Weather

Child's Play

El Niño has always been associated with economic hardship along the west coast of South America mainly because of its impact on marine life. Only recently has the warm current been shown to drastically alter worldwide weather. We'll get to the weather in just a minute, but first let's see what happens to the fish.

When the surface water piles up, the water subsides, sinking to greater depths. The water converges toward the coast, and the surface becomes deformed. The water bulges up as well as moves downward, forcing nutrients to sink to great depths in a process called continuity. It's the "jelly sandwich" principle. If you sit on a jelly sandwich, the jelly will go out the sides. So as you see in the next figure, if water is pushed to the coast like a squished jelly sandwich, the warm water will not only bulge at the surface, but also sink.

Subsidence with El Niño.

Subsidence with El Niño.

The sinking nutrients deprive many fish of their nourishment, resulting in heavy losses to the fishing industries in Ecuador and Peru. The anchovy harvest fails and sardines vanish. In addition, seabirds abandon their young and scatter over a vast area of ocean in search for food. In 1983, along the coast of Peru, 25 percent of that year's seal and sea lion adults died along with all the pups. At the same time, the warmer than normal water sent tropical fish northward into other latitudes. In 1998, prize marlin showed up in the Pacific Northwest. But at the same time, sea lions on San Miguel Island, off California, starved because the water was too warm to support the fish they feed on. The warm water also damaged the coral reefs in the Galapagos Islands. The reefs also support marine life.

Global Weather Extremes

Strong El Niños always add enough energy to disrupt normal weather patterns. This usually features a cool Peru current that sweeps northward and generates a motion of water upward from great depths. As the current moves northward from the direction of the cold South Pole, it transports colder water. Also, because the Coriolis force (see Going in Circles, "Going in Circles") causes a deflection to the left in the Southern Hemisphere, water is drawn away from the west coast of South America. That causes the nutrient-rich water to rise in what is called upwelling. Marine life thrives. But during El Niño, the pattern is reversed, and water flows southward rather than northward. The water sinks rather than rises. The shifting patterns of temperature during El Niño add heat into the atmosphere above the eastern Pacific and, from that point on, the weather begins to cook.

During 1997 and 1998, El Niño raged. It was a classic. Let's take a closer look at the impact of that El Niño.

Weather-Speak

Upwelling is the rising of cold water from the deep regions up to the surface.

The Wet Coast

California always seems to bear the brunt of an El Niño winter, with rough seas, flooding, and mudslides. During these seasons, the southward shift of the polar jet stream brings a seemingly endless series of low-pressure systems that slam into the West Coast. The train of storms is not uncommon across the Pacific Northwest during each winter, but as the jet stream pushes southward, those storms plow into regions unaccustomed to such storm attacks. Also, the large temperature contrast set up by El Niño's warm water help contribute to larger storms.

In California during 1998, wave heights reached 30 feet, railroads were washed away, and major highways were washed out by flood waters and blocked by mudslides. Entire hillsides collapsed and turned into rivers of mud that swept away homes. Along the immediate coast, luxury homes crashed into the sea. In the first week of February alone, 22 inches of rain fell in San Marcos Pass, near Santa Barbara. In downtown Ventura, 12 inches came down. Three feet of snow fell in local mountains. The punishing onslaught of storms persisted well into early spring.

Also, earlier, in the fall of 1997, Hurricane Nora poured down on Yuma, Arizona, and Hurricane Pauline slammed into Acapulco, Mexico. The warm Pacific waters set the stage for super-strong hurricanes, including Hurricane Linda, which had winds of 190 mph and became the strongest storm on record for the eastern Pacific. Only by good fortune did that storm just miss hitting Southern California.

South America

In 1998, the extremely warm waters off Peru and Ecuador caused flooding rains in both countries. Hundreds of millions of dollars were lost, and the disaster led to social and political destabilization. The Ecuadorian president was replaced. During the height of El Niño, 22,000 people were evacuated from their homes.

In contrast to the storms that struck the west coast of South America, the east coast picture was vastly different. Brazil was hit very hard by a drought that affected 10 million people—more than 50 percent of the crops were lost in the traditionally poorest region. Widespread looting occurred from famine-stricken people. Just as low pressure and rising atmospheric motions dominated along the west coast of South America, compensating sinking motions prevailed on the eastern coast. The resulting drought reached record proportions.

Weather-Watch

When you receive a flood warning and are advised to evacuate, you should do so immediately. Move to a safe area.

Western Pacific

While extreme rains punished the eastern Pacific region, Southeast Asia, Indonesia, Australia, and Japan experienced severe droughts. The drought led to great economic loss and hardship, and might have played a role in the Asian stock market plunge that eventually impacted the entire world. Fires spread throughout Indonesia, and plumes of smoke fanned out across Southeast Asia. Pollution levels were extreme. In Japan, the lack of snow early in the winter created concern about sufficient snow in Nagano for the Olympic Winter Games. Eventually, the snow did fall and then was too much.

The high-pressure area in the western Pacific that got El Niño rolling was exceptionally strong, especially early in the winter. This delivered sinking motions in the atmosphere that produced clear skies, stable air, and light winds—the perfect combination to generate hot, dry conditions and high levels of air pollution. Colder water eventually eroded that high-pressure area, but not before fires claimed over a million acres of forest in Indonesia alone.

June in January

One remarkable aspect of the 1998 El Niño was the complete lack of winter weather across most of the northern United States. The winter in the Northeast was the warmest on record. In Washington, D.C., cherry blossoms were blooming in January. In New England, crocuses were going strong by early February. There was practically no snowfall in New York City. It was the "year of no winter" for the mid-Atlantic region. The strong, warm jet stream forced the normally cold jet stream far to the north, and the typical winter chill remained north of the U.S. border.

But winter weather wasn't totally absent—the winter patterns simply shifted to the north. Northern New England and Quebec were hit with the worst ice storm in that region's history. Ice storms occur when warm air streams over a cold surface. Southern New England to northern Georgia will occasionally be hit hard by freezing rain. A cold high-pressure area near the ground causes rain to freeze on contact with the surface. Normally the precipitation will fall as snow in the deeper colder air of northern New England and Canada. But in 1998, the entire pattern moved northward, and a heavy layer of ice accumulated during a powerful January storm across the north country. Ice brought down trees and power lines. Northern New England and Quebec were paralyzed. Millions of utility customers lost power for over a week, and that was during the winter! This became one of the greatest ice storms of all time with damage of more than 1.4 billion dollars.

Southern Floods and Tornadoes

Vicious storms ripped through the southern states. In December 1997, snow even fell in Guadalajara, Mexico, for the first time since 1881. During that month, Roswell, New Mexico, experienced its heaviest one-month snowfall since 1893. Accumulations came to 21 inches. From Texas to Florida, floods and tornadoes occurred with a punishing frequency. In one tornado outbreak, tornadoes around Kissimmee, Florida, killed more than 30 people. Overall in the South, 132 people were killed in outbreaks of severe weather and floods during the winter and spring of 1998.

The tropical jet stream that moved northward through Mexico and then eastward across the southern United States was responsible for the strong and damaging storms during the early winter. The temperature contrast and upward motion associated with the flow set the stage for the storms.

Ironically, the pattern in the South completely reversed as soon as El Niño weakened in the spring. Blistering heat and drought set in across Mexico, Texas, and Florida. Fires in Mexico obscured the atmosphere in Texas. The number of droughts and fires in Florida were unprecedented. The pattern had been broken and oscillated in the completely opposite direction. During the next two years, drought and fire plagued Florida and the Southeast. Soaking rains during the early fall of 2001 finally put a damper on the firestorm that occurred after the El Niño weakened.

Atlantic Hurricane Season

Although extremely intense hurricanes occurred in record numbers across the Pacific during 1997, the storm pattern was totally different in the Atlantic. Hurricanes had difficulty developing and the storms that did form remained well offshore.

The El Niño-related tropical jet stream curved eastward across the Atlantic and effectively blocked any tropical storm that could be moving toward North or Central America. Also that flow prevented the tropical storm circulation from taking much form. The tops of the clouds were sheared off by the flow before they could reach full development. In general, El Niño years tend to have few hurricanes threatening the east coast of the United States. During 1997, tropical storm activity was 30 percent below normal. For the first time in the twentieth century, the month of August passed without a single tropical storm developing.

book cover

Excerpted from The Complete Idiot's Guide to Weather © 2002 by Mel Goldstein, Ph.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.