Catalina gets 0.48 inches in brief frontal passage

(Note written on Dec 22nd!  Something happened to the title I gave this previously, so its been titled now.)

Didn’t seem possible that such a fast moving storm could drop this much!  Neither did the mighty Beowulf Cluster at the U of AZ think so much would fall here.   But there it is, a great addition to December’s 1.34 total from the three prior days of rain, pushing our December total to 1.82 inches, just above the December average for Catalina of 1.72 inches (corrected).

Here are the ALERT system gauge reports from around the region at 5 AM AST.  You will see that the Bridge at CDO Wash and Lago del Oro got more than here, 0.51 inches, quite unusual, even though its only a half mile a way.  Its lower than here.

Don’t be fooled by all those low totals in the Catalina Mountains, that’s because the gauges don’t work when the precip is SNOW! Get your cameras ready for a spectacular, snowy Catalina Mountains scene this morning.

More precip totals can be seen via the U of AZ rainlog network here, and statewide totals here from the USGS.  The NWS will have some regional totals after 8-9 AM AST as well.

In all of this rainfall data you will see that our half inch is about the MOST recorded anywhere in the lowlands, which can be attributed to the type of storm and the flow it had, more west to southwest flow at cloud levels. That flow caused clouds to thicken up over the west side and up top of Catalina, helping to wring more rain/precip out of them than flow from the south at cloud levels.

In classic fashion, the temperature plummeted about 15 degrees as the front barged through Catalina at 2:30 AM AST, now at 38 F at 4:45 AM. Now (5:12 AM) that the rain has stopped–it will be a gorgeous, if cool day, the temperature is rebounding.  Here’s this morning’s temperature trace, pretty dramatic:

The first recording rain gauge bucket tip last night here, indicating an accumulation of 0.01 inches, happening as the rain began to beat against the windows of the house, was at 2:07 AM. The forecast for the onset of rain from this keyboard yesterday was 2:08 AM.    I hope nobody got wet due to an errant (semi-facetious) forecast…


Small Cumulus clouds, that’s it, a gorgeous day with fantastic views of the snow covered Catalinas, punctuated by passing cloud shadows.  Doesn’t get any better than this!


More precip before the end of December.  Christmas Day now a rain day according to last night’s model run.  That run indicated it would be nothing extraordinary.  But we reject that notion for the time being, that a storm on or about Christmas Day and later in the month will be more than just a run of the mill rain.  This rejection based on our venerable “spag plots” that continue to indicate stronger storms than ordinary during the last week in December and early January.  The thought here is that the run of the mill quarter inch or so rain indicated on Christmas Day is an outlier model run.   More rain on that day will show up later….we hope!  The superior Enviro Can model is make that Christmas Day storm look much more potent, BTW.

Yesterday’s clouds

What a pretty day it was!  “Pretty Cirrus” again, then some Altocumulus perlucidus, finally Altostratus translucidus, shown in order below.

10:08 AM. Cirrus uncinus (hooks and tufts at the top) and Cirrus fibratus (gently curved fibers).


12:36 PM. Altocumulus perlucidus (honey-comb pattern).

The surprise of the late afternoon, and one that strongly indicated that this front would produce more precip than expected, was the sudden obscuration of the peaks of the Catalina Mountains by Stratocumulus clouds around sunset.  I couldn’t believe it, and it was a strong sign of a moist current ahead of the front.  Still, I could not imagine a half an inch!

4:41 PM. 4:41 PM. The strong indication that last night’s front was going to be more potent as a rain producer; the sudden appearance of mountain-topping Stratocumulus clouds.
5:33 PM. Holes in the Altostratus overcast beyond the horizon led to a few underlit rays that underlit the layer, resulting in a bifurcated color arrangement.