But first, continuing from yesterday: “…and a few small to moderate sized Cumulus (humilis and mediocris) clouds as well to go with the high and middle clouds.”
Sorry I took so long to finish that up, but it was worth the effort because it was pretty darn accurate.
The storm on the doorstep
Here is your very excellent Catalina forecast as of now (4:50 AM) from the computers at the NWS. There is a statement on the exciting New Mexico weather, posted by the Tucson NWS here. You can feel the excitement in NM in this message they consider quite special, labeling it a “Special Statement.” Hope our Arizona guys and gals get on board with the NWS in ABQ and issue something special soon! Being weathercentric, of course, I am at one with the ABQ office even now.
Here’s a depiction of the incoming storm from our best model, that at the U of AZ, one that downsizes the “WRF-GFS” model to smaller scales so we can see what happens in our local mountains and valleys as it barges across California and then into Arizona on Saturday. Precip is shown to begin on the Catalinas before dawn on Saturday, but probably won’t reach here for a few hours after that. The model onset time here in Catalina is 8 AM AST on Saturday. However, this model tends to run a bit fast in these situations, so it may be mid-morning before those cold, cold raindrops start falling. But, 8 AM vs maybe 11 AM AST? Amazingly close no matter how you put it. It just shows how good our modeling systems have gotten over the years.
The amounts? Seems measurable rain is certain here in Catalina–the flow pattern jetting against this side of the Catalina Mountains favors us here. The finest scale model at the U of AZ, the first place to look, is showing a range of values between 0.25 and 0.50 inches, oddly corresponding with a ludicrous guess made too far in advance here a few days ago. Hmmm. The Catalinas are shown to get more than an inch and that calls for a celebration.
Here is the scoop from the 11 PM AST U of AZ model run for total precip (snow on the Catalinas again, the best kind of precip because it just sits there and soaks in when melting):
Out of character a bit, but also since we’re on the edge of the predicted range of amounts, I think the bottom is closer to 0.08 and the top likely amount is 0.38 inches, with a “median”, most likely amount of about 0.23 inches, to be a little silly here.
Probably (and this time I will examine the TUS sounding more carefully than yesterday), just a few isolated Cumulus clouds again, likely dissipating during the afternoon, and a couple of Cirrus clouds.
The clouds tomorrow (more interesting)
One of the interesting cloud formation zones for Arizona is over and downwind of the mountains in northern Baja (Sierra de Baja California). Gigantic plumes of Cirrus/Altostratus ice clouds often form in these situations as moisture at high levels from the Pacific Ocean (located west of Baja, California) travels over those mountains. Those clouds would be something akin to standing wave clouds, lenticulars, but because the air is pretty moist (“ice saturated”) wrapping around this powerful low, they don’t evaporate downstream once having formed but end up as a huge, icy plume across central and southern Arizona. I think we’ll can see that start to happen today, first in the lee of the Sierras of California, as the jet stream works it way down the West Coast toward us.
Eventually, the higher level moisture dries out over those Baja mountains, as it will later tomorrow, and the icy plumage source ends, and many times we see the end of that plume from those Baja mountains (Cirrus/Altostratus clouds) as a huge clearing that, oddly, preceeds the real storm; the surge of lower level clouds that carry the precip. And with that clearing as well, the passage of the core of the jet stream (in the middle levels) above us.
I know many of you have seen this sequence over and over again, the clearing of a high dense layer of clouds from the actual storm that’s on its heels.
Such a separation in those two clouds systems, the high and the low, can lead to spectacular Catalina sunsets. Tomorrow, out on a limb here, is the kind of day where that could happen–the sun sets in the distant clearing to the west as the shield of icy plumage overhead passes.
Yesterday was another one of those especially gorgeous days here in the wintertime. Delicate patterns in Cirrus, as well as the dense patches. Then, a few lower Altocumulus clouds above scattered small to medium Cumulus clouds against a vivid blue sky and limitless horizontal visibility. Here are some examples:
Kind of rushing around today, hope this is intelligible….