Rainy day GEFS; #s 4 and 17

Didn’t Bob Dylan write a song about this?   “Rainy days, #12 and 35”, or something like that? Well, we’re writing about rainy days, too, but #s 4 and 17.

Error-laden model runs1 I really like footnotes; creates a sense of erudition where there is none), #s 4 and #17, based on yesterday’s 00 Z (5 PM AST) global data,  have the best chance of a substantial storms here in Arizona in the December 20-22nd window.  So, we hope that those errors in those runs are correct!

Here they are, amongst the other error-laden runs below.  Novella-sized explanatory caption, an innovation first seen here, included:

Valid Friday, December 20th at 5 AM AST.
Valid Friday, December 20th at 5 AM AST.  The key contour at 500 mb that I had gone to some trouble to annotate, is the 558 decameter one, usually in the heart of the jet stream at 500 mb.  If that contour really swings offshore as in 4 and 17, we are in for some great precip, rain with a good chance of it turning to snow as it the situation progresses after Friday morning, the 20th.  But you can see that there are a bunch of those error-laden contours (oval) that are along the West Coast and dip down this way into the bottom of the “trough bowl” in the SW overall.  Those would bring precip here, too, though due to the drier trajectory of the air, not as much as #s 4 and 17, which we could refer to, if we named them, “rainy day women (or men), #s 4 and 17”, maybe write a song about how bad they could be….

















So, if I haven’t said that already, were going to see the actual model run based on the data as best we know that data (remember, it always contains some errors we can’t pin down), will flop around some in where the 558 contour and heart of the Jet Stream end up over these next few days.  This is because the errors grow in time the farther away the predicted map is.  So, as we get closer to December 20th, we’ll see the model runs “converge” more closely to the one that’s going to verify.  We want #s 4 and 17, but, you can see that they are “outlier” model runs (“outlaws” to add a more western motif to this attempt to explain something.  Hope like mad, too, because 4 and 17 would be real drought denting storms, and phenomenal for the wildflower bloom ahead (probably, too, for those who ski on top of Ms. Mt. Lemmon).

How about those middle and high clouds yesterday?

There weren’t any.  Hahahaha (on me, who said there would be some).

Well, except for that tiny streamer of Cirrus on the S horizon at sunset, some afternoon Cu also on the S horizon (Cu not mentioned yesterday, but there they were).  Here is the only shot from yesterday of any interest because the Cu I saw down there was about ten times larger than I imagined a Cu could be yesterday.  All in all, it was a pretty gaffey cloud day.  First, a documentation of no clouds….

4:26 PM.  Day concludes with no clouds.
4:26 PM. Day concludes with no clouds. An example,  looking SE.


4:27 PM.  Looking S about as far as you can possibly see.  Note Cu congestus down there.  Was an remarkable site for a December day.
4:27 PM. Looking S about as far as you can possibly see. Note Cu congestus down there. Was an remarkable site for a December day.

Today’s clouds and weather

Those distant Cumulus clouds yesterday were a preview.    More Cumulus, Cumulus congestus later on in the afternoon, ice likely to form in the larger ones as weak “cold upper low” goes by, freezing level comes down some.   Ice in clouds means virga and rain showers as the Cumulus congestus transition to small Cumulonimbus clouds in the area.  Lightning possible in the region.   Apparently, its too dry aloft for even mid-level clouds3; they’ll be off to the SE-S of us if we can see them at all.  All in all, a pretty cloud day is in hand even without patterned middle clouds.


The End.


1Lorenz2 or spaghetti or Global Ensemble Forecast System plots (GEFS—hahahah, should be GAFFES because they have so many errors in them!)

2I have made this name up because I think he (E. N. Lorenz) deserves that these plots, representing an attempt to resolve the weather chaos out there, be named after him.  Are you listening world?  (Well, of course not. I’m just a cloud maven person here in little Catalina and nobody reads what I write anyway…)

3This deduction from our great U of AZ model that forecasts soundings over us from which you can see what it is store for moisture profiles overhead.