Rogue or Freak waves get their name from their height, which is abnormally high compared to the sea heights observed prior to the occurrence of this type of wave. The USS Shreveports bow and crashed into the superstructure at bridge level. It knocked out every window in the bridge, and men and equip-ment were battered. Prior to meeting this freak wave, the seas were normal, based on the wind conditions at the time. Such abnormal waves are highly infrequent and totally unpredictable.

Oceanographers are not sure what causes these waves, but based on studies of encounters such as that of the USS Shreveport, oceanographers have found that these waves occur most frequently in areas of strong sea-surface temperature gradients. Such gradients exist where cold and warm sea currents meet. One such area is the "North Wall" of the Gulf Stream, off Cape Hatteras. Another area exists along the coast of

Table 1-1-3.-Combined Sea-height Table

South Africa, where the cold Benguela Current meets the warm Alguhas Stream.

Learning Objective: Define surf, and recognize the factors that affect it.

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