Dynamic High pressure zone forms over California

California is experiencing a unique early autumn weather event, a heat wave caused by a dynamically-created high pressure system. This type of high pressure system happens on the California Coast rarely, during some autumns, and can produce very high coastal temperatures. Unlike regular summertime heat, which is caused by direct sunshine, the autumnal dynamic high pressure heat wave does not even allow for a coastal marine layer to form, since it is caused by compressing air being pushed down right out of the sky.
Dynamic highs are unique in that they are caused by strong airflows aloft that run into each other from opposing directions, causing the air directly overhead to be forced straight down to the ground. Air that is pushed down undergoes a significant amount of heating up and drying out. The air hits the ground and makes its way outward, eventually towards a area of lower pressure where it can rise again, pushing away the marine layer. This is not a Santa Ana type of weather event. The smog on the coast remains in place, right over the cities that created it. While the air is technically pushing put when it hits the ground, the effect directly below is too subtle. So what actually is observed on the ground is no marine layer plus the coastline to heats up dramatically under a pall of stagnant air. The conditions are very different from Santa Ana/Mono conditions, where surface air is actually moving (offshore, downhill). These dynamic highs can stay in place a surprisingly long time, although it looks like this current one will be easing up today.
This particular event is happening earlier in the year than the last time it happened, and believe it or not is not as powerful. The last time it happened was in a mid October about ten years ago. I’ll see if I can locate the temperature readings from that event! Check out yesterday’s temperatures (degrees Fahrenheit):
Long Beach: 111; Bakersfield, 98 (see? inland, cooler temp); Santa Maria, 105; Palm Springs, 109; Santa Barbara 100; San Diego, 99; Fresno 100; and… Los Angeles, 113 (Los Angeles’ highest temperature EVER – never has a higher temperature EVER been recorded in LA!)

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  1. Dynamic High Pressure Zone Forms Over California Niiice, Dave! « Fancy Dress Uk

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