Strong high pressure in the NW along with deep thermal low pressure in SoCal and Nevada created a battle ground of wind directions at the Delta yesterday, Day started with W winds and switched to N in a matter of minutes with strong winds from both directions that overlapped.
The image above depicts winds in the upper atmosphere. When upper level winds, at about 15,000 ft are blowing directly from the west in a straight-ish line, it is said to be Zonal. Often, a surface low pressure will be ahead, on the leading edge, and another surface low pressure on the trailing edge. This…
When forecasters use the terms “cut off low,” we are referring to a smaller, trough or low pressure in the upper atmosphere that is not part of the larger and main flow. Notice in this image and outline in red there is a larger flow of the upper level winds? Below, there is a smaller…
When looking at gradients in the Gorge, we often look for a thermal low, connected to the Great Basin, which often sits in the Columbia Plateau most of the summer. But in Spring, when upper level lows are present, a surface low pressure gets created out ahead, under the highest Differential Potential Vorticity Advection (DPVA)….