Quantcast Southern Hemisphere Swell

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Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 14
tropical storm will occasionally move far enough north to cause destructive
high waves. The storm of September 1939, which passed directly over
southern California causing very high waves, is an example (Horrer, 1960).
3.1.2 Southern Hemisphere Swell
Munk, et al., (1963) point out three major source areas: The Ross Sea, the New
Zealand-Australia-Antarctic sector, and the Indian Ocean. These southern ocean
source areas are partially blocked by island chains in the South Pacific Ocean. The
South Pacific is such a large area that waves from several southern storms
commonly reach southern California simultaneously. Southern swell is most
important during the southern winter from April through September.
3.1.3 Sea
Sea is the term applied to short, steep waves that are still in or near the area in
which they are generated. Wind conditions that generate sea vary greatly as one
moves offshore from the southern California coast, changing from relatively mild
winds over the inner channels, to strong, gusty winds outside the islands.
3.1.4 Summaries of Wave Data
Directional wave information is available from various sources. Among others,
Seymour, et al. (1984) have produced storm wave hindcast estimates for the period
1900-1984 using a hindcast location near 35EN, north of Point Conception and the
Channel Islands.  Only waves with deep-water-approach directions between
SOUTHWEST and WNW were considered, because waves approaching more
obliquely would be considerably diminished by refraction as they approached the
shoreline. Further, the waves were ranked by their power (energy multiplied by
period).  This resulted in a list of 59 storms in which the resulting offshore
significant wave height exceeded 3 m (10 feet), all having periods equal to or
exceeding 12 seconds. The tropical cyclone of September 1939, a major wave
event in southern California, was added, for a total of 60 storms. These storms are
listed in Table 2.



 


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