1094 
analyses obtained by the methods discussed above.’ 
The first indications of the storm on the wave record 
were some “low-frequency noises” at 1400, 14 March 
. 1945. At that time visual observations at Pendeen re- 
vealed only the presence of 10-sec and 12-sec waves 
from another source; the long forerunners of the swell 
were too low to be visible. 
The band of gradually diminishing periods was the 
result of an intense storm which formed on 10 March 
off the coast of Cuba, 3000 miles from Pendeen, and 
’ 
8 1 (2 (5 
f 20 24 30 8 1@ (2 15 
MARCH 14TH: 
20 24 30 
0400 
0400 
= al 
20 24 30 8 10 12 15 20 24 30 
WAVE PERIOD IN SECONDS 
Fie. 5.—Spectrograms of waves recorded during 14-16 March 
1945 at Pendeen, England [1]. Hach spectrogram gives the dis- 
tribution of energy among wave periods for a 20-minute record. 
The records were taken at 2-hourly intervals. 
traveled in a general northeast direction, passing west 
of the British Isles. Four representative weather maps 
are shown in Figs. 6-9. The positions indicated for the 
“fetches” were determined according to the rules de- 
veloped for wave forecasting.’ It should be noted that 
the fetch lengthened during the time interval between 
1830, 11 March, and 1830, 12 March. 
The spectrogram in Fig. 5 can be interpreted in terms 
of the classical wave theory, according to which com- 
ponent wave trains travel independently with the group 
7. A different type of analysis based on the autocorrelation 
function has recently been applied to ocean waves by Seiwell 
and Wadsworth [14]. 
MARINE METEOROLOGY 
velocity appropriate to their period: 
(10) 
Here 2» and x, represent the location of a point dis- 
turbance and the wave station, respectively; t and t, 
the time of the disturbance and the time at which waves 
of period 7 arrived at the wave station. Equation (10) 
has a simple geometric interpretation on a time-distance 
1830 GCT 
10 MAR. 1945, 
40° 
Fic. 6—Surface weather map for 10 March 1945. Fronts are 
represented in the conventional manner, and isobars are 
labeled in millibars. Point P denotes the wave station at 
Pendeen, England. Figs. 6-9 show the passage across the Atlan- 
tic Ocean of the storm for which the wave spectrograms are 
shown in Fig. 5. (rom Munk [9].) 
diagram (Fig. 10): Rays through the pomt source 
represent the paths of wave periods, the value of each 
period being determined by the slope of the ray. The 
measurement of two periods, 7; and 7s, arriving at 
times t»,1 and t»,., suffices to determine distance and 
time of the source. 
1830 GCT 
Il MAR, 1945. 
l LN 
40° 30° 
Fie. 7—Surface weather map for 11 March 1945. 
Figure 11 shows the propagation diagram used by 
Barber and Ursell [1]. For each spectrogram (Fig. 5) the 
maximum and minimum periods were determined, and 
