells reach underneath the ocean surface. So, when you have long period swells, the shallower water due to the wide east coast continental shelf acts to dissipate the swell energy offshore.

    Of course, the water depths vary all along the coast, so some areas can handle the longer period swells more than others. Also, when you have long period swells, wave refraction plays a much bigger role, and the wave heights can vary tremendously between different breaks. You'll notice out in SoCal, there is lots of variability between breaks.

    For the Mid Atlantic area, I'd say swell periods between 9-12 seconds are optimal. Because of the CS syndrome, and also longer period swells tend to just create close outs on our average beach breaks. Further north, in New England, there are more headlands that can refract the longer period swells into nice point break stuff.

  3. #13
    Quote Originally Posted by eastcoastgilson View Post
    for those complaining about the waves being terrible, did you ride august 8th and today? both were fun days

    you gota make the best outa what we have
    making the best out of what we have here is what we do 12 months a year... this summer has been craptacular even amongst typically crappy summer surf. surfing gutless knee to thigh surf for three months, while sometimes necessary, isnt really what surfing is all about. we all gotta keep our stoke up, but we are due! sure, its been rideable, but that doesnt make it right!

  4. #14
    Join Date
    Mar 2007
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    New Jersey
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    lperiod

    closes out at my beach, too walled, long wait between sets, inconsistent, really sensitive to tide, etc it'd be good if we had pointbreaks

  5. #15
    Join Date
    May 2006
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    Baltimore, MD
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    Thanks Beaner and Micah. I knew that wave energy grew deeper as period increased, just had no idea it went THAT deep.

  6. #16
    Join Date
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    The equation for the depth a wave reaches underneath the surface with respect to wave period is:

    Depth(ft) = Period*Period * 2.56ft , where period is in seconds.

    10 sec period => 256 ft
    12 sec period => 369 ft.
    14 sec period => 502 ft.
    16 sec period => 655 ft.
    18 sec period => 829 ft.
    20 sec period => 1024 ft

    The continental shelf has depth of approx 460 ft.

  7. #17
    Quote Originally Posted by Swellinfo View Post
    The equation for the depth a wave reaches underneath the surface with respect to wave period is:

    Depth(ft) = Period*Period * 2.56ft , where period is in seconds.

    10 sec period => 256 ft
    12 sec period => 369 ft.
    14 sec period => 502 ft.
    16 sec period => 655 ft.
    18 sec period => 829 ft.
    20 sec period => 1024 ft

    The continental shelf has depth of approx 460 ft.

    Nerd

  8. #18
    Join Date
    May 2006
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    Baltimore, MD
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    Quote Originally Posted by Swellinfo View Post
    The equation for the depth a wave reaches underneath the surface with respect to wave period is:

    Depth(ft) = Period*Period * 2.56ft , where period is in seconds.

    10 sec period => 256 ft
    12 sec period => 369 ft.
    14 sec period => 502 ft.
    16 sec period => 655 ft.
    18 sec period => 829 ft.
    20 sec period => 1024 ft

    The continental shelf has depth of approx 460 ft.
    Now THAT is good information. I have done a lot of reading about wave dynamics and bathymetry over the years and I don't believe I have ever seen that before.

    Thanks again.

    And Joyner, your just jealous that you don't understand it. ~~~~

  9. #19
    Quote Originally Posted by Carson View Post
    Now THAT is good information. I have done a lot of reading about wave dynamics and bathymetry over the years and I don't believe I have ever seen that before.

    Thanks again.

    And Joyner, your just jealous that you don't understand it. ~~~~
    Hahahah, no do not forget my degree is in Information Technology. It just brought back bad memories from my programming classes.

    Micah, you coming down to ride some chop tomorrow? An I know that you know that I know I am joking about "nerd".

  10. #20
    Join Date
    May 2006
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    Quote Originally Posted by Chris Joyner View Post
    Hahahah, no do not forget my degree is in Information An I know that you know that I know I am joking about "nerd".
    Of course. I took it as a compliment

    I'm busy saturday, may hit it up on sunday, if it looks appealing...