El Nino 'pequeno' builds in Pacific

By: DAVE DOWNEY - Staff Writer | Saturday, September 23, 2006 7:30 PM PDT ∞

El Nino, one of the most feared names in weather, is back after a three-year absence.

Weather scientists say evidence is mounting that El Nino is rising again in the central Pacific, but they say the jury is out on whether the potentially brutal climatic condition will strangle Southern California with torrential rains this coming winter and spring.

"El Ninos come in small, medium, large and extra-large sizes," said Bill Patzert, a climatologist at the Jet Propulsion Laboratory in Pasadena, in a recent telephone interview.

And, at this point, the warming pool of water in the Pacific Ocean looks to be on the small side, scientists say.

"At this point, don't hyperventilate because it's way too early for the small disturbance in the force that we are looking at right now to bring us a soaker come January," Patzert said. "Right now, this is not El Nino macho, this is El Nino pequeno."

David Pierce, a program analyst in the climate research division at UC San Diego's Scripps Institution of Oceanography, said a particularly strong El Nino can deliver near-record rains, such as those that caused widespread flooding and mudslides across Southern California during the winter of 1997-98.

By comparison, the weak El Nino developing this autumn may deliver a mild winter for the upper Midwest, but it isn't likely to have much of an effect on Southern California's weather, Pierce said.

On the other hand, there is a chance that this year's weakling weather beast could grow into something more formidable, given that its growth has been rapid in recent weeks, said Doug Le Comte, a meteorologist and drought specialist with the National Weather Service's Climate Prediction Center in Camp Springs, Md.

"There is a distinct possibility that it could become a moderate-strength El Nino," Le Comte said. "Generally, that means a wet winter for Southern California and across the Southwest."

On the positive side, Patzert said, it is often El Nino that winds up filling the parched reservoirs along the Colorado River that the San Diego region depends on for watering lawns and golf courses, and taking showers.

El Nino is essentially a surge of heat in the equatorial waters off the west coast of South America. It tends to show its watery face every three to five years.

Le Comte said the heating up of the water is significant because the central Pacific is the engine for the North American jet stream. A strong El Nino tends to pump moisture into the jet stream and steer it south of its normal track, across the southern tier of the United States.

As a result, Le Comte said, southern states become more susceptible to storms.

The weather phenomenon can cause severe droughts and forest fires in Australia, Central America, Indonesia, the Philippines and southern India, according to wire reports. It is often associated with heavy rain and flooding in Bolivia, Ecuador and in the southern U.S.

This year's El Nino is being credited for the mild hurricane season in Florida and along the Gulf Coast.

The condition gets its name from the anchovy fishermen in South America who discovered it in the 19th century. The fishermen named the condition for the Christ child ---- el nino means "little boy" in Spanish ---- because it appeared around Christmas.

Pierce said scientists are sure that another such condition is brewing off the coast of South America because the sea-surface temperature in the central Pacific is running about 30 degrees Celsius, or 86 degrees Fahrenheit.

"That's bathtub temperature," he said.

Pierce said the temperature is about a degree more than normal for this time of year on the Celsius scale, or about 1.5 degrees warmer on the Fahrenheit scale.

Still, he said, this El Nino's temperature rise amounts to just one-third the increase recorded at this time in 1997.

Pierce said the last El Nino, a mild one, appeared in 2003.

"We actually had kind of a wet year that year, but the consensus was that it was largely a coincidence," Pierce said.

At the same time, a mild warming of the Pacific should not be interpreted as meaning that the residents of northern San Diego and southern Riverside counties are guaranteed a mild winter, he said.

"We can have bad winters, even when there is no El Nino," Pierce said.

Still, El Nino has been responsible for its share of wet winters. Patzert said the weather monster delivered some pretty heavy blows in 1883-84, 1940-41, 1972-73, 1977-78, 1982-83, 1992-93 and 1997-98.

In San Diego County, the rainy season of 1883-84 still ranks as the wettest on record, at 25.97 inches, according to the National Weather Service in San Diego. The second-highest rainfall total ---- 24.74 inches ---- was the one for 1940-41. And the winter of 1997-98 ranks fourth on the all-time list, at 18.71 inches.

It is unlikely, however ---- at least at this point ---- that El Nino will deliver a winter to remember like one of those.

"We've had more false alarms than real deals," Patzert said.

And to suggest this one will wreak havoc, he said, would be like "shouting 'Fire!' in a theater."

Contact staff writer Dave Downey at (760) 740-5442 or ddowney@nctimes.com.

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