[pct-l] No El Nino this year....

Brick Robbins brick at brickrobbins.com
Tue Sep 30 18:31:47 CDT 2014


California won’t see hoped-for relief from drought this winter,
scientists say, because El Niño is likely to be weak or nonexistent.

Earlier this year, many scientists anticipated a blockbuster 2014 El
Niño that would rival the record-setting 1997 event. That year’s El
Niño — a climate disruption generated by unusually warm seawater in
the eastern Pacific Ocean — triggered severe weather worldwide,
including storms and floods on the West Coast and droughts in
Southeast Asia. But now the Climate Prediction Center of the National
Oceanic and Atmospheric Administration projects that a strong El Niño
is unlikely and the chances of even a mild one forming have dwindled
to around 60 percent.

A lack of wind gusts over the Pacific Ocean left this year’s El Niño
dead in the water, researchers propose September 26 in Geophysical
Research Letters. Scientists think these winds push warm seawater
eastward, which in turn rises to the ocean surface along South
America’s coast and heats the atmosphere, causing dramatic shifts in

“If we had the same series of wind events in 2014 as we had in 1997,
we would have gone strongly toward an El Niño state,” says study
coauthor Jérôme Vialard, a climate scientist at the Laboratoire
d'Océanographie et du Climate - Expérimentation et Approches
Numériques in Paris.

An oblong pool of warm seawater more than 14,000 kilometers wide
always blankets the West Pacific. During the first few months of 1997
and 2014, this warm pool shifted east as the westward trade winds

The similarities between the two periods “set off an alarm within the
community,” says study coauthor Christophe Menkes, a climate scientist
at the Institute of Research for Development in New Caledonia, a
self-governing French territory in the southwestern Pacific. The 1997
El Niño killed an estimated 22,000 people and caused roughly $36
billion in economic losses. However, in July 2014 unlike in 1997, the
warm pool in the Pacific swung back to its normal position before
rising to the ocean surface, decreasing the chance of a full-blown El

Menkes believes El Niño conditions fell flat this year because wind
gusts called antitrade winds stopped blowing in April. These eastward
gusts, Menkes says, would have helped lock the warm pool in place
after it shifted into the East Pacific.

To determine whether the missing gusts were the key difference between
the 1997 and 2014 seasons, Menkes, Vialard and colleagues did a
virtual wind swap. Using computer simulations of the Pacific, the team
calculated how 2014 El Niño conditions would have progressed under the
wind patterns observed in 1997.

The warm pool would probably have stayed in the east and not have
retreated westward, the team found, significantly boosting the
possibility of a strong 2014 El Niño event. The results indicate that
if the antitrade winds don’t return, Vialard says, “this year’s El
Niño is more or less dead.”

And that’s bad news for the West Coast. California is in the midst of
one of the most severe droughts on record and multiple large wildfires
raged across the state this summer. Many had hoped El Niño would bring
much-needed water to the region, which has received only 55 percent of
normal precipitation so far this year.

The root cause of this year’s El Niño dud remains unknown, says
Michelle L’Heureux, a climate scientist for NOAA in College Park, Md.
“The big question is why the winds weren’t as strong and rigorous as
they were in 1997,” she says. Winds are difficult to forecast,
L’Heureux explains, and contribute randomness into El Niño development
and make the events difficult to predict.

The uncertainty in part stems from the winds being influenced by
atmospheric and oceanic conditions elsewhere on Earth, says climate
scientist Kevin Trenberth of the National Center for Atmospheric
Research in Boulder, Colo. The presence or absence of antitrade winds,
he says, may be a by-product of the overall atmospheric changes that
prompt El Niño as much as they are a cause.

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