First rain drops here at 3:30 AM. Checked sat images and they’re looking about as good as they could for us, clouds to the southwest of us, curling around that little upper level low center like a boa constrictor, buckling, and dragging all that tropical air toward us. You can see that here in a loop of the satellite imagery from the U of AZ. and take a look just off Baja and in the Gulf of California.
4:10 AM AST, the latest I got while doing this blog–I can’t keep updating it or I’ll never finish. Updating is up to you now. Thanks.
Cloud bands curling around the center and the center heading this way? Its as good as it can get for us, and means the rain bands should be pretty potent. Some Cumulonimbus clouds can be seen in the sat imagery, too, in the main rain band. Looks like it will take about 8 h for the main part of this to go through, too, with passing light showers into the afternoon and evening. So, light to moderate rain for maybe 8 h should lead to around half inch to an inch. Yay!
Paulden, near Prescott, has, as of 4 AM AST, received the greatest amount, already recording 0.95 inches. You can see the statewide totals at the US Geological Survey network here. The Pima County ALERT gage data are here, with the first measurable rain being reported at 4 AM AST. With southerly flow at mountain top level, the south sides of the Catalinas will likely get the most from this storm compared to Catalina townlet, Census Designated Place, proper. Hoping for some lightning, too, today, as there are some Cumulonimbus clouds in the main band here and there.
The best part of this situation is that most of Arizona gets drought-reprieving rains over the next 72 h, counting today, with the models thinking that all of this may amount to several inches of water in the mountains of central Arizona where its so badly needed. And with just this ONE storm sequence, January will come out looking like a decent rain/snow month in the record books.
Model musing….
In the model prediction business, today’s rain was not even seen at first while rain on the 28th has been there for at least 10 days! Then, rain began to show up today, Saturday, about 5-6 days out, but it was hardly anything at all–wasn’t even mentioned here the first time it did because it seemed so tenuous.
But look how reality has turned out! This little circulation from the sub-tropics is certain to dump more precip than the storm on the 28th, the one so long foretold. I guess this is why we weatherman like weather. The unknowns, the surprises, are still pretty great.
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4:30 AM. First hundredth of an inch, off to slow start, but like that legendary horse of old, Silky Sullivan1, should end in a hurry.
Yesterday’s clouds
7:24 AM. Rising sun illuminates the bottom of an Altostratus mammatus layer.
11:16 AM. Thickening and thinning skies all day until late, brought sunny spells as here with thin Altocumulus perlucidus.
4:18 PM. An unusual site. See note messing up photo. I worked pretty hard on it, though an english language-maven might find fault in it.
5:16 PM. Close to sunset, and almost an exact replica of the day before at this time with an overcast of Altocumulus opacus clouds. No sunset “bloom” seen, but a brief hole allowed a golden illumination of the Catalinas for just a minute or two–next photo.
5:40 PM. Charoleau Gap orangified by setting sun peaking through….through…a hole in what? Ans: Altocumulus opacus, in this case droplet clouds with little or no ice whatsoever. You didn’t see any virga did you? (“Gritty AND pretty”, $1,025)
Quitting here–haven’t even looked at models (oops, except Canadian–just remembered that; just eye-balling stuff, but this piece, long enough!
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1Hardly a person alive then in the late 1950s did not know of THAT horse, yes, just a horse! Check the video for something truly amazing! Silky Sullivan gave hope to all those that fall behind. His reputation lives on.
“Cloudy/The sky will be gray and white and clou–oooowww–deee.”
If you don’t remember the 60s and songs about weather, a silly reprise of that Simon and Garfunkel song here. If S&G had been weather forecasters, they might have written satisfying lines like the one above for today.
At times today, with all the virga around, it might really look like its, “hanging down on me” as the two depressed boys sing in that song as waves of thick middle and high clouds eject northeastward over Catalina from the tropical Pacific. Looks like the heart of the upper level disturbance and its main rain shield will pass Friday night into Saturday, with a break in rain on Sunday, then rain again on Monday into Tuesday as the cold punch of this storm sequence rattles down from the north Pacific Coast. Great news, but not new news to anyone paying much attention to our local weather forecasts.
Catalina seems destined to get a good dumping from the two combined (the warm one, then the cold one), likely to exceed a half an inch, and boy, do we need it. Nothing after this in rain, the mods say (for now).
As a note in passing, the droughty Plains States don’t get so much relief from this system now as the models have faster movement of the storm through that region than they had a few days ago when it was part of a “trillion dollar” beneficial storm sequence across the country. That faster movement of the storm has been repeated in the mods now over and over. Faster movement equals less rain, less time for humid air from the Gulf of Mexico to race northward and be ingested into the low center that forms in the Plains States in a few days. I actually feel kind of sad seeing that change happen and hope its dead wrong. “Dang”, as we would say.
Yesterday’s clouds
Here are some shots of those great Cirrus clumps and formations yesterday some of which were exceptional because of the instability up there, that is, how tall and Cumulus-looking some of the Cirrus castellanus turrets got, biggest I’ve seen. You can reprise the whole day here, from the U of AZ. First, a shot of the great sunrise.
In the AZ movie, you will also see these brighter flecks appear, brighter because they have smaller, more numerous particles in them when they first form compared to even minutes later as they disperse. The behavior of CIrrus forming like this is like a puff of smoke that suddenly appears in the sky, but no more smoke is added. As happens with these Cirrus flecks, the smoke would gradually disperses and thins after a thick beginning.
Later in the movie, you’ll see the “convective” Cirrus we call castellanus go by, producing a little virga. Another oddity, is that some Cirrus uncinus trails go by with the streamers of ice that are falling out, go faster than the higher tuft from which they fell from, indicating a wind speed increase as you go down, a little unusual at that level.
So, lots to see in this time lapse movie.
7:18 AM. New flecks of Cirrus floccus-later to be Cirrus uncinus–form beyond Pusch Ridge. Lower Ci Spissatus in the distance.1:42 PM. Here, continuing with the innovative “gritty-not-pretty” photo style: “Cirrus castellanus slightly below Cirrus spissatus, both above parking area and partially occupied buildings.” $525
2:13 PM. Giant Cirrus castellanus turret springs from Cirrus streak. When they’re flattish, you’d call them Cirrus spissatus. If in more of a sky covering layer, sans breaks, Altostratus, not Cirrus, because of the shading. ONLY Ci spissatus can have shading and still be termed Cirrus.
3:48 PM. Mostly Cirrus spissatus (dense Cirrus).
3:48 PM. Just pretty Cirrus.
5:40 PM. Not a great sunset, as was hoped for, but there was a knife-edge leading edge of an Altocumulus bank on the far horizon that added some drama to it. Note Ci uncinus, too.
Watch for a sunrise color bloom this morning. Might happen, though coverage would appear to be a bit too much right now. And with so many clouds around, a good chance of a great one this evening. Charge camera battery.
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1There’s get a modicum of applause at the end of this video; no one really wanted to hear S&G play THAT song: “Why didn’t they play something good?” And, “Why are their heads floating around in the clouds?”
Today, as everyone knows, will be the last pleasant day for quite awhile, so we’d better get out and enjoy it if you can, maybe call in sick. Likely to be a couple of AZ low temperature records set over the next week.
The skies will be great today, as they always are with some clouds present, and for a few days afterwards in the cold air with those deep blue skies along with passing Cumulus clouds, that at times and even though they are shallow, will send some virga down as the colder parts of the troughs go by. Should provide for some nice late afternoon and evening photo ops in the days ahead.
Today the satelllite imagery plus looking out the window, shows lots of Cirrus clouds today, probably devolving into dense, shady Altostratus at times. And a scenic, Altocumulus lenticularis cloud1 downstream from the Cat Mountains is pretty much a lock.
Also, in the progression of clouds today, we will probably see that clear slot that so often separates the middle and high clouds from the low, frontal clouds go by. If the timing of that clear slot is right, could be an extra special sunset.
Some Cirrus from yesterday, another one of those rarer days with virtually no contrails in the Cirrus, followed by a nice Catalina sunset:
2:36 PM. Cirrus fibratus (pretty straight fibers) looking NW. Note lack of contrails.5:45 PM. Cirrostratus fibratus (has streaks) with what looks to be a lower Cirrus uncinus (upper right and in the distance).
Rain, from the U of AZ mod run at 11 PM AST, has the rain beginning tonight after 10 PM AST and lasting but a couple of hours. Amounts here in Catalina, between 0.10 and about 0.40 inches, average of 0.25 inches, virtually no change from what was predicted 24 h ago.
Just about everything mentioned yesterday is the same today in the model, marginal cloud top temperatures for precip at the TUS site for most of the time the front goes by (in the model), but cloud tops will be colder over us and more likely to precip.
Seems temperatures will be marginal for ice-in-rain drops at the ground here since the much colder air will not arrive with the front’s very narrow rain band but encroach as it departs.
Also of some interest, the jet core at 500 mb is shown to become bifurcated with one branch overhead S as the rain moves in (another branch over NW AZ). This would be compatible with a rule of thumb about the rain and the jet at 500 mb. Rain, with extremely rare exceptions (<5% of the time), does not fall here on the southeast side of a jet stream racing to towards the NE, as we will have over us today. Will be curious to see if this “rule” holds up this time.
Tomorrow will be one of those cold days with spectacular small Cumulus clouds contrasted against the deep, dark blue of the winter sky. Should be some great scenes of light and shadows on the Catalina Mountains.
Snow ahead?
Snow falls here later in this cold, almost week-long episode, as a series of troughs plunge southward along the West Coast to AZ. Most likely day for some snowfall in Catalina, is now on the 14th2. Here’s the map for that, valid for 11 AM AST, Monday, from IPS MeteoStar:
Green areas denote those regions where the model has foreseen precip in the previous 6 h.
The weather way ahead–Dr. Jeckyl or Mr. Hyde?
Check out these bowl of rubber bands from “flapping butterfly wings” (slight perturbations put into the initial data ingested into the WRF-GFS model after which its re-run a number of times to see what slight differences do). The first one below is for the evening of January 20th, a real laugher considering its only 10-11 days away now and the mods are still clueless.
Note the yellow lines, a “control” run from last night’s 5 PM global data, and see how they BULGE toward the north over the western half of the US. Then look at the hard-to-see gray lines representing a “control” run from just 12 h earlier, that from yesterday’s 5 AM AST global data. They BULGE southward, the opposite way the yellow lines do.
The yellow lines indicate a huge ridge over the West, with little precip and seasonal temperatures in the SW US. On the other hand, the 5 AM control run shows a continuation of our present storm pattern and continued injections of cold air down the West Coast. Check out that gray line over northern Cal, for example.
So, from one model run to the next lately, our weather toward the end of the month in Catalina has gone from “yawn” to “yikes” (the latter blurted out yesterday when I saw that 5 AM output and all the storms it had). But blurted out a “yawn” when viewing the output from last evening. No precip after the cold week.
However, in deciding which of those two outcomes is most likely you have to dwell on the predominance of those blue lines that also bulge northward and are mainly located in southern Canada. Those strongly indicate that the “highs” , the bulges to the north over the western US, will prevail on the 20th, not the storms and cold weather with them.
Arrow points in the general direction of Arizona.
But how about after the 20th, at the very end of last night’s model run 15 days out? Now you see BOTH the yellow and the gray lines are bulging to the south (creating a trough bowl), AND, more importantly, those blue lines are not constrained to southern Canada, but are all over the West as well. Remembering that the atmosphere remembers suggests that the models are remembering, too, trying to regenerate the kind of flow pattern we’ve already been experiencing after a significant, quite pleasant, really, break from the cold week.
While this last panel is also a real laugher in many ways, due to all that uncertainty that’s indicated, the wildness in all those lines, you might want to hop off the fence in a longer term forecast toward the end of the month by thinking that what we’ve been having will return, a sort of “Back to the Future.”
Re-inforcing this view is how the red lines (570 dm height contours), usually on the periphery of the jet stream, become more compacted in the LATER, second plot compared with the first! This is a little remarkable since that would suggest the models have a better handle on the circulation pattern at 15 days over 11 days. Odd. Note, too, that those lines at 15 days are FAR to the south of AZ, supporting the idea of a cold trough in the SW.
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1These are the almond shaped clouds composed of droplets with smooth, sharp edges that hover over the same spot, expanding and shrinking, sometimes for hours at a time, as the grade of moisture changes in the air being lifted behind the mountains.
2Personal aside: Have friend, former WA State Climatologist who also worked at the U of WA as I did, arriving here with his wife on the 12th for a vacation from the dark days of wintertime Seattle. They will be here for the whole cold week and possible snow as it turns out, and then go back. Having looked at the progs, he now wants to take a “vacation from his vacation”, maybe head off to Costa Rica after arriving in AZ!
One of the things I like to do when I am wrong, yesterday having predicted a trace to a few hundredths of rain last night from that disturbance going by to the south, is to spend a LOT of time talking about how close I was.
Its true the zuperkomputer, the Beowulf Cluster, at our U of AZ Weather Department, did NOT predict rain here at all, but it did not have the sprinkles as close as they came to us, either! Exulting here that bit. Going to look on “trace detector” (car parked in dust and sun outside) now, just in case there is a drop image somewhere. Will report back on that later. Stand by.
Also, you should be looking around for drop images in the dust on stuff, too. If you’re going to be a “trace king”, you have to look hard in AZ so you don’t miss anything. A lot of reported traces shows that you are indeed a true CMJ! A trace of rain is incredibly important to microbes; a drop is like the ocean to them. Think about it the next time it sprinkles on you.
Below, the evidence of how close we came to one drop of sprinkle-rain last night (remember, it would NOT have been “drizzle” had it occurred; drizzle falls from LOW-based clouds that hug mountains, not from Altostratus clouds such as we had):
Sprinkle from Altostratus deck just to SE of Catalina at 1: 40 AM AST last night.
Arrow added into the SAME image as the first one in case you did not see how close that sprinkle came to us when you first looked at it. I really want you to know. I feel its quite important.
As a CMJ (Cloud Maven Junior), you would have seen and logged the low hanging virga extruding downward in one spot from that thick layer of Altostratus at sunset, that As band that also had something that looked a bit like an anvil extruding from it. Here is the “documentation” for these claims:
5:16 PM. Heavy Altostratus with scary anvil-like feature and VIRGA just to SW of Catalina about 50 miles.
Finally, this sunset shot of the same band 30 minutes later, making the same points as above again to better imprint them on you:
5:36 PM. Same band of Altostratus with anvil-like feature and virga (to right) at sunset.
The above has been, in effect, a burst of altruism. Let’s say I am hiking on the trails, I’ve missed a forecast, and you’re heading in my direction. At about 100 yards you will want to exit right or left and bushwhack it for awhile until I have passed to avoid an extended “in hindsight…”, hike-delaying conversation in which you have no real interest. Its gonna happen. It would be kinda like this blog-blab right now….
Now, feeling better, some REALLY pretty Cirrus uncinus from last evening:
5:17 PM. Pretty Cirrus uncinus along with some other varieties/species.
Now that I have gotten yesterday’s burr-under-my-saddle dispensed with, can ahead now, not stuck anymore, clouds moving away, can have new thoughts…
Will look at model outputs and see which one has the most rain/snow in it for us on the 11th-12-13th, with that Arctic blast, and think about the onset of that new “zonal” pattern after that, that pattern that will mild us1 quite a bit after the Arctic blast. Beginning look at mods now….
WHAT?!!! Its back! That “trough bowl” collecting area for storms in AZ and the Southwest, after only short respite from cold storms. What happened to theThis is remarkable, check this prog for January 22nd at 5 PM AST. If it looks familiar, its almost the same as the map for yesterday afternoon, the 7th, but 15 days later! I repeat myself in the gif for emphasis now that I see I have repeated myself.
Valid for 5 PM AST, January 22nd.
What’s the gut check here? “Spaghetti”, which seems appropriate for a “gut check.” Yesterday we saw that the NOAA spaghetti plots varied wildly 15 days out, making ANY model forecast that popped beyond about a week out pretty unreliable.
But what aspect of the atmosphere do we know about that makes a prog 14 days out that looks like weather we had yesterday look that bit more credible: the mantra, “the atmosphere remembers.”
Persistence, a forecast based on weather you’ve already had for the past week or three, and projecting it into the future is one of our more reliable forecasting techniques. Sounds silly, but its true. The pattern eventually changes, but its hard to catch that tipping point when it does. Yesterday, the mods had that pattern change and it was some support for that in the NOAA spaghetti plots. That support has weakened, though not gone, seen here if you dare.
——————Module on conversational meteorology——–making the past the future
Imagine, that on January 1st last, a neighbor asked you, knowing that you were a cloud maven junior, maybe have Asberger’s Syndrome, and in your case, focus on itty-bitty weather details and data:
“What kind of weather do you think we’ll have in January?” Without divulging details of your forecasting methodology, hindsight, and then trying to remember, if you could, what the weather had been like in the two weeks leading your neighbor’s question, i.e., the time when the new flow pattern began here, you could have furrowed your brow and said, with at least feigned authority:
“I see below normal temperatures, perhaps much below, with a good chance of above normal precip. “‘Hey'”, and then going a bit too far, you might have ventured into, “…and I think there’s a good chance of a real snow here in Catalina this month with all that cold air we’ll have.”
Today, with a severe cold spell ahead, you would be the forecasting guru of the block, icon of the next block party, and all you had to do was remember, which can be hard sometimes.
In weather, it really is true: the past is often the future.
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So what to think?
Its not a bad idea to hedge your forecast longer term forecast with “persistence”; continuing below normal temperatures, maybe not as severely cold as what’s immediately ahead on the 12-14th, precip on the 11th. Amounts, due to the speed of this thing, still 0.10 inches at the bottom, but I’d reduce the max potential to 0.40 from 0.50 inches, median then 0.30, about the same as the last prediction. The flow pattern with this will be like the last front on the 31st, and so we’ll do better than most of areas around us in amount because the clouds will bank up against our side of the Catalinas more than elsewhere. Still expecting rain to change to snow at the end of the FROPA on Friday morning, the 11th, but amounts likely to be an inch or less now. Dang, again.
Because it will be so cold aloft, and here, and there are minor disturbances that blow on through for the two days after the 11th, a passing flurry is likely (that from, as you KNOW, from “heavily glaciated clouds”, at least at times.
A bit much today, so will gift you by quitting here.
The end.
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1Using “mild” as a verb here; might be first time ever such use–William Safire, language-maven, where are you now that we need you? Remember when we made fun of Alexander Haig, the Nixon admin Chief of Staff, about the way he used nouns as verbs, i.e., “gifted him.” Now he can be considered a language pioneer since we hear that usage all the time. Don’t forget to use “mild” as a verb today at least once: “the weather pattern is going to mild us for awhile before the big freeze hits.” That would be great! Thanks.
Backdoor rain? Looks like any chance of rain will happen later this afternoon through overnight as mainly mid-level clouds twist around our low from the east. That low is now over Yuma, AZ, and the center will pass to the south of us tonight. We don’t see that happen too often. Here’s a nice loop of the circulation around it, also showing the radar echoes–very handy. (Some cloud shots at the bottom, way down there.)
Right now, our low is looking pretty dry, not much going on in it, or around it right now, and so any rain falling from mid-level cloud bands, like Altocumulus (with virga) and a likely deep band of Altostratus (also with virga), will be pretty light; sprinkles to maybe a hundredth or two. The better part of this is that with mid-level clouds coming from the east, they won’t be much dissipated by the air going downhill from the Catalina Mountains as you would expect with low clouds. However, in Mexico, since it is so cold in the center of this low, there will likely be reports of snow in unusual places, as in the last storm. The U of AZ Beowulf Cluster model, the best around for us, sees only a brief, fairly close call for rain tonight.
Still, while this low passage will be a little disappointing as far as rain goes, the skies will be great today with scattered Altocumulus, likely with a little virga, and scattered Cirrus, with a great sunset. Both of these cloud types can be very “photogenic” on days like this. Likely those mid-level clouds will clear out tomorrow morning, so get’em while you can. If you don’t, of course, this compulsive cloud photographer will.
Full cold ahead
Get ready for some terribly cold days just ahead, likely some snow in Catalina still, though the more moist Canadian model prediction for this storm has dried out overnight–tending to be more in line the with US models which have always had this cold wave as a light precip event. Precip is pretty much guaranteed here, and some snow probable in Catalina, but max and least precip totals from this storm have to be revised downward in view of the latest Canadian results. Minimum amount, 0.10 inches, max, 0.50 inches (was an inch due to how much offshore flow the prior Canadian models had the night before last). So, most likely amount is between those two extremes, or about 0.30 inches with precip beginning during the day on the 11th.
A further disappointment is that the mods now see this storm as a quickly moving event, and the precip is over by evening on the 12th, so it ends up as just a 24 h period of rain and snow chances, most coming, of course, in the first segment, a line of rain changing to snow with the frontal cloud band and wind shift line on Friday, the 11th. Dang.
What about the second cold blast on the 15th-16th?
Still coming, but this wiggle in the jet stream shooting down at us from the northwest, has a trajectory toward us that is farther east than it was shown in the models earlier, and the farther east and the further away the trajectory is from the coast, the drier these cold pushes will be. So, that second blast of cold air, while still looking very cold, is also looking pretty dry right now; may only get a passing snow flurry, or we’ll just see scattered small Cumulus with some virga.
In these latest model runs the jet stream pattern that has led to our “trough bowl”, the favored location where storms have been collecting in our region for the past month, begins shifting to the east at mid-month, and what’s more, the amplitude of the north-south oscillations in the jet stream fade to a more west to east flow.
This very different than what was depicted just the night before last. Here’s what I mean. Shown below is the first forecast panel, high “amplitude” pattern in the jet stream–always associated with temperature extremes, cold where the jet dips down, like HERE, and warmer than usual where it shoots up from the southwest,for example, there in Alaska.
Valid for the evening of January 15th. An example of “high amplitude jet stream configuration associated with temperature extremes.
This is a very common pattern. You probably remember how warm it was in Alaska during the 1962-63, and the 1976-1977 winters, but how friggin’ cold it was back East when this kind of high amplitude pattern was pretty extreme and persisted for weeks: the jet racing into Alaska from the mid-Pacific, and then shooting south into the US. Really horrible times for the East in those winters.
But look at what the model sees for the end of the 15-day forecast period, shown below! The jet hardly has any amplitude, just shoots in from the Pacific in a west to east flow. That means no temperature anomalies to speak of, and a moist West Coast regime, sometimes with precip getting this far south, too.
Valid the evening of January 22nd, a Tuesday.
What does spaghetti say about all of these changes?
Its pretty clueless, that is, slight changes in the observations make a big difference in what happens, and that’s why its so wild looking in the Pacific and the US (shown below). This means you probably can’t count on the above pattern a lot, except that the amplitudes have gone down, that seems to be a pretty solid expectation. That jet surging into AZ could just as well be intruding into Washington State in a west to east pattern. That would mean that our 30-days of below normal temperatures here in AZ, beginning in mid-December (shown here by the NWS, lower right panel), are about to end after about a week to ten days, and with that, a long dry spell likely to set in.
Yesterday’s clouds
Mostly Altostratus, thinning at times to Cirrus, and late, a few Altocumulus/Cirrocumulus patches. Here are a couple of shots.
7:22 AM. Under lit Altostratus at sunrise. Those little pouches are regions of light snowfall (virga).1:49 PM. Boring, generic Altostratus translucidus, an ice cloud. Sometimes droplet clouds like Altocumulus are embedded in them, but none can be seen here (they would be dark, sharp-edged flecks). The massive clearing that occurred in the late afternoon is visible on the horizon. If you saw that clearing, it would have been a great time to tell your friends that, “Oh, I think it will be sunny in 3 hours.” It would have been quite a magical moment for you.5:36 PM. This beauty of a patch of Cirrocumulus undulatus (tiny granulations in waves) and a lump of Altocumulus (lower left). TUcson sounding indicates they were about 15,000 feet above the ground at -20 C (-4 F). No ice apparent. It happens.
The recording raingauge, that is. A coupla drops is all that fell here in Catalina after some indications of cores around us later yesterday afternoon that were producing measurable rain. You can go to the U of AZ rainlog site to see some local amounts–the Pima County ALERT site is down right now. They’ll have some reports in the mountains and elsewhere, providing it wasn’t snow. The most I’ve seen so far is 0.05 inches, lucky dogs.
Some nice cloud sights on a day of dramatic, icy development. I wonder if you say the first Cumulus/Stratocumulus blob glaciating far to the WSW, beyond Twin Peaks? I thought it would happen first toward the NW-N because the air got colder if you headed in those directions. Yesterday’s cloud highlights, once again pioneering here the “novella-sized”, explanatory caption:
8:24 AM. Altocumulus overspreads the sky, briefly. Ac perlucidus translucidus (thin). Someday I think I will make you memorize ALL of the cloud names and their species and varieties.8:59 AM. This beauty. It appears to be Cirrus of some kind (spissatus). But then yesterday I had written that there wasn’t going to be any Cirrus, and so I will term this, Altostratus translucidus altocumulotransmutatus. Pretty cloud, but ugly name (it really exists, and this patch really did originate via the glaciation of Altocumulus clouds.)10:33 AM. Never have seen this sequence before. After the prior patch of ice cloud (some liquid cloud at top) moved off, a new wedge of Altocumulus (perlucidus) formed in the moist plume up there. Also very pretty I thought. Estimated height above ground, 18,000 feet, -25 C or even a little colder. Nature loves to form water drops before it freezes, as here, even at very low temperatures.12:58 PM. Rise of the Cumulus machine…. Here, beyond Twin Peaks, is the first glaciating cluster of Cumulus/Stratocumulus responding to the cooling aloft and a bit of surface heating below.2:04 PM. Locally, our Cumulus remained small, but in the distance is the icy tops associated with the line of sprinkles its not drizzle that came through later in the afternoon, enhanced by further Cumulus deepening around here as the afternoon progressed. Pretty sky.2:38 PM. Heavier Cumulus bases line up against the Catalina Mountains near Charoleau Gap. Looking better for precip here at this point.
2:39 PM. A tell tale ice plume is amid these smaller clouds telling the observer that it is damn cold up there for such small clouds to produce so much ice (though the one that produced this little plume would have been taller than those around it) How cold? Estimate the top of the one that produced this was at least lower than -15 C (5 F). Ice crystal concentrations? Estimate at least a few per liter of air at this time when you see an ice plume like this. Pretty soon you’ll get that Cloud Maven tee.
3:58 PM. By this time it looked very promising for a few hundredths of rain.
5:36 PM. But after all the bluster, just a trace of rain here.
The weather ahead: measurable rain!?
I am sure, that due to our fine array of weather practitioners on TEEVEE (ones that make an incredible amount of money, mind-boggling really, and ones that have the same kind of fun doing weather forecasting as I do) that rain is in the offing for Catalina in the days ahead. So why bludgeon the topic here? Well, let’s guess a range of amounts that could occur, bottom and top, based on SOP-eyeball of weather patterns and goofy, variable progs:
Last night’s Canadian run, has a near miss now, rain partitioned to the SE of us. Booo! But, then rain with a follow up system on Jan. 1st, maybe with some snow in it here. So between the first threat and the second, both happening between the evening of December 30th and the evening of the 1st, the range has to be wild, maybe not useful. At the bottom, we could be completely bypassed in measurable rain from two strong troughs (we’re still in a “trough bowl” BTW), but I guess if you’re in a drought, you only get misses. But, being the optimist, AND with our own USA! model indicating measurable rain as of last night’s run, the range of amounts over the four days of chances, has to be from a trace to 0.50 inches at most. So, a range with all the factors at play is not too useful.
The average of those two, 0.25 inches, often works out as the closest estimate. Let’s see what the U of AZ has this morning… Oops, no update, budget cuts strike some more!
I guess I don’t need to blog after that title… We’ll be lucky to get 0.15 inches, and a few hundredths is the most likely amount, and that will fall later in the afternoon to late evening hours according to me and my (U of A Weather Department) model.
How much the U of A model thinks will fall regionally is seen for this event are seen in the panel below ending at 7 AM AST tomorrow morning, but first a caveat: I just saw this run for the first time now, and did not at first notice that it was OLD, from the night before last, not based on data from last night at 11 PM AST as usual. This lack of a model run might well be due to the effect of budget cuts noted on the link above… Dammitall, budget cuts!
Anyway, check the times of the run to make sure you’re not looking at something old today. I used it anyway because things have been well predicted in our incoming trough and jet stream for a couple of days now.
You can also see that with the jet over and just to the south of us later today through tomorrow morning, that most of the precip is to the north of the jet, as per usual in the interior of the SW1.
Here’s what the jet stream does in the next 18 h, starting with the forecast for 5 AM AST (these are from the latest data!). The winds are very strong over us now, but a core of strong winds is dropping down from California toward southern Arizona and reaches us later today and then drifts south. As that happens, the air aloft is really cooling off. The temperature at 18,000 feet (500 millibars) drops almost 10 F between 5 AM this morning and 11 AM!
As that happens, the air will be getting more moist from the bottom up. Small Cumulus will form later this morning and their tops will be rising and getting colder by the minute, eventually reaching our ice-forming temperatures around here of -10 C to -12 C, but tops to -20 C are likely late in the day. When ice begins form in these “supercooled” clouds, those crystals grow at the expense of the liquid droplets and fall out.
This cloud drama, if you will, is what makes today extremely exciting; watching for that first ice to form in these lower, relatively shallow clouds. They can be shallow and still develop ice because its so damn cold aloft later this morning and this afternoon.
So, a pretty if cold day, with lots of virga around later this afternoon, and with that, a great sunset is likely, too.
Yesterday’s clouds
10:03 AM. Your really cold Altocumulus clouds; transitioned to ice shortly after this. Probably colder than -25 C.1:32 PM. CIrrus spissatus, maybe it could be called an Altostratus translucidus since its quite thick toward the horizon.1:32 PM. You got yer Altocumulus lenticulars (brighter white clouds below patchy Cirrus.5:25 PM. The major band of high and some middle clouds exits south of Catalina. No high clouds today, only low and maybe some Altocumulus/Stratocumulus formed by the spreading out of Cumulus tops.
More rain in our future after later today and tonight?
Oh, yeah, baby. Its in the bag. A “virtual” certainty (which actually means its not absolutely certain at all, but that’s because its a weather forecast based on imperfect models and humans. Remember that great metaphor about why there’s an eraser at the top of a pencil? Profound.)
OK, when? Let’s start by looking to Canada for rain in Arizona: Here’s a panel from Enviro Can for Monday morning, December 31st at 5 AM AST. Its got rain in it, rain that would have fallen in the prior 12 h leading up to 5 AM. I like this model because it has more SE AZ rain in it than the US ones….
See lower right hand panel for rain in Arizona by the morning of the 31st.
There is a fly in the oinkment. The US models have a big “anti-cyclonic” bulge in the flow over us as our the trough/low approaches us on the 30-31st. These bulges in flow, toward the inner portion of the jet stream, can have devastating effects on clouds and precip formation. A bulge like that is like a high in a low; the effect is to weaken all the upward motions in the atmosphere. The Canadian model has less of that; hence, shows more rain here.
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1Of course, if you have a copy Willis and Rangno (1971), “Final Report to the Bureau of Reclamation, 1970-71 Season, Colorado River Basin Pilot Project, Season 1”) you already know that.
Kind a bored looking at the same model runs for 10-15 days ahead now, ones that close out November with no rain even nearby for Catalina. Doesn’t seem to be even ANY HOPE for rain here, that is, some bizarre model outlier forecast with rain, as we saw a few days ago. But then, I had not had any coffee yet…
Thought I would drink some coffee to see if I’ve missed anything in these latest computer model images. I’d kind of forgotten what Consumer Reports Health Letter had warned about when you’re bored and trying to do stuff. Talked about the effects of caffeine on boredom. I reprise a portion of that CR note here, in case you, too, are looking at repetitious model outputs with no rain in them. Note the part in in this note below about “repetitious images” and “infrequent changes in patterns on a screen”; yep, that’s what we’re dealing with here in these model runs now.
OK, finished second cup, caffeinated coffee, BTW, now going back to look at those model forecast maps to see if I missed anything, subtle or otherwise…. You, too, can look at the 5 PM AST model loop here (from IPS Meteostar), but drink some coffee first.
Prepare to be “re-bored” as I have just been.
Not even the NOAA NCEP’s “ensembles of spaghetti” offer hope; no “outlier” model forecasts with Catalina rain in them anymore (for now, anyway). Bunched blue lines, demarcating jet stream, stay to the north.
But, paraphrasing Scarlet O’Hara, “6 h from now, there is another model run…”
Yesterday’s clouds
Had some great Cirrus spissatus and other varieties/species of Cirrus overspread the sky yesterday, eventually thickening into Altostratus translucidus (sun’s position still visible). Here are a couple of shots, including a sunsetter where you can see just that bit of virga hanging down.
1:19 PM. Cirrus clouds began overspreading sky from the southwest (direction that photo was taken toward).2:16 PM. Cirrus spissatus (the only Cirrus cloud that can have shading) encroaches from the southwest.4:29 PM. The Cirrus clouds have thickened in places, usually downward, to large patches of Altostratus translucidus (thin enough so that the sun’s position is still visible). Its also possible here that the Altostratus clouds were below a higher layer of Cirrostratus.5:26 PM. Under lit Altostratus clouds with likely a separate higher layer of Cirrostratus.
Today’s clouds?
Your call: ________________________________________________________________
Once again we were treated to a spectacular sunset, another one in a long series of occasional sunset spectacles, ones that probably go back before the 1900s. We didin’t have color film in the 1800s, so we can’t be for sure if there were spectacular sunsets here except via artist’s renderings, of necessity, of course, analog ones comprised of subjective estimates of sunset colors being seen, not the real ones. I you would like to read about clouds in paintings over the centuries, go here and here. In this second link, you will find that Leonardo da Vinci was quite interested in Cumulonimbus downbursts gave painting them a shot. Its not that great, to be honest.
We meteorologists often sadly ruminate on the career of Leonardo, thinking that had he only turned his attention away from art, sculpting and the like, and instead turned to the problem of weather forecasting, how much farther ahead we would be today. A real shame. Maybe we wouldn’t be relying on spaghetti plots so much.
Also got a trace of rain here in Catalina–you could sure get that smell of rain as soon as you went outside this morning.
5:25 PM. Altocumulus opacus under lit by the setting sun. Altostratus clouds were above that layer.
We also had some real interesting mottled-looking skies yesterday due to Altocumulus underneath a layer of Altostratus translucidus. Those underlying Altocumulus clouds were in a layer with a lot of instability (temperature dropped rapidly with height in it) and so there were many little spires (castellanus and floccus varieties). This happens because a little bit of warmth is added to the air when moisture condenses in it, and that bit of warmth was able to drift upward. As that happens the air around those little cells of updrafts settles downward gently to take the place of the rising air creating voids. So, you get clear air spaces between the little cloudlets. I think that’s what happened here.
3:10 PM. Altocumulus castellanus and floccus invade sky under Altostratus translucidus (thinner version).
Let see, what else is going on…. Most of that plume of moisture from the tropics is gone, and so only expect a few Cumulus today. Oh, yeah, big storm about to slam northern Cal and Oregon. Take a look at this map series from the Washington Huskies to get an idea of how its growing in size before hitting the coast.
No rain predicted here in past two model runs (last evening and last night, 06 Z) for the next 15 days, but we are quite sure that’s wrong. Will be looking for that end November early December rain to reappear because I have a subjective hunch it will. If it doesn’t reappear, I will likely pretend I never said anything about it, in keeping with long tradition in public weather forecasting.
BTW, and belaboring the point a bit, here’s an example of how errors in public forecasting SHOULD be handled; “right up front”, in this case, an anonymous Seattle forecaster addresses the terrible temperature forecast he made the previous day following day:
12:18 PM. Altostratus translucidus (sun’s position is visible).2:34 PM. More Altocumulus opacus with virga. Large clearing approaches from the west.3:46 PM. Patch of Altocumulus translucidus perlucidus (thin, with a honey-combed pattern)
Today? More pretty clouds.
The weather way ahead, like on November 29th
Just after I was asserting from this typewriter that the big storm, the Great Wet Hope in late November, was surely bogus, out popped another wet forecast for AZ n the model run crunching global data from 11 AM AST yesterday. Here it is below, first panel. You MAY remember that the nice early rains that we had in November last year were associated with a similar pattern of an upper low center near San Diego.
What to think of this “outlier” forecast, one NOT supported in the ensemble of spaghetti plots (model runs where small errors are deliberately input to see how those runs change from the ones based on the actual data). There very little support for panel 1 in those “perturbed” runs, but there it was again, a big AZ rain!
Well, its still unlikely, but the chance of it actually happening are now much improved. Something out there is causing the model to come up with a good rain in AZ at the end of the month. I did not think I would see any rain again in AZ in any more model runs.
And, sure enough, the model run based on data just 6 h later than the one shown in the first panel, took it away again! See the second map below and look at the astonishing differences over Arizona and the Southwest overall!
I won’t show it, but the “perturbed with errors” model runs that we look for to discern credibility in the longer term forecasts like these, STILL does not support much of a chance for a rain to be realized on the 29th.
But, that second appearance of an “outlier” in another model run….hmmmmmmm. Will be watching for a return; you start to get a feeling that it might well be seen again.
As I finish this blog blurb, the 11 PM global data should have been crunched by now, and will look to see if there is yet another huge change (well, there are always large changes, but here, I’m talkin’ for us!) Will let you know in about 2 minutes…. Stand by, generating new web window now…..
Oh, my gosh! Its changed again (3rd panel) to a huge West Coast troughy situation, completely different than the run at 5 PM AST last evening with the big ridge over us (bulge to the north). I have to post this latest map, again for late on November 29th. The situation you see in the third panel leads to another big rain forecast in AZ, though a couple of days later, early December! This is so great! Compare the second and third maps.
Now, you can really start to put some credibility in the supposed “outlier” forecast and, as a discerning meteorologist, say to the spaghetti plots with their little deliberate errors, “Go to HELL! You’re missing something big out there with those puny errors you start with.”
Calming down now, well, you can’t cast the thought of warm dry weather (seond panel) for late November out yet, but something IS being missed out there, which makes this an exciting period–just to see what happens. Though an admitted precipofile, at least here in AZ, not so much in SEA, I am putting my mental marbles on the trough in the West depictions now. Just a hunch.
