That likely means above-average rainfall, increased snow pack and lower temperatures until spring.
“This La Niña is really building,” said Bill Patzert, a climatologist with NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “The jet stream pattern tends to be north and its bulls-eye is on the Pacific Northwest. You’re in for six months of the diva of drench.”
La Niña is marked by an unusual cooling of the tropical Pacific Ocean and began developing last month. It is the opposite of the El Niño event, which is characterized by abnormally warm waters in that region.
Both can affect climate worldwide by changing the direction and strength of winds and altering air pressure and rainfall patterns.
This year’s La Niña is expected to last through early 2011, according to the National Oceanic and Atmospheric Administration’s Climate Prediction Service. The last one was recorded in the winter of 2007-08.
National Weather Service forecasters said this week’s rain might have been affected by the brewing La Niña but its true effects won’t be seen until at least late September.
“It makes for a dark winter that can lead to a lot of depression but there are a lot of good things that come with it,” said Nate Mantua, a research scientist at the University of Washington. “We just have to look at the positives.”
The obvious perk is that La Niña brings exceptionally good snow pack.
A study by UW’s Climate Impact Group showed that during El Niño years the snow depth at Snoqualmie Pass stopped increasing by late January but during La Niña years it kept growing until mid-March.
“Skiers should celebrate La Niña in Western Washington,” Mantua said.
Positive impacts also include decreased risk of wildfire, better salmon fishing and potentially lower energy rates because of an abundance of hydroelectric power.
The downfalls include a greater chance of flooding and landslides.
But none of that likely will matter until winter.
For now, forecasters say daytime temperatures will remain in the mid- to high-60s and the rain will continue until Wednesday.
Stacia Glenn: 253-597-8653 email@example.com