5:16 PM.
5:16 PM

Rain shafted, that is.  0.50 inches in 15 minutes yesterday between 2:43 and 2:58 PM. 0.76 inches in 13 minutes in the Sutherland Heights district above Catalina, with wind gusts to 50 mph!  One of the most memorable summer days ever here in Catalina.  One station, Oracle RIdge in the Catalinas, 1.5 miles N of Rice Peak, reported 2.32 inches.  No wonder we had a strong flow in the CDO wash yesterday afternoon!  Rafting anyone?

And what a spectacular beginning to the day, filled with portent by those ultra low Stratocumulus and Cumulus cloud bases hugging Samaniego Ridge, the humid air that enveloped us reminding one of the Phillipines, or Gainesville, FL,  in July.  That was a real key to the kind of day that likely lay ahead, those low cloud bases telling us that our humidity was not just in a shallow layer near the ground as we could feel.

But who needs Florida in July when you can be right here in Arizona?  Voluptuous Cumulus congestus clouds piled into the heavens early and often just like in FL, some with pileus veils as well, also common in FL,  in route to blossoming into Cumulonimbus calvus, then capillatus clouds, tops reaching above 40,000 feet above us.  The Charoleau Gap/Oracle area were hit often all morning and into the early afternoon with great rolls of thunder with one station reporting more than two inches (as noted) and several over an inch.

Because there was so much water in the air, unusually dense rainshafts poured forth from the bottoms of those clouds in just a couple of minutes, oblitering the scenes behind them.  Too much precip up there for any updraft to hold off for very long, then the collapse!

Here’s one sequence, the one that led to our 15 minute drenching.  The first shot shows the blockbuster that roared down through Charoleau Gap.  The ferocious NE winds that preceded the rain caused the clouds to its south (where I was) to experience a growth spurt by displacing the humid air near the ground, jacking it upward.  I noticed this happening by the second shot.   When the winds hit, you always start looking up for “surprise” developments right over you. But after that, trying to catch a daylight lightning flash from the Charleau Gap storm, forgot to check that darkening base every 12 seconds as I would normally do.  My apologies, since the third shot showing the fully collapsed, unbelievably dense rainshaft (3rd shot) was a FULL EIGHT MINUTES later.  Damn.

Finally, the last two are during the height of the storm itself.  Phenomenal intensity.

 I suppose I took too many photos, only about 0.0004% of them can be shown here, but, let us not forget those PRO photographers that had ONE day to document, was it the Chiracaua National Park a couple of years ago?   One said he had been conservative and “only” took 2,000 photos, while his friend, more promiscuous, took 8,000 that day!  I only took 200 or so…

Here’s a gallery of yesterday’s scenes, including suggestions of a funnel cloud a few miles NNW of Catalina at 10:45 AM.  BTW, you can reprise the whole day, as through you were a student standing on top of Atmospheric Sciences Building at the U of A here.

11:07 AM. Cumulus congestus trailing NWward from the Catalinas shows signs of glaciating, producing a shaft.
11:09 AM. Shaft begins to appear on the left as top more clearly becomes fibrous, also on the left side (showing that its ice, not liquid).
11:12 AM. The shaft is fully developed and the top is clearly ice; has a “cotton candy” look (now termed a Cumulonimbus calvus or maybe capillatus).
10:45 AM. Brief appearance of a funnel cloud NNW of Catalina, 5-10 miles.
1:14 PM. Lopsided sky. While Cumulus congestus boiled into Cumulonimbus clouds, toward the SW-W were only Cumulus “pancake-us”.
1:11 PM. A new round of Cumulus congestus clouds launches off the Catalinas.

















We’re still in Floridian=style air with dewpoints, a measure of how much water is in the air around us, even HIGHER than yesterday with several stations from Yuma to Tucson reporting a whopping 70 F dewpoint. Doesn’t get higher than that here, I don’t think. As pointed out, the higher the humidity, the more precip can form in those Cumulonimbus clouds, but also, that greater amount of water, showing up first at cloud base when it condenses, is also like adding a little furnace at the bottom of our clouds. This is because the condensation of lots of water in the cloud offsets the cooling that occurs as the air expands on its way up. That means its easier for clouds to rise up and dump on the more humid days.

However, along with that, the numbers and clustering of these systems is also dependent on favorable patterns high in the atmosphere, like troughs. If they are not there, and its just moist, you can still get yer Cbs, but they may be short-lived, and in the worst cases, send out huge anvils that help terminate other Cumulus clouds by keeping the surface temperatures down.

So, what kind of a day will it be? Large, long-lived clusters with their inches of rain, or localized thunderblasters that burn out fast?

I don’t know, but Bob (our local premiere scientist on convection), and later Mike, his counterpart at the U of AZ, probably will, our true Arizona summer rain experts…

I haven’t got time to get the forecast right, BUT, the AZ Mod seems to suggests big showers today coming up from the S.  So, Catalinians, keep your eye toward Orcacle Road into Tucson by later this morning and throughout the day and evening… Could be another memorable day for us.

The End.