What's Up With The Weather?

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By Newsweek Editors

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Think we've been having weird weather this year? Thanks to La Nina conditions in the tropical Pacific, this winter has been pretty much a repeat of last. And it looks like this sort of weather--more storms and cold in the North, drier in the South, quick flips between balmy and frigid in the Northeast--just might start seeming normal pretty soon. Working with satellite images of the Pacific Ocean, scientists at NASA's Jet Propulsion Laboratory believe they've seen signs of a major natural shift in something called the Pacific Decadal Oscillation (PDO). We've been in a "warm" phase of the PDO since 1977, says JPL oceanographer William Patzert. Now, as the central Pacific becomes cooler and a vast horseshoe of water surrounding that cool tongue warms up, we appear to be shifting into a "cool" phase. As with El Nino and La Nina, changes in Pacific Ocean temperatures are expected to affect weather patterns around the world by shifting the position of the jet streams, but, Patzert says, PDO shifts develop over a period of years and help to set weather patterns for two or three decades at a time.

"This looks like a fundamental shift, and we're due for one," Patzert says. "The only controversy is whether we've called it too early." If he's right, the oceanic stage will be set for more La Nina years, like the last two winters, and fewer El Ninos like the one that shook up weather patterns in 1997-98. That means drier conditions in California and the Southwest (and the threat of water shortages in newly populous sun-belt communities) as more winter storms are carried into the Pacific Northwest by the jet stream. It also means more frequent, stronger hurricanes along the Atlantic coast. Combined with the building boom there, conditions are primed for some very destructive hurricane seasons ahead. Changes in ocean currents may also help endangered Washington and Oregon salmon by boosting growth of the plankton they eat. The more abundant Alaska salmon stocks may be left short of food. While it's too early to make firm predictions, Patzert says he's already fielding calls and e-mails from long-range planners, anxious to include the shift in their forecasts. Weather being what it is, there'll still be plenty of variation from year to year. But chances are we're going to have to come up with a whole new definition of normal.

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