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Extreme Waves 4 Tempests and Storm-Tossed Seas Mariners try to avoid storms and the rough seas that accompany them. Sometimes, however, that just isn’t possible. One spring, shortly after I’d purchased Dreams, Nancy and I took our good friends Mark Reedy and Valerie Clarke to Catalina Island. They were both from the Midwest, caught in the throes of a particularly long and miserable winter, and looking forward to spending some time in sunny California. We sailed to the isthmus of Catalina Island, where we picked up a mooring and planned to spend several days hiking and exploring the island. Unfortunately, the weather took a sudden turn for the worse, and by Sunday morning, our planned day of departure, a small-craft advisory was issued, warning of winds of 30 knots and gusts of 35 or 40 knots. Since we all had travel plans for the coming week, we could not stay and sit out the storm. One option was to return to the mainland on the Catalina Express, a fast, twin-hull passenger ship destined for the Port of Los Angeles. But if I did this, it would mean leaving my new boat unmanned on a mooring in Isthmus Cove, Catalina, and there was no way I would do that. Thus, we decided that Nancy and Valerie would return to the mainland on the Catalina Express, take a taxi from the Port of Los Angeles to
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Extreme Waves Marina Del Rey, which was my home port at that time, and meet us there. Mark bravely agreed to help me sail back to Marina Del Rey. Dreams is a sturdy boat, designed for blue water sailing, with a full keel, high shear on the bow, big drains in the cockpit—everything needed for heavy weather. I wasn’t worried about the boat not being equal to the task. Mark and I got under way soon after that, one reef in the mainsail. Leaving the island, we saw that conditions really weren’t so bad, so we put up the staysail along with the mainsail and put out a fishing line. All was well for the first hour or so. After that, once we were in the San Pedro Channel and away from the lee of Catalina, the seas and the wind started building. The fishing line came in first, then the staysail was furled. As we got closer to the mainland, the wind—originally out of the northwest—swung around to the north, and soon we had both wind and waves “on the nose” as the saying goes, meaning we were going directly into both wind and wave. At this point, Mark was hunkered down in the cockpit, feet braced against the bulkhead, holding on to the cockpit rails. We both had on lifejackets and safety lines. We were also both wet and getting wetter. I had to impose on Mark to take the wheel so I could go forward and drop the mainsail—a task that he did not welcome, but he nonetheless acquitted himself well. For the next several hours we slogged our way north. After a while, I got the rhythm of the seas coming our way. I could maintain our northerly heading for six or seven waves and then we’d get a bigger one, and I would swing the boat to take it at a 30 degree angle to minimize the slamming. This worked most of the time, but not always; sometimes a second or third big wave followed the first. With the biggest waves—around 10 feet high—water would break over the bow pulpit 8 feet above the waterline and come back amidships before running off. Seawater would fly clear back over the dodger into the cockpit, drenching us as if a giant hand had thrown a trash can full of cold seawater in our faces. For those who are not familiar with the Marina Del Rey harbor, the main channel runs northeast-southwest and has two entrances, one on the northwest side and one on the southeast side, the latter our direction of approach. There was a lot of shoaling at the south entrance at this time. In front of the harbor entrance there is a long break-
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Extreme Waves water running parallel to the coast. Boats enter between this breakwater and the jetties that form the edges of the main channel. As we approached the southern entrance, I could see that good-sized seas were running down the coast, into the north entrance and out the south entrance. I informed Mark that the trip was going to be a little longer—I didn’t want to go into the south entrance with those seas running. I could imagine getting in that confined space and having the engine die or something else happen. So, we beat our way north past the breakwater and then came in the north entrance, bare poles, motor idling—at 7 knots, the fastest the boat had gone since I’d owned it! Mark and I are still good friends, but if you ask him about sailing, he will roll his eyes and say, “Let me tell you about the time….” As in many such incidents, the waves get bigger with each telling of the story. Afterwards, when we cleaned the boat up, it was amazing to see how much salt there was on it—everywhere, in every nook and crevice. As storms go, this one was puny. Later we will hear from sailors with considerably greater experience, who have braved seas two to five times higher than these, and a few who have seen seas 10 times as high—100-foot extreme waves! STORM ORIGINS The storm we experienced was not severe and was typical of those occurring during the winter and early spring months in Southern California. A common cause of such storms in our locality is wind shifts that bring cold air from Canada or Alaska south into California, as opposed to the more typical track southeast into Montana, Wyoming, and Colorado. The leading edge of a mass of cold air, moving fast at around 600 miles per day, is called a cold front. When cold dense air meets warmer air, it slides under and pushes the lighter, warm, moist air upwards. As the warm air rises and cools, its temperature drops, and moisture condenses, first forming clouds and then rain as the air saturates. Warm fronts are the leading edges of warm air masses that typically move more slowly than cold fronts (180 to 360 miles per day). In the United States, they might originate in the Gulf of Mexico, or in the Pacific or
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Extreme Waves Atlantic along the Tropic of Cancer.1 Fronts arise in response to some disturbance or force aloft. The appearance of a front is usually accompanied by a drop in atmospheric pressure. The pressure drop can be gradual or rapid; if it is rapid and prolonged, the resulting storm will be severe. Meanwhile, the entire system generally moves in an easterly direction, driven by the prevailing winds. Rain and strong winds can occur at the interface between the two fronts but also can occur elsewhere. For example, the most important weather with a traveling low-pressure system is the warm sector to the south and east of the low, where the rising air and typically strong south-southwest winds contain the most active showers and thunderstorms. Such storms are sometimes called extratropical cyclones since they have the characteristic rotating motion of a cyclone, but being outside tropical waters lack the driving force of the warm water “heat engine” that creates a true hurricane.2 AROUND THE WORLD ALONE One of my heroes is Brad Van Liew. Brad is modest, unassuming, and one of the handful of people in the world who have sailed around the world alone in a small boat. He is probably the most talented sailor I know. Consequently, I knew I had to go to Charleston—his home base—and talk to him about storms and waves for this book. A word about Brad: He started sailing at age 5; beginning at age 12 he went to Newport, Rhode Island, during the summers to work on boats for his uncle. As a teenager, he gained sailing experience by working as a crew member during the Newport to Bermuda race, the Newport to Annapolis race, and other offshore regattas. He is also an experienced aircraft pilot, with multiengine, instrument, and instructor’s ratings. For several years after he graduated from the University of Southern California, he operated an aircraft charter service. Brad first considered taking part in the Around the World Alone Race in 1990, while still in college. He took leave from the university during his junior year and tried to raise the money to get a boat and enter the race, but he was unable to get the financial backing he needed. In 1996, 28 years old and now married to Meaghan, he decided to try
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Extreme Waves again, this time for the 1998-1999 race. The race would depart from Charleston, South Carolina, and continue to Cape Town, South Africa; then from Cape Town to Auckland, New Zealand; from Auckland to Punta del Este, Uruguay; and from Punta del Este back to Charleston—a total distance of 25,400 nautical miles. Meaghan was an invaluable ally, helping raise the money needed for the race and also managing his support team. This time, with support from friends, borrowed money, and several corporate sponsors, he was successful. You sail alone in this race. There is no one to stand watch at night so you can sleep. If something breaks, you are the one to fix it. Not only do you not have a crew, but since most of the race takes place in some of the world’s most distant and inhospitable waters, you are unlikely to even see another vessel. Brad’s boat, named for his principal sponsor, was Balance Bar, an open 50 class sailboat, 50 feet long on the deck, beam of 14.5 feet. This was his home at sea for nearly five months through some of the roughest oceans known to man. It is best to let him tell the story in his own words. “I was approaching Cape Horn and was around 700 nautical miles west of the Cape, when I got word that a major depression was forming. I knew about a week beforehand that it was coming. There was a free fall of the barometer as the storm approached from the west—it dropped to around 920 millibars, as I recall. As the storm approached, winds were at 70 knots, and swells heaped up from the northwest with 20-foot-high waves. [Note: when speaking of wave height, Brad is using wave amplitude, not crest-to-trough. Crest-to-trough for a 20-foot-high wave would be 40 feet.] As the storm passed the boat, the wind became southwesterly, gusting to 100 knots, and the swell direction changed, with the swells now 30 feet and sometimes running into the swells coming from the northwest. The problem with multiple swells is that they can start colliding and at some point if you’re in the wrong place, they’ll grab you and spit you out the top.” At this point in our interview, in a courtyard near the swimming pool outside the hotel where I was staying in Charleston, South Carolina, Brad looked around and directed my attention to the hotel building behind us. “When I was in a trough, the oncoming waves were as high as
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Extreme Waves that,” he said, pointing to the building. I looked—the wall of the building loomed over us. It was five stories high. “That high?” I asked. “Yes—probably 30 feet or so—equivalent to 60 feet crest-to-trough. The top of my mast was 75 feet above the deck, and the waves were as high or higher.3 “Anyway, once the wind clocked around to where it was blowing to the southwest, it was blowing against those northwesterly swells, causing the faces to get steeper. At this point I was down below, braced at my navigation table in the center of the boat. We were running on autopilot, bare poles, and Balance Bar was surfing those big swells at 12 knots due east toward Cape Horn. Suddenly the boat heeled over 90-plus degrees so the mast was parallel to the water, and the boat slid sideways down the face of the wave. I happened to look at the global positioning satellite instrument at that moment and saw that my direction of travel was now south and Balance Bar was making 15 knots sliding down the swell on the boat’s side. “I said to myself, ‘Come on baby, come on,’ and moments later Balance Bar righted herself and the mad dash continued. Something was banging around on deck—the spinnaker pole had broken lose. At this point I decided I’d better go topside and see what things looked like. On deck, with foul weather gear, goggles, safety line, freezing water, snow, and hail—you couldn’t see without goggles to protect your eyes, the wind was blowing so hard—it was an amazing sight. I fixed the spinnaker pole and then spent about an hour on deck watching—I was mesmerized by the seas—I’d never seen anything like them before. “On most waves, the boat would ride up and the swell would pass under the boat and break later. Every now and then a larger one would come, maybe 40 to 50 feet, with the classic ‘graybeard appearance.’ The top 3 to 6 feet would be foamy streaming grayish water, churned and blown off by the wind. Below this was the dangerous stuff, a wall of water that could break the boat or crush you. As I watched, I could see the surface layer of this wall of water sort of break loose and slide down the face with a glistening, white rippling effect, resembling water sliding down a water slide in an amusement park ride. Finally one of these waves broke on the boat and we began the down-wave slide again, me
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Extreme Waves hanging on for my life as tons of water poured over me and over the boat—holding my breath as long as I could until finally the water ran off and the boat righted. At that point I decided I’d better get back down below. “I got into my ‘coffin bunk,’ so-called because it was made so I could squeeze into it and not get tossed around when the boat’s movements got pretty wild. Things were fine for a while and then all of a sudden it got dark and very quiet, and I found myself on the over-head—the roof of the boat. There was a plastic bubble above my navigation station where I could look out and see how we were doing. Looking into this, all I could see was very deep blue water. I realized that the boat had broached; I was upside down in the Southern Ocean. It was an eerie feeling. At one moment there was the howling of the wind, the rattling and banging sounds of water hitting the deck, wind whistling through the rig—then suddenly, silence. Being upside down made for quiet running. The light was surreal—no more white light from the sky, but diffuse blue light—daylight being filtered through the ocean, then coming in the windows that were underwater. “My first thought was, ‘Well, this is it. I’m going to die.’ Then I got angry—angry at the sea, angry at myself for putting myself in the position, mad about a lot of stuff. About then another wave hit the keel, gave Balance Bar a nudge, and we rolled around and came upright. After a few moments to calm and steady myself, I went topside to survey the damage. Amazingly, the rig and mainsail were still there—no major losses. There were some minor things, but I could fix them. Later I found out that the mast stays and standing rigging were badly stretched and I no longer had a nice tight rig. “I had four or five more knockdowns, but didn’t roll again, and managed to clear Cape Horn and get into Punta del Este, a scheduled four-week stopover, where Meaghan and my support team were waiting for me. We had some discussions about whether it was worth it—whether I should continue or not. Meaghan and I had previously agreed that if either of us decided it was time to quit, I would quit. But we decided that, having come this far, I would continue for the last leg back to Charleston. Besides, wasn’t the worst of it behind me? Hadn’t I made it around the Cape?
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Extreme Waves “I should have replaced the rig, but without money the best I could do was tighten everything up—retune it—and hope for the best. With this I left Punta del Este for the last leg home. Leaving the Rio Plata, near the Uruguay-Brazil border, I stayed inshore. There is a continental shelf there. This was a mistake—I should have immediately headed for deeper water. As it was, I got into some really rough water—waves that were only 6 to 8 feet high, but they had short wavelengths and really tossed the boat around, raising it and then dropping it with a crash. The strain was too much for my beat-up rig and the mast broke in three places. At that point I was really demoralized and ready to call it quits, but when I called Meaghan on my satellite phone she and the crew urged me not to quit. “I jury-rigged my spinnaker pole as a mast and got up two sails—my storm jib and another—and limped back into Punta del Este. It took me two days to get back and then seven days for repairs. Thanks to Meaghan’s efforts and the help of many other people, Balance Bar got fitted with a new mast and I restarted the race, 1,000 nautical miles behind the other competitors. With good luck and hard sailing, I managed to catch up with the fleet and finished third, only a couple of weeks behind the leaders. “So, here’s a lesson for your book; waves don’t have to be big to be mean.” There is a sequel to this story. Van Liew competed again, in the 2002-2003 race, this time in a boat called Freedom America. He not only won the race in his class but completed an unprecedented sweep of all five legs. I asked Brad how this race compared to his first attempt. “On the second race, the southern oceans were not the toughest part of the race,” he said. “I went from one low to the next. The lows march from west to east across the Southern Ocean, moving at about 30 knots. I tried to keep on the north side of the low, where I consistently had 15- to 20-foot waves and 25- to 40-knot winds. These waves were 200 to 300 yards apart (about 15 to 20 boat lengths), so I’d ride up on one and then I could see the last one out there ahead of me. I like to stay on a beam reach to a broad reach. I found that I could slalom through those swells. I was able to maintain a fast speed—averaged around 9.5 knots over the entire 7,800 miles sailed between New
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Extreme Waves Zealand and Salvador Brazil. When the wind gets above 40 knots, the waves start to heap up and you can’t go as fast. “I found the Indian Ocean to be the most dangerous. Leaving the Cape of Good Hope, you encounter the Agulhas Current. In a previous race, two boats rolled in the area. One—I think it was a modified Swan 44—pitchpoled two times. You want to get past the Cape and into deeper water. However, heading east towards New Zealand, you first pass the Crozet Islands and then the Kerguelen Islands. These lie in shallow waters and you can have some horrendous seas building there.” After 148 days at sea alone, Brad triumphantly sailed into Newport, Rhode Island, and into sailing history. He had arrived a full three weeks ahead of his nearest competitor. AN AMAZING RESCUE On the west coast of Alaska, south of Valdez, destination of oil tankers, is a mountain called Mount Fairweather. Not far from it is a beautiful, secluded bay called Lituya; more about that later. This is the area swept by the Alaska Current as it curls northwest from Vancouver and then streams west along the Aleutian Island chain. It is an area of unsurpassed fishing grounds, prolific in its production of salmon and other species. It is also unsurpassed in the spawning of storms characterized by high winds and giant waves. It became the site of an incredible rescue in horrendous seas. Fishing is a dangerous occupation—certainly in these waters, far more dangerous than coal mining or almost any other hazardous employment. At the same time, the area between Sitka and Anchorage is one of spectacular natural beauty—sharply rising mountain ranges, crystalline blue water beneath the edges of glaciers, bald eagles perched in treetops overlooking isolated coves. During the summer months, you would be hard-pressed to find any area of the world more beautiful, and during the winter months, any place with deadlier weather. Dense, cold air created near the tops of the high mountains along the coast settles down long valleys toward the sea, creating sudden, unpredictable, tumultuous winds—williwaws—that blast out into the ocean. Storms blow in from the Bering Sea or arise in the Gulf of Alaska,
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Extreme Waves creating a nightmare for boats large and small. Storm winds frequently reach Beaufort Force 12 at 80 to 110 knots and, blowing over a long fetch of up to 430 nautical miles, can produce 80- to 100-foot-high waves. Salmon trollers and others who make their livelihood from the sea depend on the United States Coast Guard as their ultimate lifeline in times of disaster. For this area, the Coast Guard operates from a base in Sitka and has a main support center in Kodiak. Here, one of the most amazing air-sea rescues of all times took place in January 1998. Late in the season, the fishing vessel La Conte went out to Fairweather Ground. In this location, about 60 nautical miles from Cape Fairweather, the bottom rises up to within 13 fathoms of the surface and there is excellent fishing for red snapper and other bottom fish, although January is a dicey time to venture out to Fairweather Ground. The La Conte, with a crew of five, got caught in a horrific storm and started sinking. Spike Walker, a writer, and a man who has fished in these same waters, interviewed the surviving crew members and the Coast Guard personnel who rescued them, and wrote a riveting account of what happened to them in his book Coming Back Alive.4 Just before La Conte was finally pushed under by a huge wave, the crew was able to get into their insulated survival suits and grab the emergency position indication radio beacon (EPIRB). Tying themselves together with a length of line, they jumped into the frigid water. Their only thread of hope for survival was the EPIRB. Fortunately, they had the newer type that broadcasts on 406 megahertz. Dreams is equipped with a similar instrument, but other than periodically testing it to make sure it is functional and the batteries are still good (they are supposed to have a five-year life), I have never had to use it. It will activate automatically if placed in water or can be turned on by a manual switch. Each EPIRB has a unique identification number that is registered with the National Oceanic and Atmospheric Administration. This provides information about the vessel: size, color, radios on board, and other information essential to a rescue operation. Once the EPIRB is activated, it sends a 406-megahertz signal to one of several overhead satellites (the COSPAS-SARSAT network). The signal enables the satellite to determine the latitude and longitude of the
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Extreme Waves EPIRB and to alert the nearest Rescue Coordination Center. The EPIRB also transmits a homing signal on 121.5 megahertz so that as a rescue vessel or aircraft gets close, it can home in on the exact location. A high-intensity xenon strobe light flashes to make visual identification possible at night. The battery is designed to last 48 hours. Within minutes, notification that an EPIRB had been activated at Fairweather Ground reached the U.S. Coast Guard base at Sitka. A Coast Guard helicopter was dispatched to the area, which was about 110 nautical miles northwest of Sitka. Miraculously, the helicopter found the tiny dot of flashing light in mountainous seas—and the four men tied together. (The fifth man had been pulled out of the rope by a large wave and disappeared from sight, presumed drowned.) The pilot tried to maneuver the helicopter into position above the men, fighting 70-knot headwinds with gusts that were even higher. Time and time again as he descended to 100 feet above the sea to deploy a lifting basket, he had to pull up when a huge wave threatened to knock the helicopter out of the sky. When he pulled up, the fierce winds blew the helicopter backwards, sometimes as much as one-half mile, and he had to fight his way back and relocate the crew. Once, flying at an altitude of 100 feet, as the pilot concentrated on maneuvering the helicopter, a crewman suddenly screamed, “Up, up.” As he looked out the door in preparation for lowering the lifting basket, he looked up and saw a rogue wave higher than the helicopter about to break on them. With engines straining at maximum power and skillful flying, they escaped by the narrowest of margins. Back and forth the battle with wind and waves went, until the helicopter reached the point of no return on fuel and had to return to Sitka. Below, the men in the sea struggled to keep their hopes up, to keep together, and to fight their way back to the surface after each 70-foot-high wave buried them under tons of water. A second helicopter was dispatched from Sitka, but the results were the same. Despite numerous heroic efforts, it could not maneuver the rescue basket close enough to the men in the water to retrieve them. A third helicopter was dispatched. By now, the men had been in the frigid waters for hours, constantly battered by waves 70 to 90 feet high, and were slowly losing what little strength they possessed to assist in their own rescue. Finally, after nearly seven hours in the water, the third
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Extreme Waves of the hurricane is as far away as 80 nautical miles. Studies have also been made on correlating the significant wave height with hurricane-strength winds in the open sea. The results indicate that with the onset of hurricane-strength winds, the significant wave height will quickly grow to 26 feet with the potential of reaching 52 feet in a Category Five hurricane with winds of 135 knots. These values can be higher, depending on the sea state prior to the arrival of the hurricane. There are few actual measured data on hurricane-generated waves in deep water where the sea conditions are violent and most vessels are occupied with remaining afloat and have no time for scientific observations. Now satellites and sensitive transducers on the ocean floor are beginning to provide more data. The available data indicate that hurricane-generated waves can reach extreme wave heights. When Hurricane Ivan approached the coast, it passed over an array of sensors placed on the ocean floor as part of a U.S. Navy research project. At one point waves up to 66 feet high were passing over the sensors every 10 seconds. Winds reached 108 knots. The largest detected wave was 91 feet high.14 As a hurricane approaches shore, the wave height increases dramatically in shallower water. So, what are the deadliest hurricanes to have hit the United States? Table 3 lists those recorded during the 104 years from1900 to 2004. Hurricane Katrina, which devastated the Gulf Coast region of the United States in August 2005, will be added to this list. It had a low of 902 millibars. The death toll had reached 1,250 and rising as this book was being prepared. HURRICANE FORECASTING Much progress has been made in recent years in forecasting hurricane wind patterns. The basic model takes into consideration the forward velocity of the hurricane, the fact that the winds flow inward at some angle (typically around 25 degrees), the central pressure, and the radial distance of the maximum winds (the latter two items being measures of the intensity of the hurricane).15 These models yield results that are shown pictorially in Figure 12; the hurricane is moving west (toward the top of the page). This is a
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Extreme Waves TABLE 3 Deadliest Hurricanes, Continental USA, 1900-2004 Rank Description Year Deaths Central Pressure (millibars) Saffir-Simpson Category 1 Galveston, Texas 1900 8,000+ 936 4 2 Lake Okeechobee, Florida 1928 2,500+ 929 4 3 Florida Keys, south Texas 1919 600+ 927 4 4 New England, New York, Rhode Island 1938 600 946 3 5 Labor Day, Florida Keys 1935 408 892 (lowest) 5 6 Audrey, southwest Louisiana, north Texas 1957 390 945 4 7 Great Atlantic, northeast United States 1944 390 947 3 8 Grand Isle, Louisiana 1909 350 — 4 9 New Orleans, Louisiana 1915 275 931 4 10 Galveston, Texas 1915 275 945 4 11 Camille, Mississippi, Louisiana 1969 256 909 5 high 12 Great Miami, Florida, Mississippi, Alabama 1926 243 935 4 13 Diane, northeast United States 1955 184 949 3 14 Unnamed, southeast Florida 1906 164 — 2 15 Unnamed, Mississippi, Alabama, Florida 1906 134 — 3 16 Agnes, northeast United States 1972 122 — 1 17 Hazel, South Carolina, North Carolina 1954 95 938 4 18 Betsy, southeast Florida, southeast Louisiana 1965 75 948 3 19 Carol, northeast United States 1954 60 — 3 20 Floyd, eastern United States 1999 57 — 2 21 Unnamed, southeast Florida, Louisiana, Mississippi 1947 51 940 4 22 Donna, Florida, eastern United States 1960 50 930 4 23 Unnamed, Georgia, South Carolina, North Carolina 1940 50 — 2 24 Carla, north and Central Texas 1961 46 931 4 25 Allison, Texas 2001 41 — ? 26 Unnamed, Texas 1909 41 — 3 27 Unnamed, Texas (Freeport) 1932 40 941 4 28 Unnamed, south Texas 1933 40 — 3 29 Hilda, Louisiana 1964 38 — 3 30 Unnamed, southwest Louisiana 1918 34 — 3 31 Fran, North Carolina 1996 26 954 3
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Extreme Waves Rank Description Year Deaths Central Pressure (millibars) Saffir-Simpson Category 32 Unnamed, Louisiana 1926 25 — 3 33 Connie, North Carolina 1955 25 962 3 34 Ivan, northwest Florida, Alabama 2004 25 946 3 Addendum (pre-1900 or not Atlantic or Gulf coast): 1 Chenier Caminanda, Louisiana 1893 2,000 948 4 2 Sea Islands, Georgia 1893 1,000-2,000 — 3 3 Unnamed, Georgia, South Carolina 1881 700 — 2 4 San Felipe, Puerto Rico 1928 312 — 4 5 U.S. Virgin Islands, Puerto Rico 1932 225 — 2 6 Donna, St. Thomas Virgin Islands 1960 107 — 4 7 Chubasco, southern California 1939 45 — TS 8 Eloise, Puerto Rico 1975 44 — TS NOTE: TS = Tropical storm. northern hemisphere storm; winds are rotating counterclockwise (as viewed from above). The winds are highest on the right side of the figure. The waves produced by the storm are a complex combination of both swell and wind-generated seas. Due to the varying direction of the wind, the resulting wave patterns are highly irregular and difficult to model. Waves on the right-hand side of the storm propagate forward with the forward motion of the storm and reach greater heights than waves on the opposite side of the storm. This is because the left-side wind speed is less, the cyclonic winds being reduced by the forward motion of the storm. At the storm’s center, the winds are near zero. A mental image of Figure 12 should be in the mind of every ship captain venturing into tropical waters during hurricane season. For the example cited above, the vessel is shown in the upper right-hand
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Extreme Waves corner of the illustration. A vessel on the upper left-hand side of the illustration would turn to the southwest to escape the storm. Efforts have been made to make measurements during storms to gather data to validate weather forecasting mathematical models by comparing the model results to actual data. These types of analyses are called hindcasts since they represent an “after-the-fact” look at the storm. In other words, forecasters say, “Okay, we measured the wind, waves, and air pressure of a storm; let’s put the data in our model and see if the results compare with what actually happened. If not, then how do we improve the model?” As difficult and dangerous as it is to make measurements during major hurricanes, some data have been collected using instruments on offshore oil platforms, islands, and weather ships stationed in the oceans or by using buoys. The sailing routes from South America to the Caribbean are littered with ancient wrecks of Spanish galleons—ships that sank under the force of giant waves caused by storms while bringing treasures from the New World back to Spain. Many of these vessels disappeared without a trace, leaving no survivors to tell the story. Now we know that given the type of sailing rig they employed, many were literally driven under the water when high winds and large waves arose suddenly before the crew was able to reduce sail. Today, thanks to radio communications and satellite phones, fewer maritime disasters go unreported. In 1995, Hurricane Roxanne crossed into the Gulf of Mexico, where several hundred offshore oil field workers were on board a large barge that was anchored in place. When seas reaching 30-plus feet began impacting the barge, one by one the anchor cables failed and the barge was set adrift in mountainous seas. An oceangoing tug (normally used to position the huge barge) finally managed to pass a cable to the barge after repeated attempts so it could be taken under tow. The tug kept the barge headed into the violent seas so it would not broach. Before long, the cable parted and the barge continued to be battered by the sea. Massive pieces of equipment—some weighing many tons—broke loose and crashed across the deck like random battering rams. The barge took on water and began to break up, sinking lower and lower in the water. The tug and two other vessels that had risked all to come to its assistance were able to rescue more than 200 crew members
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Extreme Waves who went into the roiling waters as the barge sank. This was truly one of the most miraculous rescues ever made at sea.16 STORM SURGE AND HURRICANE-INDUCED FLOODING An important side effect of hurricanes is the rising sea level, called a storm surge, caused by the storm as it approaches shallower water. Although not normally a concern to vessels at sea, storm surge is a serious problem for harbors and coastal installations and can be dangerous to a vessel attempting to make port in a storm. Storm surges arise as a result of the wind driving water toward the coast and piling it up due to interaction with the nearshore sea bottom and shoreline. Huge storm surges result when a hurricane approaches land with a concave bay and winds are flowing directly into it, especially when the underwater seabed rises rapidly just offshore. The Bay of Bengal has this scenario and is prone to huge storm surges from tropical cyclones that kill so many people. The low-pressure area in the center of the hurricane adds to the surge height. If we consider that in the eye of the hurricane the pressure is, for example, 900 millibars (equivalent to 674 millimeters of mercury), and remember that mercury is 13.6 times as heavy as water, this pressure is equivalent to a column of water that is 9,166 millimeters, or 9.17 meters, high. Outside the storm, where the air pressure is higher, closer to 1,020 millibars (764 millimeters of mercury), the equivalent height of a column of water exerting the same pressure will be 10.39 meters. The difference between these two numbers (probably a worst case or very near so) is 4 feet (1.22 meters). The pressure effect is relatively minor when compared to the winds piling up water against the shore. You can picture a hurricane conveying a large bulge of water in its low-pressure center, where the water level could be several feet higher than the surrounding ocean. The height is further increased by the force of the circular winds piling more water into the center of the hurricane. As the storm approaches shallow water near the shore, the storm-driven mass of water piles up even higher. Overall, the wind-driven effect is much more significant than the pressure effect. The
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Extreme Waves water can remain high until the hurricane winds eventually die down.17 Hurricanes with high flood waters caused by storm surge include Andrew (1992), Hugo (1989), and Camille (1969), which caused storm surges of 8 to 16.5 feet, and then most recently Katrina (August 29, 2005). This Category Four hurricane caused a storm surge of 26 feet, broke levees, and heavily damaged New Orleans and other Gulf Coast cities. When tropical storms or hurricanes impact low-lying coastal areas, casualties can be extremely high. In fact, it is estimated that 90 percent of the deaths from hurricanes are due to flooding damage and drowning.18 Nowhere is this effect more apparent than in the low-lying coastal areas along the Bay of Bengal. Tropical storms and hurricanes have caused a huge loss of life in this region during the past several centuries, for example: October 7, 1737, Bay of Bengal, cyclone combined with high tide of 40 feet—300,000 killed June 5-11, 1882, Bombay, India—100,000 die May 1833, Calcutta—50,000 killed October 5, 1844, Bay of Bengal, Calcutta—50,000 killed May 28, 1963, East Pakistan, water ran 2 miles inland and carried huge ocean liners 1 mile inland In September 1900, another hurricane traversed the Gulf of Mexico and roared into the history books by wiping out the city of Galveston, Texas. The storm surge was responsible for much of the damage and most of the fatalities—estimated at 8,000. At its peak, sustained winds were 130 knots with gusts to 170 knots or higher. Waves as high as 40 feet crashed into the city, sweeping away entire houses and multistory buildings. Water 30 feet deep ran through the city streets. Under the tremendous force of the waves, piles of lumber and debris—even entire structures—were pushed inland like giant wrecking balls, destroying all in their path. One man reported narrowly avoiding being crushed by a grand piano hurled at him by a wave. An eyewitness survivor, Dr. Samuel Young, described how the waves en-
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Extreme Waves tered the second floor of his home, seven blocks from the oceanfront, at a level 30 feet above the street. Moments later the house shuddered and floated free. Dr. Young escaped by using a door as a raft; the rampaging waves carried him clear across the city, twirled him in a whirlpool, and finally wedged the door and him, bruised and bleeding, against a pile of debris.19 Today the prudent mariner has a variety of tools—including satellite weather photos and marine weather forecasts—that help avoid sailing into the hazards of storms and massive waves. However, for a vessel already at sea, the options are reduced to steering a course away from a storm or riding it out. To elude the effects of a distant storm, it is necessary to anticipate the likely track of the storm and, most importantly, to know how waves will propagate away from the storm. This is neither an easy nor a pleasant task. FORECAST ACCURACY National weather services use several models for predicting the track and intensity of hurricanes. Track forecasts are the latitude and longitude of the storm center, while intensity refers to the maximum sustained surface wind. Forecasts are typically issued for 12, 24, 36, 48, and 72 hours. Two main types of mathematical models are used: one type predicts the storm track; the second type is used to predict its intensity.20 Of more interest for our purposes is the accuracy of such models. As might be expected, their accuracy is best in the short-term forecasts and deteriorates for the longer forecast periods. For estimating hurricane tracks, the errors are around 50 nautical miles at 12 hours (with a range of error from 40 to 60 nautical miles, depending on the model). At 24 hours, the average error is around 85 nautical miles, but can be as great as 200 nautical miles in the 72-hour forecast. Regarding intensity, wind speed errors have recently averaged around 9 knots at 24 hours, 15 knots at 48 hours, and as much as 19 knots at 72 hours. For both intensity and tracks, there are slight differences in the accuracy of the models depending on whether the Atlantic, Pacific, or Indian Ocean is involved. The accuracy of forecasts has
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Extreme Waves improved over the last several decades, but there is still much to be learned about the inner workings of hurricanes. How accurate are the predictive models in use today? Better than before, but definitely not infallible. Wind is the ultimate determinant of the size and direction of waves. While the ability to predict wind patterns has improved immensely with the advent of satellites, better mathematical models, and radar, it is still far from perfect. Local winds can vary widely from those predicted for large areas. Ultimately, it is the responsibility of the captain to use his experience and judgment to safeguard his vessel and crew. When the wind speed is already 80 to 90 knots, an error of 10 to 20 percent is not terribly significant; it implies that the resulting waves will be merely terrifying rather than horrendous. However, an error in storm position of 100 to 200 nautical miles could make a huge difference in the strategy of a ship captain desperately trying to avoid an oncoming storm, as was the case of the captain of the Fantome. THE TRAGEDY OF THE FANTOME In October 1998, Hurricane Mitch developed from a tropical storm into one of the largest (Category Five) hurricanes in recent times. Day after day, as the hurricane approached Central America, aircraft from the Weather Reconnaissance Squadron of the U.S. Air Force Reserve Command flew into the eye of the storm and collected data that were relayed to the National Hurricane Center in Florida. These data, plus radar and satellite data, were fed into the center’s sophisticated forecasting computers to predict the path of the hurricane and its eventual landfall. But modern weather forecasts are not infallible. At this time, the sailing vessel Fantome—flagship of the Windjammer fleet, a cruise line that employed tall ships—was taking on 90-some passengers for a two-week cruise. Since the first predictions indicated that the hurricane was headed due west toward Fantome’s base in Honduras, Fantome sailed north to Belize City to discharge the passengers at a safe location and to secure the $20 million vessel. Once the passengers were off the vessel, the weather forecasts showed the hurricane turning north toward Belize and the Yucatan Peninsula. The
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Extreme Waves captain and owners of Fantome then made the decision to sail the boat south to escape the hurricane. The weather fax onboard Fantome was inoperative. Had the captain been able to see the satellite image of the storm bearing down on him, his decisions probably would have been different. As Fantome left Belize, the hurricane made an abrupt turn south, almost as if it intended to intercept Fantome. The ship turned east, seeking shelter in the lee of the Bay Islands, a group situated in the Gulf of Honduras. Perversely, the hurricane now turned west, aiming directly for Fantome, no longer with options for escape.21 Up until the moment that Fantome foundered and sank with the loss of all 31 crew members on board, the captain was in contact by satellite phone with Windjammer headquarters in Miami. The captain reported that the vessel was taking a terrible beating, rolling and slamming into mountainous seas, waves 30 to 35 feet high breaking over the stern, unable to turn the boat, barely able to keep driving it straight east into confused seas. At this point Fantome was around 19 nautical miles from the eye of the hurricane. Aircraft measured wind speeds in the same location at 115 knots, gusting to 150 knots. Such winds would have produced waves with a significant wave height of 46 feet and a maximum of perhaps 66 feet. The terrible irony of this tragic loss is that the hurricane seemed to anticipate Fantome’s every evasive move, altering its deadly course to intercept the ill-fated vessel. The loss proved one other point: The hurricane also outmaneuvered the best efforts of weather forecasters. A RECORD HURRICANE SEASON At the start of the 2004 hurricane season, the National Weather Service issued its outlook for the Atlantic-Caribbean region, stating that “above-average” activity was to be expected. In retrospect, this was an understatement of what actually happened, as 2004 turned out to be extraordinary in that four hurricanes hit the southeastern United States in quick succession. First came Hurricane Alex on the South Carolina coast in July, followed by tropical storm Bonnie in August. As Bonnie moved toward Florida, tropical storm Charley arose and also began moving toward
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Extreme Waves Florida, where it soon reached hurricane strength. Charley was merely a preview of things to come. Subsequently, during the months of August and September 2004, the Caribbean area, Florida, and the southeastern United States suffered from the impact of several more large hurricanes (Frances, Ivan, and Jeanne). Charley caused $14 billion in damage and killed 10 people. Indirectly, another 20 U.S. deaths were attributed to Charley, along with 5 people killed in the Caribbean. Not since Hurricane Andrew in August 1992 had such damage occurred, and never before had four major hurricanes struck in close succession. The hurricanes arrived one after the other, one to two weeks apart. Barely had residents begun to dig out from under the damage from one hurricane when they were besieged by another. In addition to experiencing winds from 78 to 130 knots, coastal areas were impacted by extreme waves and storm tides that destroyed waterfront installations, tossed boats ashore as if they were so many toys, and altered entire sections of beach and shoreline. Total damage was in excess of $40 billion. These four hurricanes were in the range of Category Two to Four when they hit the United States, although Ivan reached Category Five several times in the Caribbean. Ivan was responsible for 25 U.S. fatalities. The 2004 season was terrible, but 2005 was worse. Hurricane Katrina (Louisiana and Mississippi, August 29, 2005), Category Four, is now estimated to be the worst natural disaster in the history of the United States. In addition to their impacts on the United States, the hurricanes caused widespread damage throughout the Caribbean. For example, Hurricane Ivan resulted in considerable destruction on Grenada, hitting the island with 100-knot winds and then moving on to become a Category Five hurricane. Ivan also damaged Trinidad, Tobago, Jamaica, and Grand Cayman, before recurving to hit Alabama and the Florida Panhandle. In terms of size, longevity, and total destructive power, the hurricanes listed in Table 4 stand out as some of the worst experienced in recent times. If hurricanes represent the worst case of storms causing large waves, how big can waves get? In all likelihood, those who could have answered this question perished in the storm. Based on the available measurements and data, a height of 90 feet certainly seems plausible.
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Extreme Waves TABLE 4 Worst Hurricanes Name Year S-S Category Maximum Winds (knots) Damage (billion dollars) Katrinaa 2005 4 150 100-200 Andrew 1992 5 125 44.9 Betsy 1965 3 118 6.5 Camille 1969 5 139 14.9 Gilbert 1988 4 101 3.0 (approx.)b Hugo 1989 4 140 12.7 Iniki 1992 4 125 1.8 Luis 1995 4 120 2.5+c Mitch 1989 5 155 Unknownd Opal 1995 5 130 4.1 aCategory Four at landfall; Category Five in the Gulf of Mexico. bLowest recorded pressure, 888 millibars. cQueen Elizabeth 2 was on the fringes of this storm when hit by a rogue wave. d9,086 dead, mostly in Central America, including crew of 31 from Fantome. Wave heights during storms are affected by the condition of the sea before the storm. Sometimes called sea severity, the sea condition influences how big the waves can become. For example, if winds have been blowing before the storm, waves will be larger than if the storm originated in calm seas. Ochi cites two cases in which winds of 12 to 27 knots had been blowing for up to 10 days prior to a storm. Waves were already 8 to 16 feet high. With the advent of the storm, they increased to 49 to 56 feet in a matter of 21 hours.22 Thus, in a fully developed sea, a smaller hurricane might produce larger waves than otherwise would be expected. The National Weather Service anticipates that hurricane activity in the Atlantic-Caribbean area will continue to increase during the next several decades. Naturally, this prediction is of grave concern to mariners who out of necessity find themselves in these waters during the hurricane seasons. There are others, however, who monitor the ocean’s great storms from afar and eagerly await the arrival of the resulting waves on distant shores. Rather than run from huge waves, they run after them, hoping to ride them on flimsy fiberglass surfboards.
Representative terms from entire chapter: