Troughs continue to pound Arizona; some wet, some dry

First, in cast you missed it, this from last evening:

5:37 PM. Under lit Cirrus/Altostratus provides a rosy glow to the evening sky above Catalina and Oro Valley.

One sad note: was planning on sending out rainful holiday wishes to ALL of the folks reading this blog, but procrastinated until it was too late.  Pretty bad when you can’t make time to sit down and write two short notes in a greetings card.  My apologies.  I hope both of you have a great Christmas Day, even if its clear and a little cool, maybe with some north breezes.

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So, as we remain in the Trough Bowl, where troughs dip down to their lowest latitude, with another fast moving trough goes through TODAY in the upper levels.   If you don’t believe me, here’s where it will be at 5 PM, the good part already past us,  You can see the whole sequence here, of course.

Any rain with it?  Nope.  Just those thick high and middle clouds until afternoon and then a huge clearing–expecting that before 2 PM AST.  Not likely to see sunset-colored clouds today.  Note our rule of thumb:  the strongest winds at this level (18,000 feet or 500 millibars) remain JUST to the north of us.  You’ll likely see some distant Cumulus or Stratocumulus on the NW-NE horizon today, representing that moist air pretty much confined by the “jet” at this level.

Next troughy day begins on the evening of the 26th, but because its a two part job (two troughs go by) it takes until the morning of the 28th to go by.   The USA! models have had some rain here on the 27th and 28th off and on, but not the latest, and the jet remains to the north, as has the Canadian Environment Canada model.   Neither models do on the computer run based on last night’s 5 PM AST global data.  However, the jet at 500 mb, at least on the Canadian model is a little south of us on the evening of the 27th, and so a little rain from Stratocumulus clouds piling up against the Catalinas in a cold, westerly flow, can’t be ruled out.  However, it does not appear that more than a few hundredths of rain could eventuate from them.  Looked juicier than this a few days ago.  Drat.

Possible behemoth still out there for early January….

Following these three trough passages over the next couple of days; todays, and the two on the 26-28th, an upper level low gets cut out of the main flow, almost disappears to the south way off Mexico, but then comes roaring northward loaded with tropical water.

The models have had the best of this wet tropical plume either over us or to the east.  The overall situation of a low far to the south of us has been well predicted in the NOAA ensembles of spaghetti.  It will be out there in a great position for us, but whether that plume and an inch of rain arrives, or a quarter of an inch is, naturally, vexmatic.  Some rain seems certain in the window of January 1st through the 4th now.  BTW, before this map, this low is SO FAR SOUTH, only an edge of it, somewhere off Puerto Vallarta, is seen in this map area!

So, lots of watery potential for the Southwest riding on this guy.  You can see THIS whole sequence here, and the computers will be updating it, as you know,  every 6 h.  There will be a bit of drama in these updates since so much is riding on it.

A very nice map, valid for 11 PM January 1st. Colored areas denote areas in which the model thinks precipitation has occurred during the prior 12 h. Hot spots of precip turn blue and Husky purple. By this time a little low center is advancing on Arizona!

Man, our vegetation really needs this one! Not much (reliably) indicated after this rainy situation ends. Drat2.

The End.