Fog, Wind, and Weather
The San Francisco Bay Area (and California in general) has some of the “best” weather in the continental United States, for which we pay handsomely. 
Of course, “best” is a relative term. It depends upon “what you like.” Fortunately, the “microclimates” of the Bay Area mean that, if you are careful and lucky (and sometimes wealthy! ) you can find a home in a microclimate that suits your likes and dislikes. Where I live, we have warm-to-hot dry summers, but can experience frost (a few days ) in the winter. We have two ranges of hills/mountains between us and the ocean, but there is a valley that allows the ocean to moderate our climate. I have learned that the weather that I experience will differ from the weather of San Francisco Bay, which will differ from the weather of the coast, and that is why I provided a blog entry with links to guide vacationers and travelers.
Today’s skies reminded me how confusing the sky is for someone who is not used to a coastal environment and the effects that it can have miles inland. The skies this morning are gray and cloudy, and there is a pretty strong breeze from the west. If this were the Mid-West, I might expect a rainstorm. However, what I am seeing is a “marine layer” that is expected to “burn off” at various times this morning, depending upon where you live. Where I live, in Livermore, the marine layer should burn off rather quickly, giving rise to sunny skies. On the coast, the marine layer may linger all day, since we are beginning a “summer pattern” for weather. The temperatures today in Livermore are not expected to reach the 79 degrees F that we saw yesterday, but should top out in the low 70s. The jet stream is dipping lower (southward) today, which means that we should have moderate winds.
There are *at least* two kinds of fog here. One is the ground fog with which folks from inland areas of the U.S. and elsewhere are familiar. Oddly enough, some folks in California call this type of fog “Tule fog,” after the marsh plants of California’s Central Valley, where ground fog is common in winter and can cause multi-vehicle pileups from people driving faster than they can stop on Interstate Highway 5. (We have heard pheasant hunters refer to Labrador Retrievers as “tule busters” for the way that the dogs charge into thickets of the rushes to “flush” pheasants.) Tule fog “rises from the ground” (actually condenses from the air ) when the moisture-laden air is cooled, causing condensation. Another type of fog is marine fog, which flows in and out from the ocean The photo above is from Crystal Springs Reservoir on the peninsula, and shows fog pouring over the coastal range from the ocean in the late afternoon. This type of fog seems “alive” in the Bay Area as it flows in regular patterns from the ocean, and people can live in a place that is cooler and foggier on a regular basis (e.g. Pacifica), if they like that kind of weather. Or not….
One of my photos of Ocean Beach in San Francisco in winter caught marine fog flowing (out this time) through the Golden Gate, with a distinct separation from the clouds overhead.
-Bill at Cheshire Cat Photo™
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