A Yahoo! search on "Santa Ana Winds," yielded promising results. The first site on the list, KFBW.com, an A.M. news station serving L.A. and Orange Counties, defined the weather phenomenon: Santa Anas are warm, dry, gusty offshore winds that blow from the east or northeast and occur below the passes and canyons of the coastal ranges of Southern California and in the Los Angeles Basin. According to San Diego's National Weather Service forecasters, winds must blow at speeds greater than 25 knots to be called Santa Anas. They accelerate to speeds of 35 knots as they move through canyons and passes, with gusts to 50 or even 60 knots.
Several meteorological conditions contribute to the phenomenon. The Bernoulli effect accounts for increased speeds when the desert wind is pushed through narrow canyons. Bernoulli's law mathematically describes the relationship between pressure and velocity in the horizontal flow of fluids. Although different scenarios may contribute to a Santa Ana event, the most common pattern involves a high pressure region sitting over the Great Basin (the high plateau that's west of the Rockies and east of the Sierras). These regional winds typically occur from October to March, and,
according to most accounts, are named either for the Santa Ana River valley where they originate or for the Santa Ana Canyon, southeast of Los Angeles, where they pick up speed. It's interesting to note that similar weather events with different names occur in other areas along the West Coast. In the Pacific Northwest, the Chinooks are caused by a downhill flow very similar to the Santa Anas. The Northern California version of this wind is sometimes referred to as the Diablo. And like other noteworthy local winds, Santa Anas have inspired stories and song.
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