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  1. #1

    Taller waves on low tide?

    Hi there everybody.

    I'm new to this forum and I've been searching for an answer to this question like mad, but nobody knows what to say about it. I analyse marine climate through numerical modelling, but I've found something that isn't very logical to me: I'm having taller waves on low tide than on high tide. I know you surfers understand the mechanics behind waves, so, what do you think? Is this possible to you?

    Thank you very much in advance!

  2. #2
    Click here... Doesn't help directly, but should send you in the right direction...

  3. #3
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    My spot loves an outgoing. High tide can swamp it out if there's not enough swell.

  4. #4
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    Sometimes yes, sometimes no.

    It's dependent on a lot of different things, not just low tide or high tide and it varies from break to break. It could be a combination of sandbar or reef or incoming/outgoing. The conditions under the water change all the time too. One day a reef could be bare rock and the next it could be covered in sand which only gets stripped away again. Sandbars move too and are affected by dredging and beach re-nourishment. The tides change with the lunar cycles, so a low or high tide one day is nothing like low or high tide the next. Waves are complicated beasties, I don't claim to understand them, I just try to grab the right board.

  5. #5
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    the waves' energy pushes the water upwards, when its shallow at low tide, the wave has less space between its bottom and the ocean floor so the energy pushes the water higher or taller as you put it. When its deeper such as during high tide, the wave energy has more room to push down

  6. #6
    Thank you all for your answers.

    I'm trying to define the worst situation for a breakwater. The wave height is the reference parameter to do the calculations. So, what I understand in my case study is that, at low tide I'm having a taller wave but also a lower water column, whereas at high tide, even though I'm registering smaller waves, I also count on the tide... In conclusion, at high tide the water height is always bigger (the difference in wave heights from low tides to high = 1.64 ft; tide = 9.2 ft).

    Thanks again!

  7. #7
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    Since we're talking tides....

    here's a couple observations I think I've noticed. Been meaning to start a thread on this but I'll post 'em here if that's ok with the OP. And I know waves, tides, and the ocean and everything involved are very dynamic and complex...these are just speculative things I've picked up on.

    1/Set interval- this really only applies to short period windswell, but I feel like the final hour before peak high tide is often when that 'never ending set' happens. You know, when you're waiting for a lull to paddle out and you think the last wave of the set is breaking than boom, here comes the next. I feel like the tidal surge can push sets a little closer together.

    2/Rips- this is like clockwork at my go to, but it's waaay rip-ier on the mid-incoming to high tide. More frequent ones and stronger. Like to the point that pre-set where you're sitting is good, then a big(relative terms) set pushes through the exact spot but now it's the middle of a rip. Not saying there won't be rips at lower tides, but I feel like when the full force of the ocean is pushing towards the shore, and all that water from the last set that broke has to get back out, this is what happens.

  8. #8
    depends on the bathymetry, generally yes

  9. #9
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    Some info for the noodle (maybe TMI):
    http://www.dfo-mpo.gc.ca/Library/487-12.pdf

    Widgets/Calculators/Charts & Graphs:

    http://www.meted.ucar.edu/marine/widgets/

    From http://www.waterencyclopedia.com/Tw-Z/Waves.html:
    Breaking Waves

    As waves approach landmasses, the wave base begins to contact the sea floor and the wave's profile begins to change. This friction slows the circular orbital motion of the wave's base, but the top continues at its original speed. In effect, the wave begins leaning forward on its approach to shore. When the wave's steepness ratio reaches 1:7, the wave's structure collapses on top of itself, forming a breaker.

    A spilling breaker is the classic rolling wave coming up a gradually sloping sandy beach. The long incline drains the energy of the wave over a large area.

    A plunging breaker approaches a steeper beachfront and forms a curling crest that moves over a pocket of air. The curling water is traveling faster.

    The classic curl of a breaking wave is associated worldwide with surfing. As a wave approaches shore, friction slows the bottom of the wave while allowing the top to continue moving, which causes the top to lean forward in this manner.

    The classic curl of a breaking wave is associated worldwide with surfing. As a wave approaches shore, friction slows the bottom of the wave while allowing the top to continue moving, which causes the top to lean forward in this manner.

    than the slowing wave base, and the water outruns itself with nothing beneath for support.

    Read more: http://www.waterencyclopedia.com/Tw-...#ixzz35aGEysDM

    Of course there is this oceanography gem someone posted elsewhere:

    http://oceanworld.tamu.edu/resources...apter16_01.htm
    Last edited by capecodcdog; Jun 24, 2014 at 06:52 PM. Reason: added ocng_textbook .. SI greymatter and what not

  10. #10
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    Quote Originally Posted by seldom seen View Post
    here's a couple observations I think I've noticed. Been meaning to start a thread on this but I'll post 'em here if that's ok with the OP. And I know waves, tides, and the ocean and everything involved are very dynamic and complex...these are just speculative things I've picked up on.

    1/Set interval- this really only applies to short period windswell, but I feel like the final hour before peak high tide is often when that 'never ending set' happens. You know, when you're waiting for a lull to paddle out and you think the last wave of the set is breaking than boom, here comes the next. I feel like the tidal surge can push sets a little closer together.

    2/Rips- this is like clockwork at my go to, but it's waaay rip-ier on the mid-incoming to high tide. More frequent ones and stronger. Like to the point that pre-set where you're sitting is good, then a big(relative terms) set pushes through the exact spot but now it's the middle of a rip. Not saying there won't be rips at lower tides, but I feel like when the full force of the ocean is pushing towards the shore, and all that water from the last set that broke has to get back out, this is what happens.
    Your rip current observations are right on bro! The higher tide and the extra energy will punch a gap in the sandbar, creating a channel for the rip to form. All the extra water bearing in on shore has to go back out (unless the dune is breached in big time storms), so it goes out the gap in the sandbar. The volume of water out the gap far exceeds the amount going in the gap, since most incoming water is still going over the bar all along the beach. I always tell inexperienced swimmers to watch out on the incoming tide. It is counter intuitive to them - they think incoming tide will push them in, outgoing tide will suck them out, but it doesn't work that way.

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