That’s about all we can muster in Catalina these days it seems, just a trace of rain.  Several drops came down out of stratiform debris clouds overhead around 7 PM.  If you weren’t outside, or driving, you would never have noticed.  I guess you could call those dull icy clouds with virga streaks hanging down from them “Nimbostratus cumulonimbogenitus” (derived from Cumulonimbus clouds) if you really want to know.

At the bottom of those were dark looking Stratocumulus droplet clouds that gave a sense of drama and portent, but they were only so dark because it was near sunset, there was a higher layer above them, and likely the high droplet concentrations in our clouds deflected what little light was reaching them back from where it came from (scattered and absorbed that bit of light).  They were not dark looking,  in this case anyway, because a deep Cumulus turret was piled up on top of those bases.  The patchy areas of light and dark help tell you that those dark bases are going to lead to zip.

6:15 PM yesterday.

Below is a reprise of the whole dramatic day, one that had a little fakery in it where for a time it appeared it was going to be a dry day, but ended up with some tremendous storms in the vicinity.

If you don’t want to look at stills, go here to the U of A time lapse movie.  The dust storm goes by at about 15:20 if you can make out the tiny time hacks.  This is a great movie and really shows how much “action” there is up there, even in those Ac cas clouds shown in the second shot.


8:36 AM.

The day started with promising heavy clouds at sunrise, then those thinned and disappeared, but there were also some great Altocumulus castellanus clouds that moved up from the S after that.

Those clouds, too,  thinned away as well under the blazing sun, and then our little Cumulus began to arise over the Catalinas, early again, just after 9 AM, a timing that is always filled with portent for a good storm day.

By mid-morning, some sharp turrets were “pluming upward” off the Catalinas, though those clouds were “behind” in size from where I thought they would be by late morning, shown next (11:45 AM shot).


11:45 AM.

Then awful things began to happen. These clouds started to stagnate in size or even wither over the next two hours! Clearly, drier air was moving in, a very discouraging thought.

While I was up on the rise at the Marana landfill to get a better look at the overall situation over the Catalinas, the stagnating Cumulus clouds began to erupt upward into Cumulonimbus clouds!   At the same time, a huge complex was moving toward Tucson from the S, one that was to shove a lot of dust up Oro Valley and into Catalina. I started to feel better, get excited.

Here are a couple of photos of that dramatic reversal of cloud fortunes:

2:15 PM, from the Marana landfill showing a cross section of the Cumulus clouds that were about to explode into thunderstorms.
2:44 PM. A large Cumulonimbus (capillatus) cloud had blown up over the Catalinas.
4:04 PM. Amid all the thunder and cloud to ground strikes, for a moment it appeared that those Cumulonimbus clouds would build westward from the Catalinas into Catalina. But no.
5:03 PM. The clouds did build out over Oro Valley and to the NW of Catalina. Here a huge, solid base tells you that a large updraft has coalesced with a ton of precip up there about to drop out. The back of the dump truck is rising now.
5:06 PM. Just THREE minutes later!
5:17 PM. A little after the main load had been dumped; some lightning for you in case you missed it.


Still enough water in the air for Cumulonimbus clouds here and there, but likely not so many as the past three days as we head for a HOT dry spell, as I am sure you all know about by now.