WHAT a gorgeous day was yesterday! Perfect. No wonder the northlanders come here in their droves now! Its great to see (via the increasingly larger number of out-of-state license plates) all the people that want to be where I am already!
While waiting for the storms and cold air just ahead now, this cloud commentary:
Along with the pretty high and middle clouds was a rarely seen phenomenon, aircraft flying into those “supercooled” Altocumulus droplet clouds were converting them to ice in their wakes. These are similar to contrails, called by me, APIPs, Aircraft Produced Ice Particles. That’s right, your Catalina Cloud Maven person named that phenomenon, though its not a great name since it could apply to usual contrails as well. Modest brain strained hard, but couldn’t come up with anything better. So, given that background, he’s probably going to make a big deal out them when he sees one or two here.
Its rare because the Altocumulus have to be pretty cold, -15 C (5 F) or so and colder1, and at a level where aircraft are flying, usually in a descent or climb pattern to their normal flight altitudes up around the higher Cirrus levels (30-40 kft above sea level and at temperature generally below -35 C). Typically because of climbing or descending, the ice canals, or holes with icy centers, are short and small. Here are a few examples from yesterday, but you really want to look at the U of AZ timelapse movie to see a bunch of them going by in those pretty Altocumulus clouds and mackerel skies we had. Note that as cold as these Altocumulus clouds were, they were not producing ice:
And there were other fine sights! Look at this display of Altocumulus perlucidus undulatus, rippled mackerel sky:
Looks like cold spell will last, once underway, into the middle of the month. SNOW indicated HERE in Catalina-land on the morning of December 11th from a crazy model run based on last evening’s global obs at 5 PM AST yesterday. Here’s what that morning looks like overhead, at 500 millibars:
BTW, the local weather services all around the SW are already worked up over the coming cold wave and have issued Special Statements, quite fun to read because they reflect the excitement we weather folk are feeling now as we look ahead to wind some rain, and a big frontal passage followed by cold air. After all, the weather’s pretty dull here in SE AZy most days of the year, and by “dull” I mean that not much is happening except for pretty clouds and nice temperatures, a weatherperson’s “dull.”
1 Yesterday afternoon’s Tucson balloon sounding which I forgot to look at until now: