In case you didn’t see it, here it is, a Cumulus fractus, a real whimper of a cloud. It had appeared in that same spot earlier in the day, before noon on Sunday. Formed again in the afternoon. It was pretty exciting, considering we have been absent clouds for about two weeks it seems. And this little tyke there, well beyond Charoleau Gap, did indicate that the humidity here had increased on us as that unusually strong low center moved across the Great Basin and into Colorado on Sunday. Perhaps its hard to tell, but that was a “boundary layer” cloud, as any form of Cumulus cloud usually is. That is, a cloud whose updraft has roots at the ground in this case.
Also, I have a new layer of topsoil in my yard now. Thank you, 35-50 mph wind gusts on Sunday. Go here to see the time lapse of a dusty afternoon in Tucson from the U of A. The Catalinas are barely visible at 17:35 PM LST.
Since this ONE little shred of a cloud popped up in the same spot a couple of times, and also downwind of the Catalina mountains, it may represents a “bounce” in the airflow in the lee of the mountains, possibly a rotor type cloud–no pilot would/should go near this thing on SUCH a windy day! Extreme turbulence can be observed below this cloud. If you could see the airflow in a side view, it likely would have appeared like a huge breaking wave with the splash off the ground represented by that cloud.
The second photo is a cross section of another mountain, Mount Shasta in northern California that MIGHT illustrate what was happening on Sunday. In this shot, a fairly laminar flow is breaking into something akin to a giant ocean wave, and the splash from that “wave” is giving rise to those ragged Cumulus clouds in the LEE of the mountain on the left of the photo. The wind was blowing strongly from right to left.
So, our one little cloud may have been due to a breaking wave in the lee of the Catalinas, one that would have produced extremely turbulent air.
On Monday, we had just enough leftovers after a dry cold front went through for this nice sunrise of Altocumulus clouds. How nice!
