OBJECTIVE
METHODS FOR FORECASTING SEA WAVES
There
are a number of different methods for forecasting sea
waves. Some of the methods are too technical or time consuming to be of
practical use of Aerographer’s Mates.
A
relationship between wave velocity (c), wave length (L), and period (T) maybe
indicated using the equation C = 3.03 T.
The
length in feet of a deep-water wave (L) may be computed using the equation L =
5.12 T. The period of a wave in seconds (T) may be calculated using the equation
T = 0.33 C, where (C) is the wave velocity.
Sea
state forecasts are divided into four categories:
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significant
wave height (HID),
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average
wave height (HAvG),
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one-tenth
average wave height (HIJ1o),
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and
high wave (Hw).
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For
more information, refer to the practical training publication Sea and Swell
Forecasting, NAVEDTRA 40560, published by the Naval Oceanographic Office.
This publication presents a method for forecasting sea
waves, and a brief summary follows.
In
order to prepare an accurate sea state forecast one must frost determine wind
speed over the fetch (U), length of the fetch (F), and the length of time the
wind speed (u) has remained unchanged within the fetch (u). These parameters are
determined using current and/or previous surface charts. Using these parameters
and the tables in NAVEDTRA 40560, an accurate sea state forecast may be obtained.
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