(see figure 25). Conversely, tremendous amounts of energy have 
to be supplied to the sea surface from the winds in the storm 
overhead. For a steady state, the energy supplied per second 
from the atmosphere to the waves must balance the energy dissi- 
pated per second by the waves in breaking at the crests and the 
energy per second which flows out of the forward edge of the storm 
area as the waves propagate into the area of calm. The balance 
must hold for each possible elemental area in a net of the p ,@ 
plane. 
At the low end of the power spectrum, very large amounts of 
energy are leaving the generating area every second. Consequently 
the lower the value of » , the more difficult it is for the storm 
to maintain a wave of any appreciable amplitude. Therefore, as # 
is decreased the power spectrum must pass through some peak value 
and then begin to decrease as # gets close to zero. 
If the oceans were infinitely deep these considerations would 
hold exactly and equation (11.21) would have to hold exactly. The 
oceans are only about 3000 meters deep. A wave 6000 meters long 
is still essentially in deep water. This corresponds to a period 
of 61.7 seconds or a » of 27/61.7 seconds. Thus for » less than 
21/61.7 seconds, these arguments do not hold exactly. However, the 
rate of energy flow out of a generating area is still tremendous 
for # less than 27/62 and the arguments are still qualitatively 
valid since the ocean is not really shallow water (C = “gh ) until 
the period of the waves becomes about 1330 seconds. The point, 
B= 21/1330, is very close to the origin in all of the forecast- 
ing curves which have been shown. 
17 
