those in Chapter 7 show that a wave group would have to last a 
considerable length of time before the elemental vectors in the 
partial sum become sufficiently out of phase to cancel out the 
wave amplitude. Note the change in the direction of the apparent 
crests. The crests appear to be coming from a point source at 
these distances. 
Period increase of swell 
If figure 22 were actually to approximate the power spectrum 
at the source, the period increase of ocean swell can also be 
explained by this model. The "significant" period for the highest 
waves passing a point of observation would increase from a value 
of approximately seven seconds in the storm to a value of ten 
seconds at distant points of observation, but it would not in- 
crease indefinitely. 
Complete reality of the final model 
The decrease in wave height with travel, the transformation 
from an irregular choppy short crested "sea" to a regular "long 
crested" smooth "swell!' the arrival of waves at points at an 
angle to the main direction of the winds in the storm, the period 
increase of the swell and the so-called forerunners of swell are 
all explained by this model. Note that the "swell" is still 
Gaussian. The author has yet to see a natural wave record even 
approximately equal to A sin 2rt/T over a time interval of 20 
minutes. 
i ee a SE. ES SS 
The final forecast formula, given by equation (9.71) and 
the auxiliary formulas given by equations (9.24), (9.25), (9.46), 
4 etal = 
