The tropical Pacific Ocean probably won’t be particularly warm or cool this winter, climatologists said Thursday, depriving forecasters of their best clue to how much snow will pile up in the Cascade Range and the rest of the Northwest.
Over the past month, odds improved that sea-surface temperatures along the equator will be close to average for months to come, according to the federal Climate Prediction Center.
Meanwhile, chances that an El Nino or La Nina weather pattern will form are slight. El Nino is linked to warmer Pacific Northwest winters. La Nina is associated with colder winters.
The center said the chances of normal, or neutral conditions, prevailing in December, January and February are 58%, up from 49% a month ago.
For farmers who rely on melting mountain snow to irrigate, the good news is that the chances an El Nino will form dropped to 29% from 41%. An El Nino prevailed in 2015 during Washington’s “snowpack drought.”
“Right now, there’s no sign of it being a terrible winter. By terrible, I mean a lack of snow,” Washington State Climatologist Nick Bond said.
The climate center, part of the National Weather Service, put the chances of a La Nina forming at 13%, up slightly from 10% last month.
A weak El Nino formed late last winter, arriving later than forecasters predicted. It yielded in the summer to neutral conditions. Ocean-surface temperatures have continued to cool slightly over the past month.
Bond said he would be shocked if an El Nino or a La Nina formed that was strong enough to influence this winter’s weather.
“We don’t have the tropical Pacific as a source for predictability this time,” he said.
To arrive at the outlook, climatologists evaluated more than two dozen forecasting models.
Most models showed neutral conditions prevailing through next spring, though some predicted a weak El Nino. One forecast stood out by predicting a weak to moderate La Nina this winter.
“It’s very much an outlier. Anything is possible, and all that rot, but I think we can dismiss that possibility,” Bond said.
In the past two months, ocean-surface temperatures along the West Coast have warmed. It’s led to speculation about the return of “the Blob,” the name Bond gave to an unusually large body of warm water in the winter of 2014-15.
Bond said the mass of warm water off the coast is not as deep this time.
“It’s really warm out there, but it’s a pretty thin layer of water,” he said. “Right now, my expectation is that as the fall storms roll through, that will decrease in intensity.”