NATURAL PHENOMENA 



UPWARD-FLOWING WATERFALL 



At Rathlin Island, off the north coast of Ireland, a small stream 

 normally falls from bare cliffs into the sea. The source of the 

 stream is a small lake on the island. With northerly winds of over 

 45 knots in force, this stream has been observed to be blown back 

 from the cliffs toward its source. From 3 miles offshore under these 

 wind conditions the water of the stream appears as cloudy mist bil- 

 lowing high in the air before drifting downward and setthng in a 

 turbulent mist. 



WATERSPOUTS 



Mariners have faithfully observed and reported waterspouts over 

 the years, and oceanographers and meteorologists have a continuing 

 interest and need for information concerning them. 



Waterspouts are the result of meteorological conditions and do 

 not affect them. Thunder and lightning, which often occur with 

 this phenomenon, evidence the state of the atmosphere that is likely 

 to generate electrical storms and waterspouts. 



This phenomenon occurs more frequently in the tropic zones but 

 also occurs in the temperate zones and have been observed off the 

 coast of England. 



Tornadoes and typhoons have their special seasons, and follow 

 fairly stable patterns of activity. Waterspouts, however, are quite 

 unpredictable. They are irregular in their occurrence, are generated 

 in gales or calms, and form over warm and temperate waters. They 

 move with, against, or across the winds, rotate both cyclonicly and 

 anticyclonicly, and move with varying speeds from slow to rapid, 

 and range from moderate to strong in force. 



The size of waterspouts varies from high and narrow to low and 

 wide. They have been observed from 10 to 5,000 feet in height and 

 from 10 to 500 feet in width. Duration averages about 30 minutes 

 but some lasting up to an hour have been observed. 



A waterspout may be simply defined as a column of water over 

 the sea sustained upright by a whirling circular wind movement. 

 Shaped often like an inverted cone they appear to descend from 

 heavy cumulonimbus clouds until they meet a cone of spray raised 

 from the sea, forming a column or spout of water between the sea 

 and cloud. The funnel point seems to descend slowly and at the 

 point of contact with the sea appears agitated with a cloud of spray 

 forming. 



The occurrence of any waterspout depends to a large extent on 

 local unstable atmospheric conditions. In many cases the cause is 

 the importation of air of much lower temperature than the sea sur- 

 face over which the air passes. It is believed that the interior and 

 exterior parts of water spouts have opposite circulation, and that 

 the descending central currents of rain precipitate around the 

 virtually empty core of the spout. 



Sometimes waterspouts dissipate quietly, but there is generally 

 some agitation. The lower part breaks releasing a torrent of fresh 

 and salt water accompanied by sleet, snow, or hail, the weight of 

 which can cause considerable damage. 



Waterspout 



52 



