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Thread: Wave Period

  1. #1

    Wave Period

    Question on the difference between the long distance, like 2000 mile, California ground swell that follows a southward current. To a close hurricane swell that's like 200 miles away with a gulf stream currant. I know nothing of wave period and that's why I'm asking. What's faster with the same wave height California or Hurricane ?

  2. #2
    Period is period...period. But I think you are making a good point on the opposing currents having an effect on period.

  3. #3
    Wave current should have little to no impact on swell. The gulf stream moves at most 1.5 mph and waves of this size move much, much faster, a swell with hurricane period like Irma in the next few days of 16 secs would be traveling around 54mph in deep water. The continental shelf will play a far greater role than anything the EC will see current wise.

  4. #4
    Join Date
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    Quote Originally Posted by notaseal View Post
    Question on the difference between the long distance, like 2000 mile, California ground swell that follows a southward current. To a close hurricane swell that's like 200 miles away with a gulf stream currant. I know nothing of wave period and that's why I'm asking. What's faster with the same wave height California or Hurricane ?
    The longer distance swell will be more powerfull, feel bottom sooner, and be better groomed. maybe slower on the peak, faster as it hits the shallows. The closer swell will be more wonky, maybe faster on the peak, slower to feel bottom, maybe slower in the shore break.

  5. #5
    16 second period from the east or the west is the same. If it comes from 2000 miles or 1200 miles if it's 16 seconds it's 16 seconds. The currents play a small part in diminishing period true. And, continental shelf, canyons etc have an affect but not sure that is what op is asking

  6. #6
    Actually just re-read op. 200 mile and 2000 mile swells would be nearly impossible to have similar swell dynamic so SIS is on the right track

  7. #7
    For deep water, the relationship between speed and wavelength is given by the formula:
    l = g x t x t / (2 x pi)
    l = t x c for all kinds of waves, substitute in above equation: t x c = g x t x t / (2 x pi)
    c = g x t / (2 x pi) or t = c x 2 x pi / g or t = c x 0.641 (s)
    where t= wave period (sec), f= wave frequency, l= wave length (m) and pi=3.1415...
    to calculate c and l from wave period t (in sec): c = t x 1.56 m/s= t x 5.62 km/hr = t x 3.0 knot
    l = 1.56 x t x t (metres)
    Thus waves with a period of 10 seconds, travel at 56 km/hr with a wave length of about 156m. A 60 knot (110 km/hr) gale can produce in 24 hours waves with periods of 17 seconds and wave lengths of 450m. Such waves travel close to the wind's speed (97 km/hr). A tsunami travelling at 200 m/s has a wave period of 128 s, and a wave length of 25,600 m.

    The website below has tons of information about open ocean waves and how they move.....

    http://www.seafriends.org.nz/oceano/waves.htm

  8. #8
    Join Date
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    Quote Originally Posted by Rocketjok View Post
    For deep water, the relationship between speed and wavelength is given by the formula:
    l = g x t x t / (2 x pi)
    l = t x c for all kinds of waves, substitute in above equation: t x c = g x t x t / (2 x pi)
    c = g x t / (2 x pi) or t = c x 2 x pi / g or t = c x 0.641 (s)
    where t= wave period (sec), f= wave frequency, l= wave length (m) and pi=3.1415...
    to calculate c and l from wave period t (in sec): c = t x 1.56 m/s= t x 5.62 km/hr = t x 3.0 knot
    l = 1.56 x t x t (metres)
    Thus waves with a period of 10 seconds, travel at 56 km/hr with a wave length of about 156m. A 60 knot (110 km/hr) gale can produce in 24 hours waves with periods of 17 seconds and wave lengths of 450m. Such waves travel close to the wind's speed (97 km/hr). A tsunami travelling at 200 m/s has a wave period of 128 s, and a wave length of 25,600 m.

    The website below has tons of information about open ocean waves and how they move.....

    http://www.seafriends.org.nz/oceano/waves.htm

    Thanks for that site, rocket--it is a good one and did in fact answer several questions I have had regarding wave speeds. Leave it to the kiwis to answer it correctly.

  9. #9
    Join Date
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    Charleston
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    wait 54mph wave , ride that cowboy yowza

  10. #10
    Join Date
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    Quote Originally Posted by frost View Post
    wait 54mph wave , ride that cowboy yowza
    No - that is 54 km/hour....not mph (about 40mph).