Such a morning, such an evening; lots in between

1) Let yesterday morning’s color show speak for itself, just incredible, speaking for it anyway.

2)  Please review the U of AZ time lapse film here to understand why it takes the biggest computer Fujitsu can build to calculate what the atmosphere is doing.  Also reviewing this let’s you escape from the tedium about to be presented below.

3)  Expect a similarly photogenic day today.

6:42 AM. Altoculumulus lenticularis downstream from Catalinas. Thought I would misspell Altocumulus to see if anyone is reading this. Sun seems to be coming up earlier and earlier....
6:42 AM. First light, this incredible scene.  Altoculumulus lenticularis downstream from Catalinas. Thought I would misspell Altocumulus to see if anyone is reading this. Sun seems to be coming up earlier and earlier….
6:42 AM. Looking to the left or north of the lenticular....
6:42 AM. Looking to the left or north of the lenticular….
6:44 AM. That leniticular again, the bottom structure now highlighted.
6:44 AM. That lenticular again, the bottom structure now highlighted.
6:49 AM. What can you say? So pretty all around.
6:49 AM. What can you say? So pretty all around.  Another lenticular was in progress to the main one.
6:53 AM. If the scene wasn't spectacular enough, an iridescent display then occurred to enhance it even more.
6:53 AM. If the scene wasn’t spectacular enough, a display of iridescence (rainbow colored area) then enhanced the original Ac len even more.  It doesn’t get better than this and I hope you saw it “live.”  I was just beside myself, taking too many photos, losing control, rationality.
8:28 AM. Both lenticulars still in place, but now augmented by a layer of Altocumulus perlucidus (honey-combed look) and a scruff of low clouds that topped the Catalinas marking the invasion of a low level moist air. The feel of rain was in the air then, too.
8:28 AM. Both lenticulars still in place, but now augmented by a layer of Altocumulus perlucidus (honey-combed look) and a scruff of low clouds that topped the Catalinas marking the invasion of a low level moist air. The feel of rain was in the air then, too.
8:28 AM, the same time as the prior photo, but looking upwind over Oro Valley, toward Marana and beyond at a line of Stratocumulus, with Altocumulus perlucidus and patchy thin Cirrus above those.
8:28 AM, the same time as the prior photo, but looking upwind over Oro Valley, toward Marana and beyond at a line of Stratocumulus, with Altocumulus perlucidus and patchy thin Cirrus above those.  Even here, the scene seemed exceptional.
9:41 AM. That Altocumulus deck began arriving overhead and you could see the little "heads" trailing ice crystals like comets with long tails. When the heads are gone, you'd call it Cirrus and never know how it got those fine strands.
9:41 AM. That Altocumulus deck began arriving overhead and you could see the little “heads” trailing ice crystals like comets with long tails. When the heads are gone, you’d call it Cirrus and never know how it got those fine strands.  In the meantime, the Stratocumulus and Cumulus clouds were slowly getting deeper.
1:19 PM. Stratocumulus was becoming the dominant cloud form. No ice, no precip, too warm, droplets in them below the Hocking-Jonas Threshold for collisions with coalescence.
1:19 PM. Looking over Catalinaville1:  Stratocumulus was becoming the dominant cloud form. No ice, no precip, too warm at top; also,  largest droplets in them below the Hocking-Jonas Threshold (30-40 microns in diameter) for collisions with coalescence to occur, if you care to learn things.
3:42 PM. One of the many pretty scenes yesterday, these Altocu perlucidus, no ice. So, much warmer and lower than those trailing ice in the earlier photo.
3:42 PM. One of the many pretty scenes yesterday, these Altocu perlucidus, no ice. So, much warmer and lower than those trailing ice in the earlier photo.
4:19 PM. Then, as the Stratocumulus filled in again, we got our late afternoon "light show", those drifting spots of sun illuminating our mountains, though here our own Sutherland Heights subdivision, if that is what it is. So pretty.
4:19 PM. Then, as the Stratocumulus filled in again, we got our late afternoon “light show”, those drifting spots of sun illuminating our mountains, though here our own Sutherland Heights subdivision, if that is what it is. So pretty.
5:19 PM. Can't be inside when this is going on.... Have problem.
5:19 PM. Can’t be inside when these scenes are happening…. Have problem.
6:13 PM. That sunset glow we see on our mountains every day, except a little more dramatic when dark clouds are overhead.
6:13 PM. That sunset glow we see on our mountains every day, except a little more dramatic when dark clouds are overhead.
6:19 PM. The day finished as gorgeous as it began as a clearing to the far west allowed the sun to light the bases of the overhead Stratocumulus layer.
6:19 PM. The day finished as gorgeous as it began as a clearing to the far west allowed the sun to light the bases of the overhead Stratocumulus layer.

The rain just ahead

Rain masses will be forming to west of Catalina today and will pound eastern Cal and western AZ for about 24 h before roaring in here tomorrow morning.  Staying the course, best guess, from extremes of at least 0.33 to a max of 1.50 here, is 0.915 inches (the average of the worst and best case scenarios) here in “Catalinaville” as the total amount from this “hit” tomorrow and the showers afterwards into later Tuesday, as a second storm part comes by.  Thunder tomorrow seems likely from this keyboard as the big rainband goes over.

During the passage of the rainband tomorrow, rainrates are likely to get up to an inch an hour, at least briefly,  (this is the rate,  NOT the duration) and typically, with several hours of moderate (0.1 to 0.3 inches per hour) to heavy rain (greater than 0.3 inches per hour) we should get a nice drenching.

The weather way ahead, 10 days or more

After a long dry spell following this upcoming rain, spaghetti is strongly indicating we have more troughiness in our future after the temporary dry spell!

Check it out, spaghetti  connoisseurs2:

Valid at 5 PM, March 11th. Note clustering of red and blue lines in trough off Cal.
Valid at 5 PM AST, Saturday, March 11th. Note clustering of red and blue lines in trough off Cal.
Ann for Sunday March 15 spag_f360_nhbg
Valid at 5 PM, Sunday, March 15th. Southward bulging red lines, so many of them, indicate a very good chance of a trough here at that time. Blue lines, for a colder part of the jet stream, also tend in this direction, a good sign.

The spaghetti plots, taken together, indicate to the present Arthur that the chance of rain twixt spaghetti 1 and spaghetti 2 shown above is about 70%.   It will be extremely FUN to see if this interpretation works out for rain between March 11-15th, at least one event anyway, to continue overusing that word.

The End, finally.

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1Didn’t Jimmy Buffet do a song about Catalinaville?  Has a nice ring to it.  Maybe we should think about it…  Or maybe, in a vein similar to Carmel-by-the-Sea, “Catalina-by-the-Catalinas.”

2Remember, spaghetti is better than the model in the medium range forecasts that are presented based on the global data.  Spaghetti is there to help you decide whether that model output is from the WRF-GFS looney bin or not.  Here’s how:

Spaghetti is the result of DELIBERATE little errors put into the model when they start crunching the data to see how the forecast that you see on the maps could go wrong if there are errors in the data.

Of course, there are ALWAYS errors in the data!  So, when the Fujitsu Computer DIvision made gigantically capable computers for us that were better than the ones we could make, ones that could do teraflops per second, we in the weather community could then run many permutations of the same model with itty-bitty errors in the initial data to see how the results changed (diverged) in the longer term.

Remember, too, in weather itty-bitty differences can add up to large ones in the longer term.  So, when the model permutations with little errors cluster and DON’T diverge, it provides more confidence that the forecast storm, for example, is more likely to happen in that fuzzy forecast range of beyond 10 days or so.   End of giant footnote.

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.