Peninsula Daily News and news services
SEATTLE — Cooler, rainy days are interrupting our usual sunny weather this September.
But storms are expected to grow more severe in the coming winter months as the La Nina climate phenomenon strengthens.
That likely means above-average rainfall, increased snow pack and lower temperatures until spring.
“This La Nina 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 bull’s-eye is on the Pacific Northwest.
“You’re in for six months of the diva of drench.”
La Nina’s cooling effects
La Nina is marked by an unusual cooling of the tropical Pacific Ocean and began developing last month.
It is the opposite of the El Nino 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 Nina 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.
More rain
It can be tricky to predict weather for the North Olympic Peninsula — with its protective rain shadow.
But the winter of 2007-2008 was marked by a Dec. 2-3 storm that thrashed the Peninsula and the rest of Western Washington with 40 mph winds and 14 inches of rain in some areas.
The storm did $5 million damage to Olympic National Park and millions more to Olympic National Forest, blowing down thousands of trees, flooding roads and campgrounds and destroying structures.
Two people died in Grays Harbor County.
National Weather Service forecasters said the recent rain across the Peninsula might have been affected by the brewing La Nina — 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 Nina brings exceptionally good snow pack.
A study by UW’s Climate Impact Group showed that during El Nino years, the snow depth at Snoqualmie Pass stopped increasing by late January but during La Nina years it kept growing until mid-March.
Hurricane Ridge
In addition to the December storm, the winter of 2007-2008 was marked by heavier than usual rain and snow on the Peninsula.
At Hurricane Ridge above Port Angeles, the snow pack was 166 percent of average.
Heavy snow and a late spring melt delayed the opening of campgrounds and trailheads until late spring.
On May 2, the Ridge still had 100 inches of snow.
Deep snow delayed the opening of the Sol Duc campground until May 23.
“Skiers should celebrate La Nina 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.
