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Extreme Waves EXTREME WAVES
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Extreme Waves EXTREME WAVES CRAIG B. SMITH ILLUSTRATIONS BY KURT MUELLER Joseph Henry Press Washington, D.C.
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Extreme Waves Joseph Henry Press 500 Fifth Street, NW Washington, DC 20001 The Joseph Henry Press, an imprint of the National Academies Press, was created with the goal of making books on science, technology, and health more widely available to professionals and the public. Joseph Henry was one of the founders of the National Academy of Sciences and a leader in early American science. Any opinions, findings, conclusions, or recommendations expressed in this volume are those of the author and do not necessarily reflect the views of the National Academy of Sciences or its affiliated institutions. Library of Congress Cataloging-in-Publication Data Smith, Craig B. Extreme waves / by Craig B. Smith ; illustrations by Kurt Mueller. p. cm. Includes bibliographical references and index. ISBN 0-309-10062-3 (cloth) 1. Ocean waves. I. Title. GC211.2.S65 2006 551.46’3—dc22 2006019554 Cover design by Michele de la Menardiere Cover illustration © W. Faidley/Weatherstock Photography Copyright 2006 by Craig B. Smith. All rights reserved. Printed in the United States of America
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Extreme Waves This book is dedicated to those who share my love of oceans.
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Extreme Waves Contents Foreword xi Preface xvii Introduction 1 1 The Calm Sea 11 2 The Four Winds and Waves 25 3 Over the Bounding Main 47 4 Tempests and Storm-Tossed Seas 71 5 Swell 110 6 Terror Waves: Tsunami 127 7 The Southeast Asia Tsunami of December 26, 2004 148 8 A Confused Sea 164 9 Freaks, Rogues, and Giants 184 10 When the Big Wave Comes: Are Ships Safe Enough? 216 11 Davy Jones’s Locker 226 Appendixes A Recent Research on Extreme Wave Models 247 B Units of Measure and Conversion Factors 251 C Glossary of Special Terms 253
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Extreme Waves Endnotes 256 Annotated Bibliography 269 Permissions and Credits 275 Acknowledgments 277 Index 281
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Extreme Waves Plates, Figures, and Tables PLATES 1 Dan Moore surfs a 68-foot-high wave 2 Tsunami damage at Hilo, Hawaii, May 22, 1960 3 Bobsled in the 1998 Sydney-Hobart race 4 Crew prepare to abandon dismasted and sinking Stand Aside 5 (A) A brisk sail; (B) Wind-blown wave in a storm 6 Tidal bore, Qiantang River, China 7 The wreck of the Memphis in Santo Domingo (1916) 8 U.S. Navy Indian Ocean wave forecast 9 Tsunami flooding at Laie Point, Hawaii, March 9, 1957 10 Man caught in tsunami, Phuket, Thailand, December 26, 2004 11 Tsunami-damaged bungalow, Koh Phi Phi Island, December 26, 2005 12 Wave victim on the Agulhas Coast, South Africa 13 Freighter in a typhoon, North Pacific 14 Merchant vessel Winter Water fights heavy seas from tropical storm Georgette, Eastern Pacific Ocean, July 28, 1980 15 North Pacific Ocean storm waves as seen from M/V Nobel Star, winter, 1989
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Extreme Waves FIGURES 1 Types of ocean waves, 13 2 Properties of an ideal wave, 14 3 Ocean surface winds in August, 33 4 Major ocean currents, 36 5 How a barometer works, 43 6 Destructive (A) and constructive (B) interference of waves, 50-51 7 A composite wave with seven components, 52 8 Rayleigh distribution of wave heights, 55 9 Typical NOAA marine weather wind-wave forecast, 57 10 Global significant wave heights, HS, in February (in meters), 58 11 Wave steepness, 64 12 Wind-wave patterns from a hurricane, 98 13 Tsunami wave height and run-up, 129 14 Map of Thira Island and vicinity, 131 15 Tsunami travel time in hours, Chile earthquake, May 22, 1960, 136 16 Map of Koh Phi Phi Island and vicinity, 153 17 Wave diffraction, Newport Harbor entrance, 170 18 Draupner oil platform wave height, January 1, 1995, 208 19 USS Ramapo wave height measurement scheme, 213 TABLES 1 The Earth’s Oceans and Seas, 16 2 Wave Height Versus Wind Speed, Duration, and Fetch, 41 3 Deadliest Hurricanes, Continental USA, 1900-2004, 100 4 Worst Hurricanes, 109 5 The Evidence for Extreme Waves, 215 6 Distribution of Vessels in the World Merchant Fleet, 217
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Extreme Waves Foreword In 2002, while we were doing research on rogue waves in the MAXWAVE project, a sudden spurt of interest from the media swept the globe. Incredible! The web page of the European Space Agency—showing images of rogue waves taken by a radar satellite at night and through the clouds—recorded more hits than some exciting recent news about film stars. E-mails, phone calls, and requests from TV teams poured in; our scientists—especially those with sailor’s beards—were in high demand as interview partners. It is fascinating that we are now able to observe from space the most dangerous waves roaring across the oceans and even do this in the comfort of an air-conditioned computer room. Now satellite measurements can be acquired in remote areas that were not observed before. From the time of the earliest civilizations, humankind has been fascinated with stories of giant waves—the “monsters” of the seas. So a book on rogue waves is obviously of interest to a wide range of people, from surfers to those who crisscross the oceans in the interest of commerce or peace and national defense, and even cruise ships, which today follow routes that in the past only adventurers would have dared to explore. And while scientists continue to debate the details of the na-
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Extreme Waves ture and physics of such waves, this book provides a fascinating, highly readable account of what we know so far about rogue waves. Extreme ocean waves are one of our most frightening images—towers of water pounding down on a helpless boat. You can observe the wall of water coming; you can even calculate when it will arrive, but you cannot run away and you cannot fight it—a classic nightmare. Can we cope with it in the future? Predict extreme waves? Control them? Ride giant waves like surfers? A tragic realization of this nightmare was the December 26, 2004, Southeast Asia tsunami, which was triggered by an earthquake beneath the Indian Ocean. Tsunami are the result of earthquakes that cause large bodies of water to be shifted, creating a long, low wave in the open ocean—but one that rises up and causes tremendous destruction when it approaches shore. Rogue waves on the open ocean—the waves that sink ships and damage offshore structures—are caused by storms. I have received many interesting e-mails offering explanations as to how rogue waves are formed. One individual suggested the possibility that a huge wave is reflected by a cliff and then by chance combines with another such wave that is coming from the other side of the ocean. Another thought that these waves might be generated by little black holes, suddenly springing into existence and causing disruptions in gravity that create walls of water. The media who contacted us were most interested in hearing about monster waves—immense waves that appear suddenly, swallow a ship, and then vanish as quickly as they arise. There is a scientific name for consecutive rogue waves to which ships fall victim—“the Three Sisters”—a term applied to a sequence of three waves that are considered to be as dangerous and unpredictable as three women aiming for the same parking spot at a crowded mall. I suspect, however, that the real explanation of why ships founder is that more accidents happen when a ship’s crew is challenged the third time. In any case, I have not found such patterns in the satellite images I scan for rogue waves. Such simple explanations as high waves being generated in extended storms or the superposition of crossing waves from two different storms seem more reasonable.
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Extreme Waves Sailors, obviously, are the ones who have frequent encounters with extreme waves. Races such as the Fastnet Rock and the 1998 Sydney-Hobart made quite an impression on the sailing community because of the rogue waves participants encountered—leading to new descriptions and fascinating photos of the waves. The harsh reality, however, is that when confronting these terrifying waves, many otherwise courageous sailors simply panic, abandoning their vessels—or, worse, their comrades. History teaches us, of course, that venturing out to sea can prove dangerous. We accept the fact that some vessels will not return home safely—an acceptance that we would find unthinkable for air travel. The shipping community is conservative, not easily open to changes. There are no black boxes on ships; no recorded last messages of the captain. Detailed results of investigations—why a ship sank, why the windows broke or the hatch locks on deck cracked, why the containers moved or the engines stalled—are not present in the news, that is, if the incident makes the news. These tragedies often are attributed to severe weather, something that is unavoidable from time to time. It seems that the main interest in ship accidents still focuses on passenger ships; maybe things have not changed that much since the Titanic, with first-class people coming first? Everything else insured? Thanks to advances in satellite technology, extended in situ measurements, and computer capabilities, vessels can improve the odds of avoiding an accident at sea due to severe weather. Statistics of past events help us predict the so-called 100-year waves in various areas of the ocean and provide a better understanding of the conditions under which ships’ crews must operate. Engineers designing ships and building offshore platforms that are farther and farther from land obviously require detailed knowledge of structural loads imposed by wind and wave. Satellite images of the North Sea do not show an empty space, but rather an area dotted by bright spots of oil platforms more densely inhabited than many land areas. The offshore industry is propelling the advancement of research on rogue waves. There are significant financial ramifications if production at offshore facilities must be halted
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Extreme Waves or platforms evacuated because of the danger posed by a rogue wave. For this reason, many oil platforms are equipped with ocean wave measurement instruments such as radar and laser altimeters and marine radar; buoys are deployed nearby and satellites are watching from above. Still, recent observations of high waves could not be explained by current models. And because platforms cannot move away like a ship, there is an additional incentive to improve construction, especially as the deck sinks during the years of extracting the oil underneath. Engineers are practical people; they have to build structures that withstand such waves. It is lucky if a rogue wave is even recorded. Often the measurements are ignored because people do not believe in them, or they are not stored but are classified as “noise” (spurious data) straight away. What is the highest wave ever observed? Has anybody validated the satellite measurements by in situ observations? Has somebody actually measured a 40-meter-high wave somewhere in the Antarctic winter? Or is it all sailors’ tales? Craig Smith told me that besides being a sailor, he has spent time on an offshore platform that had been hit by a giant wave. So, this book brings realism to the subject for the general reader. Can we predict rogue waves? At the moment, weather centers usually issue forecasts based on the significant wave height. Scientific discussions about the causes of extreme waves are still going on, so proposals for new research or reviews of scientific articles may get top marks from one reviewer and complete rejection from another. Clearly, extreme waves need much more study. For, as Craig Smith explains, numerous lives have been lost and will continue to be lost because ships cannot withstand the forces they unleash. It is our fervent hope that the shipping community will be able to make use of the data gathered by scientists to make ships and offshore platforms more robust. I myself plan to observe the behavior of surf by radar measurements (preferably in Hawaii); to go on a scientific expedition near Antarctica, where the highest waves seem to occur; to validate satellite measurements of such waves from a research vessel; to generate a wave atlas of a global 10-year time series of satellite measurements of ex-
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Extreme Waves treme wave heights;, to complete some written work on this topic as well; and hopefully to find some time to read books such as this one. Prof. Susanne H. Lehner Rosenstiel School of Marine and Atmospheric Science University of Miami and Remote Sensing Technology Institute German Aerospace Center Oberpfaffenhofen
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Extreme Waves Preface As a boy growing up in Southern California, I was never far from the Pacific Ocean and my family spent time on the local beaches during the summers. I recall lazy afternoons bodysurfing at Huntington Beach or going to Balboa Island and swimming in Newport Harbor. I had my first sailing experiences in the harbor with high school friends. We were all avid swimmers, and we went skin diving and spear fishing at nearby Laguna Beach. Turning our backs on land, looking out to sea, all noise and distraction were left behind. The ocean shuts out all other sounds. At night we built a fire and cooked our catch on long empty beaches that today are hemmed in by hotels and exclusive beachfront homes. Other memories are of fishing trips to Catalina on charter boats with my father and his friends. From these experiences came a love of the sea that has never diminished. At the time our daughter Kelly was born in 1968, my wife, Nancy, and I moved with our three-year-old son Kent and new baby to Pacific Palisades, California, to house-sit a friend’s home. The house was an old Spanish-style three-story structure on a hillside high above the Pacific Coast highway. A walkway with a thousand or more steps led down
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Extreme Waves the hillside to a pedestrian bridge over the highway and onto Will Rogers State Beach where we could swim, picnic, or surf-fish. From the balconies on three sides of the house it was possible to look out over the ocean to the south across Santa Monica Bay to Palos Verdes Point and to Catalina Island. On a clear day you could see Santa Barbara Island to the southwest and, to the west, Point Dume and the Channel Islands somewhere beyond. On winter nights when the swell from distant storms reached the coast, you could hear the waves crashing on the beach below. In the late afternoon, the sun illuminated the corrugated appearance of the sea stretching out to the horizon, the rippling water shining in an infinite variety of sparkling reflections and waveforms until at sunset as the sun disappeared over the horizon the colors would turn from blue to orange to gray. On clear nights with a full moon, a long shaft of yellow moonlight stretched out across the sea, the waves clearly visible as they made their way to shore. At night on a balcony, watching the waves, I wondered about their origins—where they came from, why they behaved the way they did, what brought about the variations in their behavior. Finally a day came when our friends returned, and we had to exchange our wonderful beach house for one in the city—a “starter home” that became our residence for the next 30 years. We were only 15 or 20 minutes away from the beaches, but it was not the same. Fifteen years after moving from the beach house, I bought a half interest in a 26 foot-long-sloop named Karess and could once more experience the infinite variations of ocean winds and waves, this time from the deck of a sailing vessel. At sea in a small boat you cannot help but take a personal interest in wind and wave and how they can toss a boat. I was familiar with famous shipwrecks of past centuries—the loss of Spanish galleons and treasure fleets during Caribbean storms or the collision of the Titanic with an iceberg while on its maiden voyage. You would think that with the technologies available during the last two centuries, the rate of loss of ships and human lives would have dropped dramatically. Surely radar, improved design, periodic safety inspections, construction using high-strength steel, and satellite weather observations would ensure that ships are lost much less frequently today.
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Extreme Waves However, in the course of conducting research for this book I learned that the frequency of ship disasters remains surprisingly high. Where do waves come from, and why are some small, some large? In Southern California where I live, every surfer knows that waves come in sets, and it is—depending on the day and conditions—that seventh or tenth wave that promises a long exhilarating ride to the beach. At my present home on the Balboa Peninsula, a few hundred yards from the ocean, I can hear the surf at night. On some nights it is a distant whisper; on others it crashes and rumbles, changing with the tides and distant storms. Let a hurricane pound Mexico’s Baja California 1,200 miles away, and a few days later surfers flock to Newport Beach to take advantage of the southerly swell that arrives, creating waves that crest from a few to a dozen feet in height. There have been occasions when I’ve sat on beaches in California or Hawaii completely awed by the majestic power of storm waves so immense and so violent that I would not have dared to enter the water. (See Plate 1.) Others are bolder than I. Roughly 87 nautical miles from the California coast lies Cortes Bank and Bishop Rock, the latter named for a ship that foundered there years ago. I’ve visited Cortes Bank in my sailboat when the swell was less than 3 feet high. With the boat standing off a few hundred yards from the bank, you can see the swell approach and then rise up in long, glistening waves as the ocean goes from extreme depth to less than 5 fathoms or 30 feet over the bank. Following winter storms, larger swells approach the bank and generate waves 50 to 65 feet high. Surfers have been known to ride these giant waves, traveling to the bank by boat and then being towed out by wave runners at 40 miles per hour to catch the wave. I’ve experienced rough seas in a 50-foot fishing boat making night crossings of the Kauai Channel between Oahu and Kauai or the Kaiwi Channel between Oahu and Molokai, and I’ve sailed my boat among California’s offshore islands when small craft warnings were posted. These experiences suffice; from them I learned the taste of an angry sea. My mouth was metallic dry with fear—even though I was not worried about the sturdy vessel I was in—but you never forget the screaming wind in the standing rigging as it vibrates under the force of mast
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Extreme Waves and sail. There was no escaping the knowledge that I was captive to forces more powerful than me and that it required my skill and a seaworthy craft to sail into the gray sky and changing landscape of a foaming, stormy sea. I write these pages in my friend Andy Youngquist’s boat, Sitting Tall, a 46-foot Bertram. It is a superb sports fisher, powered by two Detroit diesel engines capable of pushing it to 20 knots. At this early hour, just before sunrise, we are on a mooring in Avalon Harbor, Catalina Island, rocking to a gentle swell. Quite different from yesterday, when a Santa Ana wind came up suddenly on the mainland around 26 nautical miles away, and shortly after we’d left the harbor sent waves 3 to 6 feet high into the harbor, bouncing floating docks and causing one boat to founder and sink. This was a perfect example of the interaction of wind and sea; the average height of the waves is determined by the speed of the wind, the length of time it blows, and the fetch, or distance of open water, over which it blows. These were not large waves, but in the tight confines of a small harbor, they had the potential to cause a great deal of mischief. So, the sea reminds me—there are small waves and there are very large waves. As you can see from this book, giant waves—waves so large they tower as high as a 10-story building—are more common than previously believed. Most of the merchant and passengers ships that ply world trade routes today are likely to come out second-best in an encounter with an extreme wave of this height. Along the coasts of the oceans, tsunami are another source of high and destructive waves. My purpose in writing this book is to increase awareness of the hazard represented by giant waves and to suggest ways to mitigate the risk for those of us who live near the sea or whose occupations take us across oceans. May you have fair winds and following seas. Craig B. Smith Balboa, California