WAVE GROUPINESS IN LONG-TRAVELED SWELL.

The swell, with most of the energy concentrated within a narrow band of frequencies is assumed to have originated in the southern Indian Ocean. The longest run of high waves identified contained 6 waves for H greater than H//s and 16 waves for H greater than H OVER BAR . The observed probabilities of runlengths are in agreement with the theroy of A. Kimura. Very high correlation between successive wave heights and significant correlation up to 5 waves apart, which is higher than all earlier reports, are observed. It is found that the correlation coefficient between successive wave heights r//H//H is a better parameter to define the length of runs of wave heights than the spectral peakedness parameter. The high values of runlengths observed raise doubts regarding the concept of a decrease of runlengths in shallow water, which has lately been confirmed by E. F. Thompson and W. N. Seelig.