Heavy Weather

By Stefan Marti

The 2004/05 winter has been one of the deadliest in years. Heavy rains pounded Southern California and the Southwest, and a northeasterly blizzard dumped several feet of snow on the East Coast. Storms out of the Pacific came one after another in January, drenching the Los Angeles area with over twenty inches of rain. Rivers flooded, roads were destroyed, and mud slides killed ten people sitting innocently in their homes.

As the winds and rains battered California, the Pacific Ocean surged too, bringing solid swells to the Hawai’ian Islands. The north shore of O’ahu had a festive December, including 25-foot waves at Waimea Bay for the Quiksilver in Memory of Eddie Aikau Big Wave Invitational. Only six times in the past nineteen years has it been big enough (over twenty feet Hawai’ian style) to hold the event.

But in California, considering the devastating rainstorms, the swells have been nothing out of the ordinary. Mavericks broke a couple of times with 30-plus faces; Ocean Beach in San Francisco had some epic mornings with overhead barrels; and down south in San Diego, there were a handful of good waves in early December and late January. But this is, all in all, normal for winter. So the questions arise: Why the relentless storms this year? And where are the huge swells that usually accompany them? In other words, what’s going on with the 2005 weather?

The Rains

When Southern California gets hammered with torrential rains, the immediate suspicion is always El Ni§o. El Ni§o is a disruption of the ocean-atmosphere system in the tropical Pacific that affects weather across the globe. Normally, trade winds in the tropical Pacific blow west from Ecuador to Indonesia, pushing the warm surface water to the western Pacific. This creates an upwelling of colder, deeper water off South America. (Also, the sea level in Indonesia is half a meter higher than in Ecuador.) During an El Ni§o, the trade winds relax, and the warm surface water is not blown to the western Pacific. Tropical rainstorms, which follow the warm water, therefore move east into the mid Pacific, and eventually continue farther east toward Peru and California. This shift in the storm pattern has two direct effects: first, regions on the west coast of North and South America get hammered by rain; and second, parts of Australia and Indonesia suffer from severe droughts.

Although there is a mild El Ni§o occurring this year, the “little boy” is not the culprit for the winter rains (it’s too weak to have a major effect on California). This winter, two other weather phenomenons caused the devastating January storms: The MJO (Madden-Julian Oscillation) and the specific positioning of the jet streams. The MJO is an eastward-moving tropical disturbance that influences rainfall and convection in the tropical Pacific. On average, the MJO lasts for 30-60 days, while El Ni§o lasts for over a year. According to Sam Iacobellis of the Scripts Institute of Oceanography, “During early January, the MJO was in an active phase, and the rainfall and convection in the central tropical Pacific was much greater than normal. Some of the atmospheric moisture from this convection got caught up in the subtropical jet stream, which just happened to be in a position to carry this moisture towards California.” This tropical connection is also known as the “Pineapple Express” as the moisture travels across or near Hawai’i on its way to the west coast.

Combined with the MJO was the positioning of the jet streams. California weather is influenced by two main jet streams: the polar and the subtropical. Generally, it’s the polar jet stream that brings winter storms out of the Pacific to the West Coast. However, in January, the polar jet bent north up to Alaska and came down right off the coast of California. “A consequence of this positioning of the polar jet,” Iacobellis said, “is that it sometimes allows the strengthening and the extension of the stropical jet into the West Coast and California. This happened in January when there was also the large amount of tropical moisture available due to the MJO activity.” Together, these two weather patterns (the tropical moisture mixing with the colder arctic air) brought torrential rains to Southern California. They caused over 100-million dollars of damage to homes, agriculture, and infrastructure and were responsible for at least 25 deaths.

There is another factor that made the Los Angeles and Santa Barbara regions particularly vulnerable to these storms. The “Pineapple Express” comes from the tropics with southerly or southwesterly winds. The Santa Monica, San Gabriel, and Santa Barbara mountains run east to west. Hence, these mountain ranges form massive barriers for the southern storms to pass as they try to head north. To climb over these geological obstructions, the storms have to release all of their precipitation. This is why areas like La Conchita were particularly hard hit, with severe rainfall causing mud slides and flooding.

When an arid slope is saturated with excessive rain, it becomes extremely susceptible to landslides. In the case of La Conchita, residents were warned of possible slides (there had been horrible mud slides after heavy rains in 1995). They were given a voluntary evacuation order. Unfortunately, no one could have predicted the severity of the disaster. Over 400,000 tons of mud came down the hill, covering and completely destroying thirteen houses. Eighteen more homes were damaged. Ten people were crushed to death. For Jimmie Wallet, the horror is unimaginable. He went out for ice cream, and when he returned, his house was gone, buried under 30 feet of mud. All night he helped dig through the dirt and debris. In the end, his wife Michelle and their three daughters, Hannah, Raven, and Paloma, were all killed. The La Conchita landslide was clearly the greatest tragedy of the January storms, where, over a period of fifteen days in Los Angeles, seventeen inches of rain came pouring down. In the hills of Ventura, it was over 25 inches.

The fact that the rains ended in late January confirmed that it was the MJO bringing the moisture to California. El Ni§o lasts for a year, and the rains would have continued all winter-like in 1982/83, when the driving storms also brought huge swells.

The Swells

To understand the winter swells, you have to take a step back and comprehend storm patterns and how waves are formed in the first place. Swells are basically created by wind blowing and exuding pressure (transferring energy) onto the surface of the ocean. To get an in-depth understanding of how waves are formed, you should read Sean Collins’ article “Forecasting And Meteorology: So How Do We Get Surf?” in Surfline.com’s Surfology section. In short, three factors decide the size and period of ocean swells: First, the speed of the winds-the faster the winds, the greater the swell; second, the duration of the winds, or how long the winds blow over a certain area of the ocean-the greater the amount of time a storm blows on the sea, the larger the swells will be; and third, the fetch of the storm. The fetch is the distance a storm travels across the ocean. The longer the fetch, the larger the swell. If a storm comes out of the Gulf of Alaska and travels several hundred miles with 80-mph winds, it will produce much greater waves than a storm formed just off the coast of California with 80-mph winds. Even though the second storm is closer, it only generates swell for 30 miles before hitting land. Hence, a storm off the coast of the Philippines can bring swell to California if the winds are strong enough (and in the right direction) and it blows for a long time over a great distance.

During winter, the normal storm pattern for the West Coast is for the polar jet stream to dip down into the Pacific, fuel up on some tropical moisture, and head east toward North America. Depending on how far south the jet drops, it will either hit all or some of California, Oregon, and Washington. From December to February, the short, cold days make the polar jet stream dip farther south, hence bringing some rain to Southern California. In the fall and spring, the jet stream moves farther north, still hitting Northern California. Eventually, in the summer, it steers clear of California all together, bringing only occasional rain to Oregon, Washington, and British Columbia.

Therefore, in winter, the swells generally come from the northwest (290-310 degree area), or sometimes west, depending on the jet stream. This is why Northern California, which faces directly west, picks up more of the winter swells. In Southern California, the swells have to wrap around Point Conception, where they lose some energy. Also, there are the Channel Islands blocking the path.

These winter storms are usually generated thousands of miles out in the Pacific between low and high pressures. As the low-pressure air rises, high-pressure air fills the vacuum, creating massive winds that blow on the sea. And it’s these monster ocean storms that send swells to the West Coast long before the rain and winds of the storm arrive.

Even though there was a great deal of storm activity this January, the waves were lacking in size because of the positioning of the jet streams. The cold arctic air didn’t mix with the warm tropical air until right off the coast of California. Hence, the storms didn’t have enough time or fetch to generate big swells. There were still the gusting winds, though, and this created the choppy, stormy conditions. Also, because the winds were coming from the southwest, they didn’t bring much swell to Northern California.

After the January storms, the weather pattern went back to normal, and although there wasn’t much rain, the swells were coming from the northwest. Thus, Ocean Beach and Santa Cruz picked up some solid surf in early February, even though the rains steered farther north, missing the state of California. (The swell direction is generated by winds while the storm is still hundreds of miles out in the Pacific Ocean. The jet stream may eventually push a storm north, but the swells that came from it earlier were formed from the winds out at sea.)

Swells do lose energy as they travel away from the storm (wave decay) and disperse across the ocean. The major factor on whether a swell will hold its energy and size is the swell period. When swells are generated during a storm, some of the energy is pushed down beneath the ocean surface. The greater the wind, the more energy is transferred below into the ocean. As a swell travels great distances, it loses much of the surface energy (from crosswinds and opposing seas) but retains much of the submerged energy. The way to measure this energy is the swell period, the time between two wave crests. The longer the swell period, the more energy is carried below in the ocean. Hence, swells with a long period (over fourteen seconds) will retain more energy and bring larger waves than short-period swells (under fourteen seconds). “Long-period swells,” writes Sean Collins, “travel with more energy below the ocean surface and are less steep so they can easily pass through opposing winds and seas with very little effect.”

When swells approach shallow water, friction causes the wave energy to push upward, making the waves grow in height. Long-period swells have much more energy, thus they will grow much more in height. According to Collins, “A three-foot wave with a ten-second swell period may only grow to be a four-foot breaking wave, while a three-foot wave with a twenty-second swell period can grow to be a fifteen-foot breaking wave.” Swell period is a factor often overlooked by surfers but crucial to predicting the size of waves.

Another more obvious factor in the size of the waves is the direction of the swell in relation to the shore. This is why the north shore of O’ahu breath the jet drops, it will either hit all or some of California, Oregon, and Washington. From December to February, the short, cold days make the polar jet stream dip farther south, hence bringing some rain to Southern California. In the fall and spring, the jet stream moves farther north, still hitting Northern California. Eventually, in the summer, it steers clear of California all together, bringing only occasional rain to Oregon, Washington, and British Columbia.

Therefore, in winter, the swells generally come from the northwest (290-310 degree area), or sometimes west, depending on the jet stream. This is why Northern California, which faces directly west, picks up more of the winter swells. In Southern California, the swells have to wrap around Point Conception, where they lose some energy. Also, there are the Channel Islands blocking the path.

These winter storms are usually generated thousands of miles out in the Pacific between low and high pressures. As the low-pressure air rises, high-pressure air fills the vacuum, creating massive winds that blow on the sea. And it’s these monster ocean storms that send swells to the West Coast long before the rain and winds of the storm arrive.

Even though there was a great deal of storm activity this January, the waves were lacking in size because of the positioning of the jet streams. The cold arctic air didn’t mix with the warm tropical air until right off the coast of California. Hence, the storms didn’t have enough time or fetch to generate big swells. There were still the gusting winds, though, and this created the choppy, stormy conditions. Also, because the winds were coming from the southwest, they didn’t bring much swell to Northern California.

After the January storms, the weather pattern went back to normal, and although there wasn’t much rain, the swells were coming from the northwest. Thus, Ocean Beach and Santa Cruz picked up some solid surf in early February, even though the rains steered farther north, missing the state of California. (The swell direction is generated by winds while the storm is still hundreds of miles out in the Pacific Ocean. The jet stream may eventually push a storm north, but the swells that came from it earlier were formed from the winds out at sea.)

Swells do lose energy as they travel away from the storm (wave decay) and disperse across the ocean. The major factor on whether a swell will hold its energy and size is the swell period. When swells are generated during a storm, some of the energy is pushed down beneath the ocean surface. The greater the wind, the more energy is transferred below into the ocean. As a swell travels great distances, it loses much of the surface energy (from crosswinds and opposing seas) but retains much of the submerged energy. The way to measure this energy is the swell period, the time between two wave crests. The longer the swell period, the more energy is carried below in the ocean. Hence, swells with a long period (over fourteen seconds) will retain more energy and bring larger waves than short-period swells (under fourteen seconds). “Long-period swells,” writes Sean Collins, “travel with more energy below the ocean surface and are less steep so they can easily pass through opposing winds and seas with very little effect.”

When swells approach shallow water, friction causes the wave energy to push upward, making the waves grow in height. Long-period swells have much more energy, thus they will grow much more in height. According to Collins, “A three-foot wave with a ten-second swell period may only grow to be a four-foot breaking wave, while a three-foot wave with a twenty-second swell period can grow to be a fifteen-foot breaking wave.” Swell period is a factor often overlooked by surfers but crucial to predicting the size of waves.

Another more obvious factor in the size of the waves is the direction of the swell in relation to the shore. This is why the north shore of O’ahu breaks all winter and is calm in the summer. In the winter, massive storms come out of the Gulf of Alaska and head south through the Pacific, sending giant swells directly to the Hawai’ian Islands. For the same reason, powerful winter storms on the East Coast bring little swell to the shore. As they come across the eastern seaboard, they send big swells into the Atlantic, but there’s no wind sending swell back to the shore. Only if a winter storms stalls out in the Atlantic for a while (sometimes due to a Bermuda High), will it be able to generate enough wind over a long enough time to bring waves back to the eastern shore. Thus, most of the winter swells on the East Coast come from other storms, often farther south in the Atlantic.

A final factor in deciding the size of swells is the ocean floor. Swells generally slow down and lose energy as they move from deep to shallow water and drag on the ground. “One reason Hawai’i has such large surf,” Sam Iacobellis says, “is that there is no continental shelf around the islands and the open ocean waves hit the exposed reefs with a lot more energy.” This would explain why Northern California has larger surf than Southern California, for the continental shelf doesn’t extend nearly as far out into the ocean.

Yet Sean Collins is quick to argue that the continental shelf gets a bad reputation. In fact, the continental shelf often draws swell that would miss the California coast altogether. “Swell energy always focuses to shallower water,” he says. This is called refraction, when swells move from deeper to shallower water. When the ocean floor is uneven, swell energy in the deeper water will bend over toward the shallow water, multiplying the energy of the wave in shallow water. This is why there’s often larger surf at places like Blacks or Mavericks, for the deep canyons bring more swell to the shallower parts, significantly increasing the height of the waves. This also explains how swells wrap around points like Rincon, as they steer toward the shallow water. Thus, the reason Northern California has larger surf in the winter has more to do with its facing the northwestern swells.

During the heavy January rains, another occurrence was happening, shaping the future swells in California. Flooding rivers carried tons of rocks and sand out into the ocean. The deposits created inverted U-shaped sandbars, transforming river mouths into new breaks. In 1983, the unrelenting El Ni§o rains changed Trestles from a right to a left and a right. This year, several river mouths up and down the coast have built new sandbars, including some that didn’t break before (it would be unfair to locals to give them away). The ocean floor is always shifting, but it’s especially volatile after huge rainstorms when sandbars develop and change shape.

All in all, this has been an odd, erratic winter with heavy rains and snow showers taking turns with long periods of sunshine. Precipitation levels have been much higher in Southern California, with Los Angeles counting more than 33 inches for the year. This is three times more than the average (10.8 inches) at this point of the season. In Northern California, rainfall levels have been less drastic, only twenty percent above average. Meanwhile, the Pacific Northwest has been unusually dry, with precipitation levels several inches below average. On the other side of the country, the eastern shore has had a long, cold winter with another gusting blizzard blanketing New York and New England in the first hours of March. In Hawai’i, it has been an up-and-down season, with some good early swells in December followed by tailor-made-for-Pipeline west swells that lit up the North Shore in February.

On the West Coast, late February brought a second series of storms (again warm tropical moisture mixing with cool arctic air). At least twenty more people were killed in California, including two from mud and rock slides. Although the 2005 storms haven’t been as devastatiing as the ones in the winter of 1983, for many families they have been immeasurably worse.

As we look ahead, it’s unclear what the next month will bring us. But hopefully when you’re staring up at the dark clouds in the sky or watching the huge swells lining up on the horizon, you’ll have a better understanding of what’s going on with the heavy weather.

Sidebar:

Precipitation Levels Through March 1 (In Inches):

2004/5 Normal Departure from Normal

Los Angeles 33.87 10.80 +23.07

San Diego 19.64 7.47 +12.17

Seattle 21.98 27.46 -5.48

Portland 16.64 26.71 -10.07

Weather-Related Deaths In California For 2005:

45

all winter and is calm in the summer. In the winter, massive storms come out of the Gulf of Alaska and head south through the Pacific, sending giant swells directly to the Hawai’ian Islands. For the same reason, powerful winter storms on the East Coast bring little swell to the shore. As they come across the eastern seaboard, they send big swells into the Atlantic, but there’s no wind sending swell back to the shore. Only if a winter storms stalls out in the Atlantic for a while (sometimes due to a Bermuda High), will it be able to generate enough wind over a long enough time to bring waves back to the eastern shore. Thus, most of the winter swells on the East Coast come from other storms, often farther south in the Atlantic.

A final factor in deciding the size of swells is the ocean floor. Swells generally slow down and lose energy as they move from deep to shallow water and drag on the ground. “One reason Hawai’i has such large surf,” Sam Iacobellis says, “is that there is no continental shelf around the islands and the open ocean waves hit the exposed reefs with a lot more energy.” This would explain why Northern California has larger surf than Southern California, for the continental shelf doesn’t extend nearly as far out into the ocean.

Yet Sean Collins is quick to argue that the continental shelf gets a bad reputation. In fact, the continental shelf often draws swell that would miss the California coast altogether. “Swell energy always focuses to shallower water,” he says. This is called refraction, when swells move from deeper to shallower water. When the ocean floor is uneven, swell energy in the deeper water will bend over toward the shallow water, multiplying the energy of the wave in shallow water. This is why there’s often larger surf at places like Blacks or Mavericks, for the deep canyons bring more swell to the shallower parts, significantly increasing the height of the waves. This also explains how swells wrap around points like Rincon, as they steer toward the shallow water. Thus, the reason Northern California has larger surf in the winter has more to do with its facing the northwestern swells.

During the heavy January rains, another occurrence was happening, shaping the future swells in California. Flooding rivers carried tons of rocks and sand out into the ocean. The deposits created inverted U-shaped sandbars, transforming river mouths into new breaks. In 1983, the unrelenting El Ni§o rains changed Trestles from a right to a left and a right. This year, several river mouths up and down the coast have built new sandbars, including some that didn’t break before (it would be unfair to locals to give them away). The ocean floor is always shifting, but it’s especially volatile after huge rainstorms when sandbars develop and change shape.

All in all, this has been an odd, erratic winter with heavy rains and snow showers taking turns with long periods of sunshine. Precipitation levels have been much higher in Southern California, with Los Angeles counting more than 33 inches for the year. This is three times more than the average (10.8 inches) at this point of the season. In Northern California, rainfall levels have been less drastic, only twenty percent above average. Meanwhile, the Pacific Northwest has been unusually dry, with precipitation levels several inches below average. On the other side of the country, the eastern shore has had a long, cold winter with another gusting blizzard blanketing New York and New England in the first hours of March. In Hawai’i, it has been an up-and-down season, with some good early swells in December followed by tailor-made-for-Pipeline west swells that lit up the North Shore in February.

On the West Coast, late February brought a second series of storms (again warm tropical moisture mixing with cool arctic air). At least twenty more people were killed in California, including two from mud and rock slides. Although the 2005 storms haven’t been as devastating as the ones in the winter of 1983, for many families they have been immeasurably worse.

As we look ahead, it’s unclear what the next month will bring us. But hopefully when you’re staring up at the dark clouds in the sky or watching the huge swells lining up on the horizon, you’ll have a better understanding of what’s going on with the heavy weather.

Sidebar:

Precipitation Levels Through March 1 (In Inches):

2004/5 Normal Departure from Normal

Los Angeles 33.87 10.80 +23.07

San Diego 19.64 7.47 +12.17

Seattle 21.98 27.46 -5.48

Portland 16.64 26.71 -10.07

Weather-Related Deaths In California For 2005:

45

evastating as the ones in the winter of 1983, for many families they have been immeasurably worse.

As we look ahead, it’s unclear what the next month will bring us. But hopefully when you’re staring up at the dark clouds in the sky or watching the huge swells lining up on the horizon, you’ll have a better understanding of what’s going on with the heavy weather.

Sidebar:

Precipitation Levels Through March 1 (In Inches):

2004/5 Normal Departure from Normal

Los Angeles 33.87 10.80 +23.07

San Diego 19.64 7.47 +12.17

Seattle 21.98 27.46 -5.48

Portland 16.64 26.71 -10.07

Weather-Related Deaths In California For 2005:

45

CATEGORIZED: Features