Bradford R. Crain wrote: > I don't know if they qualify as a "rogue wave", but Oregon experiences > so-called "sneaker waves" on a fairly regular basis. These are waves > that appear without warning along the beaches and sweep unsuspecting > tourists and beachcomers into the ocean, where moments before they were > "safely" walking on dry sand. I've never actually seen one, but they > make the news every year, sometimes leading to fatalities. Don't know of > any scientific or statistical studies. One particular wave swept the > parking lot at the Barview Jetty at Garibaldi and trapped an elderly > woman under a parked car in 1-2 feet of water. She was rescued. Brad, sneaker waves are caused by constructive interference of two wave trains from different sources. The direction (and distance) of travel being different, now and then a crest from one source will combine with the crest from the other source in the formative stage of becoming surf. When this larger-than-normal combination surges up on the beach (or jetty), it will often be 1.5 times the height of the "average" wave from either source. And, it will run up a lot higher than the average breakers. An experienced and astute observer of the surf zone can pick these out fairly easily as they form. But, folks who are playing near the normal swash zone of "average" waves are never looking far enough out to notice the formation of sneaker waves. Sadly, the victims are often children playing in the swash zone ... now and then crushed by the movement of large logs high above the usual extent of swash. There is a good description of these in Willard Bascom's classic book (long out of print), "Waves and Beaches." As to "rogue waves," there was a good article on them in one of the popular "science" periodicals recently. Wikipedia has a good summary of what is know of these, and describes the likely sources: http://en.wikipedia.org/wiki/Rogue_wave I suspect the "non linear" hypothesis is the culprit. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sat Aug 29 2009 - 17:56:35 PDT
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