To: DizzyG who wrote (17332 ) 10/26/2007 3:36:36 PM From: tonto Read Replies (3) | Respond to Dizzy, Kenneth's problem is that the winds are formed during the cool season, not the hot season.Another popular misconception that the winds are hot owing to their desert origin. Actually, the Santa Anas develop when the desert is cold, and are thus most common during the cool season stretching from October through March. High pressure builds over the Great Basin (e.g., Nevada) and the cold air there begins to sink. However, this air is forced downslope which compresses and warms it at a rate of about 10C per kilometer (29F per mile) of descent. As its temperature rises, the relative humidity drops; the air starts out dry and winds up at sea level much drier still. The air picks up speed as it is channeled through passes and canyons.The fast, hot winds cause vegetation to dry out, increasing the danger of wildfire. Once the fires start, the winds fan the flames and hasten their spread. The winds create turbulence and establish vertical wind shear (in which winds exhibit substantial change in speed and/or direction with height), both posing aviation hazards. The winds tend to make for choppy surf conditions in the Southern California Bight, and often batter the north coast of Santa Catalina Island, including Avalon cove and the island's airport.
