by Mike Godsey
The Central Coast and Southern California had a great spring and early summer with the North Pacific High’s NW winds hanging nearby most day. But this weak a massive upper level high pressure over the western USA brought an end to those winds.
This first graphic shows the upper level high pressure air mass. Notice how it has a clockwise rotation. Air in this area is descending and compresses at it near the surface creating heat.
Notice how the parts of the USA below the upper high pressure are very hot. Also notice how the the surface North Pacific High has angled towards the Gorge and away from Southern California and the Central Coast.
This happens every late spring which is one reason the Central Coast and Southern California winds weaken in the summer.
Also, notice how the winds near the Central Coast and Southern California Bight have an NNW angle.
This angle favors the formation of an eddy over the Southern California Bight creating AM southerly winds from San Diego to Santa Barbara.
Usually, heat is good for summer winds in Southern California since it heats the inland valleys and Southern California Deserts creating a local pressure gradient that helps the winds especially in the Long Beach area and the inland lakes.
But in this case, there is simply way too much heat. The next graphic shows how the heat causes the low-pressure in the Southern California Deserts and in the Yuma Az. to Sea of Cortez are to balloon over the entire Southern California Bight.
This low-pressure plus the NNW wind coming down the Central Coast and outer Southern California Bight causes a counterclockwise eddy to develop. Typically, eddies die in the early afternoon but with such a large low-pressure over the Bight, the eddy continues until late afternoon so there is barely any time for local sea breezes to develop.
Still, as the upper high pressure weakens the next several days the isobars you see in the graphic will move closer to the coast earlier and we will see improving local sea breezes.