Strong Easterly Winds Hit the Northwest

Powerful winds have pushed through and downstream of regional gaps in the Cascades and other regional mountain barriers.

Consider the maximum gusts observed this morning (see below).  

There are three swaths of wind exceeding 40 mph (yellow colors).  One extends southwest of Bellingham and heads over the San Juan islands and then westward out the Strait.

The other extends westward north of Mount Rainer and out to Tacoma.  And another extends from the western Columbia Rivr Gorge and then over Portland and the northern Willamette Valley.


There are a few odd strong winds over some exposed ridges, like one near the Tri-Cities.

So what is going on here?

We start with a very large difference in pressure across the Cascades.  Sea level pressure (solid lines) and near-surface temperatures (color shading, blue and purple indicated cold air) for 4 AM this morning are shown.  

There is a very large pressure difference (gradient) across the Cascades with higher pressure to the east.   Cold air is denser than warm air, resulting in higher pressure near the surface east of the Cascades.


This difference in pressure drives winds, which accelerate from high to low pressure.

But there is a problem.  The Cascades block the air at low levels!  

Thus, air looks for gaps or weaknesses in the Cascades to push through, and as shown in the topographic map below, there are three of them.

One gap encompasses the Fraser River Valley and exits near Bellingham.  Another is the Columbia River Gorge, a near sea level gaps across the Cascades.  And the final one is the Stampede Gap southeast of Seattle which represents a weakness or lower area in the Cascades.


These three gaps represent favored conduits for air pushing westward from eastern Washington.

An exciting development is the growing ability to skillfully forecast the strong gap winds using high-resolution regional models.  

To illustrate, below is a 24-h forecast of the winds exiting the Fraser River gap this morning at 4 AM. You can see the swath of strong winds over Bellingham and the San Juans.


Finally, there is the issue of gap-wind tourism.  Where is the best place to experience the regional gap wind phenomenon?

My recommendation is Crown Point in the Columbia Gorge, with the Vista House being the perfect venue.  They even have a snack bar!


The winds have gotten over 100 mph at this location.  This morning it got to 74 mph.

What could be better than being buffeted by hurricane-force winds and then enjoying a hot chocolate?  For a meteorologist or weather enthusiast, nothing could be better.


Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more