El Nino conditions brewing

Los Angeles Daily News Friday, January 11, 2002

By Erik N. Nelson

Staff Writer

If meteorological conditions in the South Pacific persist, Southern Californians may

have El Nino to blame for foul weather starting this fall, scientists said Thursday.

But with improved monitoring of ocean waters, they'll have nearly a year to batten

down the hatches if the climatological phenomenon is strong enough to produce the

devastating damage it did in 1997-98.

"Over the last several months, we've seen a gradual warming of the waters in the

central and western equatorial Pacific," said Vernon Kousky, research meteorologist

at the federal Climate Prediction Center in Maryland. "What we're seeing right now is

an evolution of conditions which generally lead to an El Nino in three to six months."

El Nino, the warming of Pacific Ocean waters near the equator, alters the course of

the jet stream, which under normal conditions "only infrequently comes into

Southern California," Kousky explained.

"Whereas in an El Nino year, the jet stream is so close, you're getting storm after

storm after storm."

During the winter of 1997-1998, Southern California received double its normal

rainfall, resulting in flooding, damaging surf and landslides.

"It's really only the strong ones that produce the devastating flooding as did the one

of '97-'98," Kousky said.

It could be three to six more months, however, before climatologists will be able to

predict the intensity of the next El Nino, Kousky said.

And other climate researchers are already predicting it will be a weak El Nino.

"Our model does not compute it as being the big event," said Tim Barnett, a

research marine physicist at the Scripps Institution of Oceanography in La Jolla.

The winter before the last El Nino, climate researchers recorded periodic lulls in the

east-to-west blowing trade winds, said Michael McPhaden, director of the Tropical

Atmosphere Ocean Array, a network of about 70 buoys that record water

temperatures and weather conditions across the equatorial Pacific.

They later realized that these lulls allowed warmer water -- which winds would

normally circulate westward -- to build up in the eastern part of the ocean and create

a powerful El Nino condition.

This week, once climatologists looked at last month's data from the buoy array, they

realized that the trade winds had again weakened for more than a week. That

caused a buildup near the International Date Line of warmer water -- at this point

about 84 degrees Fahrenheit, or 2 degrees higher than normal, McPhaden said.

"Now we're seeing the same thing happening; the trade winds are weakening,"

McPhaden said. "It's a system out of equilibrium."

The question now is whether that buildup will be enough to start a "feedback loop,"

in which the warmer water calms the winds, which in turn allows more warm water

to build up to the east, closer to South America.

If the water warms to about 4 degrees above normal and spreads out to the size of

the continental United States, it would create El Nino conditions as powerful as

those of four years ago, he said.

If the water is only about 2 degrees warmer, it would amount to a weak El Nino,

which might not affect North America's weather much at all.

Using knowledge from the last El Nino, climatologists can now give more warning

about El Nino, which provides an incentive for engineers to reinforce coastal

structures and for homeowners to patch leaky roofs, buy flood insurance and attend

to other issues that rarely trouble Southern Californians.

Kousky estimated that preventive measures taken in 1997-'98 may have saved

California as much as $1 billion.