There is no “obvious indication” a long-anticipated El Nino will form this winter after all, according to a seasonal outlook issued Thursday by the National Oceanic and Atmospheric Administration.
NOAA continues to predict above-average temperatures for late winter and early spring in Idaho, Oregon, Washington and Northern California. But an expected El Nino is no longer a major reason for the temperate outlook.
A warm Pacific Ocean, El Nino’s essential ingredient, has not triggered the atmospheric conditions in the tropics that actually lead to mild winters in the northern U.S.
Washington State Climatologist Nick Bond said temperatures have been generally above normal, but not because of an El Nino. “It’s hard to argue the tropics have really played that important of a role,” he said. “It could end up being a non-event for all practical purposes.”
For several months, NOAA has predicted a warm Northwest winter because it expected an El Nino to form. In December, the agency rated the odds at better than 90 percent. In early January, the chances were downgraded to 65 percent. Since then, sea-surface temperatures have cooled more.
There remains only an “outside chance” a “marginal” El Nino will form late this winter, according to Thursday’s outlook.
“We don’t completely understand why it hasn’t,” Bond said. “We don’t have a previous example quite like this one.”
Rather than El Nino, the Madden-Julian Oscillation has dominated U.S. weather since October, according to NOAA. The 30- to 60-day weather pattern, named for the scientists who discovered it, rises up in the Indian Ocean, slowly moves eastward, and has dry and wet phases.
Heavy rains may fall in places, but the pattern generally favors drier than normal weather in the West for the next several weeks, Bond said.
Snowpacks in basins throughout the state Thursday ranged from near normal to about two-thirds of normal for this time of year.
“At least we’re not in terrible shape,” Bond said. “It’s our expectation that we’ll have below normal snowpack when we come out of this.”
NOAA estimates the chances of above-average temperatures in February, March and April at more than 60 percent in the Pacific Northwest and southeastern Alaska.
Below-normal precipitation is favored over Oregon, Northern California, southern Washington and eastern Idaho. For most of Washington and Idaho, NOAA’s outlook projected normal precipitation.