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Cool mornings but will warm up

Cool mornings but will warm up

After triple digit temps a week or so ago, these temps in the 70's seem frigid.

Some low lying places in the south San Joaquin valley may dip to the mid 30's on Thursday and Friday mornings.

An off-shore circulation will build in starting Sunday and should warm things up to seasonal or above temps... well into the mid 80's for at least through the week.

The following thread was started by Tom on October 02, 2002 at 4:41 pm PST

Santa Ana winds blowing hard here

The Santa Ana winds blew hard here last night, we didn't drop below 60F. The wind is dry and warm, with gusts up to 30 mph. Considering we had a low of 46F Monday morning, this is quite a swing. It's so dry that low lying, very wind protected places could easily have much colder lows in the next couple of days. Upper 30's seems a bit early for the valley, though, isn't it?

I am not sure what to make of the Santa Ana winds. Right here in Santa Cruz, it seems my location is getting hit much harder than anywhere else. I checked other locations, Aptos SeaCliffs dipped to 48F this morning, Watsonville hit 46F. So on one hand it's nice to have wind because it keeps it nice and warm, yet on the other hand, the wind is strong and dry, so the more tropical plants won't like that too much.


The above followup was added by Axel on October 02, 2002 at 5:18 pm PST.

new name

We need a new name. Technically these aren't Santa Ana's, I think, because I believe those are catabatic winds driven by downslope/siphoning/heating/compression effects from air descending from the higher regions to the east, whereas ours are simply easterly/offshore flow effects.

So we need a catchy new name for these late summer/fall dry, hot conditions. We already have "March winds" for the ones that occur in spring, and are very cold, very dry, and nasty. How about just "fall wind"?

Are these winds actually originating in the Great Basin, and so are catabatic in origin? Even if that is so, we need another name besides Santa Ana, that is SOoooo LA!


The above followup was added by Luen on October 02, 2002 at 6:22 pm PST.

Low 30's in oregon already

The lows this morning dropped into the low to mid 30's around Oregon, and the Olympia, WA airport already hit 30F this morning. Seems rather early for frost anywhere on the West coast. I hope this is not an indicator of what is to come this Winter. It's snowing in Alaska already, and the first snows of the season are expected in the higher elevations of Utah.

However, all of the long term outlooks point to above normal temperatures this Winter. Let's hope we're trading some early season cold for warmer mid-Winter temperatures.


The above followup was added by Axel on October 02, 2002 at 6:35 pm PST.

San Jose winds


The winds are the same as in Southern California, except that we have a lot less slope to enhance the heating. The high pressure adiabatically compresses the air and forces it downward. Even without any slopes, it dries up and warms up the lower atmosphere.

In southern California, the slopes would have caused another 10-20F warming, that's why they get into the 80's and 90's mid Winter. When the high pressure is absent, the air rushing from the upper deserts into the LA basin is cold and brisk, because there is no high pressure to adiabatically compress it down the slopes.

But we wouldn't dare associate ourselves in any way with Southern California. :) So why don't we just call them San Jose winds instead of Santa Ana winds. Where did the term "Santa Ana" winds come from anyhow?

Turns out that in a 1903 pamphlet "the Climatology of California," the NWS officialized the term 'Santa Ana winds' for the powerful "feun-like" gusts sweeping out of the desert along the Santa Ana Canyon and into the greater Los Angeles basin. What's weird is that the winds sweep out of every canyon, not just the Santa Ana canyon. But it sounds great.

Since the winds here are plowing straight out of the San Lorenzo canyon, maybe we should just call them the San Lorenzo winds, and we should call the March winds the San Lorenzo revenge.


The above followup was added by Axel on October 02, 2002 at 6:48 pm PST.


yeah, but you could say that about ALL high pressure generated winds, and I think the santa ana and other true terraform-catabatic phenomen depend on physical geographical features more. You need a higher-elevation plains area to trap the air so it can "siphon" lower. Plus they heat against the ground as they go, get drier, and go faster. The physical surface of the earth has a major effect on the wind whereas that isn't the case in the instance of a simple descending high pressure mass.

There are famous catabatic winds on some of the sub-Antarctic islands off South America which are only a few miles across, not big enough to create any true weather-system size high pressure, but they have hurricane force catabatic winds that can destroy structures. Entirely local effects.

And I am not sure that surface effect is at work with our wind much, either.

And they are blowing into San Jose as well. My question is, are they in the Central Valley too? If not, we could blame it on them. Are they in the Sierras, or the foothills?Can we blame it on Nevada? Or are they primarily a coastal phenomonen.

Since they don't always blow when the true Santa Ana winds do, and the Santa Anas don't ever reach up here, we should give them a new name, just as they have the Mariah (north africa?) the Zephyr (Europe?), Washoes (Nevada) etc. Many of these famous winds are also catabatic, but are distinguished from each other first by location then by other subleties. How about "election winds", that hot air that always comes blowing around October and November?

Or "fire winds", that is always what they talk about, and this is when the Oakland Hills fires occurred.

And it isn't the "high pressure" that adiabatically compresses the air. The pressure differences are negligible, and only important over large areas. The heating comes from compression due to the higher density of molecules, 3.5°F per thousand feet, or thereabouts. I think the reason there are cold winds is that deep cold air masses move through. And even they heat to the 3.5/1000 rule. But they start off in the teens or lower at elevation. High pressure may really help the Santa Anas along, but it doesn't heat the air. The actual density change is miniscule.

I don't know enough about the exact Santa Ana phemononen to speak at length about its peculiarities (thank god!).


The above followup was added by Luen on October 02, 2002 at 8:19 pm PST.



A couple of questions:
When air moves up it cools, when it moves down it warms. So why should the air be any warmer than were it started?

I've seen winds down there from the northeast that are very cold. Without the right high pressure system, it stays cold. High pressure does warm the air aloft, at least according to the weather guys on channel 11.

You're right, we won't get the kinds of Santa Ana winds they have down south. But for me, warm, dry offshore winds are Santa Ana winds. I understand that does hurt the ears of some hard core Norcal natives who struggle to distinguish Northern California from the south. Heck, it might be right down insulting. :) Lets get rid of all those palm trees, eeeuuu yuck, Go Maples! :)

BTW, have you ever taken a map of California and drawn a straight line through the North-South center? It runs smack-dab right through Santa Cruz. So are we in Southern California or in Northern California? Actually, the line passes right along Hwy 1, so I guess that means I live in Northern California and you actually live in Southern California. Now that explains all those king palms in your neck of the woods. :)


The above followup was added by Axel on October 02, 2002 at 9:45 pm PST.

Both are in central Ca !

So is Death valley!


The above followup was added by Jeff on October 02, 2002 at 10:17 pm PST.

reason for new name

The reason we need a new name is not because I have some problem with or competition with LA (I don't, I think the whole idea is stupid) but because it is a separate, disconnected phemononen that really has nothing to do with the true "Santa Ana Wind."

It starts for different reasons, doesn't blow at the same time except by coincidence, and so should be recognized as a separate entity. They don't call 'Washoe Winds" a "Santa Ana Wind" because it isn't near Santa Ana and doesn't blow when they do. So we just need to pick a new moniker for what we regularly see as a distinct weather incidence.

And I have heard from some who consider that Southern California starts somewhere south of the Ventura County line!!

Anyway, I have to be in Northern California because I am where " the palm treeeee-eee meets the pahnnnnn!"

If air moves up X it cools down A, when it moves down X it warms A, yes the temp will be the same. But Santa Anas move from the Mojave Plateau downslope, I think (getting on thin ice here - I don't remember exactly!) so they have a net loss of altitude and so compressional heating - just like filling up a tire.

I don't know, but would guess that the exact postion of the high pressure area determines the starting location of the air mass and hence its starting temperature.

If you do the math on the high/low pressure vs. altitudinal change, you will see what I mean. You go from what, 1131 millibars to 1129 millibars and you have a huge change in weather. Miniscule difference.

Consider the actual increase in density compared to that in going from sea level to say, 10,000' MSL. I can't find the density for 10k quickly, but I know that for every 6 kilometers in the troposphere you have half the density, or about 4 miles, or about 20k feet, and 10 should be about half that, so probably about a 25% reduction in pressure. Huge difference.

Make sense? (I hope I got that right!)

I love Death Valley. Spent a few days driving around there after the last Comdex, went to Racetrack Playa, spent the night out under the stars for that incredible meteor shower, no one within 40 miles of me (very literally), and about beat my Explorer to death on that road, it still isnt' the same. That is a bad, bad road.


The above followup was added by Luen on October 03, 2002 at 0:07 am PST.


I hope no one is taking any of this tongue and cheek stuff all too seriously. :)

Luen, just wondering, wouldn't the air in the upper desert be colder to begin with since it had to rise to get there? According to adiabatic heating and cooling laws and conservation of energy, there would not be any changes. So something else is happening as well.

BTW, depending on the angle of the line on the map, it goes through Modesto, about a block south of Jeff's house. Ooops, sorry Jeff, you're in Nor. Cal, so no king palms for you either. :)


The above followup was added by Axel on October 03, 2002 at 1:09 am PST.

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