Hi,

H2%=1.39*SignificantWaveHeight

Explanation:

H2%=2.23*MeanWaveHeight (e.g., Lopatoukhin. 2004, Wind Waves, ISBN 5-87403-050-6)

SignificantWaveHeight = 1.6*MeanWaveHeight  (e.g. Janssen. 2004, Interaction of ocean waves and wind, CUP, 385 p.)

hello

They are slightly different definition

1) Sig. wave height= four times the standard deviation of the surface elevation – or equivalently as four times the square root of the zeroth-order moment (area) of the wave spectrum (ref. Holthuijsen, Leo H. (2007). Waves in Oceanic And Coastal Waters. Cambridge University Press. p. 70. ISBN 978-0-521-86028-4). or

2)  The significant wave height  is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves (H1/3).

There are small differences between the two definitions

Concerning H2%, I think it is equivalent to percentile 98th of the wave distribution

See attach document:

http://www.mxak.org/weather/pdfs/waves.pdf

Good luck

Thanks for the reply Natalia Sukhikh and A. Robichaud

Hello,

I understand that H2 and Hs (average significant wave height) are the same thing which is the wave height of the 1/3rd highest waves in a given time group.

The percentage the Hs value is of all the waves in the group is = (.66 +1)/2 = .83

hence the conversion of average Hs to Havg is Havg = Hs*.83

So, the average wave height [Havg] of all the waves in the group where the Hs = .25 m would be = .25 * .83 = .2075 m