First of all, let me assure quesy readers that the jet leaving the contrail at left was not “flaming out” and about to crash as it traversed the sky at this time, as the staccato nature of the contrail at left might suggest. The staccato nature of the contrail is due to vagaries of humidity at flight level. Where it was quite dry, the contrail disappeared immediately behind the jet.
Its a little unusual to see such short segments like this, however.
What was really interesting and a bit inexplicable (again) except via a LOT of hand-waving is the crossing patterns seen in the clouds at left and in the next shot. Pretty darn remarkable. In the second photo, icy strands of cirrus (“fibratus”-the strands are straight in this variety) are seen running SE-NW, “whilst” above there are Cirrocumulus clouds with ripples and little cloudlets oriented from SW-NE! All of these clouds were moving rapidly from the SW.
Maybe its too complicated; we should forget about it and go to the movies. Well, the cloud movies…
Here is yesterday’s cloud movie presented by our own University of Arizona Wildcats. This will help.
First, if you take the time to load this time lapse movie, you will enjoy the tiny cloud “tumbleweed” that goes by at 12:02 PM. It really acts like one, as you will see! Its an entertaining sight, and one that illustrates the wind shear in the atmosphere yesterday.
And that’s what these remarkable crossing cloud configurations are about, changes in wind direction and speed with height, something we “met men” call “wind shear.”
Some of the clouds in the second photo passed within the viewing area of the U of A time lapse movie between 1:59 and 2:03 PM LST and you can just make out the cirrus clouds going by with their lower portions draining off to the right very slowly. In these blog photos, looking as those clouds approached from the SW, the trails appear to originate on the right and “drain” to the left, a mirror image.
Ice crystals in cirrus clouds often form in sudden appearing, tiny flocculent specs like the Cirrocumulus (Cc) clouds. In these photos, in these photos, the Cc clouds are above the icy cirrus clouds. What normally takes place is that the ice crystals grow and the largest ones fall out producing strands below the “head” of the cloud. The slower they fall, the more apt the fallstreak is to be drawn out over a long distance away from where the burst of ice formation took place, and if there is a sharp wind shear, the more angled and contorted the trail will look. Still, at right angles? The Tucson sounding for yesterday afternoon doesn’t reveal much wind shear in the moist layer where these clouds were forming, 23, 000 to 27,000 feet above sea level. On the other hand, balloon soundings would not show extremely sharp changes in wind direction/speed over very small height increments. So, it remains somewhat of a mystery. In view of the orientation along the jet airway upwind of this site that runs in the direction of the line cirrus in these photos, it is possible that these are contrail remnants. There jets that flew at low enough altitudes at times to glaciate some of the Cc-Altocumulus clouds and one short ice trail produced by an aircraft in them can been seen in the U of A movie at 2:43 PM.
Along with these interesting alignments were numerous optical phenomena yesterday, some of which I could not identify, such as in these three. I suspect the first one is something called a parhelic circle, if you happened to have seen this bright arc radiating away from the sun’s position. A bit more mysterious, at least to me, was the sudden brightening of the contrail segment above the Catalinas and the cirrus (uncinus) cloud, last two photos.
OK, enough. I tried my best to explain everything and I have failed.