Weather Blog

More evidence La Niña usually means more snow in Seattle

More evidence La Niña usually means more snow in Seattle
Snow in Dayton, Wash. on Feb. 10, 2009

We've all heard La Niña is here (unless you've been living in a cave, in which case, you're not reading this anyway). There have been all sorts of stories touting the importance of preparing for a snowy winter (some more "energetic" than others) but now there is some good data to back up the snowy forecasts.

Karin Bumbaco, assistant state climatologist with the office of Washington State Climatology, announced Wednesday they went back and examined the snowfall amounts and frequency over the past 60 years for Seattle, Bellnigham, Olympia and Vancouver, Washington and correlated the findings against La Niña, neutral and El Niño winters.

(La Niña is when the waters in the equatorial Pacific Ocean cool, which in turn changes the engines that drive the weather across the planet. For the Pacific Northwest, higher pressure over the eastern Pacific ocean, which drives the jet stream farther north toward Alaska, then weaves southeast toward the Pacific Northwest. An airflow pattern originating from our northwest usually translates into cooler and wetter weather.)

The results? La Niña does, on average, make for snowy winters in the Western Washington lowlands, and for Olympia and Bellingham -- it's turned out significantly snowier.

Here is her chart, showing average number of events and average annual snowfall:

Bumbaco says despite the lack of statistical significance in many cases, the relationship between lowland snow and the El Niño/La Niña cycle is consistent among her brief analysis, a 1993 research paper, and an analysis done by the Spokane office of the National Weather Service.

She says it's not a perfect correlation - citing the La Niña winter of 2007/2008 had below average lowland snow. But "even so, on average, the relationship is clear and tilts the odds towards the potential for more lowland snow this season."

You can read her full report at climate.washington.edu