Less splotchy; more filling

The clouds yesterday were supposed to be “splotchy”, big clearings between interesting middle clouds like Altocumulus with long virga strands.  Instead there was a vast coverage of Altostratus opacus “dullus” with long streaks of virga, with a few drops reaching the ground here and there but not here.  There was some mammatus-t clouds, too.   Also, the end of the clouds didn’t get here until after nightfall, not in the afternoon as anticipated from this keyboard.

The result was a much cooler day than expected, too.   On TV, they were talkin’ low 80s for yesterday, a reasonable expectation given “splotchy clouds”, but in Catalinaland, it only reached 73 F under the heavy overcast.  Very pleasant for being out-of-doors.

Oh, well.  Maybe I’ll try building model airplanes and talk about those instead. Or make up historical anecdotes that aren’t true, mixing characters up from different eras and see if anybody notices.  Now that would be fun! (Naw.  Too silly.)

Here’s your day, beginning just before sunrise when some fabulous, fine-grained Cirrocumulus clouds came over top:

6:31 AM.  Finely grained Cirrocu top of photo, line cloud would also probably qualify as Cc, though calling it Ac would not result in a fine from C-M.
6:31 AM. Finely grained Cirrocumulus (Cc) top of photo, line cloud would also qualify as Cc, though the granulation is larger, still not large enought to be Altocumulus.  With a little imagination, the top center cloud appears to be hanging down like those house Christmas lights.
Also at 6:31 AM. Here are your splotchy clouds. I can’t believe how good the forecast is going after an hour! There some much ice in the center cloud that you’d have to call it Cirrus spissatus, but an hour ago it was likely an Altocu cas, or floccus, one at very low (not “cold”, to be proper) temperatures.
7:41 AM. Clearings between clouds disappearing! Passing by, and from a thick Altostratus opacus cloud, a display of mammatus/testicularis left center (trying to be even-handed here in cloud nomenclature).


Also at 7:41 AM. More mammatus-t over there, too. My mind has kind of drifted off to mammatus now. Quite nice dispay here. Note: Not associated with thunderstorms, as some urban myths have it.  Look, I’m trying to make a dull day interesting.  Its hard.
1:04 PM.  Line of heavy virga from what else, Altostratus opacus, tops at Cirrus levels.  Chance of late sun pretty much gone by now.  BTW, if you saw a time lapse of mammatus clouds, you would see that the upside down Cumulus turret look, opens up to fibrous little shafts like these.
1:04 PM. Line of heavy virga from what else, Altostratus opacus, tops at Cirrus levels. Chance of late sun pretty much gone by now. BTW, if you saw a time lapse of mammatus-t clouds, you would see that the “upside down Cumulus turret” look (as in the prior two shots), open up to fibrous little shafts like these.
6:50 PM.  Good sunset, not great, as backside of As clouds finally comes into view on the horizon.
6:50 PM, just before Husky softball defeated No. 2, ASU last night in Tempe, the heart of devil-land. Good sunset, not great, as backside of Altostratus (As) clouds finally comes into view on the horizon.  The lower cloud specks at the base of the As layer are those comprised of droplets, not ice, as is the higher As.  This shot helps show how different in appearance clouds of the two phases,  liquid and ice, are. When they’re together, mixing it up, we call that a “mixed phase” cloud.  Because there are so many particles that droplet clouds can form on (typically, in continental settings, there are hundreds of thousands per liter) those clouds have more detail and the drops are too tiny to fall as precip.  In the higher Altostratus layer, the concentrations of ice particles that comprise it are probably only in the tens per liter, and those ice crystals/particles are far larger than the droplets in droplet clouds.    Most of the ice particles in the As, therefore,  are settling downward, evaporating.  However, all ice clouds can produce light precipitation to the ground, one of the THREE ways we get precip out of clouds; all ice, mixed phase, and all liquid processes.  (Some textbooks I’ve seen only talk about the latter two, BTW.)





















































































If you want, you can go to this loop from the U of WA Huskies Weather Department here and see how the little splotchy cloud thing with that passing upper trough became a big fat thing as it came by.  Also in this retrospective, you should examine the U of AZ Weather Department time lapse film.  You’ll be amazed at all the stuff going on in a day that looked pretty dull all in all.  Also, at the end (after 5 PM AST) you’ll seen the winds aloft change completely in direction as the backside of the trough, the clearing side, approached.  I saw stuff I didn’t know was happening.  You’ll also see how the mammatus pouches, if I may, open up into fibrous virga.  Thank you, U of AZ Weather Department, for posting these great instruction films!

Not expecting clouds for most of today, but will likely see a couple of Cirrus streaming in from the NW late.

The weather ahead

Still no precip in sight, unless you consider lithometeors a form of precip, dust accumulations, that is, such as we had a few days ago.  Half inch (of dust) I predicted wasn’t that bad (hahahah).  Dust accumulations expected now on the afternoon of the 16th, and again on during the afternoons of the 25th and 26th of April.

C-M alive, local, and… finished with the dust report, now back to the studio.

The End.

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.