Cumulus on the run

After a sumptuous day of Cumulus and Cumulonimbus clouds yesterday, a long period mostly devoid of any Cumulus clouds  is expected to begin after today.

Cumulus congestus and Cumulonimbus clouds rose early and often to the north of Catalina, but did not launch off of the Catalinas as expected with a minor exception that only the best of the CMJs would have noticed.  If you want to see the whole day, devoid of blabber, take a gander at the U of AZ Weather Department time lapse film here.  Very summer-looking video yesterday with the Cu moving from the SE as we see on most summer rain season days.

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9:30 AM. Heavy Cumulus clouds erupt on the high terrain NNW-NE of Catalina.
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9:53 AM. Cumulus over the Catalinas are beginning to shoot small turrets up.
10:45 AM. Lookin' good for a Cb launch at this point, especially with all the Cbs on the N horizon by this time, indicating unusually fertile grounds for a big cloud growth.
10:45 AM. Lookin’ good for a Cb launch at this point, especially with all the Cbs on the N horizon by this time, indicating unusually fertile grounds for a big cloud growth on the Catalinas.

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1:58 PM. As Bob Dylan wrote, "You Ain't Goin' Nowhere."
1:58 PM. As Bob Dylan wrote, “You Ain’t Goin’ Nowhere”, you Cumulus clouds.  But why?  Too dry aloft right here over Catalina, and less so to the north?  Probably.

The wait for an explosive development over or near the Catalinas went on and on with nothing happening.  In the meantime, Cumulonimbus clouds were getting closer and closer to the north of us.

2:22 PM. As close as they got. Cumulonimbus calvus ("bald") protrudes above the lane divider line on Oracle, about 20 miles N of Catalina.
2:22 PM. As close as they got. Cumulonimbus calvus (“bald”) top about 20 miles N of Catalina protrudes above the lane divider line on Oracle Road.
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3:25 PM. One pitiful Cumulus congestus cloud rose up to ice-forming levels, glaciated and died. Its head passing almost directly over the house, as you will see. Here, no ice is evident externally, but its in there if you could judge how much higher this cloud was than those that preceded it.
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3:30 PM. Dissicated by the surrounding dry air, that poor turret dies, leaving visual evidence of the ice inside. Can you see it? Anyone under this would have felt a few drops of rain at this point.
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3:33 PM. Only three minutes later, death is almost complete, leaving more visual evidence of the ice that had been inside it. The cloud in the foreground obscures the highest part of the turret that shot up so much higher than its nearby brethren. Feeling pretty sad here.
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3:33 PM. Life-size close up so that you can see what I am trying to describe. The faint veil between the cloud shreds is composed of ice. The shreds are droplet clouds, but also with some ice in them.
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3:42 PM. The icy top of that lonely turret finally shows.
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3:42 PM. Close up, just about looking straight up.
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3:43 PM. Frame from the U of AZ time lapse camera showing icy top over Catalina. Was it the “Little White Cloud That Cried?”, produced a few raindrops? I think so, since you really have to have ice nearly all the time around these parts to get rain.  I’ve spent a LOT of time on this cloud.  Maybe its because we won’t see anything like this for so long now.

 While the rain at the beginning of April has disappeared altogether in recent model runs (ones after 11 AM AST yesterday), it will likely return in the future.  Also, mods now think some rain might occur  a week from now.

The End, for awhile.

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.