Ocean temperatures hint at a new El Niño

But besides producing drier, warmer weather and possibly threatening the health of salmon runs, the weather phenomenon would likely have a modest influence here. The tropical oceanic warming of an El Niño is only one of a number of factors that determine Northwest weather, scientists say.

The national Climate Prediction Center reported yesterday that the sea-surface temperature in the equatorial Pacific Ocean is warmer than usual. This may be a sign, the federal researchers said, that an El Niño is on tap for next year.

The climate center said other indications of oceanic warming include increased cloudiness and rainfall over the equatorial Pacific for the first time since the last El Niño in 1997-98, which produced severe flooding in California and along the Gulf Coast.

"Considering the observed oceanic and atmospheric circulation patterns and their recent evolution, it seems most likely that warm-episode conditions will develop in the tropical Pacific over the next three to six months," said Vernon Kousky of the climate center, a division of the National Oceanic and Atmospheric Administration.

The first area to be affected by El Niño would be the tropical Pacific, he said, with Indonesia likely to get drought relief thanks to expected torrential rains.

Even if an El Niño develops as expected, this region may experience the same old wet and cold winter, said Chris Hill, chief meteorologist with the National Weather Service in Seattle.

Think of the primary determinants of Northwest weather as a six-sided die, Hill said. El Niño might change the temperature numbers on one side, he said, but something else might cancel El Niño's effect by changing the temperature numbers in one or two other sides.

"In short, we can get an El Niño and still have a normal year," Hill said.

Western Washington, he noted, had a drought last year followed by serious flooding now without having any unusual phenomenon driving the weather.

Another periodical shift in the ocean-weather cycle, called Pacific Decadal Oscillation, swings between cold and warm phases on the order of decades at a time and likely has more effect on the Northwest than El Niño, scientists say.

The Northwest has been in a warm-phase ocean cycle since the 1970s, but some experts believe a shift is under way.

"It's hard to say for sure, but all the indications are that we're in a cold phase," said Nathan Mantua, a University of Washington scientist who studies ocean-weather cycles for the Climate Impacts Group, a scientific consortium.

The ocean temperature off the Northwest coast today is significantly lower (about 4 degrees Fahrenheit) than it was during the 1990s, a trend that Mantua says is reflected by the region's higher salmon runs.

A severe El Niño can warm up the coastal waters enough to hurt the runs temporarily, Mantua said, but it's too early to determine the power of this El Niño should it materialize.

In any case, he said, "it's not much to get too worried about here."

Not in the Northwest anyway.

In Louisiana eastward to Florida, and possibly Southern California, El Niño could produce wetter than normal conditions, the climate center's Kousky said. The northern Great Plains could experience unusually warm conditions, he said.

El Niños are associated with increased rainfall across the east-central and eastern Pacific and with drier than normal conditions over northern Australia, Indonesia and the Philippines.

During an El Niño, December-February will usually see wetter than usual patterns along coastal Ecuador, northwestern Peru, southern Brazil, central Argentina and equatorial eastern Africa.

Drier than normal conditions are generally observed over northern South America, Central America and southern Africa during this period.

During June-August of an El Niño, it will be drier than normal over eastern Australia and wetter than usual in the intermountain regions of the United States and central Chile. During December-February, it tends to be abnormally warm across Southeast Asia, southeastern Africa, Japan, southern Alaska and western-central Canada, southeastern Brazil and southeastern Australia.

The causes of El Niño are not fully understood, but climate records show that the event has been occurring for hundreds of years.

Historically, El Niños occur every two to seven years and can last up to 12 months. Sometimes an unusual cooling of the tropical Pacific -- called La Niña -- occurs in between.

El Niño means little boy in Spanish. The effect was named by Peruvian fishermen who noticed its impact on their catch around Christmastime and called the phenomenon after the baby Jesus.

This report includes information from The Associated Press. P-I reporter Tom Paulson can be reached at 206-448-8318 or tompaulson@seattlepi.com

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