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.


By Art Rangno

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


  1. Great photos and descriptions, Art. I particularly like the 9:03 am one, but all are instructive. Thanks a lot for taking the time to post and explain the pictures.

    That sundog in the last pic must have been really intense to the eye, given its brightness in the picture.

    1. Hi, Jon,

      Thanks for your comment. It quite a day, don’t remember one where so many of those hole punch and ice canals have occurred. Usually, the clouds lower to higher temperatures, clear off, or something disturbs the special conditions. The brightness of that sundog was one of the things that made me think the ice crystals were artifacts from an aircraft.

      Good to hear from you, Jon! Will be posting some spectacular Cirrus from yesterday today.

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