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CRAMP: South Swell

South Swell is generated by Antarctic Southern Hemisphere winter storms. These waves are generally encountered in summer and early autumn. South Swell impacts Hawaiian coastal areas primarily from a dominant southerly direction of 190°, but this can vary between 236° and 147°. Typical wave heights range from 1 to 4 ft. with periods of 14 to 22 seconds. Under extreme conditions waves may reach heights of from 5 to 10 feet. Waves generated in the southern Pacific take 6-8 days to reach Hawai‘i and lose much of their energy due to spreading before they reach the islands. These waves are well sorted. South Swell rarely approaches the heights seen on the northwest shores in winter. The largest South Swell waves on record (June 1955) had faces over 6 m (20 ft) breaking in shallow water.

 

The first large Antarctic storm of the 2001 season reached high intensity as shown by this WAM nowcast for 6 July 01 and verified by satellite data. Data from NOAA/NCEP website. (Click for larger view)

 

Storm waves generated during this storm increase in wavelength and decrease in height as the spread and move north toward Hawai‘i. Note the increase in wave period to over 20 sec. with travel time shown in the figure. Travel time to Hawai‘i is approximately 6 days. Peak storm surf reached Hawai‘i on 11 July 01. Data from NOAA/NCEP website. (Click for larger view)

 

Last Update: 04/21/2008

By: Lea Hollingsworth

Hawai‘i  Coral Reef Assessment & Monitoring Program

Hawai‘i  Institute of Marine Biology

P.O. Box 1346

Kāne‘ohe, HI 96744

808-236-7440 phone

808-236-7443 fax

email: jokiel@hawaii.edu