WASHINGTON—After weeks of relentless, record rain, hurricane-force winds, floods and heavy mountain snows, scientists are starting to wonder when El Nino will show up and provide a break in the ugly weather that's been pummeling the Pacific Northwest.
A week ago, the National Weather Service said that this winter's El Nino was intensifying, and it predicted that it would last longer than expected next spring. So far, however, there's been no sign of the weather phenomenon, which usually brings milder and drier conditions to the Northwest, wetter and cooler ones to the Southwest and warmer and drier winter weather to the nation's northern tier.
It may still be a little early for El Nino to arrive, but the nasty weather in the Pacific Northwest has left climate experts such as Nate Mantua at the University of Washington hesitant to predict that the worst is over and quietly speculating that some other meteorological force may be at work.
"It could be something we haven't picked up on is happening," said Mantua, the assistant director of the university's Climate Impacts Group in Seattle.
Other scientists counsel patience.
"Often there are no signs of an El Nino until January, February or March," said Mike Halpert, the forecast chief for the National Weather Service's Climate Prediction Center in Maryland.
Halpert, however, also cautioned that no two El Ninos are alike.
An El Nino begins with a warming of the ocean's surface in the equatorial Pacific that spreads eastward to the tropical coast of South America. South American fishermen first discovered the meteorological event, which occurs every three to seven years. They dubbed it "Christ child," or "El Nino" in Spanish, because it appeared around Christmas.
As an El Nino grows, it influences the strength and position of the high-altitude jet stream that flows across the northern Pacific. That, in turn, affects the weather in the United States. Winter storms typically track along the jet stream and first hit Washington state and Oregon. But during an El Nino, the jet stream slips farther south, and those storms can clobber central and southern California instead.
So far this year, that hasn't happened. The Northwest has been drenched. November was the rainiest month ever recorded at Seattle-Tacoma International Airport, with 15.59 inches of rain. It snowed last month during a Monday night Seattle Seahawks football game. Meanwhile, California has been dry, with Santa Ana winds and brush fires. Southern California has had no significant rainfall since May.
Yet there've been anomalies.
The Northern Plains have been warmer than normal, typically a sign of an El Nino. The low in Bismarck, N.D., one day last week was 38 degrees. The average low at this time of year is 5 degrees. Scientists also think El Nino reduced the number of hurricanes along the Atlantic seaboard in what had been expected to be a very active hurricane season.
In the tropics, Mantua said, this year's El Nino was unfolding "according to script" with a warming ocean, a shift in the trade winds and drought in Southeast Asia.
But the shift in rainfall patterns hasn't moved east, and the Pacific Ocean off the West Coast of the United States hasn't warmed as expected in a typical El Nino, Mantua said.
"There are lots of puzzles when it comes to El Nino," said Mantua. "The last six weeks have been exactly opposite of what El Nino looks like."
Mantua was reluctant to tie the uncertainty about El Nino to global warming, suggesting that it could be linked instead to anything from concentrations of sea ice to soil moisture content in Southeast Asia.
Mantua concedes it still may be a little early for the effects to be felt on the West Coast, but he also said that it's possible El Nino could fizzle out.
"El Ninos come in many flavors," he said. "It may not happen."
Halpert of the National Weather Service remains confident that El Nino will arrive.
Even if the "zonal jet stream" is now farther north than normal in an El Nino winter, Halpert expects it to slip south.
Australian weather officials said in early December that El Nino was entering its "mature phase" with ocean temperatures, wind and cloud patterns lining up as expected. Based on computer models, the Australians predicted that this winter's El Nino would peak in January or February.
Halpert said that while the drenching, stormy weather in the Northwest over the past several months may be unusual, he's confident that the weather will moderate as El Nino arrives.
"It will kick in," he said.
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(c) 2006, McClatchy-Tribune Information Services.
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