HONOLULU -- There is trouble brewing in the steamy heat of the tropical Pacific, where scientists say they're watching what could become the most powerful El Nino event ever recorded.
El Nino is an ancient, but only recently recognized, eastward pulse of sun-warmed water in the equatorial Pacific. With growing confidence, climatologists have linked it to patterns of subsequent droughts, floods, typhoons and other costly weather extremes around the globe.
Forecasts based on El Nino data aren't yet foolproof. But University of Hawaii oceanographer Roger Lukas says that if he were living in a flood-prone area of Southern California this winter, "I would think about taking a couple hundred dollars out of the bank to buy flood insurance."
Scientists are also predicting:
Increased tropical storm and hurricane activity this fall in the eastern and northern Pacific, including Hawaii, but a diminished hurricane season in the Atlantic.
A relatively mild winter in Alaska and improved fishing off California for tuna, mahi mahi and other tropical species.
Drought during the coming year in Hawaii, Australia, Indonesia and northeast Brazil.
Increased rains in northern Peru, where an important fishery has collapsed as cold-loving anchovies have fled warming waters.
Predictions much beyond the Pacific grow less certain with distance. But scientists are saying that North Americans can anticipate, at the least, a winter of weather extremes -- unusually mild or cold, wet or dry.
"During an [El Nino] the number of weather records that fall hits a peak," Lukas says. "As for what's going to happen in Baltimore, I feel very confident in saying you're going to have a wild ride."
El Nino events generally correlate with cooler and slightly wetter winter weather in Maryland and the Southeast. The most recent big El Nino events -- 1982-1983 and 1992-1993 -- coincided with deadly blizzards in Maryland and other East Coast states.
A decade of research
Lukas has led a decade of El Nino research in the Pacific and guided the development of the Coupled Ocean-Atmosphere Response Experiment -- a network of 170 data buoys spread across the Pacific. Add ship reports and satellite imagery, and this promises to be the "best-observed [El Nino] event ever, with a higher level of understanding of what's going on," Lukas said.
The data have produced increasingly reliable forecasts that emergency planners and policy-makers are beginning to heed.
In Hawaii, the National Weather Service's Central Pacific Hurricane Center is on heightened alert this fall. Warning coordinator Thomas A. Heffner says the state's worst natural disasters -- hurricanes Iniki and Iwa -- occurred during El Nino events in 1992 and 1982. Hawaii is also preparing for drought this winter.
Australians are already battling El Nino as drought threatens agriculture and water supplies, and raises the risk of brush fires.
Missed El Nino forecasts can be costly. Northeastern Brazil typically faces drought in an El Nino, and forecasters there won praise in the 1980s after farmers heeded their warnings and avoided disaster by planting drought-resistant crops. But more recently, their predictions failed, and the drought-resistant crops produced relatively meager yields. The forecasters were fired.
Peruvian TV officials are seeking El Nino data, the better to advise citizens how to prepare. "It's a very positive sign," says Dr. Michael Glantz, senior scientist at the National Center for Atmospheric Research in Boulder, Colo. But official commitment El Nino planning around the world is still spotty and inconsistent. "My feeling is that the next El Nino [after 1997-1998] will be the one when we will be better prepared."
El Nino is Spanish for the Christ Child, so named because its impact on rain and fisheries was typically seen on the west coast of South America around Christmas. Satellite and buoy data can now detect a developing El Nino eight or nine months before that.
In normal years, persistent trade winds in the equatorial Pacific blow from east to west. The winds blow warm surface water away from South America, and permit the upwelling of nutrient-rich cold water along the equator west of South America. Oceanographers call it the "cold tongue."
But every three to five or six years, on average, high pressure systems build near New Guinea and weaken near Tahiti -- a divergence scientists measure as the Southern Oscillation Index.
The pressure changes cause the equatorial trade winds to weaken and reverse, blowing from the west. The warm surface waters begin to "slosh" back toward the east. They invade and warm the "cold tongue," triggering rain, thunderstorms, tropical storms and typhoons.
In the low-lying Marshall Islands, 2,300 miles southwest of Hawaii, residents say the rainy westerlies arrived this summer, a traditional harbinger of dangerous typhoons.
The warm, moist air and currents push on toward South America, and veer north into subtropical and temperate regions, often with dramatic weather consequences. Alaska typically sees a mild winter, but the collision of tropical air with colder, drier air produces waves of powerful storms that begin to batter Southern California, triggering floods and mudslides.
Farther inland, the tropical pulses create stronger weather fronts, deeper lows and sharp changes in temperature across the continent. The Gulf Coast also gets more tropical moisture.
The strongest El Nino on record occurred in 1982-1983. But by some measures -- chiefly, water temperature -- the current event has equaled that, and may get stronger, Lukas says.
This summer, buoys signaled that surface water temperatures in the "cold tongue" have risen as much as 9 degrees Fahrenheit above normal. More recently, Glantz said, there have been readings 11 to 12 degrees above normal in spots off Peru.
But Lukas says extreme readings may not lead to correspondingly extreme weather elsewhere: "Some of the strongest [weather] anomalies in North and South America have occurred during weak [El Nino] events."
Just why El Ninos occur isn't clear. Eileen Shea, executive director of the Center for the Application of Research on the Environment, says they may simply be the planet's way of dissipating heat from the tropics -- like steam blowing from a tea kettle.
Many questions remain
But scientists have many questions. How often did El Ninos occur in the distant past? Is global warming increasing their frequency and severity? If so, are we all facing more extreme weather? Could we get "stuck" in an El Nino?
Today, anyone with access to the Internet can read the forecasts and follow on colorful maps as an El Nino develops. "This information is now in the hands of the public and policy-makers," Lukas said. It is now up to them to find ways to prepare for or profit from the events as they play out.
"The opportunities are there," he says.
For more on El Nino, try the Internet at www.dir.ucar.edu/esig/enso
Pub Date: 8/29/97