CAPE. A relatively extensive land area jutting seaward from a continent or 

 large island which prominently marks a change in, or interrupts notably, 

 the coastal trend; a prominent feature. 



CAPILLARY WAVE. A wave whose velocity of propagation is controlled primarily 

 by the surface tension of the liquid in which the wave is traveling. 

 Water waves of length less than about 1 inch are considered capillary 

 waves. Waves longer than 1 inch and shorter than 2 inches are in an 

 indeterminate zone between CAPILLARY and GRAVITY WAVES. See RIPPLE. 



CAUSEWAY. A raised road across wet or marshy ground, or across water. 



CAUSTIC. In refraction of waves, the name given to the curve to which 

 adjacent orthogonals of waves refracted by a bottom whose contour lines 

 are curved, are tangents. The occurrence of a caustic always marks a 

 region of crossed orthogonals and high wave convergence. 



CAY. See KEY. 



CELERITY. Wave speed. 



CENTRAL PRESSURE INDEX (CPI). The estimated minimum barometric pressure in 

 the eye (approximate center) of a particular hurricane. The CPI is 

 considered the most stable index to intensity of hurricane wind velocities 

 in the periphery of the storm; the highest wind speeds are associated with 

 storms having the lowest CPI. 



CHANNEL. (1) A natural or artificial waterway of perceptible extent which 

 either periodically or continuously contains moving water, or which forms 

 a connecting link between two bodies of water. (2) The part of a body of 

 water deep enough to be used for navigation through an area otherwise too 

 shallow for navigation. (3) A large strait, as the English Channel. (4) 

 The deepest part of a stream, bay, or strait through which the main volume 

 or current of water flows. 



CHARACTERISTIC WAVE HEIGHT. See SIGNIFICANT WAVE HEIGHT. 



CHART DATUM. The plane or level to which soundings (or elevations) or tide 

 heights are referenced (usually LOW WATER DATUM). The surface is called a 

 tidal datum when referred to a certain phase of tide. To provide a safety 

 factor for navigation, some level lower than MEAN SEA LEVEL is generally 

 selected for hydrographic charts, such as MEAN LOW WATER or MEAN LOWER LOW 

 WATER. See DATUM PLANE. 



CHOP. The short-crested waves that may spring up quickly in a moderate 

 breeze, and which break easily at the crest. Also WIND CHOP. 



CLAPOTIS. The French equivalent for a type of STANDING WAVE. In American 

 usage it is usually associated with the standing wave phenomenon caused by 

 the reflection of a nonbreaking wave train from a structure with a face 

 that is vertical or nearly vertical. Full clapotis is one with 100 

 percent reflection of the incident wave; partial clapotis is one with less 

 than 100 percent reflection. 



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