Aloha,
No ice here tonight, but, big waves on Hawaiian beaches tonight.
Consider:
Beaufort Wind Scale: Force 12 = 73 mph winds, 45-foot seas
very quickly, just a few hours!!
Height of waves is directly proportional to how hard the wind
blows, how long it blows, and how much room on the ocean
there is: speed, duration , and fetch. Force 12 winds over Lake
Michigan can generate wave heights of 35 feet after 10 hours or
so, but no higher -- Lake Michigan is not big enough with open
water to generate bigger waves. At Force 12, on Lake Michigan
after 10 hours, the "sea" is fully developed. Every wind speed has
a minimum fetch (sea size); ocean waves driven by Force 12
winds take about three or four days to reach their full potential:
across a thousand miles of ocean, Force 12 for 60 hours will generate
waves of significant height of 97 feet!! And peak heights of about
twice that. However, such waves have never been recorded --
they would take to the bottom any ship or instrument that could
possibly be in position to record such data!!
The harder the winds blow, the bigger the waves get
and the more wind they can catch. It's a feedback loop:
the waves rise exponentially with wind speed. The total
amount of wave energy in a storm does not rise linearly
with the wind; but to the fourth power!! The seas
generated by a forty knot wind are not twice as violent
as a twenty knot wind: they are 17 times as violent.
Storms South of Alaska, such as those sweeping across the
North Pacific tonight, and those far, far to the South off
Antarctica can and have generated swells that are half a mile
between crests and travel 30 or 40 miles an hour. When they
reach the beaches here in Hawaii, breakers up to forty feet
high can result!!
There is more, but you get the idea about Force 12.
Sleep well you island and coastal land dwellers.
73, Jim, KH7M
On the Island furthest to the North in Hawaii, Kauai.
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