1989). The first is low wind situations, where the wave field is characteris- 

 tically low- frequency swell propagating in from distant storms in the open 

 Atlantic Ocean. These waves typically arrive from the east to southeast. 



82. The most common wave -generating winds are Northeasters which arise 

 from either frontal passages or extratropical storms. Frontal systems 

 typically arrive from the west to northwest and have a north- south to north- 

 east-southwest orientation. Winds preceding a frontal passage are typically 

 from the south to southwest. Few nearshore waves are generated because such 

 winds are directed offshore so the regime is fetch limited. Following a 

 frontal passage, winds typically come from the north to northeast. These 

 winds actively generate waves and, if the front stalls near the warm Gulf 

 Stream, considerable nearshore seas can build. Extratropical storms originate 

 as cells of low atmospheric pressure south of the site along the south 

 Atlantic coast. These storms tend to migrate northward along the coast, 

 creating high winds from the east to northeast. 



83. Less frequent but more intense wave generators are hurricanes, the 

 fourth type of disturbance. These originate in the equatorial Atlantic, 

 migrate west to northwest, and can make landfall on the Gulf and Atlantic 

 coasts with very destructive winds and waves. Although several hurricanes 

 have passed over or near the FRF since its founding in 1979, none did so 

 during this study. 



Physical Description of the Array 



84. The high-resolution directional wave spectra obtained in this 

 investigation are derived from two fundamental parts. The first is an array 

 of sensors which sample sea surface displacement at several points in (hori- 

 zontal) space. The second is the mathematical treatment of these data to 

 obtain estimates of wave directionality. The two parts are coupled; gage 

 positioning is tuned to optimize the effectiveness of the analysis algorithm. 



85. The fundamental principle of operation is based on sampling a 

 moving wavy surface with more than one gage. If a single gage samples this 

 surface, no directional information is obtained; a time series from a single 

 gage will not vary with wave propagation direction. If two, slightly separ- 

 ated gages are used, then a wave crest will generally be detected at one gage 

 before it is detected at the other. The time difference for this wave crest 



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