Another Catalina rain day for May 2015

We received 0.08 inches here in “The Heights” for a third day with measurable rain in May already.  0.12 inches fell at the Bridge on Golder Ranch Dr. , while Saddlebrooke got up to a quarter of an inch (as estimated by CMP) in a tiny streak of clouds that erupted into shallow Cumulonimbus clouds, anvils and all yesterday afternoon between 4:30 and 5:30 PM. It was pretty much all over by 6:00 PM,  those shower clouds passing off toward Mammoth.

No rain was reported at mountain sites, to give you an idea of how localized that was, localized practically to Basha’s Market parking lot,  Sutherland Heights’ Equestrian Trail Road,  and Saddlebrooke’s Acacia Drive, to exaggerate some.

The astounding aspect of a tiny line of showers that suddenly erupted over and a little downwind of Catalina was that it was EXACTLY predicted  in the University of Arizona’s 5 AM AST model run yesterday morning, one whose results are available by mid-morning!  So, there would have been a few hours notice of possible rain here in Catalina.

There is no rain predicted in that model run anywhere else except in extreme NW Arizona, just that tiny ribbon of rain right over us, and the U of AZ “Beowulf Cluster” weather calculator got it right.

However, unless you were in the right spot, you might not have even known that it rained, the shower streak was so narrow.

Below, the astoundingly accurate predictions for 3, 4, and 5 PM for that model run from yesterday morning.  No rain whatsoever is shown at 3 PM, as you will see.
3pm

Ann 4pm

Ann 5pmTo be “fair”, NO RAIN was predicted anywhere NEAR Catalina by that same model crunching the data from 5 PM AST the evening before our little rain event, leading CMP to be a little asleep at the wheel yesterday morning, no blog.

Some cloud shots before and as this predicted (or unpredicted, as the case may be) rain began to happen.  Of course, if you want to go to the movies and see this, go here, from the U of AZ:  Yesterday’s cloud movie

DSC_6158
3:23 PM. Looking upwind. Nada going on, clouds to shallow for ice.
DSC_6165
4:04 PM. Hmmmm. Clouds definitely fattening up upwind of us in a nice cloud street from upwind of and over Pusch Ridge to Catalina. Nice scene, anyway, even if nothing happens.
DSC_6171
4:12 PM. Cumulus clouds are looking to gather down there at the corner of Pusch Ridge and Oracle Road, Huh. And they’re heading in this direction. Can ice really form in these guys today?
DSC_6172
4:23 PM. Clouds over and downwind of Pusch Ridge continuing to gather while heading toward Catalina. Looking for ice now or virga, but don’t see any anywhere.
DSC_6173
4:33 PM. Ice begins to show up in even modest clouds! And it started to show up everywhere in the form of virga. But then then the virga became thin shafts all the way to the ground. Cloud Maven Person is beside himself, but must go indoors for a social engagement!  Those of you who fancy yourselves as Cloud Maven Juniors, should have recorded this sighting of “first ice” in your cloud diaries for yesterday.
DSC_6176
Also at 4:33 PM. Ice is now readily visible in that Cumulus mediocris massing upwind of Catalina and is not about over the south part of the Catalina CDP (“Census Designated Place” that might one day be absorbed by Oro Valley, rumour has it.)
DSC_6180
4:41 PM. Just minutes before the first drops fall in Saddlebrooke, and CMP’s last photo of this incoming masterpiece of weather forecasting and little rain band; he can no longer comfortably jump up from dining room table in mid-conversation to say he has to pee again whilst actually taking a photo. You can only say you have to pee so many times in 10 minutes and still have your credibility intact. But, how can you say repeatedly, “I have to go look at some clouds?”, so I can’t hear the rest of your quite interesting story……”  Really came down for a couple of minutes several times there in Saddlebrooke between a quarter of five and 6 PM as one little raining cloud formed after another in this cloud stream.

Below,  sat view of this cloud streamer with radar, from IPS MeteoStar.  The image below is at the same time as the last photo above:

Satellite and radar imagery for 4:40 PM AST.
Satellite and radar imagery for 4:40 PM AST.  Note the many lines of clouds running almost due south to north into SE AZ from Mexico.

Here some more cloud stuff from the sounding launched at the U of AZ around 3:30 PM AST.

The TUS balloon sounding ("rawinsonde") for yesterday afternoon.  Looks like most tops were dabbling with the ice forming temperature of -10 C, but the sounding suggests that somewhat deeper tops could easily have arisen (and did!).  Interestingly, the model "knows" when ice forms, and it must have "known" that the ice-forming temperature was going to be surpassed in that little cloud line coming off Pusch Ridge.  Astounding, for the Nth time.
The TUS balloon sounding (“rawinsonde”) for yesterday afternoon. Looks like most tops were dabbling with the ice forming temperature of -10 C, but the sounding suggests that somewhat deeper tops could easily have arisen (and did!). Interestingly, the model “knows” when ice forms, and it must have “known” that the ice-forming temperature was going to be surpassed in that little cloud line coming off Pusch Ridge. Astounding, for the Nth time.  Bases were pretty cold, 0 C (32 F).

Here’s a diagram of when ice forms in the type of clouds we mostly have in Arizona, “continental” ones with high droplet concentrations, and when ice should form in them.  As you can see, ice should form in them soon after the top temperature gets colder than 10 C WHEN the base temperature is about what it was yesterday.

 

From a survey of the onset of ice formation in continental clouds by Rangno and Hobbs (1995)1
From a survey of the onset of ice formation in continental clouds by Rangno and Hobbs (1995)1

 

“CMP” is not mentioning it at all, but yesterday was another kind of mucked up sky, not a Catalina postcard sky,  with lots of aerosols making the sky a whitish-blue, the lower aerosol stuff again from Mexico, but there was also a layer far above the cloud tops, likely a long-range transport event from thousands of miles away.

This higher haze layer still seems to be around if you look toward the horizons right now (5:59 AM).

We’ll be between two jet streams today, kind of a jet stream sandwich, and the stronger one is now approaching from the northwest with that mega upper low over Cal.  That means no rain today, subsidence rules, though we’ll have small, non-ice producing Cumulus, and likely some Altocumulus lenticulars, maybe a Cirrocumulus patch here and there.  Should be a pretty nice day for cloud photos, haze aside.

The best chance for rain is still after midnight tonight into mid-day tomorrow as the core of the stronger jet stream goes just about over us.  Still thinking a tenth of an inch will occur here, though mod run from the U of AZ at 5 PM completely dry.   A little snow likely on Ms. Mt. Lemmon, too!

The End, FINALLY!  Brain empty.

———————————-

1From “A New Look at the Israeli Cloud Seeding Experiments.”