Basic Marine Weather
45
What is a “steep” wave?
•Subjective.
• 9' by 9 second is definitely steep.
• The “square” rule is popular, but:
•
• 9x9 implies 9' x 400'   (pretty steep)
• 20x20 implies 20' x 2000‘ (not steep)
The square rule only applies to a small range of wave heights, up to about 11feet‘ by 11 seconds.  A 20 foot by 20 second wave is not steep, for example.  The problem is that wave length is equal to the period squared.  As the period increases, the wavelength increases much faster.