The odds now strongly favor an El Nino forming in the Pacific Ocean, federal climatologists said Thursday, tilting the long-range weather outlook toward a warm winter in the Northwest.
The cool waters that ruled the seas along the equator since last fall have warmed to normal or just-below normal temperatures. The federal Climate Prediction Center, a branch of the National Weather Service, puts the chances that waters will heat to El Nino levels by December at 70 percent.
El Nino winters are generally warmer and drier in the northern U.S. But it’s not a sure bet, Washington State Climatologist Nick Bond said.
“It’s completely possible we’ll have a cold winter, but more likely it will be on the warmer side,” he said. “The odds of having a little below normal snowpack are higher than usual.”
A month ago, the prediction center put the odds of an El Nino by winter at just under 50 percent. The center said the increasing odds heavily influenced its updated outlook, especially for the fall and winter.
The forecast favors higher-than-average temperatures in California, Idaho, Oregon and Washington state from now until August 2019.
Washington state, Oregon and the western half of Idaho are expected to receive below-average precipitation through February 2019.
California and eastern Idaho have equal chances of below-, above- or average precipitation during that time, according to the prediction center.
Last May, the prediction center said the odds slightly favored an El Nino. Instead, a La Nina, a cooling of the ocean, formed. “It shows you have to keep an eye on things,” Bond said.
The center predicted an El Nino in May 2014 and was correct that time. The following winter was mild and led to Washington’s “snowpack drought” of 2015, when precipitation was plentiful but it fell in the mountains as rain instead of snow.
“It’s possible it could happen again, but that was so extreme, it’s really unlikely,” Bond said.
El Nino persisted and grew stronger for the winter of 2015-16. Average temperatures statewide were above normal, but enough precipitation fell to erase the drought.