The Northwest’s late spring, summer and fall likely will be hotter and drier than usual as the Pacific Ocean warms up, leading toward a possible El Nino next winter, the National Oceanic and Atmospheric Administration reported Thursday.
Sea-surface temperatures along the equator are slowly rising from below normal to average, according to NOAA. By fall, climatologists anticipate temperatures will be above normal, a heating of the ocean associated with warm winters and low snowpacks in the Cascades.
“Right now, I’d have to forecast a less than average snowpack. I reserve the right to change my forecast,” Washington State Climatologist Nick Bond said.
NOAA’s Climate Prediction Center foresees above-average temperatures and below-normal precipitation for May, June and July in Idaho, Oregon, Washington and Northern California.
Bond said he had more confidence in the temperature forecast.
“I would say that with the (forecasting) models there is a pretty strong consensus that it will be on the warm side,” he said. “I would be loath to put too much stock in the precipitation forecast.”
NOAA’s outlook relies heavily on the Pacific Ocean transitioning from La Nina, a cooling of sea temperatures, to El Nino, a warming. La Nina has prevailed since last fall, but chances are good that sea temperatures will be normal by May, according to NOAA.
La Nina generally means colder and wetter winters in the northern U.S. and the opposite in the southern U.S.
Although never strong, this La Nina has delivered for Washington irrigators.
Snowpacks in 11 basins monitored by the Natural Resources Conservation Service were all well above average Thursday. Northern Idaho snowpacks also are well above normal, and some Northern Oregon snowpacks have rallied to above or near normal after a slow start.
To the south, snowpacks in the rest of Oregon and Northern California are below normal. A drought in Eastern Washington that covers almost one-third of the state is expected to persist for at least the next several months, the U.S. Drought Monitor reported Thursday.
Ocean temperatures may gradually increase over the summer. By October, the odds begin to favor a weak El Nino.
NOAA cautioned, however, that climatologists have been fooled before. “Though we appear headed a toward a cold-season El Nino, there have been several false starts in recent years where promising El Ninos simply faded away,” NOAA stated.
If NOAA’s forecast holds true, sea-surface temperatures will be much as they were the winter of 2014-15, the year of Washington’s “snowpack drought.” That winter, however, El Nino was combined with an unusually warm mass of water off Washington’s coast.
“Right now, there’s no indication it’s really going to warm up along our coast,” Bond said.
If an El Nino forms, it’s no sure bet that snowpacks will suffer. The last El Nino classified by climatologists as “very strong” was the winter of 2015-16, when Washington snowpacks and reservoirs were generally above average. By the end of the winter, the state had pulled out of the drought that had started in 2014.
“We kind of lucked out in the winter of 2015-2016,” Bond said. “What that shows is that each El Nino event is unique.”