El Nino Condition May Affect Drought : Weather: Weak system has begun warming Pacific near South America at Equator. Experts say it could end dry spell dramatically or make it much worse--but it’s too early to tell.

A weak El Nino condition has begun warming the Pacific Ocean near South America at the Equator, sparking scientific speculation that if the phenomenon grows stronger it could either end California’s drought dramatically--or make it much worse.

It is still too early for researchers to tell whether the new El Nino, the first to form since 1986, will grow strong enough to affect weather and wildlife along the North American coast.

But the new current has already touched off informal weather warnings in South America, where El Nino conditions usually bring heavier-than-normal rainfall, and in the western Pacific near Australia and the Philippines, which may become drier than usual.

If the warm current spreads and begins to alter wind circulation patterns, as several previous El Ninos have done, one of two things could happen, researchers said.

“Sometimes when there’s an El Nino, the main strength of the jet stream curves northward toward Alaska, and when that happens, the storms all go into Alaska and . . . the Pacific Coast is literally left high and dry,” said Jim Wagner, a senior forecaster in the prediction branch of the federal Climate Analysis Center in Maryland. “Other times during an El Nino, the jet stream roars straight east, carrying all kinds of rain with it.”

That is exactly what happened in 1982-1983, during the strongest El Nino ever recorded, and “really the last truly wet winter you folks had,” Wagner said.

That winter, tropical storms slammed one after another into the California coastline, triggering flooding, mudslides and severe property damage.

And California did not take the hit alone. Some scientists described it as the worst natural catastrophe of the century, outranking in terms of economic damage even volcanoes and earthquakes. El Nino disrupted normal weather patterns across three-quarters of the globe, dumping record rainfall in normally arid areas as it parched tropical lands accustomed to several feet of rain.

The phenomenon, which wreaked havoc among fish and bird populations on both sides of the Pacific, was blamed for 1,500 deaths, and between $2 billion and $8 billion in damage.

In its wake, U.S. researchers set up an advisory system to issue informal warnings to nations threatened with storms or drought because of future El Ninos. The system was used to warn Peru of heavy rains and India of impending drought when a moderate El Nino developed in 1986-1987.

The Climate Analysis Center issued similar cautionary advisories earlier this month after researchers found sudden, albeit slight, increases in water temperature along the Equator east of the international date line.

Peruvian fisherman first named the unusual warm current El Nino, or “the Christ child,” because it usually peaks along their coast during the Christmas season.

Scientists readily admit that El Nino conditions are among some of nature’s least understood phenomena.

An El Nino generally occurs every six or seven years, scientists said, although some El Ninos have been spaced as close as two years apart and as distant as 10 years. It is characterized by an unusual spreading of tropical warm water from the western Pacific to the east.

In most cases, strong easterly winds precede an El Nino, causing an accumulation of warm water in the western equatorial Pacific, said Vernon E. Kousky of the Climate Analysis Center. As the warm water builds up, wind patterns begin to change: Winds either die off or, in extreme circumstances, reverse and blow the weird weather toward South America.

In either case, the warm water expands, crosses the international date line and moves toward the South American coast, triggering the temperature increases that are called El Nino.

So far, Kousky said, the water temperature has increased an average of two degrees Fahrenheit. The increase roughly mirrors what was measured at the onset of the 1986-1987 El Nino.

Scientists are having a hard time predicting how intense this will become over the next six months. “At the moment it classifies as a weak El Nino,” Kousky said. “We look for things to take shape in the fall as to whether it’s going to strengthen or weaken.”

Researchers said it is unlikely that the El Nino is affecting Southern California, but Wagner said it is possible that this summer’s persistent band of coastal fog and dreary weather may be a side effect of El Nino’s development.

The stronger-than-usual jet stream coming up from around Hawaii to the California coast is “the type of response you’d expect to see from a developing El Nino,” he said. “There would be a slight tendency for . . . more air to come northward from the tropics. When you have humid air with relatively large quantities of moisture moving over cold water--and your ocean temperatures are slightly below normal there--the result is fog.”

If the El Nino grows stronger, warmer ocean temperatures could push north this fall or winter, researchers said. Wildlife following the warmer temperatures during the 1982-1983 El Nino created bizarre sights off Southern California, including sea horses, marlin, giant squid and pelagic red crabs, all of which are common to the tropics.

Researchers note that, while each El Nino shares characteristics with the others, each also brings scientists its own share of surprises.

“Each El Nino does something a little different from all the others,” said Stephen Zebiak, a researcher at the Lamont-Doherty Geological Observatory at Columbia University. “The real-world physics is such that there are nearly an infinite number of possibilities for how these might behave.”

Zebiak has spent the last few years developing a computerized model that tries to predict when and how strongly the phenomenon is likely to develop.

The computer predicts that the new El Nino “will not be a very powerful event,” Zebiak said. But scientists have only been able to study 10 El Ninos this century, he noted, so there is insufficient data to know whether the prediction will be accurate.

“Right now, we’re just finding some satisfaction in the ability to get the right year, more or less, within a season or so,” he said.

The new El Nino already has provided scientists with one quirk, said Kousky of the Climate Analysis Center.

“We’re missing one key indicator in this one--organized cloudiness and precipitation in the central equatorial Pacific,” he said. “Usually it establishes itself over the real warm water out there (and) that alters the circulation patterns in both hemispheres. That hasn’t happened yet.”

Because of the ever-changing nature of an El Nino, most researchers are unwilling to say what effect this one might have on California--if it ever strengthens.

“It’s the $64,000 question,” said Daniel Cayan, a climate researcher at Scripps Institution of Oceanography in La Jolla. “It’s hard to say which flavor of storm routine we’re going to get. There may be a tendency to have an extreme situation--wet or dry--but it wouldn’t surprise me if we got something in between too.”

AN EL NINO IS BORN

A weak El Nino ocean current--characterized by an unusual spreading of tropical warm water from the western Pacific Ocean to the east--has begun warming the eastern Pacific at the equator. There is some speculation that a strong El Nino might dramatically alter the California drought. But it is too early to tell whether the new El Nino, the first since 1986, will grow powerful. What Is El Nino?

Normally, trade winds and ocean currents in the equatorial Pacific flow west, from the South American coast toward Australia and the Philippines. As warm surface water is pushed that way, cold water wells up along Peru and Ecuador.

But during El Nino conditions, the trade winds die and sometimes reverse direction, allowing the warm water to flow back toward South America. If an El Nino grows strong enough, it can override the cold northbound Humboldt Current and alter global weather patterns. Effects So Far

Informal weather warnings in South America and in western Pacific History

In 1982-83, the century’s strongest El Nino disrupted normal weather patterns across most of the globe, dumping record rainfall in normally arid areas while parching tropical lands. It was blamed for 1,500 deaths Possible Patterns

If the warm current spreads and warms further, it can alter wind patterns and either:

Force jet stream east from tropical Pacific, bearing heavy rain to California.

Or force jet stream north toward Alaska, leaving the Pacific coast dry.