El Nino Is Headed Our Way Bearing Meteorological Mischief : Weather: Ocean-current phenomenon due as early as November is marked by persistent warming and spreading of tropical water. Although weak, it could bring heavy rains or more drought.

It may be a wimp, but it’s heading this way: El Nino.

The bizarre weather phenomenon warming the equatorial waters is, indeed, an El Nino and could reach California as early as November, said a federal meteorologist.

“We haven’t called it an El Nino, but we’re calling it a weak El Nino now,” Gerry Bell, a meteorologist with the federal Climate Analysis Center in Maryland, said Tuesday.

For California, this unusual weather condition--the first El Nino to form in five years--could mean rain or more drought, experts say.

“In California, you guys are in an interesting position--the weather varies from one El Nino to the next,” Bell said. “California is in a very sensitive spot. It will be wetter than normal or drier than normal.”

Swell.

During the 1986 El Nino, California was parched. But the 1982-83 El Nino, the strongest ever recorded, resulted in one tropical storm after another, triggering mudslides, flooding and extensive coastal damage.

The newest El Nino has raised the temperature of the water in the Pacific by 2 degrees around the central equatorial region, Bell said.

This persistent warming and spreading of tropical water is one of the key markers of an El Nino, which occurs about every six years. As the warm water spreads, wind patterns shift, sometimes even reverse from the usual. Generally, the water warms, crossing the international dateline and sprawling along the South American coast.

In fact, during the 1982-83 El Nino, the warm water spread to California’s coast, bringing along tropical sea creatures not usually seen here, such as sea horses, marlin and pelagic crabs.

As early as next month, experts expect they may begin seeing the effects of the El Nino, particularly if it gathers strength. In New England, it will be warmer than normal. In Gulf Coast states, such as Mississippi, Louisiana and Georgia, an El Nino means more than normal amounts of rain and cooler than normal temperatures, Bell said.

Although Bell and others describe this as a weak El Nino, they cannot yet predict whether this “event”--as they like to call it--will become strong or moderate. They simply know it’s happening now, and they cannot predict how it will affect San Diego or the rest of the West Coast.

“There will be some type of impact, even if it stays weak,” Bell said.

Experts are watching for other key markers that will allow them to learn more about the El Nino. These signals include consistently reduced trade winds, a change in sea-level air pressure between Tahiti and Darwin, Australia, an alteration in the jet stream level along the Equator, and an increase in thunderstorms over the central equatorial Pacific.

“Remember that El Ninos are like everything else--they come in different flavors,” said Dan Cayan, a climate researcher at Scripps Institution of Oceanography. “There can be a gentle nudge or a hard push that’s sometimes caused by the El Nino effect.”

Now, there is a high pressure area above the West Coast that blocks storms and precipitation, Cayan said. To bring relief from the drought, Cayan said, weather watchers hoped to see a low pressure area off the shore. “That’s the most immediate signature of a wet winter,” he said.

Others doubt that the El Nino will bring rainfall.

“Is this drought going to break? There’s not a high correlation between an El Nino and rainfall,” said Warren White, a Scripps research oceanographer.

Especially because the El Nino is now regarded as weak, assistant research oceanographer Arthur Miller said, he doesn’t believe it will gather sufficient strength to draw rain to the West Coast.

“During an El Nino, weather has its own life cycles. An El Nino is a pusher and mover, it helps redirect things,” Miller said. “Based on indications, it now looks like a mild event. I’d be surprised if such a mild event would have an impact on rainfall in the Western U.S.”

But Miller and others agree that the El Nino, characteristically unpredictable, could abruptly change.

“It could just suddenly pick up and take off,” he said. “We just don’t know.”

An El Nino Is Born

A weak El Nino 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 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 that 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 well 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.

Possible Patterns

If the warm current spreads and warm 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 Pacific coast dry.

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.