Very exciting day ahead as the south to southwest winds pick up this afternoon to gusty proportions with some dust-haze in the air. Cold front coming, as you you know. Surface low pressure center passes to the north. Very exciting, to repeat for emphasis.
Rain? Oh, yeah. This time ALL of it After Midnight (different “reminder” version of this song of when-the-rain-will-start than the one I used last time; different comments, too, on YouTube by people who drink beer late into the night instead waiting for rain… In fact, not one person mentions that he/she was up waiting for rain to start “after midnight”, as you and me might do today.
How much rain here in Catalina this time?
Well, let’s start out by guessing…from weather maps, pattern recognition, and stuff like that. Oh, bottom (estimated 10% chance of less than this): 0.10 inches (namely, it shouldn’t be a dud with no rain at all).
Top amount potential, if everything goes well (only 10% chance of more): 0.40 inches. It doesn’t have the potential of the last blunderbuss of a storm (day 1 of that one where the top of 1.00 inches was realized), but “hey”, its a nice rain in the desert again, helping to plump up those just-ahead spring flowers and grasses.
Best estimate, most likely amount: the average of those two guesses, 0.25 inches1.
OK, now I have JUST looked at the “B-Cluster” output from the U of A 06 z (11 PM AST) model run for OBJECTIVE guidance, not SOP stuff as above: Rain begins here in this model at 1 AM AST (probably too soon by a couple of hours), and the total amount, as predicted by a computer that might have cost billions? Pretty much the same as me, 0.10 to 0.25 inches! I must be wrong! (hahahahaha).
Serious note: the U of A could really use a donation from you to help keep stuff like the Beowulf computer cluster going; I’ve contributed. See online U of A Department notice in RED letters, calling out a dire situation here. It would be a shame if some of their stuff goes away.
Now if you’re a pattern person, you will be noticing that this trough is the type in which Catalina amounts are significantly greater than those to the south, such as in Tucson and the surrounding lowlands, and often this comes toward the end of the storm when we see the rain hanging on for an extra hour or two and the clouds pile up against the Catalina Mountains on our side of them as the wind turns more perpendicular to them as the trough goes by. Always a nice time to look at radar because you see little echoes popping out of a no-echo but cloud filled sky, ones that then head toward us. Here where that trough is at 5 AM AST tomorrow morning, its apex right over you and me!
Note above, in timing the onset of the rain, that by 5 AM AST, the strongest winds of this trough (at this level, 500 millybars) has gone by–forecast the rain to have begun by this time; nice rain beginning time window, with the Beowulf being a bit fast (as per usual): Between 2 AM and 5 AM AST tomorrow morning. Set alarm clock. This is so much fun! For extra razzle dazzle for your neighbors, tell them the rain will start between 2:08 AM and 4:32 AM. You can’t get this kind of forecasting precision elsewhere! This is so much fun!!!
As you know, too, the temperature will PLUMMET during the frontal rainband early tomorrow morning as it always does, maybe 10 degrees F or more in an hour, along with the familiar pressure check (sudden rising pressure, one that occurs just about the instant the wind at the ground shifts from wind from the southwest to northwest zephyrs (sounds like a soccer team).
There weren’t any. Hahahahahaha. From the 16th, a picture of a “frosty Lemmon.” (Its amazing how you can just be sitting here, and after one or two cups of coffee, this kind humorous creativity just bubbles up from below. The brain is really something, as the special issue of Science mag will tell you, talkin’ about the hippocampus and neocortex and the mysterious things they do, like thinking that “frosty Lemmon” is funny. You really should read this whole issue to find out what’s going on up there in that cranial cavity you have.)
————Footnote in middle of blog for a deliberate change in normal protocol—————
1Kind of like footnoting, makes me feel like a real author or librarian… I came up with this technique in Durango, Colorado, in the early 1970s with the Colorado River Basin Pilot Project, a gigantic randomized cloud seeding experiment covering much of the San Juan Moutains. Its based on the fact that we meteorologists often have a better idea, a more concrete one, of what’s NOT going to happen. By estimating the extremes of a storm (the crude weather models of that day off this way or that some), it turned out that you could engineer in a way, a better forecast of the amount that would actually occur. In a sense, doing that was performing a “mental ensemble” or mental spaghetti plot have two members (outputs)1(kind of like footnoting…).
Of course, in Durango, CO, we had an objective forecast scheme based on the work of the late Dr. J. Owen Rhea, former chief project forecaster in Durango, who came up with the basic idea behind what is now called the PRISM method of estimating rainfall between gages in complex terrain. Used today to present statewide rainfall averages such as this one for Arizona, courtesy of the Western Region Climate Center. This is a very nice guide if you’re unhappy about the rain/snow you’re getting and want to live where there’s more, a true precipophile:
Those big storms just ahead
They’re definitely in the pipeline…. (Here you can feel the confidence slacking that bit from “count on it” yesterday to “definitely” today. Was chagrined by model outputs during the day yesterday, that, while having many AZ rains, were ones having reduced amounts, and were less numerous.
Still, will ride the “Big Storms Wave” right into oblivion if necessary because that’s what I saw in the “ensembles of spaghetti” and they have NOT let me down once that I know of (another fudge phrase).
BTW, what happens after you have seen those wavey lines in the “ensemble members” (each line is called a “member”) is that you come to expect a disappointing output or two–but you don’t really worry TOO MUCH about them, because the Big Boys will be back if the ensembles are correct, as well as your interpretation of them.
So while yesterday during the day the outputs backed off so much rain here as foretold at this very blog, during the night, with the 00 Z (5 PM AST run) not too surprisingly those big rains came back.
In sum, watch for strong storms and big rains in the last week of December into early January.