SI wave height scale

Discussion in 'All Discussions' started by mattybrews, Nov 25, 2014.

  1. mattybrews

    mattybrews Well-Known Member

    Apr 14, 2013
    Looked all over the site and forums for this before posting and couldn't find anything. What scale does SI use when they give their wave height predictions? Is it face height or measured from the back? I know it can't be 100% accurate, but for a few spots out here it seems like going by face height it's consistently a foot or two bigger than the forecast. And the forecast is pretty reliable.
  2. seldom seen

    seldom seen Well-Known Member

    Aug 21, 2012

  3. nynj

    nynj Well-Known Member

    Jul 27, 2012
    0'-22' - FLAT
    23' - Firing
    24'+ - impossible
  4. sisurfdogg

    sisurfdogg Well-Known Member

    Jun 17, 2013
    I always go surfing with my entire quiver: 9' Gun, 7'2" semi-gun, 6'8" step up, 6'2" hbsb, 9'2" hplb, 9'6"noserider, 5'6" groveller, 6' fish, 6'4"rocket fish, kayak, jet ski, 12' douchecanoe, and a pair of swim fins and a handplane. You just never know what the waves will be like when you get there.
  5. titsandpits

    titsandpits Well-Known Member

    Sep 4, 2012
    the face in Nj at least
  6. Mitchell

    Mitchell Well-Known Member

    Jan 5, 2009
    Do you really take note of a bunch of wave heights for a few minutes and then compute the average.

    I'm not trying to be sarcastic, I just suspect many wave height forecasts are based on the output from models that predict average wave heights, or dominant wave heights which might be like the 65th percentile average of all waves coming in.

    I think a lot of surfers stand on the beach for 10 minutes, look at mostly the set waves that they would be interested in riding and not all of the in-between waves and then conclude that its 4-6 foot (for example) when TONS of 2-3 foot waves also come in, bringing the average height down to say 2-4 foot and then conclude that the forecast is an undercall because SOME 4-6 foot waves are coming in. Also we tend to look at the "peak" section of the wave which is higher than the shoulders.

    Just my 2 cents.

    Also, there are spots that consistently just exceed the surrounding beaches and probably aren't representative of the forecast for a "zone" of coast.
    Last edited: Nov 25, 2014
  7. EmassSpicoli

    EmassSpicoli Well-Known Member

    Apr 16, 2013
    They base it off the 8-10' principle.
  8. CDsurf

    CDsurf Well-Known Member

    May 10, 2014
    they must have measure the faces today because there is no way it was head high where I surfed. Waist to chest high at most.
  9. daeggman

    daeggman Well-Known Member

    Sep 18, 2014
    lol actually laughed out loud
  10. NJ glide

    NJ glide Well-Known Member

    Jun 8, 2013
    They measure it with my 23ft Johnson in Belmar while I bench.
  11. ibc

    ibc Well-Known Member

    Aug 3, 2014
    Don't fergit that SUP witha stripper pole. Git-R-Done
  12. spikeb122

    spikeb122 Well-Known Member

    Jan 13, 2009
    interestingly enough, the significant wave height is the average of the top 1/3 of waves. it is a convention that was first adopted when asking people how big they thought the waves were they often gave this number of the top 1/3 of wave heights. from a statistical standpoing it's 4 times the standard deviation of the surface elevation. ... there's plenty more but then you start getting into oceanography :cool:

    to answer the original question... it's face height. and you should feel lucky that it's consitantly bigger than the forecast.. not everyone's so lucky. also the models aren't as accurate in some places as others. to improve the model there's the + 0 - scale next to the graph of forecasted wave heights . .. this provides feedback for the modelers to let them know when they've under/over predicted the swell events. with out this feed back how is a guy in delaware going to know the wave heights in oregon are under predicted on this or that swell
  13. mattybrews

    mattybrews Well-Known Member

    Apr 14, 2013
    You are probably right. If you're sitting way outside waiting for the big sets you tend not to notice all of the smaller sets breaking inside. If that's the case then it's pretty spot on most of the time going by face height.
  14. SI_Admin

    SI_Admin Guest

    There used to be a scale... But, if you look at the forecast, you will notice it offers a text descsription (ie. head high), and also a wave height in feet (4-5ft), so I'm not sure a scale is necessary at this point, since its pretty explicit.
  15. CDsurf

    CDsurf Well-Known Member

    May 10, 2014
    SI kicks butt though, they are usually pretty spot on
  16. Mr.Belmar

    Mr.Belmar Well-Known Member

    Aug 19, 2010
    I actually rather the forecast be undercalled... Then when you do get those 5 ft days that are perfect and uncrowded, you can thank for calling it 2-3ft

    Unless, that is, you head straight to Belmar,NJ where the waves are always at least double the size of the surrounding towns... Just because it's Belmar
  17. Mr.Belmar

    Mr.Belmar Well-Known Member

    Aug 19, 2010
    I agree, usually the text description is spot on...
  18. Sandblasters

    Sandblasters Well-Known Member

    May 4, 2013
    hey bro can i buy the 12' douchecanoe and the ski i want to do tow in one 2 foot days?
  19. worsey

    worsey Well-Known Member

    Oct 13, 2013
    shaq and tattoo are still arguing about it.
  20. Riley Martin's Disgruntled Neighbor

    Riley Martin's Disgruntled Neighbor Well-Known Member

    Aug 22, 2012
    For what its worth, nynj, you are my favorite.