Video: Upper level high pressure bakes California and The Gorge but big winds a-coming!
by Mike Godsey, mike@iwindsurf.com
It is rare to have a single satellite video that shows so much weather action. In fact so much is happening today that it is easy to get lost. So first let’s freeze frame all the action and identify all the major actors in the graphic to the right. Then scroll down to the video and watch the action! Or first read the text below for details.
The Red Story: The big news today is the near record heat wave that has been baking inland California and will heat up the Gorge. In red notice the upper ridge at ≈ 18,000 ft. In the curve of the upper ridge is a zone of high pressure air. This upper level high pressure has created a surface high pressure area which you can recognize by the clockwise spinning winds around the high pressure.
The air within this area is descending and compresses which heats up the air creating a heat wave. It also creates a strong thermal low pressure at the surface. Now you are thinking, “if there is such strong low pressure why aren’t the Gorge and Sherman Island howling?”. Basically because the isobars of the low pressure have expanded outwards from the California Central Valley and the Columbia River Basin so they have come over much of the sailing area leaving the pressure gradient near zero.
The Blue Story: Now look out in the pacific and find at ≈ 18,000 ft. the Upper Trough. Also find the Upper low and its counter-clockwise spinning winds. This system has been blocked in this location for over a week due to the upper high pressure over the western USA.
The SW MARINE SURGE Story: Now notice that SW flow in the graphic at ≈ 18,000 ft. West of that flow and at the surface is strong SW flow. That flow is capable of creating a deep marine layer and powerful gusty winds in the Gorge and in parts of the S.F. Bay Area. But
only when that SW surge gets to the coast. So we are in a waiting pattern.
The Waiting Story: Today and tomorrow all of the models have that the upper level high pressure anchored in place keeping the heat wave going. (Well, actually one older low resolution model, the GFS. briefly hinted at the surge arriving in the Gorge today. But glassy waters at dawn today seem to belie that model) But by Tuesday afternoon or Wednesday dawn the upper high pressure is modeled to retreat eastward. Once this happens the upper low slams into the coast and marine layer clouds will surge to the crest of the Cascades and over the Golden Gate Bridge. All that cool air is relatively high pressure and all the residual heat in the inland valleys creates a deep low pressure. This pressure gradient creates a marine surge bringing strong winds to The Gorge and parts of the S.F. Bay Area.