Posted on: Monday, September 20, 2004

By Jan TenBruggencate
Advertiser Staff Writer

Scientists have unprecedented tools to forecast El Niño climate events, but still are very cautious about predicting what an El Niño will mean for the Hawaiian Islands.

A new, comparatively weak El Niño has begun moving through the Pacific, which climate experts say can mean dry winter conditions and increased likelihood of more and stronger tropical cyclones around our part of the globe.

In many years, however, it doesn't happen that way.

Reporters, farmers, politicians and others push climate experts for a clue on what's going to happen next, only to learn that they can't say for certain.

El Niño is a climate pattern with global impacts. It involves the eastward movement in the Pacific of a vast pool of warm water near the equator. This causes changes in rainfall, wind patterns and atmospheric pressure.

Australian weather can be affected, as can weather on the U.S. Mainland. Even European and African weather is at stake — as well as, of course, weather in Hawai'i.

But the impacts themselves aren't predictable.

For example, statistically, tropical storm activity in the Atlantic is reduced during El Niño years. But this year, the Caribbean is being pounded by storm after storm.

It's dangerous to make predictions from slightly increased probabilities, said Axel Timmermann, an associate professor of oceanography at the University of Hawai'i and a researcher with the university's International Pacific Research Center.

If three out of five El Niño years are drier, that may be statistically significant. But nobody is on solid ground predicting whether next year will be one of the three dry years or two wet ones.

"There is almost nothing you can say with much certainty," he said.

It's also difficult to tell how strong the El Niño will get, or how long it will last.

Computer climate models now suggest this El Niño will be modest. But the big El Niño of 1997-98 started the same way, and grew stronger.

The problem: While models are pretty good at predicting moderate conditions, they are not so good at predicting strong conditions.

As with predicting the impacts, "our best knowledge is a little bit shaky," Timmermann admitted.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766, e-mail jant@honoluluadvertiser.com or call (808) 245-3074.