Improved Chances for a Big Northwest Windstorm This Winter

We have gone several years since the last big windstorm from off the Pacific.

This year may be different.  This blog will tell you why.

The Chanukah Eve Storm of December 14, 2016

Major Northwest windstorms are associated with intense low-pressure centers reaching our coast and then moving to the northeast.   As illustrated below, these storms possess intense pressure differences around them, which produces strong winds.

Big Pacific cyclones hitting the Pacific Northwest are rare during strong El Nino and strong La Nina winters.

To illustrate this fact, the figure below shows you the sea surface temperature difference from normal in the central tropical Pacific, the key indicator of El Nino and La Nina, from 1860 through 2000.   Normal (or neutral years) are found from -0.5 to 0.5 C.  Moderate to strong El Ninos occur when temperatures are more than 1°C above normal.  Moderate to strong La Nina's when temperature is more than 1°C cooler than normal.  

The red dots show years with strong storms and high winds hitting our region.    Notice how they never occurred for strong El Ninos and La Nina.  Most windstorms occur in neutral to near neutral conditions (tropical Pacific sea surface temperatures are within 1°C of normal)

And now the key point.  The latest forecasts suggest we will be in neutral conditions or a  weak La Nina this year, a situation in which many big windstorms have occurred in our region.

Below is a graph showing a collection of predictions using different methods, some statistical, some using physical models.  Most are predicting neutral or weak La Nina conditions.   Good windstorm potential.

Why are neutral years better for strong low centers approaching our coast?

Major Pacific low centers/cyclones are closely associated with the jet stream.

During strong El Nino years, the jet tends to go south into California (see figure)

In contrast, for La Nina years, the jet stream tends to swing north of us, leaving our region in a northwesterly flow not favorable for strong windstorm development.  The last few winters have been dominated by El Nino conditions.

No guarantees, but I suspect we have a decent chance at a major blow this winter.

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Announcement:  Free Public Lecture at Kane Hall on October 10:  Global Warming, the Jet Stream, and Cold Waves

All of you are invited to attend what should be an excellent public lecture by Professor Jonathan Martin on how global warming affects the jet stream and cold air outbreaks.

It will be a timely and interesting lecture accessible to non-meteorologists and given in honor of UW Professor Peter Hobbs.

The talk will be at 7 PM in Kane Hall room 210.

If you would like to go, please register online here:

Parking is available (at a modest cost) in the UW Central Garage, which is located directly under Kane Hall.  Or take the light rail (the UW stops are a 5-10-minute walk away).