Kathie Dello is the Deputy Director of Oregon’s state climate office.

What to Expect From El Niño in the Pacific Northwest

  • Dec 21, 2015

What happens in the tropical Pacific doesn’t always stay in the tropical Pacific. Activity at the equator influences our winter climate here in the Northwest in a big way. But that’s only one of the reasons that this winter’s El Niño is drawing so much attention. The 2015-16 El Niño is one of the strongest yet recorded.

Sea surface temperature anomalies for the week of Dec. 7

Sea surface temperature anomalies for the week of Dec. 7.

Credit:

El Niño is the warm phase of one of the dominant modes of climate variability, the El Niño-Southern Oscillation. El Niño events consist — very broadly — of an area of warm water in the equatorial Pacific coupled with changes in atmospheric circulation. This year has seen record high sea surface temperatures in the Nino3.4 region, the area of the Pacific Ocean where these events are commonly measured.

El Niño can affect climate the world over, producing effects ranging from droughts to downpours. This year’s El Niño has been forecast to peak in the winter. And while this is typical of other El Niños, the impacts here in the Northwest will last well beyond the winter pinnacle.

In El Niño years, temperatures in the Northwest tend to be warmer than average, while precipitation often tends to be below normal — especially in western Washington. Another notable effect of El Niño events is on local sea levels off the Northwest coast, which tend to be higher in El Niño and can — often coupled with other factors such as high tides — lead to coastal flooding. But this is about all we can realistically project about this year’s unprecedented El Niño.

That's because there aren’t many events of similar strength to compare to this year’s El Niño. The exceptions are the 1982-83 and 1997-98 El Niños, both of which were wetter than normal in western Oregon and Washington, and warmer than normal across the entire Northwest region. But not all El Niños are alike. Given the magnitude of this year’s event and the availability of only two past data points to compare it to, it’s difficult to draw comparisons with past events.

What might also make this year’s El Niño stand out is that the entire North Pacific is already warm. El Niño seems to be pushing “the Blob” — that massive, oddly shaped stretch of conspicuously warm water in the northeast Pacific Ocean — around as its influence spreads north, but warmer-than-normal temperatures off our coast still remain. 

What’s more, our region has seen nearly two decades of warming since the 1997-98 El Niño. Add them up, and all of these factors contribute to what is the best guess climatologists are projecting for the rest of our winter and early spring: warmer-than-normal temperatures across the entire Northwest and drier-than-normal conditions in Idaho, eastern Washington and eastern Oregon.

Precipitation is a big question. The two weeks before this publication have seen unusually high precipitation in much of the Northwest. But the influence of El Niño grows stronger as winter proceeds, so it’s still possible that the months of December, January and February will end up drier than normal.

Either way, much like last winter, if we do have above normal temperatures that could mean we’re dealing with another snow drought. (See “This Year’s Drought: A Glimpse into the Future,” Terra.) El Niño is typically a skier’s nightmare. The good news is El Niños — even this year’s monster one — are relatively short-lived events that rarely last for more than one winter.