Category Archives: Altocumulus clouds

More March rain ahead; and not so far ahead

High cold ones that are headed this way in a curvilinear path. Image was made at 5 AM AST, annotation later.

That means that a deep Altostratus overcast will be in place by tomorrow with a load of virga and sprinkles, not really much rain since the bases will also be cold and…high.  Top possible rain amount from these high cold ones is a tenth of an inch, but more likely will be traces.  Chance of a trace in the area?  Oh, about 99% IMO.

But that’s not our full rain destiny.

On the horizon, only a week from now, is the likelihood of a significant rain.  Check the models and the spaghetti:

Valid at 5 PM AST, March 16th. You don’t need the precip prediction for this day when the 500 millibar pattern is like this, the core of the wind at that level south of Tucson. Its not a sufficient criterion for rain, but a necessary one in the cool half of the year. (Only about 5% of the rain in TUS falls outside of this criterion in the cool half of the year.

Here’s the rain prediction which I have not looked at until posting now to make the point you don’t need to look at it:

Where the model thinks it will have rained in the 6 h prior to 5PM AST on March 16th. I hope you’re happy now.
Valid at 5 PM AST March 16th. Blueish lines of cold and rain (546 decameter geopotential height contours) way down the Cal coast, and somewhat bunched (confidence indicator) for a major trough to affect all of Arizona, keep the current greening underway.

Would say the chances of measurable rain from this “incoming” are at least 90%; i. e.,  virtually certain.  (Note that “virtually certain” is not the same as 100% certain,  but its damn close.)

Problems with hoster and connections to hoster continue–must wait seconds to see what I’ve typed, then have to go back and correct the gibberish.  So, not doing much as a result.

But here are a couple of cloud shots from yesterday anyway:

6:17 PM. Altocumulus perlucidus appearing to spread out, though likely a perspective tomfoolery. Thin Cirrostratus above.
6:39 PM.

Addendum:  Coupla of days ago saw the rare “Cumulo-cirrus” clouds, ones that appear to be Cumulus but are fakes, up at Cirrus-levels.  You might call them Cirrus castellanus.  I feel these are worth sharing so that the young cloud maven person doesn’t embarrass himself or herself when making a cloud call to friends and neighbors, as you would do.  They occurred on March 7th between 11:30 AM and Noon.  Can you tell, upon “zooming big” that these are mostly ice clouds?  If droplets were present they were there for only a short time, thus (is that still a word?) indicating that these rag clouds were at very low temperatures.

Some sounding detective work below

The 5AM AST sounding for March 7th. The sliver of moist air at 16,000 feet above sea level is not deemed the source of those rag clouds.
5 PM AST, March 7th sounding with writing on it.


The End

Another day with Altocumulus clouds, and what else? The usual: aircraft-produced ice canals

They seem to go together every time we have Altocumulus clouds; aircraft flying through them create holes or canals!  Have been photographing this phenomenon since the early 1980s, and I have not seen it so consistently occur every time there was a flake of Altocumulus around as has been the case here this winter!  Its likely because our Altocumulus clouds have mostly been so cold, having temperatures lower than -15° C.    Mid-level Altocumulus clouds can range in temperature from well-above freezing to below -30° C.

What was unusual about yesterday afternoon, if you caught it, was that you could make out the aircraft producing  the “high temperature contrail” (aka, APIPs), a four engine prop aircraft flying just under the bottom of the Altocumulus layer.    Even if you see a contrail in the Altocu, you can almost never make out the aircraft type for sure because its too high or in the clouds.   But, because of our cool spell, those cold Altocumulus clouds were lower than usual, around 15,000 feet off the ground, or near the 500 millibar pressure level.   The temperature at the bottom of this layer was -21° C.  See annotated NWS sounding, courtesy of IPS Meteostar,  below:

The National Weather Service sounding launched from the U of AZ about 3:30 PM, near the time that the “high temperature” contrail was being produced. A slight amount of Altocumulus was over and downwind of the launch site.

Here’s your aircraft shot, full size so’s you can really zoom in and see those engines:

3:37 PM. A four prop engine aircraft flies just below (maybe 100-300 feet is all) the base of the Altocumulus layer and left a LONG contrail.
3:37 PM. The long contrail behind that plane. Note that it goes into clear air; cloud droplets not required.  Looks exactly like a normal contrail, those produced by jets at temperatures lower than -35°C when the air is moist.
3:44 PM. That contrail now extended from horizon to horizon. it appeared that he climbed through this layer on the way out.  The broadening  with visual evidence of ice is in the upper right hand corner.
4:16 PM. Now the classic ice canal is obvious in our Altocumulus layer.  More aircraft produced ice is present as well.
4:16 PM. Zooming in on a segment of this canal shows that while its completely ice, there are no virga trails showing. Am guessing that those prop engines produced prodigious numbers of ice crystals via prop tip cooling to below -40°C, where homogenous nucleation of ice occurs (producing prodigious concentrations of ice crystals, maybe tens of thousands per liter in the immediate lee of the prop tip).  Here the crystals have spread out due to turbulence, but there are just too many competeing for the available vapor to produce crystals big enough to have much of a fall speed.
5:12 PM. Due to the low windspeed at cloud level, just 15 knots or so, this ice canal was visible for more than an hour and a half. It was remarkable how close to natural Cirrus looked at that time. It would be almost impossible to assign this ice to the level of the Altocumulus. Check the close up, next.
5:12 PM.  Cirrus uncinus homogenitus (I’m not kidding. that would be the name for this Cirrus, having been produced by man (well, or a woman pilot, of course).
5:13 PM. Unperturbed Altocumulus perlucidus translucidus (the latter, little or no shading due to thinness of elements).
5:14 PM. Shadow drama on the Catalina Mountains from those Altocumulus clouds, made even more interesting by the presence of a weather station in the photo.



5:58 PM. The setting sun illuminates that last bit of the aircraft-produced ice canal (“homoCirrus” on the right).  This was probably the longest viewing time for any such event over one location, again due to the light winds up there.

The weather ahead, WAY ahead

Not a single model run since two days ago has produced a big trough in the SW US, in complete opposition to the interpretation of spaghetti ensemble output at that time.  This would be, IMO, one the greatest busts of all time (not for me, of course), but for spaghetti ensembles (I was only foretelling what they told me), spaghetti considered to be one of the great forecasting advances of all time when computers became powerful enough to produce them in a timely manner.

If we believe these later model runs, it will be relatively hot and dry here, not cold and wet, as was suggested here.

But being of a stubborn nature,  Cloud Maven Person is not yo-yo-ing on his forecast just yet.  Surprises are almost certain  in these model runs, since spaghetti still supports troughing beyond 10-12 days…  Standing by  for model yo-yo-ing….

A laugher (???) below from our very latest computer run (from IPS Meteostar again). This map in incredible in the lack of jet stream activity over most of the US!

This 500 millibar map is based on global data from 11 PM AST. last evening.  Its valid for February 7th, 11 PM AST, way out there.   This is a remarkably quiet map for wintertime in the US! Can it possibly be right? Hope not, at least in our area.

The End

Sutherland Heights logs 0.22 inches yesterday; Jan now at 1.32 inches; average is 1.60 inches, water year at 1.71 inches

0.22 inches was, indeed. how much rain fell in the form of drops  from Nimbostratus clouds yesterday as a modest little rain band generated by a rapidly moving trough swept through during the afternoon.  Regional precip values can be found here.  Our local area got the most, up to about a quarter of an inch, as often happens in marginal storms.

Yesterday’s storm marked the beginning of the new, more normal weather regime for southern Arizona, as has been blabbed about here in recent weeks.  No more week after week of droughty weather with temperature far above normal, the kind of weather that has marked this whole fall and winter so far!  I. e., “Thank you very much, a snowbird might say,  but get the hell out!”,  the rest of us might conjure up, thinking about the needs of our  desert’s wildlife and vegetation.

Indications are now that below normal temperatures and above normal precip are ahead for us and all of Arizona in late Jan and early February.

The evidence for these claims?

Below, the stunning, jaw-dropping evidence for this seemingly outlandish assertion in the form of an ensemble (spaghetti) plot generated by NOAA last night.  I have followed these charts for almost ten years now, and I cannot remember when such a strong signal (clustering of flow lines) 15 days out has occurred before in our region.

So, excessively excited this morning when I saw it!  Its been annotated with excitement text.

This troughy pattern begins to take place on January 30th.  Until then, a strong but dry cold front with a lot of wind comes by in a few days, on the 25-26th.

Valid at 5 PM AST, February 4th. You can pretty much count on a trough hereabouts in two weeks. Since the blue lines, the colder portion of the jet stream,  do not dip down this way so much, our troughiness likely would be in the form of something we call a “cutoff low.”   A full latitude trough extending from the “blue jet” up there in Canada, instead of a “cut off”, would be excessively cold.  We probably don’t want that anyway.

 Yesterday’s clouds

The whole interesting, if excessively gray story is shown below:

7:24 AM. It was breezy already, and with Cirrus underlain by Altocumulus lenticularis clouds in the lee of the Catalina Mountains, you knew that a storm day was ahead without turning on your favorite TEEVEE weatherman.
8:53 AM. With Cirrus and Altocumulus spreading rapidly from the SSW, lenticulars downstream from the mountains, the wind gusting to 25-35 mph, you knew a great gray cloud day was in store!
11:32 AM. Before long, an entire sheet of Stratocumulus spread over the sky, making you sure that rain would fall.
12:50 PM. First drops begin to fall on Sutherland Heights. That layer of Stratocumulus appeared to be deepening as it approached from the SSW to where the tops were getting just cold enough upwind of us to produce ice and snow that melted into those sparse drops.  Not enough ice /snow formed to hide the bases, though, in virga.
1:26 PM. Snow begins to fall on the Lemmon.
2:04 PM. Lower Stratocumulus clouds begin to show up below the original deck that overran us.


3:16 PM. Pretty and dramatic.  Stratocumulus piling up over and upwind of our Catalina Mountains/Pusch Ridge.
3:19 PM. Oh, so pretty.
3:27 PM. Crazy, I know, but I thought these scenes were so pretty!
3:28 PM. As that rain band approached there were some nice lighting highlights.
3:40 PM. Here comes that rain band  across Oro Valley/Marana.
4:19 PM. A truly great scene for a desert; mountains partially obscured in precipitation.
4:19 PM. Nimbostratus. Its hard to get a better photo of rainy Nimbostratus than this. Drops coming off the roof, NOT raindrops, can also be seen.  This was at the peak of the rain, too!  Very exciting.
5:54 PM. Sunset Stratocumulus, hold the ice. Yet, that Stratocumulus was cold, way below freezing.


The weather way ahead

The title sums up where we are now.  Will we go have more rain? Oh, yeah.  But not right away, as you already know.



Sun and Altocumulus clouds combine to provide a colorful sunrise and a sunset on the same day! Rain on tap!

“Rain on tap” does not  refer to a microbrew, for those who’ve accidentally stumbled onto this site.

Our nice sunrise and sunset, featuring supercooled1  Altocumulus clouds:

7:22 AM.
7:26 AM.
7:29 AM. Ice crystals trail down from this region of cloud cover toward the north. Was it hers or ours? This Altocu layer was at -15°C (about 4°F), cold enough for some natural ice, but not as prolific as this. The fact that the ice does not trail downward much indicates the crystals in this virga were really small, also suggesting a non-natural event since an aircraft can produce thousands per liter of ice crystals, none of which can grow to very large sizes. Maybe ours?
9:20 AM. Well, what’s a day in Arizona with supercooled Altocumulus without an ice canal caused by an aircraft. So, they were occurring yesterday.  We don’t see them much in the summer because the Altocumulus clouds are warmer.


4:36 PM. Our steady diet of Altocumulus yesterday is topped here by a veil of CIrrostratus, all leading one to expect a colorful sunset.
5:52 PM. So pretty again….


5:52 PM. Wider view of the same scene.


Rain on tap?  Oh, yeah….finally.  One forecaster friend is predicting 0.5 inches!  How nice would that be?  The rain will likely begin toward midnight–check it here from our nice U of AZ Weather Department.

Looking for more rain in AZ after mid-month, toward the 20th.

The End

Cloud patterns excite Catalinans; storms continue to pile up for January

A swatch of Altocumulus perlucidus translucidus (sorry, that’s the way we talk around here) passed over Catalina early yesterday afternoon, each “unit” nearly perfectly evenly spaced with its fellow cloud element creating a brief period of cloud awe for those Catalinans (or is it, “Catalina-ites”?  “Catalinians”?  Who knows, who cares?).  Here it is, in case you work indoors and missed it.  It was truly a fabulous sighting!

1:16 PM.
1:16 PM. Starting to take too many pictures of the same thing!
1:16 PM.
1:16 PM, of course.  So pretty.

The afternoon was marked by a melange1 of middle clouds:

1:52 PM. Altocumulus opacus with a Cirrostratus above.
3:11 PM. Some equestrians on horses (haha) went by the house.  Sometimes we focus too much on just clouds here, and so we offer the reader who visits here an occasional relief from cloud fatigue.
3:12 PM. Those equestrians were being shaded by a Altcumulus perlucidus and by an overcast of Cirrostratus.  If you look real hard, you can see a faint halo.  The Cirrostratus was thickening upwind as an upper level wave approached and was increasing the amount of rising air aloft over us. The Altocumulus clouds also thickened toward sunset.  See below.
5:07 PM. Heavy Altocumulus approached from the SW, keeping the sun from under-lighting the Altocumulus as it went down, so no flaming sunset last night. The Cirrostratus overcast continues. All in all, a fine day for Catalinians!

The weather just ahead

The local TEEVEE met men are, of course, pounding out the good news rain is just ahead for Catalina.  Looks like, oh, 100% chance to CMP (Cloud Maven Person) starting after midnight Tuesday to Wednesday.  How much?

This is a potent, but fast moving trough.  Maybe will have only 2-4 h of rain with the passage of the cold front and its rainband.  But, coming from the sub-tropics, should have a appreciable rain band with it.

I would expect rainrates to reach “moderate” as the heart of the band goes by for a coupla hours, anyway.  Moderate rain is defined by the NWS as 0.1 to 0.3 inches per hour.  So, only two hours of moderate rain should be at LEAST  0.2 inches, and most likely more.

We’re thinking here that there’s a 90% chance of more than 0.15 inches, and a 90% chance of less than 0.70 inches.  So, averaging those two leads to a best estimate in CMP’s opinion of 0.425 inches!  Wow.  Nice.

Now, I will look at the U of AZ nested model and see what it thinks.  Kind of game we play here, seeing how a seat of the pants forecast, made over a coupla minutes, measures up to a computer model with billions if not trillions of calculations:

Cumulative rainfall ending at 3 PM AST Wednesday afternoon. Catalina is in the GREEN, indicating that the Beowulf Supercluster thinks we’ll have over half an inch (Ms Mt. Lemmon, over an inch!) I am so happy!

The weather way ahead

After the nice rain just ahead, we have to get through the week-long dry spell before we move into a new stormy regime.  First, a spaghetti depiction of the ridge after our nice storm:

Valid at 5 PM on the 14th. Huge ridge has stacked up along the West Coast, making it look like the drought will continue ad nauseum.  You’ll be discouraged when the middle of January comes around (though by then, everyone will know this is a straw ridge, will collapse in almost hours from this time from the outputs made in real time then.)

Here’s what’s been exciting for a few days now, and below, from last evening’s global model output:

Let’s see what the actual and very latest model run from IPS Meteostar has for us:

From the 11 PM AST last evening global model output this big boy. Unlike so many prior troughs that were bogus this winter at this time ahead (two weeks), this one has spaghetti support and will be real!!! And, it won’t be the only one!!! I’m shouting again!!!

How much these coming rains can benefit our spring wildflower bloom and spring grasses I don’t know, but I sure hope they can resuscitate what otherwise will be a dismal spring.

Expecting a snow event during the “new regime” that takes over after mid-month,  too.  Be ready!


The End

Artifact skies

I use that expression not only to draw attention to myself since my name is Art, or, “Artie boy” to mom, but also because I had a role in bringing this phenomenon to the attention of the scientific community; that is, that an aircraft could glaciate portions of clouds at temperatures as high as -8°C.  This in a peer-reviewed article  so controversial it was rejected twice by journal reviewers  before “getting in “(pdf here)!  Some background on why this happened is found in a footer way down below….

Its common knowledge today that an aircraft can produce in essence a contrail in clouds at temperatures down to about -10°C and must be avoided when researchers are sampling the same cloud over and over at below freezing temperatures.

Back to the beginning:

The day began well enough with a nice sunrise over the Catalinas:

7:28 AM. Really cold Altocumulus perlucidus lurks over the Catalinas.   The sounding suggests that this layer was at -26̂°C, and yet no ice or virga is present.  This is not unusual.  Ice tends to form more readily when the droplets in clouds are larger–these were likely tiny, 10-15 microns in diameter, and, being a layer high in the atmosphere, not connected to the ground, meant there would be a dearth of ice-forming substances like dirt, well, kaolin mineral particles.
8:01 AM. Well, OK, for the really sharp-eyed cloud maven juniors, yes there was a trace of ice here and there in those clouds.

Here’s the early morning National Weather Service  balloon sounding from the U of AZ:

This sounding was launched about 3:30 AM AST yesterday morning. During the day, the bottom of the Altocumulus clouds lowered and got a little warmer, but still plenty cold for aircraft ice production.

Then, as the Altocumulus layer filled in from the west, the aircraft effects roared to life.  An example from yesterday, one that passed right overhead of little Catalina!

10:01 AM. A parch of aircraft-induced ice in this Altocumulus perlucidus translucidus composed of supercooled droplets otherwise, is about to pass overhead of Catalina.


10:08 AM. High temperature contrails rip through a Altocumulus perlucidud translucidus layer up around -25°C.
10:10 AM. Looking for some optical fireworks here, such as a tangential arc (halo curving the wrong way), but only a hint of one showed up. Can you see it?
11:23 AM. Another clearing with ice below it is seen just SW of Catalina from the parking lot of Basha’s where I went to get some cottage cheese.
11:33 AM. Sun dog (parhelia) lights up in the ice patch above after I came out of Basha’s with some cottage cheese.  Note to writers;  little, seemingly irrelevant details like what you bought in a supermarket makes your writing come alive for the reader.
1:21 PM. There’s another couple! They were just everywhere yesterday!
3:52 PM. Later as the moist layer deepened and lowered further, there was ice aplenty, but it was impossible IMO to tell whether it was au natural or aircraft-induced. Surely, some was due to aircraft penetrations of supercooled clouds. However, when the air is rising enough, a hole or ice canal may not appear since droplets can reform rapidly.
3:52 PM. Looking more to the west where the long trails of ice are more visible.
4:14 PM. I feel asserting here. I assert that this one is from an aircraft, but with droplet backfill that prevented a hole from forming.  Looks like “phony” virga to me, and, of course, to you, too, as a certified member of the cloud maven society.
5:21 PM. Interestingly nearly all virga disappeared about this time, certainly nothing extraordinary that led to the suspicion of aircraft induced ice. The sounding suggests that the higher temperatures that the Altocumulus layer was at may have been the reason. See below…
The U of AZ balloon sounding launched at 3:30 PM suggests the bases of the Altocu have dropped down to about 18,000 feet above sea level, 15,000 feet or so above Catalina, and are much warmer, and thicker than when the day started as we could see.



The weather ahead

More interesting middle and high clouds, probably a great sunset/sunrise or three, but no rain, just virga.  The present mass of middle clouds passing over has some virga and sprinkles, but that’s about it  from this episode.  No real support yet for a change in our dry, warmer than normal weather regime in spaghetti plots though one trough a week or so out is forecast to bring a little rain.

The End

Some background on “APIPs”

This phenomenon had been shot by photographers for decades, yep, DECADES,  BUT, it was believed (apparently) by those doing cloud research, that it only happened at very low temperatures such as those when the normal contrails we see occur (at temperatures lower than -35°C), viz.,  it was ignored.

Another factor was that all of the rare photos of this phenomenon, dubbed “Aircraft Produced Ice Particles” (APIPs, by yours truly, though not the greatest name)  appeared in lay or quasi-lay publications and were likely missed by those with big Ph. Ds. who only read technical journals.  An example of this was on the cover of  the Bulletin of the American Meteorological Society in 1968, a cover shot which drew the greatest amount of reader comments that the journal had ever seen!  They went on for a couple of months, some suggesting that the ice and hole in cloud was due to a meteorite!

Also, it was a rare case indeed when the photographer could report the temperature at which it occurred. 

Altocumulus in transition; water to ice

I was thinking how great yesterday was for you.  Started out with a spectacular sunrise (lasted just a couple of minutes), and then you could watch for pretty much the WHOLE day, orographically-formed Altocumulus opacus and castellanus transition to ice crystal clouds (in this case, Altostratus with virga and some mammatus) right before your eyes!


7:16 AM. Flecks of Altocumulus clouds below Altostratus.

After sunrise….this odd scene below of an extended Altocu lenticular cloud:

7:33 AM.
12:24 PM. Altocumulus opacius shedding ice as they moved westward across Oro Valley.
3:01 PM. Altocumulus castellanus forming just upwind of the Catalinas, moving toward the west (to the left in this photo). No ice is falling out yet, though tiny ice crystals are likely starting to form.
3:01 PM. Looking farther downstream from the prior photo. Some ice is beginning to show up and fall out (center and left side of photo).
3:02 PM. Looking still farther downwind, those Altocumulus clouds are mostly glaciated, that is, mostly consist of ice. This transition has taken about 10 minutes of travel downwind. The sounding near this time, indicated that tops a little downwind of the U of AZ campus release site, were about -27°C (-17°F). However, tops were likely rising some small amount in this region downwind of the Catalinas, and so were almost surely, even a little colder than that.
4:33 PM. Nice example of what some of the Altocumulus castellanus looked like yesterday. That tallest turret will fall back. Its partner is just to the right, one that was previously as high, but fell back, its load of ice crystals drifing down. Some of the ice in the taller one is still being held up there until it, too, collapses. A error in aircraft sampling can occur if you don’t realize that tops have collapsed from lower temperatures, such as when collecting ice concentrations in the collapses one. You could easily assign a cloud top temperature that was too high; would not reflect the temperature at which they really formed.

More “pretties” below; yesterday’s sunset:

The afternoon sounding from the U of AZ campus.

The End

Cirrus uncinus scenes for a lifetime, well, mine, anyway

I hope you had a chance to venture out late yesterday morning and see some of the most spectacular Cirrus (uncinus) displays with HUGE streamers that you will ever see.

The early Cirrus cloud were nothing very special, not showing clues about what was to happen a few hours later:

7:46 AM. A complex sky with Altocumulus on the right and various species of Cirrus such as Cirrus spissatus, center.

But by mid-morning, racing in from the west, these:

10:58 AM. From the Rillito Bridge at Swan, this amazing scene with Cirrus uncinus and those gigantically long tails of ice!
11:08 AM
11:08 AM. Mimics trees in a way, both reaching upward.
11:14 AM.
11:12 AM. From the Rillito Bridge at Swan again.  Kind of running around like a chicken with its hat off!  The heads of the Ci unc are overhead.
11:11 AM.
11:14 AM. One final shot.


There was an interesting  contrail distraction later that day.  Are these “castellanus” crenelations, or is it perspective?  Those knobs are usually pointed downward due to the action of the wingtip vortices that take them downward behind the plane.  Maybe they’re just sloped down at us, not puffed up.

1:10 PM.


Late in the day some Altocumulus advanced from the west, providing a nice sunset, but a layer once again impacted by aircraft holes.   Can you find them (with their trails of ice slanting downward?)

5:38 PM.

The End

Well, there is still a chance of some rain late in the month, late or after the TG holiday weekend…..  FIngers crossed.   Poor wildflower seeds.

A day dominated by cold Altocumulus punctuated by aircraft-produced hole punches and ice canals

Hope you saw them and recorded them in your cloud and weather diary.  I’m thinking that at the next Cloud Maven Junior meeting we should devote a lot of time to this issue.  It was a rare day yesterday that the WHOLE day had that phenomenon occurring as aircraft penetrated those clouds, usually on ascent or descent.  Sharp descents/ascents produce holes.  See the sequence below if you don’t believe me (ppt from a recent talk):

Aircraft inadvertent cloud seeding for Julie Mc.

Yesterday’s clouds:  lots and lots of  aircraft-produced ice

(btw, see note below about pop-up ads in this blog, ones that started to appear after downloading latest WP software)

6:44 AM. Altocumulus at sunrise. As we say so many times here in old AZzy, “So pretty.”
Also at 6:44 AM. From a smartphone, color not so great, though not bad either.
U of AZ Wildcats balloon sounding, launched at about 3:30 AM yesterday. Those Altcumulus clouds were way up there for Altocu, 22,000 feet above Catalina, 25,000 feet above sea level.because they were so high, were so cold, AND were composed of supercooled liquid water, they ripe for aircraft to create ice going through them, likely on climb out and descent from TUS and perhaps PHX as well, Davis-Monthan.  What was unusual, was that it was happening most all day as the clouds filled in some.  They remained liquid, high, and cold.

7:23 AM. Wasn’t long before aircraft made their presence known in this cold, cold layer.
6:54 AM. I should point out that a colder topped Altostratus layer was present to the N. Its not represented well in the TUS sounding. That layer was all or mostly all ice (the rosy colored segment of this photo).
7:37 AM. An unperturbed view of Altocumulus perlucidus (“Mackerel sky”). Are there any mackerel left?    Also, from a cloud viewing standpoint, these are much higher than one would guess. The fact that aircraft were making ice in them is a clue that they were higher than we would normally think of a “middle-level” cloud.   I like patterns like this.  I thought you would like to know that about me.
9:03 AM. Slicing and dicing. An aircraft has left a contrail through a Altocumulus line . What’s really unusual here is the ice contrail so far outside the liquid water cloud. It is thought that hole-punch and ice canals are limited to regions where there are liquid droplets, and so this is quite an anomaly, one that suggests the humidity was almost 100% with respect to water outside the cloud boundaries. Also, can you just make out the partial 22° halo, indicating very simple ice crystals like columns and plates?  Streamers of tiny ice crystals are also evident, trailing to the right, below the contrail?  This shows that the wind decreased rapidly with height just below the flight level, but was still from the southwest to west.
9:24 AM. Coming at you, another ice-canal has formed SW-W of Catalina, a favored locale for the formation of these canals on days like this.
9:40 AM. What’s left of it is almost to Catalina.  Note streamers of ice.  Below, a close up of a couple.
9:40 AM. The intensity and narrowness of these streamers point to an artificial origin. So, even if you didn’t see the canal, and here, some of the clouds are reforming at the top of the streamer, you would make a good guess that this was not natural ice.  Sometimes the canals can fill back in if the air is in overall ascent at cloud level.
9:57 AM. Here’s what those contrails in Altocumulus look like as they first appear. Can you spot’em? There are two.
1:45 PM. Another aircraft-produced ice event as the Altocumulus increased and became thicker, making detection of these events less obvious. Sometimes a canal clearing is very muted.
4:12 PM. Aircraft-induced hole punch cloud with ice below the hole. Can you spot it? See close up below.
4:12 PM. Close-up of that hole punch, ice mostly below the Altocumulus layer.
4:35 PM. That hole punch cloud 35 min later. The long trail indicates high humidity well below the Altocumulus layer in which it appeared.
The 3:30 PM balloon sounding from the U of AZ. A study in ambiguity.
The day ended with an unusually bright sun dawg, mock sun, or parhelia. So bright it did, again, suggest a plume of ice from a prior aircraft passage through extra cold Altocu or Cirrocu clouds. But, just wild speculation here.  Hope you don’t mind.
5:41 PM. Nice sunset, but one strongly impacted by clearing from aircraft-produced holes and lines of ice, the ice now mostly gone.

The End


——————About those nuisance ads—————

Note to me and the two other people that drop by my cloud or “clod” blogulations:  The embedded pop-up ads are due to a WP third party plug-in that needs to be repaired.  It will likely happen today.


After consultations about ads…

Oddly,  those pop-ups and blue highlighting and double underlining do not seem to be present outside of my personal view of my own blog, this according to hoster, “godaddy.”  Even using a different browser other than FIrefox does not show them as I have just verified.