Category Archives: Aircraft Produced Ice Particles

Intriguing jet stream pattern arises in computer models

First, your sunset for last evening:

5:38 PM. Altostratus with nearly straight lines of lower hanging virga in the distance. One cannot help but wonder if the passage of an aircraft enhanced the ice falling out and that’s why they are so linear.  There were quite a few aircraft-induced lines of ice yesterday, but all developed in cold Altocumulus clouds.  There’s one over there to the north….
5:33 PM. Lppking over there to the N and you can see a rivulet of ice falling below that patch of Altocumulus. one of many yesterday, though this is the prettiest one.  You can also see that there is something “wrong” here.  The trails below appearing to be slanting toward the west and the flow was from the east.  This indicates that the flow was stronger at lower elevations, an oddity.

Brain’s been pretty empty lately, not much to say except “same old same old”, as here.

But then some wild computer forecasts came out last evening that were worth mentioning in light of the fires that have plagued southern California.

Why?

Because they suggest that a belt of tropical flow will break through under the gigantic ridge that has blocked storms from the entire West Coast over the past weeks.

Sometimes, as most weathermen know, such persistent ridges get too big for their britches, that is, over-extend to the north, and then fracture, letting through moist tropical air from  lower latitudes of the Pacific ram into the West Coast.  Often the very greatest rains in California are associated with such patterns, as you could guess since there is so much water with those lower latitude-originated jet streams that strike the coastal mountains head on.  Here’s  the concern, this output valid for Christmas Day:

This from last night’s 5 PM GFS global model run, valid for 5 PM AST Christmas Day. What is shown is that the tropical input is about to combine with a trough over the Bay Area. When this happens both are energized.

Rain is forecast to have fallen in southern Arizona before this point, however;   our measly 0.01 inches so far here in Sutherland Heights so far  in December will likely be added to along with a switch to uncomfortably cold weather.

Of course, we look for support in these longer range forecasts by having some spaghetti–that is, take a look at what we call “spaghetti”, those crazy plots in which the model starting conditions are tweaked that bit to see how the model runs change.  Here are some plots, also from last night’s model.

As you can see in this first plot for the evening of December 22nd AST,  the clustering of blue and red lines off the West Coast, that our blocking ridge (composed of a deep mass of warmer air)  is extruding all the way almost to where Santa Claus lives, yes, that far to the north.  In fact,  so far that it will be unsustainable  over that distance fromt the deep tropics to almost the North Pole.  At this point,  cold air is pouring  down the east side of that ridge and into the Pac NW and eventually down toward us.  Does that extremely cold air make it here?  Not sure yet, but its something to watch out for before that ridge fractures and allows warmer, moist Pacific air to reach us.  So much uncertainty, so much fun!  I am really pumped up about all this uncertainty!

Valid at 5 PM December 22nd. This is really strong support for a major trough in the SW, and likely rain in southern AZ, Sutherland Heights around this time.

Below is the spaghetti dish for the “breakthrough” flow situation shown in the prog output valid for Christmas Day with some annotation on it.

Looking at the above, I think we can count on a breakthrough flow pattern from the Pac.  Where it barges into the West Coast will be subject to question over the next week or so.  That really can’t be determined right now.

I am sure those in southern Cal  hope, if there is a breakthrough from the Pac,  it comes in farther north than shown in the model run here today!  Patterns like the one shown in that  run  can routinely produce 10 inches in a day once they get going  should something burst through at low latitudes.

The brighter side would be that the chances of a significant rain here droughty southern AZ would at last  increase.

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.

 

Looking ahead to May, and something about the new Int. Cloud Atlas

April’s been kind of a weather dud here in Catalina so far (no rain so far, and the chance on the 20th, mentioned here some weeks ago, has receded to Utah and points north), so lets take a look at how May is shaping up, only two weeks ahead:

 Valid at 5 PM, May 2nd. Nice!
Valid at 5 PM, May 2nd. Nice!

I thought you’d be pretty happy when you saw this, as I was.

 

BTW, there is a new International Cloud Atlas out there.

Its possible there is a photo from Catalina, Arizona!  I have not checked yet.  Its just been published by the World Meteorological Organization of the United Nations.  Still needs a little work, but overall is VERY, very nice.  Came out out on March 23rd, so we’re a little behind here as usual.  The thing that makes it different from prior and sometimes flawed atlases is that each photo is accompanied by some weather data and in many cases maps, radar or satellite imagery at the time of the photo.

Some new expressions to toss around to your fellow cloud-centric folk are things like “Cirrus anthrogenitus”–Cirrus evolved from contrails and “Cumulus flammogenitus”, a Cumulus formed at the top of a fire, something we used to call, “pyrocumulus”, an unofficial term that somehow seems preferable to “flammo”.

However, something that has drawn great attention over the past 20 years or so was not given a name, aircraft-produced ice in Altocumulus and Cirrocumulus clouds, which have been referred to by Heymsfield and colleagues as “hole punch clouds.”1

Hole punch clouds pdf

Ice canals amid Altocumulus are also fairly common.  Ironically, a hole punch cloud with ice in the center, and an ice canal in an Altocumulus cloud layer can be readily seen on the new International Cloud Atlas submission site, now closed.  They’ve mistakenly, IMO, referred to “ice canal” photos as “distrails” without mentioning the ice canal “cirrus” down the middle.  Formerly, distrails were clearings produced by aircraft in thin clouds without any change of phase in the cloud induced by the aircraft, unlike those holes and clearings produced when the ice-phase is triggered by an aircraft passage.

Certainly a “hole punch” cloud is not a distrail, a linear feature, and should have a separate nomenclature.

In keeping with the new terminology regarding “anthro” effects, maybe it should be, since we’re talking about the Cirrus induced by an aircraft, albeit at much lower levels than true Cirrus clouds:

“CIrrus Altocumuloanthroglaciogenitus.”  (??)

Here’s a classic one of those that erupted over Catalina, posted here last January:

11:27 AM, January 2nd. The ice canal in the middle of an Altocumulus layer that might in the future be termed a Cirrus altocumuloanthroglaciogenitus.
11:27 AM, January 2nd. The ice canal in the middle of an Altocumulus layer that might in the future be termed a Cirrus altocumuloanthroglaciogenitus.

 

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5:53 PM. An example of the various cirriform clouds we’ve been treated to the past week or two, ones that have been giving us those nice sunrises and sunsets. Doesn’t seem like there’s been a cloud below 50,000 feet for about that long, too. (I’m exaggerating just a little.)
7:04 PM. Seems like sunsets are occurring later and later.
7:04 PM. Seems like sunsets are occurring later and later.  Here the setting sun allows some of the “topography” of Cirrus clouds to be accentuated.

 

The End

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1It should be pointed out immediately if not sooner  that Catalina’s Cloud Maven Person had plenty of time to rectify, or suggest changes to the Atlas as he could have been part of this process, but didn’t really do anything except submit some images for consideration.

More patterns galore, but with natural holes in them that made for an extra fascinating day!

The TUS balloon sounding launched at around 3:30 PM from the Banner University of Arizona
The Banner NWS TUS balloon sounding launched at around 3:30 PM from the Banner University of Arizona.  The temperature of the Cirrocumulus was indicated to be about -36° C, at about 26,000 feet above Catalina (29,000 feet ASL) and yet portions of the Cc had liquid droplets.  The higher vellums of Cirrostratus or Cirrus were located.

Photos of yesterday’s patterns

I could literally hear the cameras clicking all over Catalina and Oro Valley as these patterns showed up, moving in from the southwest as the increasing numbers of cloud-centric folk lost control of themselves.  Reflecting that general loss of control, which affected yours truly, too many photos will be posted here.  Below holey clouds with icy centers, but not ones caused by aircraft:

DSC_3203 DSC_3201 DSC_3198 DSC_3197 DSC_3187 DSC_3186 DSC_3181

And look closely at the fine patterns, lines and granulations in these shots!  Truly mesmerizing.

DSC_3222 DSC_3221But what’s missing in this photo above?  There was no iridescence seen around the sun where we normally look for it suggesting that those Cirrocumulus clouds nearest the sun were composed of ice crystals, and not tiny droplets.    Iridescence is rarely seen next to the sun due to ice crystals because they are usually the result of the freezing of existing droplets, that then grow rapidly as ice particles to sizes too large to produce diffraction phenomenon  close to the sun.  Where’s my Lear jet,  so’s I can confirm these speculations?!!  I would very much like to have one on “stand by”, in case I think of something.  Below, a wonderful example of no iridescence even though newly formed clouds are by the sun:

4:21 PM. An outstanding example of no iridescence, maybe one of the best ever taken!
4:21 PM. An outstanding example of no iridescence, maybe one of the best ever taken!  The power pole shows signs of being in an archaic neighborhood.

A jet runs through it

Or so I thought.  In this chapter of cloud-maven.com, we inspect the photos of a commercial jet flying at or near the level of these clouds and determine what happened.  I was quite excited to see this happen because we would now determine whether there were any liquid droplets in what to the eye of the amateur cloud watching person would be a liquid droplet Altocumulus clouds.  Here the size of the elements are just a bit too large to lump it into the Cirrocumulus category, if you care.  So, with heart pounding, took this sequence of photos:

4:23 PM. A commercial jet streams into it seems, the Altocumulus layer. Or did it? CMP thought so.
4:23 PM. A commercial jet streams into it seems, the Altocumulus layer. Or did it? CMP thought so.

Let is go zooming:

4:23 PM. Looks to have descended to below this layer. Note sun glint on aircraft.
4:23 PM. Looks to have descended to below this layer. Note sun glint on aircraft.
4:23 PM. Zoomin' some more.
4:23 PM. Zoomin’ some more.
4:26 PM. But, as the location of the aircraft path slipped downwind rapidly, there was NOTHING! I could not believe it! No ice canal with a clearing around it, and no contrail inside these clouds. The clearing would have occurred had the aircraft penetrated supercooled droplets leaving an ice canal. But, if the cloud was all ice, a penetration by an aircraft should have left a contrail, as they do in cirriform clouds. The conclusion? As close to this layer as the aircraft was, it did NOT apparently go into it. Amazing to this eye.
4:26 PM. But, as the location of the aircraft path slipped downwind rapidly, there was NOTHING! I could not believe it! No ice canal with a clearing around it, and no contrail inside these clouds. The clearing would have occurred had the aircraft penetrated supercooled droplets leaving an ice canal. But, if the cloud was all ice, a penetration by an aircraft should have left a contrail, as they do in cirriform clouds. The conclusion? As close to this layer as the aircraft was, it did NOT apparently go into it. Amazing to this eye.
4:25 PM. Looking downwind at those "Altocumulo-cirrus" clouds, all ice from almost the very leading, upwind edge due to that -36°C temperature they were at.
4:25 PM. Looking downwind at those “Altocumulo-cirrus” clouds, all ice from almost the very leading, upwind edge due to that -36°C temperature they were at.  Though overhead, as you saw in the photos below, they might be reckoned as plain Altocumulus, and not solely composed of ice ones.

By the way, if you caught it, there were a couple of standard, aircraft-produced, “hole punch” clouds at the very upwind, formative portion of this patch of clouds before it got here. These photos pretty much prove that the Cc at the formative end at that time was composed of highly supercooled droplets and that the passage of an aircraft produced ice, that caused a fall out hole.

1:52 PM. Hole punches caused by aircraft in the Cirrocumulus to Cirrus patch that moved over us later. Clouds like these do not move at the speed of the wind, about 60mph up there yesterday at this level, but rather, the air moves through it a hump in the airflow that moves much more slowly than the wind.
1:52 PM. Hole punches caused by aircraft in the Cirrocumulus to Cirrus patch that moved over us later. Clouds like these do not move at the speed of the wind, about 60mph up there yesterday at this level, but rather, the air moves through it a hump in the airflow that moves much more slowly than the wind.  Note the slight iridescence in the hole on the right.

 

The End–quite enough, eh?

Some optical stuff; some holey stuff

Once again we had a brief period of optical fireworks, as a rare “circumzenithal arc” developed overhead of Catalina in some Cirrus strands.  Hope you saw it and bragged about it to your less observant friends.   After saying that, follow it up in a moment of feigned reflection,  speaking to no one in particular, with a comment about “how sad it is when people don’t notice the beauty in the world around them.”   Your friend will appreciate what a sensitive person you are.  That would be great!

Here are the scenes so many missed because you only have SECONDS to see them light up, peak out and disappear (but I saw it!):

9:28:31 AM. First highlight begins, center, leading edge.
9:28:31 AM. First highlight begins, center, leading edge.
DSC_0927
9:28:44 AM. Here we go!
DSC_0933
9:29:43 AM. Starting to really light up!
9:30 AM. Where were you? Of course, like a rainbow, you would have to be where I was to see this exact sight, but I was alone.
9:29:45 AM.  Zooming in….   Of course, like a rainbow, you would have to be exactly where I was to see this exact same sight, but I was alone and therefore, the only person in the world to see this.
9:30:29 AM. Last little wisp of color goes over.
9:30:29 AM. Last little wisp of color goes over.

Whew, that was pretty much the climax of this event.  Began to relax. calm down,  as the possibility of seeing more “arcs”, began to fade.  No more Cirrus was upwind.

Most of these I have seen have been due to aircraft-produced ice particles (“APIPs”, as named by Rangno and Hobbs way back in 1983, J. Appl. Meteor.), i. e., contrail like events produced by aircraft that occur at much higher than expected temperatures in “supercooled” clouds.

No Altocumulus clouds were around this line of Cirrus uncinus clouds at the time this passed over, though there were plenty around, however.  Likely this was produced upwind by an aircraft in Ac clouds, and the Altocumulus droplet clouds just evaporated.

These aircraft produced ice clouds start out having prodigious, unnaturally high concentrations of ice, thousands per liter, and that in itself would lead, due to the competition of vapor among them, to tiny, pristine ice crystals like solid columns that would refract the sun’s light.  So, that’s my thought on the origin of this line of Cirrus uncinus, the line itself raising suspicions about its origin.  It extended much farther than shown in these photos, and was intermittent, likely reflecting where the Altocu was, and where there were holes in the coverage.

Then, a great cloud iridescence:

11:03 AM.
11:03 AM.  Iridescence, about as good as it gets.
11:07 AM. Iridescence lights up a portion of an Altocumulus cloud.
11:07 AM. More iridescence.  Hope you saw this, too.

 

Next, holey stuff.

Never seen anything quite like what happened in those quasi-laminar clouds that developed later in the morning over and near the Catalinas, so must show :

11:08 AM.
11:08 AM.  Intrusions of dry air started punching holes in clouds all over.
11:09 AM. Holes started to appear in adjacent clouds.
11:09 AM. Holes started to appear in adjacent clouds.
11:09 AM. Zooming in at this strange phenomenon.
11:09 AM. Zooming in at this strange phenomenon.
11:11 AM. Geeminy Christmas, the sky is falling!
11:11 AM. Geeminy Christmas, the sky is falling!
11:12 AM. Closer to life size here. Pretty remarkable. Outside border of hole seemed to have collapsing cloud filaments supporting a localized downdraft punch.
11:12 AM. Closer to life size here. Pretty remarkable. Outside border of hole seemed to have collapsing cloud filaments supporting a localized downdraft punch.
11:12: More holes began to appear next to the main one.
11:12: More holes began to appear next to the main one.
11:14 AM. More hole craziness!
11:14 AM. More hole craziness!
11:15 AM. Wow. Look at the complexity in that hole.
11:15 AM. Wow. Look at the complexity in that hole.
11:17 AM. This lenticular had an exceptionally smooth top, but a hole started to develop underneath and a little downwind.
11:17 AM. This lenticular had an exceptionally smooth top, but a hole started to develop underneath and a little downwind.
11:17 AM. Another dry air hole punch appeared. What an interesting day this has been so far, and its not even noon!
11:17 AM. Another dry air hole punch appeared. What an interesting day this has been so far, and its not even noon!

 

Well, as you could imagine,  I could go on and on about this, with many more photos, but need to quit here.  And besides, it pretty much cleared off in the afternoon, and the hole phenomenon ended.

The End.

—————————-

Yesterday, one of these went over (“the rest of the story”)

First, the background, precursor shot:

11:23 AM. Altocumulus perlucidus.
11:23 AM. Altocumulus perlucidus.

Then this, looking straight up when CMP first noticed it because he wasn’t paying attention:

11:24 AM.
11:24 AM.

A few minutes  later, as it moved away:

11:27 AM.
11:27 AM.

What happened?  How cold were these Altocumulus clouds?

(Answers printed upside down below).

There were more, off in the distance, too.

Here are a few more shots of this phenomenon:

11:29 AM. As it went over the horizon to the east.
11:29 AM. As it went over the horizon to the east.  You can really see how strange it made the sky look.  Note, too, the contrail from a much higher flying aircraft (at Cirrus levels).
4:02 PM. Those fine trails of virga, center of photo, were "probably" created by an aircraft. They don't look natural to me, though when this happens without producing a ice canal or a clearing, its much more difficult to be certain. Those trails look too flat, a result of likely very high concentrations of ice crystals, all of which remain small due to the competition for the vapor in that cloud, and would be too small to collide with cloud droplets. There would be no hole or canal because the rise rate of the layer is producing droplet cloud faster than the ice crystals could take it away. In the prior photos with the ice canal, which did not fill in, you can guess the rise rate of the layer that produced the Ac per was nil. Those clouds did not fill in as the ice settled downward and out of the layer. Whew, lotta typing just then.
4:02 PM. Those fine trails of virga (center of photo, trailing in strands to the right), were “probably” created by an aircraft. They don’t look natural to me, though when this happens without producing a ice canal or a clearing, its much more difficult to be certain. Those trails look too flat, a result of likely very high concentrations of ice crystals, all of which remain small due to the competition for the vapor in that cloud, and would be too small to collide with cloud droplets. There would be no hole or canal because the rise rate of the layer is producing droplet cloud faster than the ice crystals could take it away. In the prior photos with the ice canal, which did not fill in, you can guess the rise rate of the layer that produced the Ac per was nil. Those clouds did not fill in as the ice settled downward and out of the layer. Whew, lotta typing just then.
DSC_0878
5:23 PM. Numerous holes were being punched in that cold Altocumulus layer out to the southwest of us. If you are pretty observant, you know that there is an airway out there, often filled with contrails. These, though are likely produced by those aircraft below the normal Cirrus levels, but rather would be ones departing or landing, in descent or climb modes, maybe from TUS?
5:41 PM. Pretty, but not natural.
5:41 PM. Zooming; pretty virga, but not natural.

Now, we’re really quitting because I have other things to do, ones that have to be done, like discovering why our attic has so many rodents in it?  Well, one, every so often,  dammitall.  Why is life one problem after another?

2017010212Z_SKEWT_KTUS
The pre-dawn TUS sounding, PRESUMMED representative of that Ac per layer. It would have been where the two lines pinch together, and if somehow you can read the temperature, its between -25° and -30° C.
For the evening aircraft effects, there are two choices of layers. Probably was the lower, warmer one IMO.
For the evening aircraft effects, there are two choices of layers. Probably was the lower, warmer one IMO.

——————————–

Answers not printed upside down instead:

It was an ice canal created in a highly supercooled layer of Altocumulus perlucidus.  How cold?  Whenever you see one of these in  a middle cloud like Altocumulus, you can guess that its colder than -20° C.  They’re rarely seen in warmer clouds.  The TUS soundings suggested this layer was between -25° and -30° C.  It mostly was ice free, bur regions of some slight (natural virga) were seen,

It was probably created by a jet, though the rarer prop aircraft can’t be ruled out.  Seems to be associated with cooling around prop tips or some say over the wing cooling momentarily below around  -40° C, though visually I would offer that  its from the water-loaded exhaust, at least in jets, rather than air cooled as it goes over the wing.

The End

Strange sunset brew of clouds and color; but was it natural?

Cutting to the chase:  I don’t think so.

Yesterday,  after an ordinary beginning,,  finished in a spectacular, if likely artificial way.  Let us work our way through yesterday’s cloudulations:

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7:39 AM. I thought this was a cute display by this little cloud, making its own little shadow rays as the sun made its way up from behind the Catlinas.
7:40 AM. But what kind of cloud is it? It, to these eyes, is all ice, but LOOKS like an Altocumulus cloud. But those clouds are all or mostly comprised of liquid drops. And you can see that this little guy is well BELOW a higher layer of ice cloud, we might call CIrrostratus, or a thin Altostratus. Oh, well, let’s move on to something explicable….

 

7:41 AM. Hmmmm. Quite a linear virga feature over there.
7:41 AM. Hmmmm. Quite a linear virga feature over there.  There are THREE cloud layers evident here, a thin Altocumulus layer, that dark cloud on the left, and patch of what I could call, Altostratus extending from the left corner to the right corner, and a thin layer of CIrrostratus on top.
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7:41 AM. Let’s go zooming and check it out…. Though we don’t know for SURE, anytime you see this kind of linear virga anomaly, you should be smelling aircraft exhaust.  Now, when you think about our fabulous sunset last evening and what that looked like, take a closer look at this photo.

Later that morning…..

10:53 AM. 10:47 AM. It was nice to see low clouds topping Sam Ridge, the lower boundary layer air (where convection takes place) moist for a change.
10:53 AM. It was nice to see low clouds topping Sam Ridge at dawn yesterday, the lower boundary layer air (where convection takes place) moist for a change.  Later they devolved into small Cumulus (humilis and fractus).
3:29 PM. A day with mostly ice clouds on top of Catalina, but here, off in the distance below the Cirrostratus, is an invading layer of Altostratus and Altocumulus that will set the stage for sunset glory later.
3:29 PM. A day with mostly ice clouds on top of Catalina, but here, off in the distance below the Cirrostratus, is an invading layer of Altostratus and Altocumulus that will set the stage for sunset glory later.  You may be able to detect a faint halo, upper center.  By the way, Cirrostratus typically deepens downward to morph into Altostratus, usually an ice cloud, too, but is deep enough to produce gray shading, and when its really thick or has embedded droplet clouds, hides the sun.
4:02 PM. Yep, moving right in.
4:02 PM. Yep, moving right in.  This is a very complex scene.  There’s aCirrostratus ice layer. upper right quadrant , on top of everything.  Below that, what appears here as a distinctly lower separate layer, a mix of Altocumulus (those dark cloudlets composed all or mostly of liquid droplets) and Altostratus (mostly or all ice, the smudgy more diffuse dark areas) .  We can never forget that Altocumulus can morph into Altostratus, which would then be called, “Altostratus altocumulotransmutatus.”  Tell that to your friends!  (Well, maybe not.)
4:15 PM. Caught this bumpy aircraft contrail at CIrrus levels. Look how how the exhaust and water vapor that formed this, though output from an aircraft in a steady state, how the wing tip vorices (apparently) get entertwined at regular intervals with more exhaust and water vapor in those blobs.
4:15 PM. Caught this bumpy aircraft contrail at CIrrus levels. Look how how the exhaust and water vapor that formed this, though output from an aircraft in a steady state, how the wing tip vorices (apparently) get entertwined at regular intervals with more exhaust and water vapor in those blobs.

But let’s go zooming up to flight level and take a closer look for a second:

A mammatus (or as the ladies like to call it) testicularis contrail. Almost certainly this is due to combining wing tip vortices. Many aircraft now have devices to defeat wing tip vortices, phenomenon that reduce flight efficiency.
A “mammatus” (or as the ladies like to call it. a testicularis contrail (the resemblances are pretty good). Almost certainly this is due to combining wing tip vortices.  Many aircraft now have devices to defeat wing tip vortices, phenomenon that reduce flight efficiency.  In both cases above, the ice particles have not grown enough to produce fallstreaks.  These images tell us that SOME aircraft that produce ice in supercooled Altocumulus clouds, as we in Catalina have seen lately, are likely to have bunches of ice trails rather than a continuum if produced in a uniform cloud, anyway.

Now, where was I?  Got mammatus on my mind again. I love mammatus so much…   Oh, yeah, that sunset yesterday…..

5:13 PM. Ran out to check sunset status, and saw this feature advancing rapidly toward Catalina.
5:13 PM. Ran out to check sunset status, and saw this feature advancing rapidly toward Catalina.
5:18 PM. Zoomed view; getting close to passing overhead. You might be able to notice that these pretty regularly spaced trails are BELOW the Altocumulus clouds, and there's a clearing that's been produced. All evidence of an artificial production of these trails. But belng below the Altocu, you might also have started to wonder whether the setting sun would light them up....
5:18 PM. Zoomed view; getting close to passing overhead. You might be able to notice that these pretty regularly spaced trails are BELOW the Altocumulus clouds, and there’s a clearing that’s been produced. All evidence of an artificial production of these trails. But belng below the Altocu, you might also have started to wonder whether the setting sun would light them up….

And the sun did its job….producing one of the greatest sunset scenes we’ve seen in a long time, even if phony (haha):

5:23 PM. Not zoomed, still a few minutes away to overhead passage. Very exciting to think this was going to pass overhead!
5:23 PM. Not zoomed, still a few minutes away to overhead passage. Very exciting to think this was going to pass overhead!
5:23 PM. Zoomed view. Again the pretty regular spacing is circumstantial evidence that nature didn't do it.
5:23 PM. Zoomed view. Again the pretty regular spacing is circumstantial evidence that nature didn’t do it.
5:25 PM. Thank you sun! Looks pretty round again, which is good.
5:25 PM. Thank you sun! Looks pretty round again, which is good.
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5:27 PM. Oh, so pretty.
5:27 PM.
5:27 PM. Zooming again. Wow.
5:28 PM. Another view of the same thing.
5:28 PM. Another view of the same thing.
5:28 PM. Our trails compared to the rest of the Altocumulus deck. Not much going on elsewhere in the way of natural virga.
5:28 PM. Our trails compared to the rest of the Altocumulus deck. Not much going on elsewhere in the way of natural virga.
5:29 PM. Taking WAY too many photos of the same thing. Out of control... Here I demonstrate that with another photo of the same thing.
5:29 PM. Taking WAY too many photos of the same thing. Out of control… Here I demonstrate that with another photo of the same thing.

 

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5:30 PM. After the trail hoopla, it was time to concentrate on the fabulous sunset taking place to the southwest of Catalina.
5:30 PM. Zooming in on interesting features; long trails, one with a clearing above it. Was it another aircraft-induced trail of ice and clearing above it? Probably. The trails to the left aren't as obviously produced by an aircraft, but I do think so anyway in this burst of objectivity. Recall that I have been trained as a "scientist" and don't care if I am wrong, but only about truth, as best as I can make it out.
5:30 PM. Zooming in on interesting features; long trails, one with a clearing above it. Was it another aircraft-induced trail of ice and clearing above it? Probably. The trails to the left aren’t as obviously produced by an aircraft, but I do think so anyway in this burst of objectivity. Recall that I have been trained as a “scientist” and don’t care if I am wrong, but only about truth, as best as I can make it out.

Finally, let look at the TUS sounding for last evening, see how cold those Ac cloud were with the ice trail in them:

The Tucson rawinsonde balloon launch yesterday at about 3:30 PM. Goes up at about 1,000 feet a minute, so takes about 100 minutes to get to 100, 000 feet. They pop somewhere around that height or a little above. THought you like to know that. They have a little parachute to that when they come down, they don't bonk you too hard. Once in awhile people find them in remote areas downwind.
Results of the Tucson rawinsonde balloon launch yesterday at about 3:30 PM. Goes up at about 1,000 feet a minute, so takes about 100 minutes to get to 100, 000 feet. They pop somewhere around that height or a little above. THought you like to know that. They have a little parachute to that when they come down, they don’t bonk you too hard. Once in awhile people find them in remote areas downwind.  You can send them back in to the NWS, too!

The astounding thing here, something that goes against everything I believe about clouds, is that it is indicated that the Altocumulus, lacking much natural ice, was at -30° C!  Yikes!  No wonder aircraft were producing ice trails and stuff yesterday afternoon.

You have to conclude there were almost no natural “ice nuclei” up there at, oh about 24,000 feet above sea level.  This is not the first time for such an occurrence of liquid clouds sans much ice at low temperatures1, but they are rare IME.  This would never occur in a boundary layer cloud, that is, one where material from the earth’s surface is getting into the clouds,  like the omnipresent dust, or biogenic ice nuclei.

The weather ahead

Some “fantasy” storms with rain in them for Catalina, are now seen on the model predictions beyond a week.  Spaghetti is favoring this new development now.  So, something to keep an eye on.

The view from here?  Precip here is “in the bag” because going on subjective feelings, I really want to see a good rain here!

 

The End

——————————
1The famous John Hallett said he saw an Altocumulus lenticularis sans ice at -35°C in a conference preprint! Rangno and Hobbs (1986) claimed to have detected droplets in Altocumulus like clouds at the top of a storm on the Washington coast at -44°C. Their claim, first published in a conference preprint, was later rejected by the J. Atmos. Sci.

In case you missed them…a 2008 full moon and, moving ahead, yesterday’s sunrise

The full moon of December 11, 2008. Thought maybe you'd like to see it again coming up over the Catalinas.
The full moon of December 11, 2008. Thought maybe you’d like to see it in case you missed it, or see it again if you did see it.  Maybe you had a special memory with this moon.
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7:09 AM. Altocumulus perlucidus with a little lenticular underneath.
7:43 AM.
7:10 AM. Zooming and zooming.
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7:10 AM. Zooming some more.
7:14 AM. Iridescence is evident in the cloud ripples just above the mountain silhouette.
7:14 AM. Iridescence is evident in the cloud ripples just above the mountain silhouette.
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7:16 AM, Contrails were soon visible in our Altocumulus layer, the aircraft making it at the right edge of the photo. Appeared to be in a climb out going right to left. And, when you see these “high temperature contrails” in Altocumulus, you can be sure ice will form and rifts will develop as a little bit of light snow develops and falls out.  The jillions of ice crystals in the contrail cause the droplets in the Altocumulus to evaporate, in a way, gutting it. An ice crystal is like a low pressure center when amid droplets;   the droplets evaporate and those water molecules deposit themselves on the ice crystal, a process named after the discoverers, Wegner-Bergeron-Findeisen.   Eventually the crystal is large enough to settle out and a clear streak results unless the air is rising rapidly and can replace the droplets (as generally happens in storms).  Sometimes the lift in the Altocumulus layer is enough that a clear canal caused by an aircraft can fill back in after many minutes.
7:18 AM. Two aircraft contrails, about a minute old.
7:18 AM. Two aircraft contrails, about a minute old.  After two or three more minutes, they will not be visible within the cloud, though ice is forming, decimating the droplets around the intense streamers of ice in the contrail.
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7:28 AM. The small ice canal (the ice is hanging just below the Altocumulus clouds–kind of hard to make out, but its there.
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7:42 AM. Those little clear streaks are hardly noticeable now, partly because they were quite narrow, and because of perspective and things bunching up in the distance.

 

From the Cowboys in Laramie, Wyoming, this TUS sounding for yesterday morning in the pre-dawn hours:

Suggested locations of cloud layers. The Altocumulus layer in which the contrails were embedded seems to be at -25°C, a "normal" temperature for this kind of "high temperature contrail". In general contrails are not supposed to occur until the temperature is below about -35° C and the air is moist, thus they are usually seen amid or near Cirrus clouds. not down in Altocumulus.
Suggested locations of cloud layers. The Altocumulus layer in which the contrails were embedded seems to be at -25°C, a “normal” temperature for this kind of “high temperature contrail”. In general contrails are not supposed to occur until the temperature is below about -35° C and the air is moist, thus they are usually seen amid or near Cirrus clouds. not down in Altocumulus.   See usual contrail height at Cirrus levels  in moon photo.

As the morning wore on, the Altocumulus deck faded away, moving east, and we were left with some Cirrus clouds, but what kind?

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10:58 AM. Cirrus of some type, but notice there is absolutely no fibrous details (strands and such) as we normally see in Cirrus.  Could be transverse waves in a Cirrostratus deck since Cirrostratus can be fog like, have no detail, in a version we call, Cirrostratus nebulosus.  The up and down motions would cause clearings perpendicular to the wind up there.  The lack of strands and uniformity in these bands suggests very tiny ice crystals, ones having very little fallspeeds.
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2:34 PM. Some nice “hovercraft” clouds, Altocumulus lenticularis off in the distance SSW. Hung around out there for a couple of hours.
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3:17 PM. This one appeared to be concave upward, which was a little odd. Zoomed view next.
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3:17 PM. Looks like the inside is higher than the outside. Huh.

Well, that was  it for photography yesterday.

Doesn’t seem to be any reliable indication of rain in sight.   Oh, sure, rain here pops up in the models almost every day, but its about 12-15 days out.  As the model gets closer to the day it predicted rain, it seems to go away like the “water mirage” on a hot paved road; always ahead of you, but you never get to it.  We’ve had some major rains indicated in the models as of a few days ago, but spaghetti was never very high on those events (clustering those crazy lines in a trough over us), so it wasn’t even worth mentioning.

And, even that rain is a gonner in the model runs from last night!

The End

A stragne and wonderful day

Many strange1  and wonderful sights were seen yesterday; I could feel the excitement out there as one cloud  microstructural mystery after another regaled our Catalina skies.

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7:24 AM. Here, a tiny highlighted flake of Altocumulus floating above a mass of light snow/ice crystals, maybe straight below it. This is one the classic mysteries we deal with in “cloud microstructure”;  the oddity of nature preferring to generate a droplet before an ice crystal at least to somewhere in the -30°s C. Liquid clouds often are at the top of Altostratus and Nimbostratus (rainy or snowy days) providing the tops aren’t too much colder than -30° C. How strange is it to have liquid water at the lowest temperatures in a cloud system, with all the ice and snow underneath, as shown in this photo (though here they are no longer connected).
7:24 AM/ I think there is itty bitty droplet cloud at the very top bright dot there.
7:24 AM/ I think there is itty bitty droplet cloud at the very top bright dot there.  A droplet cloud was likely much broader to have produced all the ice we see below that bright dot of liquid cloud.
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7:26 AM. Looking afar, to the SW, there’s what appears to be an Altocumulus (droplet cloud) with a few ice crystals underneat it, especially to the right.

How cold are these clouds?  Lets look at the TUS sounding, launched at about 3:30 AM yesterday morning.

The TUS rawinsonde balloon data for yesterday morning before dawn.
The TUS rawinsonde balloon data for yesterday morning before dawn.  That Altocumulus layer, and the other clouds above were likely at the pinched point above, topping out at -27°C and up around 23,000 feet above sea level (400 millibars), pretty darn cold.  But, as you saw in the 3rd photo, not a lot of ice is being generated at this temperature by that patch of Altocumulus clouds to the SW.  Not sure why, but its pretty remarkable and that is likely due to small droplet sizes AND a lack of ice nuclei, most of which are known to originate with soil particles  When you see these rare occurrences of all or mostly droplet clouds at low temperatures (<-20° C in particular, get ready to see hole punch and ice canals produced by aircraft, a kind of inadvertent cloud seeding.

That bank of Altocumulus was racing at more than 50 mph toward Catalina, and so it got here in a hurry.    And, as it got closer, it was also getting more into some airways at that height, possibly descents into PHX since the height of those clouds was below normal jet cruising levels at 23,000 feet Above Sea Level.

7:55 AM. This is one of the strangest sights I have ever seen. Why? On the left side of this photo, the clouds are completely glaciated, composed of ice, while along a line to the right, there's no sign of ice in Altocumulus clouds that appear to be at the same height (namely, temperature). I have no explanation for this scene, except those involving a lot hand-waving, so we'll just let go.
7:55 AM. This is one of the strangest sights I have ever seen. Why? On the left side of this photo, the clouds are completely glaciated, composed of ice, while along a line to the right, there’s no sign of ice in Altocumulus clouds that appear to be at the same height (namely, temperature). I have no explanation for this scene, except those involving a lot hand-waving, so we’ll just let go, except that we speculate that the Ac layer was a little lower (warmer)?  Could have been.

Now for the aircraft effects.  Hardly a few minutes go by before aircraft began marking up this cold Altocumulus layer.  Notice that it doesn’t seem to be producing much or any ice on its own, making aircraft inadvertent seeding lines and holes where tremendous numbers of ice crystals are generated immediately present.   Here’s the first of many:

8:16 AM. An icy canal due to the passage of an aircraft rips through this pristine layer of Altocumulus whose temperature was around -25° C.
8:16 AM. An icy canal due to the passage of an aircraft rips through this pristine layer of Altocumulus whose temperature was around -25° C.  The view is looking S toward Tucson, but is unlikely to have been an aircraft landing there because this layer was above 20,000 feet Above Sea Level.  An aircraft lanidng at TUS would be much lower, this close.  The passage of the aircraft was likely 10 or more minutes before this photo.
8:19 AM. The ice canal is broadening due to turbulence, and ice is not plainly evident to all Cloud Maven Juniors or we will have to go over discerning ice from droplet clouds at the next club meeting.
8:19 AM. The ice canal is broadening due to turbulence, and ice is not plainly evident to all Cloud Maven Juniors or we will have to go over discerning ice from droplet clouds at the next club meeting.
8:20 AM. A view of the northwest end of this aircraft-produced ice canal. Several others became apparent, too.
8:20 AM. A view of the northwest end of this aircraft-produced ice canal. Several others became apparent, too.

Heading for Catalina, this:

9:11 AM. Heading for Catalina, a whole mess of aircraft induced ice in that poor Altocumulus layer. The hole punch was likely due to an aircraft climbing out of or descending into TUS. The age of a hole that large, with ice below it like this would be something of the order of at least half an hour to an hour old. Just behind the hole is a new contrail in the Ac clouds,
9:11 AM. Heading for Catalina, a whole mess of aircraft induced ice in that poor Altocumulus layer. The hole punch was likely due to an aircraft climbing out of or descending into TUS. The age of a hole that large, with ice below it like this would be something of the order of at least half an hour to an hour old. Just behind the hole is a new contrail in the Ac clouds,
9:23 AM. Hole punch area and ice canal arrive over Catalina! Losing control here, taking photo and photo, now looking for stragne optics, usually observed with aircraft produced ice particles because they are so numerous, compete for the available moisture and therefore remain tiny and perfect, prisms, plates, short column ice crystals, ones that can do a lot of optical stuff.
9:23 AM. Hole punch area and ice canal arrive over Catalina! Losing control here, taking photo and photo, now looking for stragne optics, usually observed with aircraft produced ice particles because they are so numerous, compete for the available moisture and therefore remain tiny and perfect, prisms, plates, short column ice crystals, ones that can do a lot of optical stuff.

Here’s the south end of that ice canal:

9:24 AM.
9:24 AM.  Also note iconic horse wind vane, and real wind vane atop a personal weather station.  Doesn’t everyone have a “PWS”?

Looking straight up at the icy heart of a hole punch region caused by an aircraft.  I am sure you have never done this before!  This is gonna be a great blog with all these new things for you!

9:27 AM. Look at the detail in the ice, those fine, fine strands! Amazing. The thickest strand might be due to the higher liquiid water in the heart of one of those little Altocumulus cloudlets. ???
9:27 AM. Look at the detail in the ice, those fine, fine strands! Amazing. The thickest strand might be due to the higher liquiid water in the heart of one of those little Altocumulus cloudlets. ???  Look how much wind shear there is, those little itty bitty ice crystals falling so far behind the parent cloud, the streamers flattening out because the poor little guys, already undersized to begin with, are getting smaller and smaller, the fall velocity getting less and less until the strands are almost horizontal.
9:27 AM. Looking at this gorgeously uniform layer of Altocumulus perlucidus 9honeycomb of elements) translucidus (no shadows).
9:27 AM. Looking at this gorgeously uniform layer of Altocumulus perlucidus 9honeycomb of elements) translucidus (no shadows).  To me this is a phenomenal scene, though maybe to u, not so much, which is understandable.
9:30 AM. The expected intense optical phenomena began to occur in these aircraft contrail remains.
9:30 AM. The expected intense optical phenomena began to occur in these aircraft contrail remains.  Here a parhelia, or sundog.  More fireworks in a bit.
9:30 AM. While the parhelia was in its full display, very intense, this was the ice canal passing overhead. Look at the regular spacing of these strands of ice, Might be due to the spacing of the cloudlets in the Altocumulus layer, the spaces between them not producing much ice, or, as we know, contrails tend to clump behind the aircraft likely due to wingtip vortices interacting and combining masses of exhaust water and crud.
9:30 AM. While the parhelia was in its full display, very intense, this was the ice canal passing overhead. Look at the regular spacing of these strands of ice, Might be due to the spacing of the cloudlets in the Altocumulus layer, the spaces between them not producing much ice, or, as we know, contrails tend to clump behind the aircraft likely due to wingtip vortices interacting and combining masses of exhaust water and crud.   This is now about an hour and fifteen minutes old, since we saw it way out to the west at 8:16 AM shortly after it formed.
9:37 AM. Here's what a new aircraft contrail in these clouds looks like, this one about 60 s old looks like
9:37 AM. Here’s what a new aircraft contrail in these clouds looks like, this one about 60 s old looks like.  Note all the irregularity in the contrail from the get-go.

As the south end of the original ice canal began to enter the refraction zone for simple ice crystals around the sun, usually at the 22° degree halo position, things began to light up with a particularly bright circumzenithal arc (more often observed on a halo) or colorful (in this case) partial  “reverse halo”.   The colors (iridescence)  due to the refracting of light within very small ice crystals.   Normally iridescence is seen near the sun in Cirrocumulus clouds or the then edges of other droplet clouds.   Very exciting.

9:44 AM. Halo curving in the wrong direction, away from the sun!
9:44 AM. A part of a halo curving in the wrong direction, away from the sun! (This is actually called a circumzenithal arc).
9:44 AM. Taking up you up thousands and thousands of feet via a zoomed view.
9:44 AM. Taking up you up thousands and thousands of feet via a zoomed view.   Pretty cool, eh?  Notice how much its moved in just seconds,  You really have to let your coffee get cold if you’re a photographer and you want to get the best shots of this kind of phenomenon.  You really can’t do anything but keep watching every second!
9:44 AM, again. All these changes took place within the minute between 9:44 and 9:45 AM!
9:44 AM, again. All these changes took place within the minute between 9:44 and 9:45 AM!  Here, the next grouping of ice strands is being lit up.
9:48 AM. Just a pretty scene. Altocumulus perlucidus translucidus, pocked with aircraft contrails, if you look real close.
9:48 AM. Just a pretty scene. Altocumulus perlucidus translucidus, pocked with aircraft contrails, if you look real close.  Make me move:  $1 billion dollars…
9:54 AM. Its not even 10 AM and now this comes along, this fabulously complex zone of CIrrocumulus (at the same level of the Ac clouds) at the tail of the Altocumulus. You can see the much higher Cirrus going crossways, lower center. See TUS sounding for height of Ci.
9:54 AM. Its not even 10 AM and now this comes along, this fabulously complex zone of CIrrocumulus (at the same level of the Ac clouds) at the tail of the Altocumulus. You can see the much higher Cirrus going crossways, lower center. See TUS sounding for height of Ci.

Then this strange sight:

12:29 PM. A row of Altocumulus or Cirrocumulus, each formed by a little upward bump in the atmosphere of a layer just a hair below saturation. Just rising a few hundred feet or so causes these cloudlets to form. Why aren't they everywhere? Might be drier. Bumps like this are always present in the atmosphere, especially if there are mountains upwind.
12:29 PM. A row of Altocumulus or Cirrocumulus, each formed by a little upward bump in the atmosphere of a layer just a hair below saturation. Just rising a few hundred feet or so causes these cloudlets to form. Why aren’t they everywhere? Might be drier. Bumps like this are always present in the atmosphere, especially if there are mountains upwind.  Not taken while driving, of course, ; just looks like it thanks to photoshop.

The day closed out with a lower layer of Altocumulus moving in, this layer, according to the TUS sounding, at “only’ -17° C, and little ice detected.  Below, at 2:09 PM:

2:09 PM. Altocumulus perlucidus translucidus. A natural conversion to ice is occurring on the right side of the photo.
2:09 PM. Altocumulus perlucidus translucidus. A natural conversion to ice is occurring on the right side of the photo.
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4:42 PM. So pretty these Altocu.

 

4:41 PM. A strand of finely patterned Cirrocumulus shot out of the SW as the sun declined.
4:41 PM. A strand of finely patterned Cirrocumulus shot out of the SW as the sun declined.
The Tucson afternoon rawinsonde . launched around 3:30 PM.
The Tucson afternoon rawinsonde . launched around 3:30 PM.  The Cirrocu in the above photo was likely also at the Cirrus level indicated above.

U of AZ mod thinks so light rain will develop around here in the mid-later afternoon.

The End

—————————————–

1“stragne” above, originally an inadvertent typo, but left in place as another cheap trick to get draw the curiosity of readers who might wonder what stragne is.