Poor August winds and upper level high pressure
by Mike Godsey, firstname.lastname@example.org
Perhaps you have noticed all the cranky comments perhaps brought on by the mostly crappy August winds.
So for diversion let’s take a look at some of the major factors behind this wind drought. Perhaps using our brains will reduce the bile.
Take a look at the satellite video below from 9AM today. Find the nagging counter-clockwise spinning upper low at about 18,000 feet over the ocean west of the Gorge. Normally upper lows like this drop towards down from the Gulf of Alaska and swiftly pass over the Gorge. Innormal years as these lows pass the Gorge they do 3 things:
1. They compact the isobars of the North Pacific High against the coast so the large scale pressure gradient goes up to the desert.
2. They deepen and push the marine layer clouds towards the corridor so dense air towards the coast creates a stronger local pressure gradient from about Viento to out east.
3. Their strong SW to W wind aloft hits the crest of the cascades creating turbulence that helps transfers some momentum to the surface wind. You experience this as strong wind with blasts at the Hatch that smooth out as you get further from the Cascades eg. The Wall.
Then, in a normal year, as the upper low departs we see more moderate winds focused more in the corridor
But this August has been different……Why?
Again looking at the video find the upper level high pressure covering the western USA east and south of the Gorge. This feature has been anchored in this location for much of August. So a succession of pacific upper lows, that normally would produce late season wind events, have approached the Northwest only to be blocked by the this upper level high pressure. So they sit for a week or more west of the coast. And with time they induce a surface low pressure below the upper low that pushes the North Pacific High far to the south so the Gorge pressure gradient fades away.
That leaves us with surface low pressure to the West and a scant marine layer so the Gorge wind engine sputters and fails and can even produce mild east wind.
It looks like this blocking upper level high pressure will loiter along the coast for at least another day. Today it has wobbled towards us so the winds should improve even if UP AND DOWN.
What will happen when this low finally comes over the Gorge? Looking at the video again you can see that we want the upper low to pass to our North so we are on the W to SW wind quadrant. Right now that does not look likely.