Wave height vs Seas in feet.

[Stumpalump]

In the thread about followings seas I was wondering how people measure wave or sea height. My understanding is a 4' sea is 4 feet above flat which gives an 8' wave. I know suffers confuse it by measuring height from the front in some areas and the rear or even "surfable wave height". On a TV episode of Wicked Tuna most would not go out in 4-6' seas. I assumed that was because a 12 foot wave from trough to crest was possible. Throw in a narrow inlet or a rouge taller wave and that makes a 4-6' sea not navigable for a lot of those large experienced tuna boats. So what is your understanding and who exactly is calling a 4' sea on the marine radio?

 

[alldodge]

Wave height is = a 4 foot wave is 2 feet above flat and 2 feet below. So a 4 above and 4 below is an 8 foot wave

 

[Old Ironmaker]

I know when Transport Canada Marine Weather Service report current conditions of 1 to 1.5 meter waves which is around 4.5 to 6 feet there are not 12 foot waves , no way we are fishing in 12 foot waves. Is there something lost in translation?

 

[airshot]

It is really quite simple....distance from highest point of wave to lowest point of wave equals wave height. On inland water there is no tide to be concerned and the waves are closer together than on the ocean. For example on Lake Erie in the great lakes, waves average approx. 7-8 ft from one wave to the next or distance between waves. In the ocean the waves might be 50 ft apart so a tall wave in the ocean may not seem very high due to the distance between, however on our lake a 3-4 ft tall wave seems really rough due to the short distance between waves. I have been on the ocean in 12 ft waves and barely realized the boat going up and down because of the great distance between them. Bottom line is... top of one wave to bottom of another wave is wave height.

 

[Old Ironmaker]

It is really quite simple....distance from highest point of wave to lowest point of wave equals wave height. On inland water there is no tide to be concerned and the waves are closer together than on the ocean. For example on Lake Erie in the great lakes, waves average approx. 7-8 ft from one wave to the next or distance between waves. In the ocean the waves might be 50 ft apart so a tall wave in the ocean may not seem very high due to the distance between, however on our lake a 3-4 ft tall wave seems really rough due to the short distance between waves. I have been on the ocean in 12 ft waves and barely realized the boat going up and down because of the great distance between them. Bottom line is... top of one wave to bottom of another wave is wave height.

I'm a slow learner at times. Great explanation thanks. Yes those waves are larger than they appear to be to me. I need to learn and then understand something everyday. I watched waves here this morning and yes they are larger from below flat or bottom to crest than I thought they were. What I would have described a 1 foot chop is actually 3 feet or so. Boaters contact me regularly and ask what I see from the cottage, maybe now I can tell them what the wave height actually is.

 

[Stumpalump]

I'm a slow learner at times. Great explanation thanks. Yes those waves are larger than they appear to be to me. I need to learn and then understand something everyday. I watched waves here this morning and yes they are larger from below flat or bottom to crest than I thought they were. What I would have described a 1 foot chop is actually 3 feet or so. Boaters contact me regularly and ask what I see from the cottage, maybe now I can tell them what the wave height actually is.

Fresh water is less buoyant so you dig in deeper and faster compounding the short wave issue but I'm still confused on your "1 foot chop". That's what I would call it and expect 3' waves. What will the weather report on the marine radio call that and what should we call it? Is it one foot seas?

 

[shrew]

For example on Lake Erie in the great lakes, waves average approx. 7-8 ft from one wave to the next or distance between waves. In the ocean the waves might be 50 ft apart so a tall wave in the ocean may not seem very high due to the distance between,

The distance between two wave peaks is referred to as 'period' and it is measured in time (seconds) not feet. Wind speed and bottom conditions dictate the period. The closer the period (shorter time in seconds), the steeper the waves. I agree that you can't just go by avg height. You need to consider wave period as well. 8 footers with a 20+ second period is like driving on a rolling country road.

What the OP sounds like he is describing is the difference between the average wave height, and the 'Significant Wave Height'. Significant wave height, WVHT, is approximately equal to the average of the highest one-third of the waves, as measured from the trough to the crest of the waves.

http://www.ndbc.noaa.gov/wavecalc.shtml

 

[alldodge]

In fresh water (not talking great lakes) it would be called a 1 foot chop, or waves. In the ocean it would be Sea State 2.

Sea State with pics
http://www.wdcs.org/submissions_bin/WDCS_Shorewatch_Seastate.pdf

All states in Meters

 

[shrew]

Incidentally, There are two things to consider here. In Wicked Tuna they are sitting at anchor on a ledge. The waves stand-up and get much taller and steeper (period reduces) as they move from deep to shallow water. NOAA broadcasts conditions for large regional areas. Whatever the predicted sea-state, it will be worse over a ledge, reef, or shallow point. Sitting on anchor is much different, and much rougher than drifting. Sitting on anchor in rough conditions beats the crap out of you.

 

[dingbat]

On a TV episode of Wicked Tuna most would not go out in 4-6' seas. I assumed that was because a 12 foot wave from trough to crest was possible. Throw in a narrow inlet or a rouge taller wave and that makes a 4-6' sea not navigable for a lot of those large experienced tuna boats.

Boating in 4-6 ft. seas isn't bad in itself. A bit "sporty" but nothing that would keep us off the water with money on the line.

I can only assume the 4-6' seas where coupled with tight wave periods at which point, they become a personal safety issue.

Boating in a tight, 4-6 ft. sea is like riding a bucking bronco for hours on end at a time. It will kick the stuffing out of you. It's also downright dangerous. It's hard enough to stand up in those conditions let alone man the deck of a fishing boat. Slip, fall, bang your head, help is an hour or so away at best. Get thrown overboard and

I did a lot of "combat" fishing when I was a much younger, foolish kid. Come back to the dock with legs burning and bruised from head to toe. Not so much any more.

I fished a three day tournament in 4-5' last Spring. Ibuprofen is your friend.

 

[fhhuber]

I think I've seen every sea state possible...

We had a wave break over the bow of the USS Carl Vinson ( 93,000 ton aircraft carrier...) and wash over the whole flight deck.
Once you've experience that... you have a huge respect for water.

We got to watch the destroyer escort play submarine with just the top of its stack above water a couple of times.

When they say sea state 9 is phenomenal... its something you have to experience to understand.

I think I'll stick to waves that aren't taller than my boat.

 

[airshot]

The distance between two wave peaks is referred to as 'period' and it is measured in time (seconds) not feet. Wind speed and bottom conditions dictate the period. The closer the period (shorter time in seconds), the steeper the waves. I agree that you can't just go by avg height. You need to consider wave period as well. 8 footers with a 20+ second period is like driving on a rolling county road

http://www.ndbc.noaa.gov/wavecalc.shtml

Been a boater for all these years and did not know about the "period".....no matter how old I get I still learn new thing every day! I understand it, just never heard the term, Thanks for the info.

 

[sphelps]

All I can add is when I drop in after the bottom turn and have to look up to see the crest ... I'm calling it over head ...
I guess in Hawaii that would be called 2 to 3 ft ...