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  1. #1
    Join Date
    Apr 2008
    Location
    Wilmington, NC
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    236

    Someone want to explain swell periods to me?

    I get how winds, swell direction, etc effect the surf. But I always hear "X feet at Y seconds." What is the significance of the swell period?

  2. #2
    Join Date
    Mar 2008
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    wb and you can find me at crystal and sweetwater and all over wb.
    Posts
    1,538
    good question. i wish o could help you but ive actually been thinking of the same thing. hopefully it will be answered so we both can understand what it means.

  3. #3
    Join Date
    Jul 2008
    Location
    Wilmington
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    I'm pretty sure that it affects the power of the swell and the consistency of sets.

  4. #4
    Join Date
    Mar 2008
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    WB: C-street and Mase and Sweetwater and all sorts of chill places around WB. Its rad.
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    559
    the longer the period, the farther away the swells coming from. The farther the swell travels in the open ocean, the more powerful and organized it is, thus meaning longer period swells will produce better, more consistent waves.
    Right?

  5. #5
    Quote Originally Posted by conway View Post
    the longer the period, the farther away the swells coming from. The farther the swell travels in the open ocean, the more powerful and organized it is, thus meaning longer period swells will produce better, more consistent waves.
    Right?
    that is correct.

  6. #6
    Join Date
    May 2006
    Location
    Lewes, DE
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    Swell period as in swell height is influenced by wind speed, wind fetch, and wind duration.
    As speed, fetch, and duration increase, so does the swell period.

    The wave period is directly related to the wavelength. So the longer the period/wavelength, the more energy is in the wave. It would be clearer with a picture, but I'm not feeling that motivate right now.

    What this means to you... The longer the period, the more potential for a larger wave.
    A swell with 5ft @ 7 (swell A) seconds and a swell with 5ft @ 12 (swell B) seconds can be much different.

    Swell A will likely be in the chest high range, maybe some bigger peaks, but much weaker than Swell B, which can be head high easy, and in general much more powerful and produce a longer line.

    What happens is the wave rolls through in the open ocean... when it approaches shallow waters is starts to feel the ocean bottom. As it does this, the wave becomes bigger and bigger before it topples over and breaks. The longer the wavelength (or period), the more chance for the wave to build up before it topples over.

    Also, the longer period swell will be much more influenced by refraction. This will cause greater variability between breaks as compared to the shorter period swells.

    Sorry for the long winded answer, but its hard to clarify without giving some detail.

    I hope that helps.

  7. #7
    to truly understand how a swell period effects the quality and size of a wave you also have to understand the shoaling effect we get arond here. (its certainly worse in sc than nc)

    damn that frying pan!

  8. #8
    Join Date
    May 2006
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    Lewes, DE
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    Quote Originally Posted by pawley View Post
    to truly understand how a swell period effects the quality and size of a wave you also have to understand the shoaling effect we get arond here. (its certainly worse in sc than nc)

    damn that frying pan!
    exactly. I was explaining a simplified version of the shoaling process above.

    The longer wave periods reach further down into the ocean depths.

    For you guys in south carolina, you deal with very shallow offshore waters. So, the shoaling (where the wave starts to interact with the ocean bottom), starts further offshore. And, what happens is on the longer wave period swells, a lot of the swell energy can be dissipated before the swell energy makes it to the beach.

    So, as I mentioned the longer the wave period, the bigger potential for wave heights. However, this is completely dependent on the bathymetry (ocean depths) of each individual area and surf break. And, it is the long period swells, where you have the most variability between different areas due to the shoaling and refraction processes.

    It is the areas with deep water off the coast, that allow for bigger surf. All of the big wave spots are this way. They go from deep water, to shallow water quickly.

    And if you compare say, Hawaii, where it is just a volcanic island in the middle of the ocean, to say the East Coast which has an extended continental shelf, you will see big differences between swells of the same magnitude.

  9. #9
    Quote Originally Posted by pawley View Post
    to truly understand how a swell period effects the quality and size of a wave you also have to understand the shoaling effect we get arond here. (its certainly worse in sc than nc)

    damn that frying pan!
    not to mention the direction we face and our most dominant winds. I love pawleys and have seen it epic....yes epic . we just seem to get cut off from alot of swells. Gulf stream=60 miles. thats alotta flats