They would be giants

Cloud bases were very warm again yesterday, 15-20 C (59-68 F) paving the way for thunderstorm rainfalls similar to those seen in the Southeast US, inches in an hour or so.  Didn’t happen locally, but just to the north of us toward Park Links Road and up toward the Florence area, likely happened as one giant cell after another formed between Saddlebrooke and Florence.

Those were the only clouds that produced thunder yesterday.   Less vigorous clouds rained, but didn’t have the ingredients to be thunderstorms, stronger updrafts, apparently.  Also, at times it appeared some of the rain, to this eyeball, was “warm” rain, rain formed without ice, a rarity here in Arizona (something that happens all the time in Hawaii, and over the oceans.)

And if you were sharp, you saw something happen yesterday that is also quite rare; the clouds erupt in our vicinity into Cumulonimbus by 9 AM from surface heating (they weren’t those nighttime showers that tend to fade as the sun comes up).  That was exciting because when they took off, it seemed like a day destined to have giants here.

But then something happened, drier air began to move in from the east, and pretty soon, the ONLY large clouds were to the west and north, a sure sign a disturbance aloft was moving through and less favorable conditions for rain would follow it, the normal “couplet”, or sequence.

Sure enough, the clouds over the Catalinas, after such an auspicious start, struggled to grow into Cumulonimbus clouds, as they did elsewhere to our southern flank, while we watched one magnificent Cumulonimbus after another rise up to the north.

Fortunately, a moistening and destabilizing regime of air is moving this way from Texas across northern Mexico toward Douglas, and so our day here in Catalina should be more enlightened, by lightning.

Yesterday’s clouds

6:15 PM  Cumulus congestus forms over Oro Valley in smoky air.  Died away in 20 min.
6:15 PM Cumulus congestus forms over Oro Valley in smoky air. Died away in 20 min.  Nice, isolated example of that cloud, anyway.
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1:42 PM. Another one of the large Cumulonimbus capillatus clouds forms just north of Saddlebrooke.
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1:36 PM. Looked like a promising sign that the clouds on the Catalinas might still erupt into Cumulonimbus after the brief shower an hour earlier. But no. Looking like someone exulting over a three-pointer, hands raised, it turned out to be  a case of cloud erectile dysfunction. It flopped back down in minutes.  HELL, we can talk about things like that because we hear about them all the time during our favorite TEEVEE shows!  BTW, “TV party tonight!”
12:27 PM.  The very most hopeful part of yesterday.  Forming over Charoleau Gap was this beauty.  I thought I was going to see the first strands of large drops/and graupel pour out of it at any moment.  I was so happy then.  But then, only misty-looking rain fell out, no strands, filaments, suggesting maybe that it was rain due to drops colliding together than from ice/hail mechanism.  Well, did get measurable rain, but only got  0.07 inches.
12:27 PM. The very most hopeful part of yesterday. Forming over Charoleau Gap was this beauty. I thought I was going to see the first strands of large drops/and graupel pour out of it at any moment. I was so happy then. But then, only misty-looking rain fell out, no strands, filaments, suggesting maybe that it was rain due to drops colliding together rather than from ice/hail mechanism. Well, did get measurable rain, but only 0.07 inches.
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10:55 AM. What a behemoth this was, dumping its inches, producing the first thunder of the day, north of Saddlebrooke.
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9:13 AM. First Cumulonimbus forms out of the growing field of Cumulus clouds. Can you see the ice shield peaking out on the left?
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8:26 AM. To see real (ground launched) Cumulus sprouting like this so early in the morning was incredible; hopeful signs of “big day.”

 

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.