Typical breezes here come out of the west, passing over cool waters of the Pacific. This typically gives us the proper mix of humidity and cool weather, although as you move away from the beach, those breezes don't mean as much and the morning fog and cool weather doesn't make it to you. Santa Ana winds develop maybe 4-6 times during the year, typically in the Fall, and last a day or two on average. They arrive when we have low pressure in our area and high pressure over the Great Basin - nominally the Nevada/Utah/Colorado area. So the winds are reversed and life as we know it is reversed for a few days. These santana winds (yes, they're really called that but we have a city here called Santa Ana and don't have much of an attention span so we started calling them that instead).
So the Santa Ana winds come from the desert, bringing warm dry air into Southern California. We're a little locked in by various mountain ranges, the same ones that keep our smog here. As the wind arrives, much of it at lower altitudes is blocked. Like early settlers arriving here, the wind must use canyons and passes to make its trip west. Populated areas below those canyons and passes typically see wind gusts of between 40 and 80 MPH. Instantly, we have perfect weather for fires. We sometimes get a few of those, some of which have been devastating. Thousands of trees and tree limbs come down. Power lines come down. Pretty much anything that isn't ready for the wind becomes a problem. Take a close look at the LAX tower: it's anchored by cables on one side only. The Santa Ana's are the only source of strong wind and only come out of the east. Therefore, anchors on one side only.
Speaking of airports, aircraft nearly always take off and land into the wind so they can achieve flight at a lower ground speed. Imagine a small plane ready to take off, facing into an 80 MPH wind. He only has to drive down the runway at 10-20 MPH before the wind picks him right up. So most of the area airports direct planes to take off and land in the opposite direction, i.e. toward the east. Okay, back to the "growing up in Upland" part. Well, when Ontario Airport would switch directions because of the Santa Ana winds, we'd have a steady flow (before it became a trickle, but that's a topic for another blog!) of passenger aircraft on final approach, flying right over us before banking left over Claremont, and essentially executing a U-turn to land at ONT, toward the east.
In case you're interested, planes typically land on runway 26 at ONT. This number is an abbreviation for the heading in degrees, i.e. 260 degrees without the last zero. 90 is East, 180 South, and 270 points West. So the ONT runway points slightly to the south of due West. Well, when the Santa Ana winds come to town, the planes take off and land on Runway 8. This isn't a different set of runways, just the same ones but used in the opposite direction. Let's do the math: 260 - 180 = 80, so Runway 8!. Now living in Chino Hills, we get to see aircraft coming in right over us on their way up over Pomona before turning right to land at ONT. This takes me back to my early plane-watching days in Upland.
So go out and enjoy the winds, falling leaves, clear skies, sunshine, 85-degree weather, and parade of planes this week!
