Re: Any meteorologists out there? Re: Santa Ana conditions

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Posted by JIm Hoffmann on September 25, 2000 at 16:45:20:

In Reply to: Any meteorologists out there? Re: Santa Ana conditions posted by Eins on September 25, 2000 at 12:42:26:

Eins,"Offshore" flow occurs when the pressure is higher over the land than over the ocean, often resulting in north-east winds over Southern California. This is also referrd to as the Santa Ana effect, or the Santa Ana Winds. The terrain here often enhances the offshore breezes because as the winds are forced through the narrow canyons, they increase in speed. This is referred to as the Bernoulli effect. This is why during Santa Ana's some places will have winds exceeding 50 mph and others will have almost nothing.
The complex topography of So. Cal. combined with various atmospheric conditions create numerous scenarios that may cause widespread or isolated Santa Ana events. Commonly, Santa Ana winds develop when a region of high pressure builds over the Great Basin. Clockwise circulation around the center of the high pressure area forces air downslope from the high plateau. The air warms as it descends toward the So. Cal. coast at the rate of 5 degrees F per 1000 feet due to compressional heating, Thus, compressional heating provides the primary source of warming. The air is dry since it originated in the desert, and it dries out even more as it is heated.
Santa Ana winds commonly occur between October and February with December having the highest frequency of events. Wind speeds are typically north to east at 35 knots and below passes and canyons with gust to 50 knots. Stronger Santa Ana winds can have gusts greater than 60 knots over widespread areas and gust greater than 100 knots.(KFWB Webservice:Santa Ana Winds)
Northeasters will smooth-out the surf on our south facing beaches, but play hell with Avalon and front side of Catalina.

Jim Hoffmann
Scuba Toys

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