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Wave height...??

Discussion in 'General Yachting Discussion' started by P46-Curaçao, Jun 16, 2016.

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  1. P46-Curaçao

    P46-Curaçao Senior Member

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    Just wondering... I read a lot of comments that people don't go out if waves are over 3 ft... we almost never have it less then 4ft and I go out on almost every wave height!

    So therefore am I comparing the right figures, please see below of our actual situation on Curacao:

    Screenshot_3.jpg
  2. Capt Ralph

    Capt Ralph Senior Member

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    First of all, weather forecasters are SFBs and would not know a wave when it slaps them down behind their air conditioned office desk.
    After my SA comments on people behind a desk that have never been on the water, let me give your thought a try. My observations, nothing solid.

    Waves are a peak to peak water movement. Depending on the forecaster reporting, it could be height over the mean level or total height + / - (peak to peak). Buoy data is usually peak to peak. The raw data coming in from an instrument that does not know where mean level is and can truly deliver total height, period in time and some reasonable direction.
    Wind chop and cross slop is hard for a buoy to report.

    My father told me, whatever you see, double it. You have no reference to truly gauge wave height even when your in it. OR, it makes the story better when you get home.
    Honestly, I have learned to double what I think I see. It has proved more accurate when comparing buoy data later.

    It looks like you subscribe to a weather server. I use Bouyweather.com (cheap). It's pretty good reporting peak to peak but still does not report wind slop.
    I usually see twice the local foretasted wave height in comparison. If you dig deeper in the NWS or high seas forecast, it seems to match the buoy data.
    Wind slop is in the better forecaster (not around here).

    Forecasters use wind data to "help" predict wave height (old school formula here somewhere) and I believe there resulting numbers are height over mean water, NOT peak to peak.

    From behind the desk, they also have no idea of combined swells, natural swells or what happens 500 miles away.

    Your also in a unique part of the world (wish I was there). Your weather may change every 15 minutes.

    So;
    People don't go out on 3 foot seas (3 over mean) that means 6 peak to peak.
  3. olderboater

    olderboater Senior Member

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    There are a lot of people who don't go out over 3 or 4' measured top to bottom, peak to valley, distance above mean to distance below. We find we go out regularly in conditions that others don't.
  4. P46-Curaçao

    P46-Curaçao Senior Member

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    I use the WindGURU free version, and we all find it very accurate!

    FYI, we almost never see less then 4ft measured top to bottom, and we find that a real quite sea...
    One time went to Bonaire on a 10ft (measured top to bottom) sea... that was quite a ride, but no problem at all, just took an extra hour (before the rum)...
  5. Capt J

    Capt J Senior Member

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    Yeah, but you don't go far in the waves you have usually, if you want to fish you run 5 miles.

    Different story if you plan on running 200 nm a day in it and for 8-10 hours....... Also wave period and direction is huge in regards to ride quality.

    I'm leaving tomorrow with a 62' motoryacht express for Nassau 160 NMs.....boat cruises 28 knots......2-3' on the way over.......Supposed to come back on Monday but calling for 4-6' seas and occassional 9' seas. I'm NOT coming back in that...The boat will take it, I'll take it....but not worth breaking a bunch of stuff on the yacht........I have the owner and his wife......SIL and daughter late 30's and 4 kids under 11 years old. Not going to happen...won't even attempt it with the kids that age....their second yacht trip and I'm not going to scar them for life......so will either wait and fly them home.....or hope the forecast (which doesn't make sense compared to the wind) changes by then.
  6. Capt Ralph

    Capt Ralph Senior Member

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    Then,
    To many wimps out there, missing another great day to enjoy the seas.

    OB seems to get out when the sea are empty also.

    We have never waited for weather windows during our personal trips. Rarely get chased back in (it has happened). Old Bertram has no problems. I feel we are usually ready, good ole boat under us, only one kat gets sea sick. Poor ole kat. Were still waiting to stabilize the ole Bert for him.

    I find it a drag during deliverys when customers tell me not to go outside. I have to remind my self I'm working, getting paid and not get upset. Still a bummer.

    Did I ever tell anybody how much I hate the ditch???
  7. Capt Ralph

    Capt Ralph Senior Member

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    Oh nightmare; Owner AND kids on board.
    Sorry my friend.

    Hate it when owners are on board......
    I don't operate when kids are on. Lost income,, yes. Sleep at night,, very well..
  8. P46-Curaçao

    P46-Curaçao Senior Member

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    You are right CaptJ, we usually don't run more then 1-2 hours (one way) and Bonaire is 2.5 - 4 hours depending sea condition... funny thing, my former girlfriend get scared and I told her to lay down in the master bedroom.... and she slept for 3 hours and just woke up when we arrived... downstairs no problem with the 10ft sea, she told me...
  9. Silver Lining

    Silver Lining Member

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    We are heading over to Lucaya Sunday morning and then onto the Abacos, then Harbour Island, Atlantis, and the Exumas for 6 a week trip. I have been watching the weather closely in preparation and it is a bit of a strange weather system for June with a large swell coming down from activity in the North Atlantic that will push into the gulf stream Sunday night. It is the combination of local wind waves and a strong distant northern swell that will make Monday unpleasant.

    I want to share a new web site access from NOAA that I am really happy with and are now using and find to be by far the best. I have always been happy with passageweather and their graphics, but now realize that I think they are getting their data from the environmental modeling center at NOAA and the NOAA Wavewatch III product viewer. The Wavewatch III gives full access to the ensemble models being used to generate the marine forecasts by NOAA. You can independently access wave heights, winds, wind waves, distant swell etc. with 7 day forecast modeling and really piece together a better understanding of the current and near future waves. It is by far the most comprehensive and in depth tool I have used. Try looking at the east coast global model.
    Last edited: Jun 17, 2016
  10. Capt J

    Capt J Senior Member

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    I'd rather put 10 hours in on the ditch than 8 hours in a sea. Can walk around, grill lunch during long slow speed zones. A little more concentration, but more scenery to look at, but less wear and tear on your body. I do A LOT of miles each year on deliveries, it's tough on your body, and quite frankly have a lot of aches if it's rough......all manageable, but I'm not taking a 50' MY out in 6' seas for the day by choice..... a 50' SF sure.

    Depends on the size of the boat. A 50' MY and you can run at cruise most places in the ICW . I've done Jekyll Island to New Smyrna in a short winter day and New Smyrna to Jupiter in a day in December and the boat only cruises at 21 knots. That being said the boat is range short and 170 NM MAX, and on the way to Baltimore from Key West, only days on the ICW were Southport to Wrightsville Beach (20NM) and Beaufort, NC to Norfolk by choice. We also did Fernandina to Jekyll, wife jumped on then did Hilton Head and then Charleston on the inside, she jumped off and we jumped outside again. Just got home from that 1200 NM trip last Sunday and leaving for Nassau tomorrow and back possibly Monday.

    Monday is calling for occassional 9' with a 10 second period so sounds like swells we can run at least 24 knots in if 29 is too much...... I only have fuel to run 8 hours at cruise MAX in this boat, but Nassau is 5 1/2 port to port, so the speed makes for shorter days and if you do 7 hours or so at cruise at least you're getting somewhere.

    Wavewatch III has been around a very long time. I used to use it a lot 10 years ago or so. Very few people know about it for whatever reason.
    Last edited: Jun 17, 2016
  11. Sea Gull

    Sea Gull Member

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    Wave period must be taken into account. A 4' height with an 8 second period is very different from a 4' wave with a 3-4 second period. Also keep in mind that waves are not uniform, so while the reported dominant wave height might be 4', there are going to be 6-8 footers in there as well.
  12. Capt Ralph

    Capt Ralph Senior Member

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    rite below the running graphic for WavewatchIII

    About this product:
    The significant wave height is a measure for the wave height, and closely corresponds to what a trained observer would consider to be the mean wave height. Note that the highest wave height of an individual wave will be significantly larger.

    Depending on the trained observer location (behind his desk or on a real deck), this may be an example to my comments above (#2). Some systems report mean waves (not average), some total height (peek to peek).

    I feel this ads to the confusion when people compare forecast with 2 different wave heights predicted.
    Last edited: Jun 17, 2016
  13. olderboater

    olderboater Senior Member

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    I don't see any confusion. First, the definitions. Wave height is the distance between the trough and the adjacent crest. What is reported in forecasts is "significant wave height." That is a measurement of the average of the highest 1/3 of the waves over a given period of time. That's simply a method of smoothing. In the course of a 24 hour period the tallest wave may be as much as twice the significant wave height.

    Every forecasting service I'm aware of uses these rules.

    Now, remember these are forecasts. Actual is then reported by buoy measurement or other means after. Like any weather forecasts, there is error.

    The variation between forecasts has nothing to do with the meaning of wave height, but is simply different forecasts.

    As to what one personally considers too high for getting out, depends on boat, on reason for traveling, on tolerance and comfort for conditions, on experience of crew, on distance to be covered, on confidence in the forecast, on possible means of escape if conditions worsen.

    It makes perfect sense that with us covering 17,000 to 20,000 miles a year and boating over 1,000 hours a year, we'll be comfortable getting out in conditions someone boating 50 hours a year would not. Commercial ships would be inclined to get out when we wouldn't as they have more experience, bigger boats, and aren't concerned with comfort of guests.

    We judge height and period together. We look at wind waves and swell. We boat for pleasure so ultimately if we believe it's going to not be pleasurable, we don't go. Again, that differs for different people. I know people who consider 4' at 6 seconds to not be pleasurable. We consider it fine. Length and speed of boat factor in. They determine how many times in a minute I'm going to go up and down.

    Surprisingly, I've seen those who travel at displacement speed in trawler type boats often the ones who will get out in the least. (Contrary to the small number of them who cross oceans). It sounds illogical until you understand. First, many of those do the majority of their cruising in the ICW. They have no experience in rough conditions. They haven't practiced in rough seas or developed knowledge or skills. Second, they have no ability to pick the best speed as they have one speed and one speed only. Nor can they vary direction significantly as taking a slightly different direction adds hours to their trip time and could quickly double it. Third, many of their boats lack stabilizers. Fourth, many of their boats do not handle waves from some directions well at all and can't adjust speed to do so better. Fifth, their boats are often least equipped to go out of inlets and to return into inlets. Sixth, they are going into the wave getting the greatest of it's force. They lack the ability to get on top. And they are getting every single wave as opposed to a boat on top that might go from crest to crest.

    The OP is use to his area and comfortable with it and thinks nothing of it. the PNW was new to us. 10' waves sounded large at first until you realized they were 10' at 13 second swells. However, the bars/inlets were the challenge in those areas and small displacement speed boats could easily lose control to the waves through them.

    Then there are personal preferences. Many prefer the ICW. Capt J likes it sometimes. We avoid it as much as possible, only using it when outside conditions force us. And then it's who is aboard. The majority of people who travel with us are seasoned boaters and experienced and use to less than ideal conditions. Were we taking first time boaters out we'd be far more selective. Were we taking children far more. Size of crew plays a role. Today we have 9 of us on board. 4 of us are licensed captains, one an engineer, 2 others have some experience handling boats and the other 2 have experience as crew on a boat. If I was the only experienced operators with 8 friends with no experience along for the first time, it would be far different.

    I consider how long we'll be in less than ideal conditions and what happens if they worsen. If I'm on a 6 knot boat crossing from Nassau to Fort Lauderdale, then if it's uncomfortable it is so for a long time plus conditions can change radically in the time it takes me to cross. Plus I know the gulf stream will be worse than what I'm seeing starting out. If I'm cruising at 25 knots I'm looking at a very short window. I could also quickly change course for Bimini if conditions ahead and in the gulf stream were turning much worse very quickly. Still, if I know tomorrow is going to be much nicer, I'll choose to enjoy today at Atlantis.
  14. Capt Ralph

    Capt Ralph Senior Member

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    Our wants to avoid the ditch (Savannah to Miami) are multi fold;
    Since I was a kid, I've been in this ditch. I've seen it and am bored silly.
    If I'm doing 10 or 25 kts, the many other people are in my way (sometimes, I'm in their way) make a relaxing trip a chore.
    We adjust our Bert for best ride between 10 to 12 kts (our fuel). Other boats (others fuel), comfortable speeds can go higher. When the owner request we stay in, we do, it's their boat and money.
    No shallow concerns.
    No PIA bridges.
    No "No Wake or Manatee Zones".
    I can see traffic miles away and adjust course in plenty of time, No hurrys or confusion around a bend, marina or bridge.
    I feel relaxed more and beat up less off shore. Josie and I can rotate naps. Hard to nap in the ditch, speed up, slow down, speed up, slow down, turn sharp, speed up... How can you nap thru that?
    I have run the ditch at night, don't like it. Luv outside at night.
  15. Pascal

    Pascal Senior Member

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    The most important factor is the boat. You try running th NW channel to Nassau with just 4 footers off the beam in an unstabilized enclosed flybridge boat with tender jetski and spare wheels on the top deck... Not fun. Or run into 3 footers with a boat with wide bloated entry because they had to have a centerline queen with walk around at the bow!

    Then you have 4 footers and you have 4 footers. The stream is a prime example with short steep waves which even if they are just 4' will feel like long 6 footers. Or the lower Delaware when wind opposed current. Nasty with a capital N

    As to the ditch vs outside I prefer the ditch unless I am on a tight schedule. Sure you got to play the tides sometimes and pay attention but it s a smooth relaxed ride. Again depends on the boat. If you re stabilized, and don't have too much stuff to secure outside is fine. But when you have to spend an hour securing everything inside inc the galley, furniture the another hour rinsing the salt all the way to the FB... Not fun Nice run most of the ditch at night over the years, no big deal and no worrying about hitting a log or container 15 nm offshore In fact I prefer running some shallow stretches at night with high tide than during the day with low tides

    All comes to the boat and personal preferences.
  16. HTMO9

    HTMO9 Senior Member

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    One man's trash is another man's treasure

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  17. Capt Ralph

    Capt Ralph Senior Member

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    A+
  18. captainwjm

    captainwjm Senior member

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    Nothing to add; just thanks to all the commentators for a thoughtful, respectful and informative discussion.
  19. P46-Curaçao

    P46-Curaçao Senior Member

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    +1
  20. P46-Curaçao

    P46-Curaçao Senior Member

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    FYI, I found the definition of the wave number in my WindGURU sheet:
    Significant wave height in ft. It is the average height (from wave crest to trough) of the one-third highest waves at a location.

    More details, see: http://www.windguru.cz/int/help_index.php?switchlang=1