where
Ho = deepwater significant wave height in feet
Ts = the corresponding significant wave period in seconds
R = radius of maximum wind in nautical miles
△p = Pn " Po> where p^ is the normal pressure of 29.92 inches
of mercury, and p$ is the central pressure of the hurricane
V? = The forward speed of the hurricane in knots
Ufl = The maximum sustained wind speed in knots, calculated for
30 feet above the mean sea surface at radius
R
where
U„ = 0.865 U
(For stationary hurricane)
(3-33)
U„ = 0.865 U
+ 0.5 V„ (For moving hurricane)
(3-34)
XT
TTl CuC
X*
= Maximum gradient wind speed in knots 30 feet above the
water surface
umx ’ °-868 I78 (P« - Po)1/2 - R(0.575f)J
(3-35)
f = Coriolis parameter = 2œ sin4>, where œ = angular velocity of
earth = 2tt/24 radians per hour
Latitude ()
25°
30°
35°
40°
f (rad/hr)
0.221
0.262
0.300
0.337
a = a coefficient depending on the forward speed of the
hurricane and the increase in effective fetch length,
because the hurricane is moving. It is suggested that
for slowly moving hurricane a = 1.0.
Once
is determined for the point of maximum wind from Equation
3-3 lit is possible to obtain the approximate deepwater significant wave
height Ho for other areas of the hurricane by use of Figure 3-34.
The corresponding approximate wave period may be obtained from
T =2.13
(in seconds) ,
(3-36)
where Hp is in feet (derived from empirical data showing that the wave
steepness H/T2 will be about 0.22).
3-58