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COLUMN:Enough Santa Ana winds to fill all sails

THE HARBOR

January 26, 2007|By MIKE WHITEHEAD

Ahoy.

We are experiencing great winter weather, and this weekend will be good with partly cloudy skies. The ocean conditions are typical for this time of year, but the Santa Ana winds with their offshore direction have been helping to keep the near-shore seas flat. Lately, it seems that the winds will never leave, and I am receiving a flood of e-mails inquiring why the recent Santa Ana winds were cold and not hot, plus what is the wind's true name.

Let's start with the name. The National Weather Service deems the winds Santa Anas, the name most likely coming from the Santa Ana Mountains from which they blow.

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The main question, though, is why the winds are cold as the definition of the winds is hot and dry. Let's start with the basics of how these winds are formed.

The winds are created when there is a high-pressure system east of the local mountains, and a low-pressure system off our coast. Naturally, the winds will blow from high to low pressure, hence the northeasterly or easterly direction. If you would like to test this theory of high- to low-pressure then simply let the air out of your car tire. The higher pressure in your tire will be released into air, causing a wind.

Most people think the winds are heated by blowing over the hot desert, but that is incorrect. As the winds rise in elevation over the mountains, the air cannot hold the moisture vapor commonly known as humidity, which drys out the winds. Remember when you went snow skiing and your lips cracked from the dry air?

Now comes the very interesting part of this equation. The winds heat up when the air molecules come smashing (for the lack of a better word) down this side of the mountain, and the smashing creates fiction that generates the heat. Have you seen pictures of a space capsule or the space shuttle reentering the atmosphere with heat shields ablaze? This is from the friction with the air molecules.

The winds continue on their path to find the low pressure. But will the winds make it to the low center? Probably not.

Now, cold winds can blow over our area when the original winds are very, very cold from a winter cold front moving across the great basin. In this situation, there is simply not enough "fall" to smash the molecules together to create enough friction to heat the winds. Plus, the actual location of the high and low pressures can be slightly different. The analogy would be turning on the cold water in a hot bath.

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