EL NINO'S HEART STRENGTHENS; SCIENTISTS SAY DICE LOADED FOR FIERCELY WET WINTER FOR CALIFORNIA.

Byline: David R. Baker Daily News Staff Writer

New satellite images show the pool of unusually warm Pacific water that fuels El Nino is growing again and still packing enough power to pound Southern California with fierce rains, researchers said Thursday.

The pool's swelling size suggests that El Nino still may be gaining strength at perhaps the worst time - the months of January through March, when prior El Nino episodes have caused millions of dollars in damage locally, scientists said.

``We're going into 1998 with this thing at full strength, with record size,'' said Bill Patzert, a research oceanographer at the National Aeronautics and Space Administration's Jet Propulsion Laboratory in Pasadena.

The latest findings do not automatically herald heavy rain for California, Patzert and others cautioned. There is a chance the jet stream, which in El Nino years typically aims moisture straight at California, may stay to the north of the state or move further south, sending most of the rain elsewhere.

But researchers warned that the strength of this year's El Nino still suggests a rough winter for the area.

``You've clearly loaded the dice for California to get heavy precipitation in the next three months,'' said Klaus Weickmann, a meteorologist with the National Oceanic and Atmospheric Administration in Boulder, Colo.

Earlier satellite images, released by JPL two weeks ago, showed the warm water pool shrinking by about 10 percent after peaking in November. But in the latest images, compiled from data taken Dec. 10 and released Thursday, the pool had regained about half of the volume previously lost and was continuing to swell.

The rebound, JPL researchers said, appears to be part of the normal life span of El Nino, named after the Christ child because Peruvian fisherman first noticed its effects around Christmastime. The cycle of waxing and waning currents, scientists said, reveals much about how the phenomenon builds and releases energy.

The warm water pool, which many consider the heart of El Nino, forms when winds that normally blow from east to west die or reverse course, pushing warm water from the central Pacific toward the Americas. When those winds are blasting hard, they add energy to the pool. When they slacken, the water loses more energy to the atmosphere than it takes in, and the pool shrinks.

The fluctuations, Patzert said, form El Nino's heartbeat. ``These pulses are where the energy of El Nino comes from,'' he said. ``Without these pulses, El Nino would go away,'' he said.

This year's El Nino is not likely to disappear anytime soon. Lee-Luen Fu, a scientist with the satellite imaging project, said that the winds that have helped form the warm ocean pool are still gusting, and the pool is still growing.

``I'm expecting El Nino to keep its current strength for the next few weeks,'' Fu said. ``It's going to dissipate, it's just hard to say when.''