Watch Video of an upper trough jazzing the Gorge winds while a Cut-Off Low does the same in the Bay Area.
by Mike Godsey, firstname.lastname@example.org
Today the weather pattern far above the pacific is perfect for creating strong winds in the Columbia River Gorge
and San Francisco’s Sherman Island. Before looking at the video let’s identify the main actors in today’s wind play.
In the Gorge the Columbia Basin to the east is very hot creating a surface low pressure which in turns creates a pressure gradient between the Basin and the North Pacific High west of the coast. But this situation existed yesterday and we only had mild 4.2M winds. What is so different today with wind in the mid 30’s?
Looking at the imagery to the right notice the blue arrows. These mark the wind and water vapor flow at about ≈ 18,000 ft. above the pacific.
Notice as this flow comes over the Gorge it brings SW flow over the Oregon Washington border. This SW flow deepens the marine layer creating higher pressure from Portland to the Coast. And as this SW flow encounters the Cascades it creates turbulence in the flow and some of this transfers momentum to the surface which is why the wind is so strong and so gusty today. It also increases the wind in the eastern Gorge but the wind there will be steadier since the turbulence is weaker.
Meanwhile in the Bay Area the upper trough does basically the same thing to the Bay Area wind however the bay is on very edge of the upper trough so the impact is small.
More important in the Bay Area is the counter-clockwise spinning Cut-Off Low low you see in green in the imagery. Notice how this delivers SW flow over the Bay Area and jacks up the East Bay and Sherman Island winds.
Now let’s look at the satellite imagery and watch all of this in action.
If you are wondering why you don’t see many clouds way above the Gorge it is because this imagery only shows water vapor which is invisible to the human eye unless conditions aloft cause condensation and clouds to develop.