It was beginning to seem like measurable rain could not fall again here! But then those Stratocumulus clouds because closing in in the afternoon, then soon after that some snow virga began to trail down from them here and there, and the next thing, large regions of the sky were suddenly shedding virga and rain at the ground. Also, as with the day before anmd at the same time, a windshift line moved across the Tortolita mountains and into Oro Valley helping to augment those Stratocu. Here’s the pictorial record:
Quickfire quiz: Why isn’t there virga trailing down from those clouds in the 2nd photo, except in the very far away clouds where you can see just a tad????
(Answer, printed upside down if I could): “They are not cold enough yet to have ice form in them, and ice in clouds is necessary for rain at the ground, as a rule in AZ.”
So those Stratocumulus and some of them are starting to look more like Cumulus clouds at about this time (2nd photo), have to get colder by deepening upward some, and/or colder air must move in aloft to chill them down.
Weird factoid about ice in clouds: A cloud will form MORE ice for the same top temperature as its bottom gets warmer! That could be a whole 100 page discussion. Now, if you’re really pedantic, you can go here to read about all the mysteries that we (those who make a living studying clouds) are going to try to solve in a project in the Virgin Islands this summer, called “ICE-T” here.
In the 3rd and last photo, the nose of the windshift coming across Oro Valley is marked by that highlighted shred cloud in the center of the photo. It was moving from R to L, undercutting the higher based clouds that were still moving from the SW. As you can see by the obscured bases all around, there is widespread areas of rain at this time, augmented by taller clouds with thicker, darker shafts of rain, probably leaning toward a “weak” Cumulonimbus classification if you could see the whole thing. Note how the distant hills and mountains are obscured in rain. Yay!
It was after this shot that Catalina got its little amount.
Next “storm” this being 2 of the model foretold six days of rain some time ago? Wednesday. However, the mods are unimpressed with the moisture in this and none that I have seen have a drop as this upper air disturbance goes over us. At the LEAST, we should have some nice Cirrus, and probably Altocumulus clouds. And you know what that means now…. The possiblity of a trick sunset due to a parhelia (aka, sun dog, mock sun).
Also, I really like the the Canadian model run today that calculated where the highs and lows are going to be for the next several days based on last evening’s weather measurements around the globe. I really, really like it because it shows a huge storm here and in the SW six days out. My preference has nothing to do with objective science. The models have been fluctuating on how this next storm is going to be, minimal or gigantic, sometimes that’s just the way the models are when there is a lot of uncertainty about things upwind of us. Its one of those that is accompanied by an Arctic blast down the West Coast. Can’t wait!