Wave height judgement

[Champagne Murphy]

Is there a useful method of assessing wave height whilst at sea? I ask because on Wednesday, returning from Nieuwpoort to Ramsgate we saw everything from lumpy to flat and always find the ‘lumpy’ hard to judge in ‘real’ height.
Just curious.

 

[Leighb]

When an oil tanker disappears in the troughs when viewed from the upper deck of the Harwich Hook Ferry you know it is seriously rough!!

 

[Yngmar]

Lower your viewpoint until the top of the nearest wave obscures your view of the rest. Depending on wave height, you'll have to peek out a portlight down below, over the cockpit coaming, or climb up the bottom two mast steps

Then estimate (or measure) the distance from your eyes down to the the average waterline of the boat. Multiply by two (wave height is measured peak to through).

I don't think "lumpy" is a well defined term though, and the unpleasantness of seas is about much more than just wave height. For example on the Portugese Atlantic coast we regularly sailed in 3-4m swell (couldn't look over the top of waves while standing up at the helm) and it was no big deal. But that was large interval (distance between waves) swell. In comparison, when a gale on the way to Almerimar rapidly kicked up just 1-2m swell, but very steep (short interval), things got very unpleasant surprisingly quickly (different oceans behave differently).

And then there's direction, cross seas, tidal overfalls, etc. that are major factors for safety and comfort. We puked a fair bit on the first leg across Biscay, because there was a three-way cross-swell shaking the boat in every direction. Once it picked one direction and stuck to it, we were fine and the ride a lot more comfortable.

 

[capnsensible]

This is 'a bit bumpy'.

 

[Sybarite]

(wave height is measured peak to through). .

In Adlard Cole's "Heavy Weather Sailing" he defines wave height as the distance from mid point to the crest of the wave ie half the height as measured from trough to crest.

 

[Stemar]

When you're standing in the cockpit and find yourself looking up at the dinghy you're towing, it's lumpy. In the Solent, it's more than just lumpy, it's 'orrible.

I suppose the Solent chop is far nastier than normal seas of the same size because of a much shorter wavelength

 

[[3889]]

In Adlard Cole's "Heavy Weather Sailing" he defines wave height as the distance from mid point to the crest of the wave ie half the height as measured from trough to crest.

That's normally referred to as amplitude.

 

[Yngmar]

In Adlard Cole's "Heavy Weather Sailing" he defines wave height as the distance from mid point to the crest of the wave ie half the height as measured from trough to crest.

Not in my 7th edition. "Crest to trough" is the terminology used. Which is also the definition in fluid dynamics: https://en.wikipedia.org/wiki/Wave_height

 

[AndrewB]

If when standing up in the cockpit, the nearest wave blocks out the horizon, then you have 3m waves. Above that is big, below that is small.

 

[Sybarite]

Not in my 7th edition. "Crest to trough" is the terminology used. Which is also the definition in fluid dynamics: https://en.wikipedia.org/wiki/Wave_height

That's possible. I have a much earlier version.

 

[KellysEye]

I think assessing wave height comes with experience the more you see the better you get. I remember over the Atlantic one morning we had we had 12 foot swells and six foot waves. Also in the distance you can see rogue waves that are much higher than others.

 

[mjcoon]

I think assessing wave height comes with experience the more you see the better you get.

How does that work unless you get calibration feedback? Could be more like "the one that got away" that gets bigger every time it gets mentioned... ;-)

Mike.