Signs of Possible Wet Winter Spotted

A sudden shift of trade winds in the remote reaches of the Pacific Ocean picked up by orbiting satellites may signal an El Nino-driven wet and wild winter on the way for Southern California, according to scientists at the Jet Propulsion Laboratory in Pasadena.

Two JPL instruments saw evidence of large mounds of warm water near the equator, one the size of the United States, making their way across the Pacific--harbingers of the notorious El Nino weather conditions that bring downpours to Los Angeles, droughts to Australia and Africa, and balmy February days to Manhattan.

“It’s a preview of possible coming attractions,” said JPL oceanographer Bill Patzert.

The signs are still only tentative, said Patzert, but convincing enough that the National Weather Service “went out on a limb” and issued an El Nino alert for the coming winter. (Named after the Christ child because it normally arrives in December, El Nino means “the little boy.”)

What excites the researchers most is that they were able to see the signs of El Nino coming from lonely areas of ocean completely devoid of ships or islands. The satellites, in effect, go where no researchers have gone before, taking unprecedentedly accurate measurements.

One NASA instrument flying aboard a Japanese satellite bounces microwaves off the ocean’s surface, measuring the strength and direction of the little waves known as “cat paws” throughout the globe every two days. It detected wind reversals in December and February.

The other instrument, flying aboard the U.S.-French satellite TOPEX/Poseidon, uses a similar system to measure the ocean’s height every 10 days. Because warm water expands like hot air balloons, a higher ocean surface means warmer ocean temperatures. The satellite measured two mounds of water that reached up to 8 inches above sea level in March and April.

By plugging those numbers into increasingly sophisticated climate models and letting high-speed computers calculate the outcome, climatologists for the first time may be able to predict El Nino half a year in advance.

“El Nino has never been predictable, and it’s never been the same decade to decade,” Patzert said.

But he is optimistic that better measurements and more powerful computers may change all that. “This is the beginning of a new era in climate forecasting,” he said.

*

The El Nino that may be on the way is not as severe as the one that drastically altered weather patterns around the globe in the winter of 1982-83. “Potentially, what’s developing here is not something catastrophic,” said Patzert, but something more like the short duration El Nino of 1994-95.

Normally, the steady trade winds that have carried sailors across the oceans for centuries blow regularly in predictable ribbons from east to west. When they reverse--even for a short period--masses of warm water pile up and “slosh back eastward,” said Lee-Lueng Fu, TOPEX/Poseidon project chief at JPL.

This enormous pool of warm water that usually sits off the coast of Australia winds up off South America, where it alters the global jet streams that direct the course of weather worldwide.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

Shifting Currents

A spreading mound of warm water in the Pacific Ocean near the equator could signal the approach of another El Nino. It would bring with it the threat of abnormal weather this winter--_either downpours or drought, or both.

An enormous pool of warm water usually sits off the coast of Australia. These satellite images show it moving toward South America, a change that could move the jet streams and alter weather patterns worldwide.

When water heats up, it expands and raises the sea level. The white areas are about eight inches above normal sea level, and they are the warmest bands. The next-highest are shown in red, followed by yellow.

The green areas are at sea level; blue and purple are below sea level.

Source: Jet Propulsion Laboratory