This could be hard to imagine now, but with a rare third consecutive La Niña winter in the forecast, Washington could be in for a colder than usual winter, according to assistant state climatologist Karin Bumbaco.
The La Niña pattern that has been in effect for over two years has a good chance of extending into early next year, according to the National Weather Service’s Climate Prediction Center. The center is predicting colder than usual temperatures from December through February.
During La Niña events, trade winds are stronger than usual, pushing more warm water toward Asia and increasing the cold water upwelling on the western coasts of the Americas, according to the National Oceanic and Atmospheric Administration. These cold waters in the Pacific push the jet stream northward, leading to drought in the southern U.S. and heavy rains and flooding in the Northwest and Canada. During a La Niña year, winter temperatures are higher than normal in the South and lower than normal in the North, according to NOAA.
Recall, if you will, a few highlights from our past two winters.
Between Feb. 12-14, 2021, about 6-12 inches of snow fell from the Everett area south into Oregon, with Portland receiving 9 inches of snow.
At Sea-Tac, 8.9 inches of snow fell Feb. 13, making it the snowiest single day recorded in February at the airport and the snowiest single day at Sea-Tac since Dec. 31, 1968.
In some areas, the heavy February snow was followed by lots of freezing rain, according to Logan Johnson of the National Weather Service in Seattle.
Last December, during our second consecutive La Niña winter, an arctic blast brought some of the lowest daily temperatures on record to the Puget Sound region and more snow than usual. The weather blanketed roads in snow and led to holiday travel disruptions and power outages.
On Dec. 26, the low at Sea-Tac was 20 degrees, beating the previous low-temperature record of 22 degrees for that date, set 73 years ago in 1948. On Dec. 27, we had a second day of record-breaking lows with the high only reaching 17 degrees.
“If it happens, this will be only the third time with three La Niña winters in a row in our 73-year record,” said Emily Becker of the University of Miami/CIMAS in an ENSO blog post.
The La Niña cycle, which is linked to more potent weather events, occurred about 28% of the time from 1950-1999, according to an analysis by The Associated Press. But in the past 25 winters, they’ve been brewing nearly half the time.
“[La Niñas] don’t know when to leave,” Michelle L’Heureux, head of the National Oceanic and Atmospheric Administration forecast office for La Niña and its more famous flip side, El Niño, told The Associated Press.
Her analysis shows La Niña-like conditions have occurred more often in the past 40 years. Other new studies are showing similar patterns.
The whole La Niña and El Niño system has a great influence on weather and climate during the cold season in the Northern Hemisphere.
The jury’s out on how we’ll fare in fall.
Last year, more than 19 inches of rain were recorded at Sea-Tac between Sept. 1-Nov. 30, compared with 11.81 inches in a normal fall, according to NWS Seattle.
One condition that’s different from years past, according to Bumbaco, is that La Niña winters typically bring above-average precipitation and lower temperatures, but this year the Climate Prediction Center says the odds are equal for above average, average or below average rain.
The Climate Prediction Center’s three-month outlook for August through October predicts above-normal temperatures statewide.
Information from The Associated Press is included in this report.