A significant wave height of 43 foot means that the mariners should expect about 1% of the waves will be 71 feet.
From When Do Ocean Waves Become ‘Significant’? A Closer Look at Wave Forecasts
If you read a marine weather forecast predicting “SEAS 10 FT,” what is really being conveyed in that forecast?
Hs = 10 ft
H (mean) = (0.64)Hs = 6.4 ft
H (most probable) = 6 ft
H1/10 (10% highest waves) = (1.27)Hs = 12.7 ft
H1/100 (1% highest waves) = (1.67)Hs = 16.7 ft
Hmax (highest wave you should be on the alert for) = 20 ft!
This is not something mariners should be confused about. In 20 foot seas about 1% of the waves would be expected to be 33 feet. If a mariner believes he has encounted 30 foot seas when it was in fact 20 feet he will not understand what it means when the forecast calls for 30 foot seas (1% 50 foot waves)
