WITHOUT EL NINO AND LA NINA TO STIR ATMOSPHERE, FORECASTERS FACE WEATHER CHAOS.

Byline: Orith Goldberg Staff Writer

With the death of the El Nino and La Nina global weather patterns, forecasters reluctantly conceded Monday that they have no clue as to the long-range forecast for the winter - and it is driving them crazy.

The two most identifiable weather patterns that have driven Southern California for the past three years have disappeared, leaving forecasters to puzzle over what kind of winter weather to expect.

``This winter is definitely up in the air,'' said Dan Cayan, a researcher for both the Climate Research Division of the Scripps Institution of Oceanography in La Jolla and the U.S. Geological Survey. ``I think right now there's quite a lot of uncertainty. I'd think most forecasters are pretty unsure about what's going to happen.''

Only recently have researchers begun to understand that El Nino, a warming of the sea surface in the central and eastern tropical Pacific, often brings more rainfall than normal in Southern California. And La Nina, an opposite condition, often causes drier weather locally.

This year, long-range forecasters said to be prepared either for normal weather or an extreme - because, without strong weather generators, the jet stream could act chaotically.

``We've gotten so smug about being able to forecast the climate,'' said Alexander Gershunov, a researcher for the Scripps Climate Research Division.

``For people who study climate, it's just another reminder that no matter how well you think you can understand Nature, she always has something up her sleeve.''

Despite overwhelming uncertainty among forecasters, Patzert said he believes Southern Californians could be in for a dry winter, with average or below-average rainfall. He bases that on the tendency for La Nina patterns to persist even after the signs disappear.

``In some ways, when you have a big signal like El Nino or La Nina, it's a little bit of a no-brainer,'' Patzert said, conceding, however, ``This year it's a little tougher.''

This winter will be the first since 1996-1997 when an El Nino-La Nina cycle has seemingly disappeared. But that year, forecasters said there were other weather generators elsewhere in the world, something that is not the case this year.

If the winter is normal, downtown Los Angeles would receive 14.77 inches of rain, a figure calculated over the past 130 winters, said National Weather Service meteorologist Bruce Rockwell, stationed in Oxnard.

This past winter, 11.57 inches of rain fell, as La Nina persisted.

If forced to guess, Rockwell said, he'd predict the region will get about 15 inches of rain, average for winter.

It wasn't until the 1960s that researchers first became aware of El Nino and La Nina patterns and started to understand them, Gershunov said.

The nicknames came about when Peruvian fishermen noticed unusual fish in their nets around Christmas because of unusually warm waters. They named the phenomenon El Nino after the Christ child.

Since the winter of 1982-1983, when huge El Nino influences took researchers by surprise, they have devoted a lot of effort studying it and its alter ego, La Nina, Gershunov said.

``We are only learning now how to predict La Nina and El Nino,'' he said.

Usually, when either of the two patterns develops throughout the summer, it becomes clear to forecasters which will be dominant during the winter. This past summer, there were hints of La Nina, but they disappeared, Gershunov said.

The uncertainty in this winter's forecast has vexed meteorologists and seriously frustrated commodities traders, utility suppliers and others who depend on accurate forecasts to make business decisions.

``It's probably concerning people who in the last three years have gotten used to using those forecasts,'' Gershunov said.