Thursday, January 21, 1999

La Niña likely to bring
unusually long, wet winter

The forecast is for relief after dry conditions
left by El Nino last summer

By Helen Altonn


Hawaii can expect a longer and wetter winter than usual this year. You can thank, or blame, La Niña -- El Nino's opposite.

The winter forecast comes from Anthony Barnston, research meteorologist in the National Weather Service's Climate Prediction Center in Washington, D.C.

Here for briefings yesterday on La Niña at the Honolulu forecast office, Barnston said more rainy systems and small Kona storms may occur here this year, but hurricanes are less likely.

El Nino and La Niña events involve large-scale changes in sea-surface temperature across the eastern tropical Pacific.

Waters are warmer during El Ninos and colder, or more neutral, with La Niñas, Barnston said. The system oscillates from one episode to the other on an average of three to four years.

La Niñas aren't as well known as El Ninos, but they've always been around, Barnston said. "La Niñas never get as strong as the strongest El Ninos, so they're not quite as easy to notice."

He said this year's La Niña will reverse some of El Nino's effects, but it won't affect global climate as strongly.

It is a moderate La Niña -- not as strong as one in 1988-89 but stronger than one in 1995-96, he said. However, it will bring wet relief after dry conditions left by El Nino before it faded last summer, he said.

"We're now trying to figure out if La Niña will last into the next winter (2000)," Barnston said, noting "a little buildup of warm water in the western Pacific under the surface." That precedes El Nino, he pointed out.

"The fact that it's small enough makes us think we could have another year of normal or slightly La Niña-ish conditions next year before the buildup of warm water gets to be really significant."

When warm waters move to the western Pacific, leaving cold water under the surface, it leads to La Niña.

"We don't know exactly why it builds up rather than getting transported immediately," Barnston said.

"We think it has to do with the shape of the Pacific Basin, that the distance between Australia and Indonesia and South America makes this buildup possible."

Ocean heat and other conditions are monitored by a network of buoys and satellites. The Climate Prediction Center uses computer models to predict trends.

"It's not abnormal to have El Nino and La Niña," Barnston said, describing them as normal fluctuations.

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