Yesterday’s cold front packed a few more rain “calories” than expected…. Kind of wrecked my play on beer in yesterday’s blog title as a way of making fun of it, you know, “Front light”. See rain amounts below.
But before that, a heads up: 1) More rain on way next week, at least a 100% chance of measurable rain during the week, and more storms after that (people will be complaining before long);
2) there are some pretty cloud photos at the very bottom in case you’d like to skip over a lotta verbiage; quite dull writing, hand-waving, that kind of thing about what happened yesterday.
The official totals are pretty amazing, too, considering our best model was predicting something like 0.01 to 0.10 inches here in Catalina just before the rain started1. Note below the 2.20 inches at Mt. Lemmon. BTW, we’re now just about at our average rainfall total for December here in Catalina of 1.86 inches and we’ve gotten 1.85 inches so far.
Here’s a truncated rain table for our area from the Pima ALERT gauges (its a rolling archive and so you’d better get there early if you want to see the full lineup of totals for yesterday’s storm):
Pima County Regional Flood Control District ALERT System: Precipitation Report
Precipitation Report for the following time periods ending at: 04:14:00 12/14/14
(data updated every 15 minutes)
Data is preliminary and unedited.
—- indicates missing data
Gauge 15 1 3 6 24 Name Location
ID# minutes hour hours hours hours
—- —- —- —- —- —- —————– ———————
1010 0.00 0.00 0.00 0.00 0.51 Golder Ranch Horseshoe Bend Rd in Saddlebrooke
1020 0.00 0.00 0.00 0.00 0.55 Oracle Ranger Stati approximately 0.5 mi SW of Oracle
1040 0.00 0.00 0.00 0.00 0.63 Dodge Tank Edwin Rd 1.3 mi E of Lago Del Oro Parkway
1050 0.00 0.00 0.00 0.00 0.55 Cherry Spring approximately 1.5 mi W of Charouleau Gap
1060 0.00 0.00 0.00 0.00 0.75 Pig Spring approximately 1.1 mi NE of Charouleau Gap
1070 0.00 0.00 0.00 0.00 0.67 Cargodera Canyon NE corner of Catalina State Park
1080 0.00 0.00 0.00 0.00 0.59 CDO @ Rancho Solano Cañada Del Oro Wash NE of Saddlebrooke
1100 0.00 0.00 0.00 0.00 0.43 CDO @ Golder Rd Cañada Del Oro Wash at Golder Ranch Rd
Santa Catalina Mountains
1030 0.00 0.00 0.00 0.00 0.47 Oracle Ridge Oracle Ridge, approximately 1.5 mi N of Rice Peak
1090 0.00 0.00 0.00 0.00 2.20 Mt. Lemmon Mount Lemmon
1110 0.00 0.00 0.00 0.00 0.55 CDO @ Coronado Camp Cañada Del Oro Wash 0.3 mi S of Coronado Camp
1130 0.00 0.00 0.00 0.00 0.79 Samaniego Peak Samaniego Peak on Samaniego Ridge
1140 0.00 0.00 0.00 0.00 0.71 Dan Saddle Dan Saddle on Oracle Ridge
2150 0.00 0.00 0.00 0.00 1.34 White Tail Catalina Hwy 0.8 mi W of Palisade Ranger Station
2280 0.00 0.00 0.00 0.00 0.59 Green Mountain Green Mountain
2290 0.00 0.00 0.00 0.00 0.98 Marshall Gulch Sabino Creek 0.6 mi SSE of Marshall Gulch
Hell, there wasn’t any rain in the cloud band west of us when I got up, and so I thought with some lifting, and that jet core at 500 mb slipping southward from southern Cal as the day went on, rain would develop farther south in the frontal cloud band. It did, of course, but still thought it would blow through in 2 h or so, something akin to the models as well. The rain fell for about 5 and half hours! The clearing took place a little before sunset, not in the early afternoon as expected.
So what happened?
I think you and I overlooked a disturbance aloft behind the frontal band. It was sliding SEwd fast from Nevada, catching up to our little frontal band. When those things happen, clouds magically seem to be appearing on the backside of the frontal band, fattening it up, holding its progress back; and the rain areas get bigger. The frontal band was MUCH fatter when it went by TUS than it had been just a 100 or so miles to the west at 4 AM AST yesterday morning. Here are contrasting satellite and radar images for two periods yesterday, before the band fattened up and the second, when it was raining so much here:
If you’re a true C-M disciple you noticed something else yesterday: true DRIZZLE in the rain. Drizzle may be even more rare than snow here. And the thick low visibility rain consisting of smallish drops from drizzle sizes, 200-500 microns (a couple to a few human hairs in diameter) and raindrops just above those sizes for much of the time the rain fell, should have made you start thinking of a warm rain process day. Maybe there was no bright band in the radar imagery during those times, something that happens when rain is ONLY formed by colliding drops that get big enough to fall out; no ice nowhere. In the heavier rains, sometimes when visibility was improved, ice was very likely involved.
The TUS sounding really can’t shed light on this question since the morning was had shallow clouds that weren’t raining yet, tops barely below freezing, and the 5 PM AST sounding, with tops at -10 C (14 F), was a little too late, though that layer that was sampled did produce what appeared to be ice virga in the direction of TUS about the time of the sounding. BTW, its well known that “warm” rain processes that don’t involve ice occur at temperatures below freezing, so the expression is a bit of an oxymoron.
So, without radar imagery over us during the time of the thick rain and drizzle, we can’t say for sure, but it sure looked like it to C-M, which is what you should think as well I think. Thanks in advance for thinking what I think.
Enough of my excuses2, let’s rock and roll with yesterday’s clouds
Your cloud day
The best scenes of all were when the clouds began to part in the late afternoon and evening sun. I hope you caught these beautiful scenes:
1Total rain prediction from our best model, the one from the U of AZ with the predicted totals through 3 PM AST yesterday. The model run was at 11 PM AST the evening just before the rain began:
2Your Catalina C-M did have a correct range of amounts that could fall in yesterday’s storm right up until the last minute. For weeks he was predicting, and staying firm with, 0.15 inches on the bottom, and a voluptuous, if that’s the right word, 0.80 inches potential on the top.