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NW Fishletter #251, September 4, 2008
 La Niña Lingers, But For How Long?
La Niña is lingering, but that part of the world where El Niños are born is warming once again. In the equatorial Pacific, waters have warmed to above-average temperatures in some places, from several degrees below average last winter.
The waters off Washington and Oregon have remained 2 degrees F. below average. How long that will last is anybody's guess.
The Sept. 2 update from the National Oceanic and Atmospheric Administration's Climate Prediction Center says El Niño/Southern Oscillation-neutral conditions are expected to continue through the fall.
The University of Washington's Climate Impacts Group reported that 14 of 20 climate models predict neutral conditions through February.
The Climate Prediction Center also calls for a greater-than-33-percent chance of below-normal August-October temperatures for western Oregon and Washington; more than a 40-percent chance for below normal temperatures at the Oregon coast; and an equal chance of below, equal to, or above-normal temperatures for the rest of the Northwest.
As for August-October precipitation, the center calls for a greater-than-30-percent chance of below normal in many places, exceeding 40 percent in eastern Oregon and Washington and western Idaho. Southeast Idaho, northwest Oregon and western Washington are forecast to have an equal chance of below, equal to, or above-normal precipitation.
But you may want to take the CPC's forecast with a few grains of salt. According to a June report in the Bulletin of the American Meteorological Society, cited in the Aug. 15 issue of Science, "About the only time forecasters had any success predicting precipitation was for winters with an El Niño or a La Niña." But even when they included years with an ENSO event from 1994-2004, the study authors said the CPC predicted precipitation levels only a few percent above mere chance.
The CPC did better with temperature predictions, according to the study, boosting its skill level to 13 percent from 8 percent for the decade before (100 percent is a perfect prediction). During El Niño or La Niña events, the forecasters' skill level at predicting temperatures out eight months exceeded 85 percent across the eastern United States, and was also high out to a year for temperature forecasts in the West.
With ocean temperatures 2 degrees below average for Oregon and Washington coastal waters in July, conditions for salmon have remained good, and while the La Niña lingers, conditions for forecasters' predictions may be better as well. -B. R.
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