Wave Height Estimation - Hawaii
The link you just followed used to
point to this page: surfing.about.com/blwaveht.htm ("Estimating
Wave Height"), but that URL is no longer valid. It was a
brief article on how surfers decide wave height and offered
a
good description of the Hawaii-surfer estimation standard by a
well-known Australian (I think) surfer (I can't recall his name).
If I'm remembering correctly, the gist
of it was: (1) take the wave face and divide by two; (2) examine
the result, the quotient, to see how many multiples of five it
contains; and, (3) for each multiple subtract one foot. That's
it.
For
example:
How big is a wave with a 20-foot face?
(1) 20 / 2 = 10
(2) 10 / 5 = 2
(3) 10 - 2 = 8
Answer: 8 feet. |
Thusly, a wave with a 30-foot face is a
12-foot Hawaii-style wave. This particular calculus gives the
most accurate result based on my experience. That is to say, it
is the best mathematical expression of how most people use the
Hawaii-surfer method of underestimating wave height.
Some comments. First, you just have to guess
as to the base wave-face value. This definitely will vary with
the observer. One way would be to use a surfer on the wave as
a measuring stick. Again, this is necessarily a subjective exercise.
Second, for wave-face heights of less than
ten feet you could use the alternative measure of body-reference
points, e.g., knee-high, waist-high, chest-high, head-high, slightly
overhead, etc. Basically, I would call a slightly-overhead wave
a 3-footer; a head-high wave, a 2-footer.
Lastly, it often helps to verify or arrive
at an estimation by asking other people for their opinion. This
is determination through consensus. If I really care about figuring
a height, then I might ask some of the other surfers in the water
or even someone watching on the beach. It's surprising how the
responses of several people will usually converge toward a narrow
range, that is, they will be in general agreement.
Here are some articles on the topic:
"Isle
converts to global wave measures" (from the Honolulu
Star Bulletin).
"Hawaiian
Scale: Measuring Wave Heights in Hawaii" (by Neal
Miyake, in his Hawaii
Surf Scene column).
"Willard
Bascom: Estimating Breaking Wave Height."
Back to Extempore
