Heavy Altostratus to bring sprinkles-its-not-drizzle (educational title)

Also, lotta footnotes today.

Beginning to wonder, with all the middle cloud thickness out there over and SW of Baja that’s headed this way if we won’t get sprinkles that produce a little measurable rain later today or overnight….

7 AM AST.  Look at all those clouds over Baja and to the west of there.
7 AM AST. Look at all those clouds over Baja and to the west of there.You can see this whole loop from the Washington Huskies here.

Models beginning to wetten things up here as well, like that Enviro Can model that sees our tropical surge high and middle clouds passing over us now,  as deep enough for measurable rain later today and overnight.  Huh.    U of AZ mod, the best one for us, is still dry around here except on  mountain tops.  Our larger scale model, however,  also has some very light rain in this area now,  later today into tomorrow morning.

What’s intriguing is that a little jet core at 500 mb (up there at about the height of middle clouds) passes south of us as this happens, key for precip here1 in the cool season.   The major jet stream is far to the north.

As you know,  we have a bit of an El Niño going, both a “Classic Niño” as well as the “New Niño” going, and El Niños strengthen the southern portions of jet streams in the very way that we’re seeing in this situation.

They do that because its warmer than usual in the central and far eastern Pacific tropics due to heat in extra big Cumulus and Cumulonimbus clouds that pump away down there over that extra warm water,  and that rising warmth produces a greater than usual difference in temperatures throughout the troposphere between the tropics and the mid-latitudes.  Since  jet streams are the products of temperature differences between warm and cold air around the globe, so unusually deep warmth in the tropical eastern Pacific gives a little strength tweak to jet streams coming into the coast2.

SInce there are two of these lower latitude “waves” traveling along in the southern branch of the jet stream, there are TWO chances for slight rains including that for later today.  The next one barges in on the 6th of December.  Will again be dense middle and high clouds with virga at its worst, like this one, though again a hundredth or two could happen.

Next real rain chance, and major front passage with air that’s too cold for us, will be on the 12th.  Spaghetti folk, or “Spaghetti Busters”, those who can make sense of these balls of yarn, can EASILY see that trough on the 12th and a cold front with are “in the bag” even though that’s ten days away.  Rain occurrence is more dubious, since the trough may land a bit too far east to produce rain, only a lowering of temperatures.  Here is that plot from last evening.  Enjoy.

Valid at 5 PM, December 12th.  Pretty clear a nice trough will be in the area then.
Valid at 5 PM, December 12th. Pretty clear a nice trough will be in the area then.

 

Your yesterday’s clouds

11:44 AM.  Up and down, up and down, those wavy air motions that produced this interesting line.
11:44 AM. Up and down, up and down, those wavy air motions that produced this interesting line.
DSC_0200
3:37 PM. Classic Altostratus translucidus (sun’s position is visible).
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5:20 PM. Sunset Altostratus (ice clouds) and Altocumulus (droplet clouds).

BTW, for horsey people, the Cement Trough had water in it yesterday after being completely dry ten days ago:

11:44 AM. At the Cement Trough headed to South Gate.
11:44 AM. At the Cement Trough headed to South Gate.

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1See Rangno, 1973, unpublished manuscript and figures for the whole US using only the horizontal shear in jet stream at 500 mb as a definer of precip occurrences.  Its really quite something, though, I guess you can’t see it.

2This was figured out by the Great Jacob Bjerknes of the Norwegian School of Meteorology while he was cruising into retirement (“Emeritus” status)  at UCLA in the 1960s, though Chuck Pyke3,4, his grad student,  did most of the work.  Did a lotta work on the big “Classic” El Niño of 1957-58, which, per chance turned out to be an International Geophysical Year with a lot of extra observations!  How lucky wazzat?

3Chuck, as you may recall was in the National Guard whilst at UCLA and was sent to Biloxi, MS, for two weeks of training and while there, was “gifted” with the passage of the eye of Hurricane Camille, one of the strongest of the century.  Later the remnants of Camille, to go on and on, produced 31 inches of rain in 6 h in Virginia.

4Chuck P, who now lives in Arizona, also was very thorough in his evaluations of rainfall in his other studies concerning the seasonal timing of rainfall throughout the West.  He once told me when I visited UCLA once  to get Bjerknes autograph5 that he had gone to every rainfall measuring site in his study! Now some people go to every baseball park in America, but going every rain gauge site would be more interesting to cloud mavens.  He further told me he found one that had not moved for 30 years, but the rainfall had been decreasing.  When he went to that gauge, he found that it was being overgrown by a tree!  This is why you have to check things.

5I failed.  He was “Emeritus”;  too good to be in his office that day.  You see, your Catalina cloud maven was a strange person even then,  wanting an autobgraph by Bjerknes rather than one by Mickey Mantle, though one by Mickey M would be worth a lot more today.