We’ll have to suffer through a few days for the next storm, i. e., experience sunny weather with pleasant temperatures. Its amazing that people all over America come to Tucson to experience sunny days with pleasant temperatures!
0.45 inches total in The Heights of Catalina in this latest round of rain, sounds of rain. Actually, there was also some tiny graupel/soft hail in the rain yesterday, too.
Graupel indicates a lot of cloud droplet water overhead, and that ice crystals were colliding with them until they lost their identity and became little snowballs. In regions where there are very few ice crystals, graupel and the harder version, hail often form. Its likely that nearly all those rain drops that came down with the little baby graupel were melted graupels.
Graupels….. Makes me think of that rock group, Led Graupelin, didn’t have the impact of Led Zepelin. But I have LG’s one and only album entitled, “Compare to Led Zepelin.” Was only $2.99, too! Where’s my guitar? I think I will play, “Stairwell to Heaven” now…
When graupel or hail occur, there’s a pretty good electric charge up there in those Cumulonimbus clouds. Its best to be indoors when its hailing until you know if a strike might occur (if there hasn’t been one already). Besides, its not comfortable being out in hail. And if you were listening to the rain, you heard a few blasts of thunder toward Lemmon around 2 PM that came out of one of the more enthusiastic Cumulonimbus clouds that went by. Got 0.12 inches total to add to the night before’s rain of 0.33 inches.
Yesterday in clouds; a sojourn in clouds from morning to evening, in that order with no times noted
I know how much you like to see pictures of rain, so here’s one. You’re not like the “others” are you those people around you every day?
Then the piston of atmospheric subsidence slammed down to squash our Cumulus cloud tops to levels and temperatures where ice could not form….
Two picures in a row of a NWS-style rain gauge. Probably has never been done before. Has been getting a workout lately. Everyone should have one.
The weather ahead
Kind of funny to see the Canadian GEM model internally plagiarize itself. Compare last night’s panel at 500 millibars (below) with that same level’s panel foretold for six days from now.
Yep, its the same thing over again in six days, though with less rain IMO:
In another interesting model development, the best USA model, the WRF-GFS is having an internal CONFLICT of major proportions. Check these progs out generated by data only six hours apart. The first one, showing a big trough coming into Cal, was generated by global data taken at 5 PM AST last evening. The panel below it was generated by the same model based on global data taken just six hours later, at 11 PM AST (so it the most recent WRF output available) and has a big ridge along the California coast.
Valid at 5 PM AST November 20th.
“Which one will the fountain choose?”, to quote old song lyrics1:
Truly LATE breaking news, untimely really, but Augustober 18th was too special a day to ignore:
Giant clouds, dense rain shafts, frequent lightning in the area throughout the afternoon, dewpoints in the high 50s to 60 F; can it really be after the middle of October? Or, is this some kind of preview of climate change we can look forward to in the decades ahead, that is, if you’re thunderphilic?
5:05 PM. An amazing scene, and thunderstorm with such powerful updrafts that when those updrafts are blocked by the inversion at the base of the Stratosphere, they force the winds at that level to slow or backup and the anvil protrudes upwind (center left), something that is common with severe thunderstorms. This was significant here because the winds at 40,000 feet were around 50 kts, far stronger than anything we have here during a typical summer rain season. Summer Cumulonimbus cloud anvils can splash outward easily against weak winds up there in summer when they hit that barrier at the top of the tropopause. This just in from Mark A: severe thunderstorms, I have just learned here on the 20th , were observed in the PHX, and the NWS has a great link going describing all the mayhem it produced. I did not know this until just now in the middle of writing this first caption when I read Mark’s e-mail.1:40 PM.
1:56 PM. Anvil of the Cumulonimbus over west Tucson, drifts overhead of Catalina, and in three minutes, rain drops started to hit the ground. This is amazing because those drops had to fall from at around 20, 000 feet above the ground (estimated as bottom height of this thick anvil) and could only have happened if those isolated drops had been hailstones ejected out the anvil, something that also only occurs with severe storms with very strong updrafts in them. So, if you saw those few drops fall between 2 and 2:05 PM you saw something pretty special.
6:26 AM. Early portent: Cu congestus, aka, “heavy Cumulus) piling up this early.6:29 AM. Mammatus of the morning., an extraordinary scene for mid-October, pointing to the possibility of an unusual day ahead with strong storms. as was the scientific basis for giant clouds on the 18th in the amount of CAPE predicted, over 1,000 units of Convective Available Potential Energy, later that day from computer models. That is a lot for mid-October, take my word for it.3:45 PM. Strong storms did not form over or near the Catalinas yesterday, but they did get something. As you can see the top of this guy (Cumulonimbus calvus) is very subdued compared to the giants that formed elsewhere.5:53 PM. Peakaboo Cumulonimbus calvus top east of Mt. Lemmon provided a nice highlight after sunset. And to have convection like this going on this late was remarkable. Some heavy showers and a thunderstorm formed downwind of the Catalinas about this time,, too.5:51 PM. Pretty nice, summer-looking sunset that day, too.
The weather just ahead, and this might be it for precip for the rest of October
A nice-looking upper level trough is ejecting over us from the SW this morning but the computer model says its going to be a dry event. A second low center forms just about over us in the next day. AZ model doesn’t see much rain for us throughout these events, and rain doesn’t begin here until after dark today.
I think that is WRONG; bad model. Watch for some light showers this morning, then a break and rain overnight (which the models do predict). Due this quite bad model forecast, as seen from this keyboard, I feel must interject for the blog reader I have, an improved rain prediction for Catalina over that rendered by a computer model.
Feel like guesstimating a minimum of 0.25 inches between now and Thursday evening, max possible, 0.60 inches, so the median of those two, and maybe the best guestimate being the average of those two, or 0.425 inches here in Catalina. When you see a prediction of a rainfall total down to thousandths of an inch, you really know that the person predicting it knows what he is doing…..
Below, your U of AZ disappointing, but objective, take on the amount of rain based on last evening’s data and one that is the result of billions of calculations. One must remember that cloud maven person’s calculation of the rainfall amount for Catalina is only based on three.
From the 5 PM AST run executed by the U of AZ Beowulf Cluster.
6:25 AM. Altocumulus perlucidus. According to my cloud chart, informally known as “America’s Cloud Chart”, it could rain within 6 to 196 hours. Its quite useful.10:24 AM. Altocumulus opacus. Note the rumpled look of the sky. Indicates that the clouds are rather shallow and composed of droplets rather than a mix of ice crystals and droplets. However, if you strain your eyeballs and look to the horizon, you can see a smoothing and a little virga showing that the cloud tops are rising and they’ve gotten cold enough to produce ice. According to my cloud chart, when you see “Ac opacus” it could rain within 6 to 196 hours.1:44 PM. While the clouds are pretty much the same gray color as in the prior photo, they’re much thicker here and are “Altostratus opacus”. “opacus” because the sun’s position is not visible, though it wouldn’t be in this direction anyway, but to the right. The bottom of this is smooth due to widespread, light falling snow, though it not in a localized area enough to be called virga in this shot. The lack of bunched or heavy virga somewhere tells you that the cloud tops are pretty smooth, too, not a lot of variation in height. The base is really determined by the point that you descend out of this precip, in this case up around 10 kft above the ground over Catalina.4:12 PM. Altostratus opacus praecipitatio or Nimbostratus, either name will do. Recall the quirk in our cloud naming system that makes, “Nimbostratus” a middle-level cloud. The base of these clouds is the general level where the snow falling out has evaporated. Due to bulging tops, and stronger updrafts, a little of the precip was able to fall out because the snowflakes coming out the bottom had grown larger and were able to survive the dry air below cloud base.
Some rain fell about this time in Catalina. Not enough to darken the pavement completely at any time. The main thing to take away from that hour of very light rain is that it was not “drizzle” as even some errant meteorologists call such sprinkles.
You will be permanently banned from attending any future meetings of the cloud maven club if you refer to such rain as we had yesterday afternoon as “drizzle.” Drizzle is fine (200-500 micron in diameter drops that are very close together and practically float in the air. Because they fall so slowly, and are so small to begin with, you can’t have drizzle at the ground from clouds that are much more than a 1000 feet or so above the ground because as soon as they pop out the bottom, those drops start evaporating and fall slower and slower by the second, and in no time they can be gone even in moist conditions. That’ s why its somewhat hilarious and sad at the same time, when, in particular, military sites for some unknown reason, report ersatz “drizzle: (coded as L, or L-) in our hourly aviation reports from clouds that are based at 5000 feet or something CRAZY like that.
This band of Nimbostratus/Altostratus had a backside that approached as the sun went down, and as you know, that clearing let some sunlight enrich and dramatize the views of our beloved Catalina Mountains:
5:39 PM.5:41 PM.
Finally, dessert:
5:47 PM. Rainbow lands on the University of Arizona Wildcat’s Skycenter atop Ms. Mt. Sara Lemmon.5:48 PM.
The amazing rains ahead
Nothing that you don’t already know about, so no use me blabbing about it too much. But in case you haven’t seen it, The Return of Joe Low (after over-hydrating over the warm waters of the eastern Pacific), is expected over the next couple of days, with a little help from another disturbance, to bring colossal rains to eastern Arizona and especially New Mexico.
Below, from our friendly U of A Wildcat Weather Department a model run from yesterday’s 5 PM global data (the Wildcat’s downsize the US WRF-GFS model in this awesome depiction).
Check out the totals expected by the evening of October 23 rd. Stupendous. Usually these totals are a bit overdone, but even so…… Will take a nice bite out of drought.
Precipitation totals expected by 5 PM AST October 23rd. Looks something like a tie-dyed Tee.
Through deliberate deception, the title is likely to bring in quite a few football-centric people, since “jumbo package” is a term used when an offensive team bring in all the “Sumo wrestlers” they have, usually in attempts to score a touchdown from 6 inches outside the goal line.
The “jumbo package”, however, is about some weather, essentially at “mid-field” rather than on the goal line (i.e., just ahead):
A large and very strong upper low center is forecast to arrive on Sunday, October 25th, football day, the last reference to football in this blog. As it passes over Arizona, the first snow of the year would likely fall on the ‘Frisco Peaks by Flagstaff.
Tremendous rains, too, would occur here in AZ with this low, espepcially2 here the SE corner, should it happen. See WRF-GFS model outputs below, as rendered by IPS MeteoStar:
Valid on Sunday, October 25th at 5 PM AST.Valid on Sunday, football day, October 25th at 5 PM AST. The bluish regions denote especially heavu rains having fallen in the prior 12 h.
But does it happen?
Let’s check the spaghetti from NOAA for a hint about whether this weather happenstance has much chance of occurring:
Valid on Sunday, October 25th, at 5 PM AST.Same map as above, except annotated for those who found the first map geographically challenging.
You, too, as an expert on spaghetti now, are as crestfallen as I was to see this spag output from last night, showing that the espepcially strong low is, in fact, an outlier; a not impossible situation, but an unlikely one since we don’t have the bunched blue contours where the jet stream is strong, down thisaway. Rather, those blue lines are grouped over the Pac NW, and only one or two bluish contours are down here, ones that would be associated with that upper low on the 500 mb map above for Oct. 25th
Still, even when you know its an outlier, it brings hope for a bountiful rain, which is good. Will monitor this as the days go by, in case the outlier spaghetti output is an outlier.
The weather just ahead
Of course, as all weatherman know, we still have our boomerang friend Joe Low returning with rain; that’s in the bag, and has a little “friend” following behind him. These, combined, should bring substantial rains overall in AZ and in the Catalina area, in the form of scattered showers and TSTMs that persist over several days beginning later Thursday through Monday. Joe et al. are slowpokes, which is good.
Haze and smoke are up, if you’ve noticed that our skies have been not so blue, but whitish. Stuff is coming up from Mexico it appears; (Smoky) Joe will bring more of that before it gets here. So, look for a hazy patches of Altocu and/or Cirrus in the next couple of days. Maybe a small Cu off in the distance.
2:06 PM, October 11th. Shows the kind of hazy, smoky conditions we’ve been having lately. There is also some delicate Cirrus up there contributing to the whiteness.
The End
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2“Espepcially” is a word I made up via some inadvertent key strokes, but I kind of like it: “In particular, but with some energy.” BTW, Coke tastes better than Pepsi, if that new, unexpected word made you think of a soft drink.
Rarely do passing lows get a two chances to produce rain, but the low passing overhead today and tomorrow, does. Ten days from now, its overhead again! How funny izzat? And precipful, too.
Measurable rain will fall today in Catalina CDP (“Census Designated Place”, i.e., its not a city), and in about 10 days when the SAME low returns after a boomerang trip down Texico way, thence to Baja, thence to so Cal, and back over Arizona on the 10th-11th after picking up some juice over the east Pac.
Thinking, as you are now, of a minimum of 0.05 inches and top of 0.50 inches, the latter larger amount if projected afternoon thunderstorms land on us. Thus, best estimate, average of those two extremes, thinking Gaussian conceptual model modal value here, about 0.275 inches.
BTW, should be something in the way of an arcus cloud, or a batch of low scudding clouds underneath Cumulus and Cumulonimbus bases this afternoon as a windshift to the NW comes through in the afternoon or early evening hours, well in the next 18 h or so. That could be a dramatic sight, and with that windshift, the temperature will drop 5-10° F.
When the low trudges over us the second time around in mid-October, the estimated extreme amounts are a trace minimum, and 1.00 inch max, in other words, pretty clueless here about how much could fall the second time around ten days from now.
If you don’t believe me about all this, here are is the WRF-GFS prediction for this afternoon, followed by the WRF-GFS model prediction 10 days from now, today being October 6th, in case you don’t know what the date is today, maybe you’re retired and lose track of the days and dates because you don’t have a lot to do everyday, just kind of sit there:
5 PM AST, today, October 6th. Joe low goes by, heads toward Texas.5 AM AST, Friday, October 16th, the day before football day. Joe returns after visiting NM, TX, MEX, Baja, east Pac, then SC. Full cycle here, from IPS MeteoStar. Pretty humorous to watch this happen.
Yesterday’s clouds, punctuated by a large worm
6:57 AM. If you thought the clouds were fatter to the north most of the day yesterday, you were right. Many modest Cumulus passed overhead of Catalina and then fattened up to the north because the lifting mechanism aloft was stronger to the north of us. Quite a few moiuntainstations registered over an inch to the north of us.
However for a moment, we did have a shower threat move toward us from the south, this:
11:52 AM. Whilst on a hike up the Baby Jesus Trail, this appeared. Looked promising! But, vaporized into mere sprinkles. If you saw this, you almost immediately were thinking of ice forms like needles and sheaths, since the cloud was relatively shallow, and its still warm aloft. Needles and sheath (hollow columns) only form at temperatures above -10° C. Such an occurrence is rare in Arizona, so, quite an interesting bit of hand-waving here.10:57 AM. Hike up the Baby Jesus Trail was punctuated by seeing a very colorful worm of some kind. Not much else happened in weather or wildlife the rest of the way, Morning glory coverage was a little disappointing.4:17 PM. I am sure when you saw this Cumulus congestus that you, as I was, thinking you’d see a little ice emit out the right, aging and descending side of this cloud. In fact, no ice was visible. However, it was kind of neat to think how close we are now days in our cloud assessments, right or wrong.
The last data point is for 2014-15. These data are an amalgam of the Our Garden site on Pinto and Columbus, from the top of Wilds Road, and the last two years from Sutherland Heights.
OOPS. I was listening to a Southwest CLIMAS podcast, originating at the U of AZ, and realized I missed in the above graph what can only be termed an “ineffectual Niño” that which occurred in 1986-88 and did not produce a precipitation “signal” here. How lame was that?
So, while we are excited about the prospects of extra rain this winter due to the current, supersized El Niño, like all things weather, some doubt must be in place.
Rather than hiding the omission of the “ineffectual El Niño” period, I am inserting the corrected water year history plot here with slightly revised annotation so you can compare them both.
These data are mostly from Our Garden, 1977-78 through 2011-12, located at Columbus and Stallion. The data after that are from Sutherland Heights, Catalina, some 2 mi or so to the SE of that site, and about 300 feet higher in elevation. So there is a bit of what we would call a “heterogeneity” in the data.
The downward trend is misleading, since the Our Garden record began with extremely wet water years, due to a combination of a shift in the Pacific Decadal Oscillation that occurred in 1977-78 (a shift that squelched the then record West Coast drought) and a Niño or two.
That kind of downward trend shown for Catalina in cool season precip does not show up in the Statewide averages for the whole year, anyway, shown below.
Those annual data show the usual oscillations between drier and wetter epochs in Arizona. In the plot below, you can see that had the Catalina record started in 1950 or so, there would likely be little in the way of a trend since so many of those years were drier than average. You can also see the effect of the PDO change in the late 1970s where year after year was above for the State of Arizona as a whole.
The annual (Jan-Dec) state averaged rainfall for Arizona through 2014.
The weather ahead
Rain, tropical skywater, still appears headed our way around the 4-6th of October.
For the second time this month, cloud-centric folk had a rare and happy sight: “naked” Nimbostratus, that is, the well-known mid-level1 precipitating cloud layer was present for all to see, but without the obscuring lower cloud decks normally associated with it, clouds like Stratocumulus or Stratus. Time and time again those pesky lower layers prevent one from seeing whose really producing the rain or snow at the ground because when precip is falling, its normally moist enough that lower clouds are present.
Those lower layers are important in enhancing precip because while they aren’t precipitating themselves (though it may seem like it) the drops falling into them from the Nimbostratus higher up, 1) won’t evaporate inside the cloud, and 2), if the droplets in the Stratocu are large enough, some of them will be collected by the raindrop falling through it and it becomes larger, the rain that bit heavier! How great is that?
Its really hard to compare how rare yesterday’s sight of “naked” Nimbostratus was yesterday, but offhand, I would say its about as rare as a professional wildlife photographer2 catching a shot of Cockrum’s Gray Shrew, aka, the “Hairy Packrat” or just “Harry Packrat”, shown below:
Oh, yeah, that Nimbostratus layer sans lower clouds….
12:37 PM. A layer of pure Nimbostratus produces very light, steady rain in Catalina. Cumulostratus3 clouds line the Catalinas below it.
Except for the rarity of the view, not much to see. The bottom is blurred by falling precip, and when its snow, where that snow melts into rain is perceived as the base of Nimbostratus. So…….in the warmer time of the year, “naked” Nimbostratus has a higher perceived “base” than in the cooler time of the year.
There was also another unusual situation, a cloud layer that really has no good name which I will now call from here on, “Cumulostratus.” See below:
12:07 PM. An example of the newly named cloud, “Cumulostratus.” Really there is no existing name that really hits this, maybe Stratocumulus castellanus.
2:07 PM. Kind of fun to see the hide and seek the “Cumulostratus” clouds were playing with Samaniego Ridge and Ms Mt Lemmon, too.
Not much immediately ahead in weather, oh, maybe some scattered showers later Sunday through Tuesday. Nothing really great jumps out of the spaghetti plots in the longer term.
The Canadian model thinks the newly formed desert lands of northern Cal all the way down to “Frisco” will get drenched, beginning in five days or so. That’s good. The USA model, using the same global obs at 5 PM AST yesterday, do not see that happening, but rather just some very light rains. Go Canada!
The End
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1Probably doesn’t seem like Nimbostratus should be grouped with mid-level clouds like Altocumulus and Altostratus, but it is, strangely believe it, as I like to say. On synoptic weather maps it was placed above the station circle, indicating a mid-level or high cloud was present, as a “lazy F”, the character “F” lying on its back. Cloud types are no longer plotted on surface weather maps since today, clouds are mostly detected by machines, not humans. “Rise of the machines.” You know the story.
2The shot here forwarded to me with much excitement by pro photographer, Rick Bowers, of Bowers Photo, who had tried to photograph this vermin for about 20 years he reported.
3“Cumulostratus” is a name I made up because IMO there really is no satisfactory name for the cloud that lined the Catalinas/Samaniego Ridge yesterday.
But likely, not excitement TODAY, July 27th. Hang on for a wild ride in the last three days of July, the 28th, 29th and 30th. There are no more days in July than that1. August looks pretty active for storms. So far we’ve haven’t even had an inch of rain in July! Awful. No re-greening of the desert, either, as we usually see by now.
In the meantime, nice sunset yesterday; not much else.
7:30 PM. Altocumulus and Cirrus spissatus.
The End, except for the next part, which I just thought of:
Educational module
Let us look at the rise of sea level we’ve heard so much about. Here’s the only measurement I have looked at whilst looking for something else, actually. I found it amazing so I thought I would pass it along. From Astoria, your last 100 years of sea level measurements:
100-years of Astoria Sea Level measurements. Sea level has been going DOWN! How could this be?
From this site: “The mean sea level trend is -0.27 millimeters/year with a 95% confidence interval of +/- 0.34 mm/yr based on monthly mean sea level data from 1925 to 2014 which is equivalent to a change of -0.09 feet in 100 years.”
Well, I have been “informed” by a Mr. Mark Albright, U of WA, Seattle, that the sinking tectonic plate under Astoria and offshore has more than accounted for the minimal rise in sea level associated with both coming out of the Little Ice Age and anthropogenic warming. Still, fascinating to find a location where sea level is sinking!
I think I would consider, in view of this info, moving from the Pac NW to avoid the inevitable Big One, that 8 or 9 mag earthquake that we know can happen in subduction zones…
Misspelling the word, “high” was inadvertent; but leaving it was deliberate, thinking it might work as another cheap attempt to get more than one reader1, presently my mom. Hi, mom. Glad you enjoyed your mom’s day dinner yesterday, followed by the exciting trip through the Catalina car wash. Really squirts, doesn’t it?
Continuing….people might wonder if “hihg” a new word or acronym they haven’t seen before, maybe wonder if it describes something they should know about. So, I am looking to capture one or two extra folks today.
Our next “storm” will occur mostly above 20 kft above Catalina in the form of light snow showers of single ice crystals from Cirrus clouds, typically those crystals that fall out of Cirrus clouds are bullet rosettes.
What’s a bullet rosette? See below:
University of Washington flight engineer, Don Spurgeon. monitors the Stratton Park Engineering Company’s images of “bullet rosettes” in flight. Chad Slattery, Smithsonian mag free lance writer, took the shot. Sadly, Don and the other crew members did not get into the Smithsonian article, only Pete Hobbs and me. Pretty sad for them but happy for me! Yes, I was on this flight! Except it wasn’t a flight, we were sitting on the ground at Paine Field, Everett, WA, where our plane was kept, and Don brought up that image so that Chad could take what would appear to be an “action. in-flight” shot in his article.
Oh, there could be an Altocumulus cloud, too, by tomorrow. But that’s about it. Our last storm was not actually a storm, btw, though there were some low clouds. I guess it got pretty windy, but not rain fell here, nor did it snow whatsoever atop Ms. Lemmon, though it was cold enough to. Boohoo.
But, the overall trend for upper cyclonic systems to nest over the Great Southwest continues, insuring a mild May here in Catalinaland, and also a ton of precip in other parts of the SW, with only brief interruptions of hot air, like the kind that comes from this weather keyboard.
The pretty, and high Cirrus clouds should begin arriving this afternoon, except that some are already arriving (5:20 AM)! Cloud maven seems to be on a wrong streak!
Next Catalina rain chance, graciously presented by the Canadians, is overnight, May 14-15th, just a few days from now. Check it out. This graphic been arrowated and texted for your convenience and understanding.
Valid at 5 AM AST, May 15th from the Enviro Can GEM model. Lower right panel shows where The Model thinks that rain has fallen during the prior 12 h, and it includes Catalina!
The End
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1Still can’t get over that Atlantic article about, “Blogging for dollars”; its like a song hook, maybe like the one from, The Model, by the very Germanic Kraftwerk techno-pop group, and yet after two years, I have made nothing! With millions of readers, you can make a LOT of money, get some great advertising like the various stuff that precedes the viewing of The Model, which has already accumulated more than 4 million views!
So I continue to reach out for readers and money.
What would a neurotic-compulsive, self-described “cloud maven” do with “a LOT of money”?
Underground power lines in his neighborhood. They obstruct sky and cloud views. Used to be quite a movement around the US to do that, but not so much anymore.
We received 0.08 inches here in “The Heights” for a third day with measurable rain in May already. 0.12 inches fell at the Bridge on Golder Ranch Dr. , while Saddlebrooke got up to a quarter of an inch (as estimated by CMP) in a tiny streak of clouds that erupted into shallow Cumulonimbus clouds, anvils and all yesterday afternoon between 4:30 and 5:30 PM. It was pretty much all over by 6:00 PM, those shower clouds passing off toward Mammoth.
No rain was reported at mountain sites, to give you an idea of how localized that was, localized practically to Basha’s Market parking lot, Sutherland Heights’ Equestrian Trail Road, and Saddlebrooke’s Acacia Drive, to exaggerate some.
The astounding aspect of a tiny line of showers that suddenly erupted over and a little downwind of Catalina was that it was EXACTLY predicted in the University of Arizona’s 5 AM AST model run yesterday morning, one whose results are available by mid-morning! So, there would have been a few hours notice of possible rain here in Catalina.
There is no rain predicted in that model run anywhere else except in extreme NW Arizona, just that tiny ribbon of rain right over us, and the U of AZ “Beowulf Cluster” weather calculator got it right.
However, unless you were in the right spot, you might not have even known that it rained, the shower streak was so narrow.
Below, the astoundingly accurate predictions for 3, 4, and 5 PM for that model run from yesterday morning. No rain whatsoever is shown at 3 PM, as you will see.
To be “fair”, NO RAIN was predicted anywhere NEAR Catalina by that same model crunching the data from 5 PM AST the evening before our little rain event, leading CMP to be a little asleep at the wheel yesterday morning, no blog.
Some cloud shots before and as this predicted (or unpredicted, as the case may be) rain began to happen. Of course, if you want to go to the movies and see this, go here, from the U of AZ: Yesterday’s cloud movie
3:23 PM. Looking upwind. Nada going on, clouds to shallow for ice.4:04 PM. Hmmmm. Clouds definitely fattening up upwind of us in a nice cloud street from upwind of and over Pusch Ridge to Catalina. Nice scene, anyway, even if nothing happens.4:12 PM. Cumulus clouds are looking to gather down there at the corner of Pusch Ridge and Oracle Road, Huh. And they’re heading in this direction. Can ice really form in these guys today?4:23 PM. Clouds over and downwind of Pusch Ridge continuing to gather while heading toward Catalina. Looking for ice now or virga, but don’t see any anywhere.4:33 PM. Ice begins to show up in even modest clouds! And it started to show up everywhere in the form of virga. But then then the virga became thin shafts all the way to the ground. Cloud Maven Person is beside himself, but must go indoors for a social engagement! Those of you who fancy yourselves as Cloud Maven Juniors, should have recorded this sighting of “first ice” in your cloud diaries for yesterday.Also at 4:33 PM. Ice is now readily visible in that Cumulus mediocris massing upwind of Catalina and is not about over the south part of the Catalina CDP (“Census Designated Place” that might one day be absorbed by Oro Valley, rumour has it.)4:41 PM. Just minutes before the first drops fall in Saddlebrooke, and CMP’s last photo of this incoming masterpiece of weather forecasting and little rain band; he can no longer comfortably jump up from dining room table in mid-conversation to say he has to pee again whilst actually taking a photo. You can only say you have to pee so many times in 10 minutes and still have your credibility intact. But, how can you say repeatedly, “I have to go look at some clouds?”, so I can’t hear the rest of your quite interesting story……” Really came down for a couple of minutes several times there in Saddlebrooke between a quarter of five and 6 PM as one little raining cloud formed after another in this cloud stream.
Below, sat view of this cloud streamer with radar, from IPS MeteoStar. The image below is at the same time as the last photo above:
Satellite and radar imagery for 4:40 PM AST. Note the many lines of clouds running almost due south to north into SE AZ from Mexico.
Here some more cloud stuff from the sounding launched at the U of AZ around 3:30 PM AST.
The TUS balloon sounding (“rawinsonde”) for yesterday afternoon. Looks like most tops were dabbling with the ice forming temperature of -10 C, but the sounding suggests that somewhat deeper tops could easily have arisen (and did!). Interestingly, the model “knows” when ice forms, and it must have “known” that the ice-forming temperature was going to be surpassed in that little cloud line coming off Pusch Ridge. Astounding, for the Nth time. Bases were pretty cold, 0 C (32 F).
Here’s a diagram of when ice forms in the type of clouds we mostly have in Arizona, “continental” ones with high droplet concentrations, and when ice should form in them. As you can see, ice should form in them soon after the top temperature gets colder than 10 C WHEN the base temperature is about what it was yesterday.
From a survey of the onset of ice formation in continental clouds by Rangno and Hobbs (1995)1
“CMP” is not mentioning it at all, but yesterday was another kind of mucked up sky, not a Catalina postcard sky, with lots of aerosols making the sky a whitish-blue, the lower aerosol stuff again from Mexico, but there was also a layer far above the cloud tops, likely a long-range transport event from thousands of miles away.
This higher haze layer still seems to be around if you look toward the horizons right now (5:59 AM).
We’ll be between two jet streams today, kind of a jet stream sandwich, and the stronger one is now approaching from the northwest with that mega upper low over Cal. That means no rain today, subsidence rules, though we’ll have small, non-ice producing Cumulus, and likely some Altocumulus lenticulars, maybe a Cirrocumulus patch here and there. Should be a pretty nice day for cloud photos, haze aside.
The best chance for rain is still after midnight tonight into mid-day tomorrow as the core of the stronger jet stream goes just about over us. Still thinking a tenth of an inch will occur here, though mod run from the U of AZ at 5 PM completely dry. A little snow likely on Ms. Mt. Lemmon, too!
Then the piston of atmospheric subsidence slammed down to squash our Cumulus cloud tops to levels and temperatures where ice could not form….
![Desert-Shrew-or-Cockrum's-Gray-Shrew-0002[2]](https://cloud-maven.com/wp-content/uploads/2015/09/Desert-Shrew-or-Cockrums-Gray-Shrew-00022.jpg)
