620 



GROEN AND GROVES 



[chap. 17 



Fig. 7. Three synoptic charts of sea-surface disturbance heights during the storm-surge of 

 31 January- 1 February, 1953, in the North Sea. Disturbance heights are given in 

 meters. 



The peak water level usually occurs considerably to the right of the hurricane's 

 track, and the region of high water extends further to the right than toward the 

 left. (These remarks refer to the Northern Hemisphere.) 



The resurgences are oscillations occurring after passage of the hurricane and 

 the hurricane surge. A good example is the Atlantic City record in Fig. 6. They 

 can be particularly hazardous as they are often unexpected, arriving after the 

 storm appears to be subsiding. If the phase of the astronomic tide is right, one 

 or more of the maxima may be higher than the original hurricane surge itself. 

 The resurgences are due to more-or-less free ijiotion of the water, not under 

 much influence of the hurricane once they are generated. Munk et al. (1956) 

 attribute them to a "wake" of waves in the trail of a hurricane (analogous to a 

 ship's wake) progressing along the coast. The period would be that of a free 

 edge wave, whose phase velocity is equal to the velocity of motion of the hurri- 

 cane (see page 640). Observations of many trains of resurgences seem to be in 

 agreement with this hypothesis. But Kajiura (1959) points out that there are 

 large differences in the period between ports separated by less than a wave- 

 length of the supposed free-edge wave, and attributes the resurgences to a free 

 onshore-offshore standing wave on the shelf. 



Other types of meteorological disturbances and other environments give rise 

 to surges of varied characteristics. Surges in the open ocean have been observed 

 at islands. The amplitude is seldom large at islands rising sharply from the deep 

 ocean. Islands in shallow regions can experience large surges, such as the 

 damaging one at Wake Island, January 17-18, 1953. 



