October 24, 2007

Yin-Yang weather

After last weekend's cold front, we're back to enjoying perfect fall weather here in Utah. Perfect weather that is directly causing the hellish conditions in California. A dome of high pressure situated over the Great Basin brings us clear, crisp, blue skies. But the clockwise kick delivered by the high arc of the jet stream around this high pressure ridge spins off currents of air south and west toward Southern California. During the summer, hot air rising from the Mojave and Sonoran Deserts effectively stoppers the sink. But in the fall, all this gorgeous high pressure air drains out of the Great Basin and tumbles across the cold deserts, picking up additional energy ("adiabatic heating") as it falls five thousand feet to the ocean, warming and accelerating, and finally turning into the scorching Santa Ana winds.