Last of the Cumulonimbus

10:56 AM. Things looked promising except clouds like this over the Catalinas moved away from us. And no Cumulonimbus clouds formed over them, but rather downwind toward and beyond the town of Oracle late in the afternoon.
Ann DSC_8118
3:30 PM. Not much going on; a very thin veil of ice was dropping out of these clouds, once the tops of the Cumulus cloud to the right and out of view. Hope you caught it. There weren’t very many ice displays until later.
5:31 PM. That blasted haze/smoke layer is still evident! at the center is a glaciating turret, giving hope this whole cloud cluster could erupt into something. The model from the overnight run suggested just such an event!
6:09 PM. Hah! A shower at last! And the movement is in the general direction of Catalina!
6:36 PM. Stupendous sunset view, and this cluster is getting closer!
6:42 PM. Zoomed view near last light. Portions of this complex consisting of a weak thunderstorm  did pass over, but no shafts, just a few drops for a “trace” of rain.  By this time bases had risen to about 14,000 feet above sea level, or about 11,000 above Catalina and near the freezing level, so a lot of evaporation on the way down for those poor droppies.

Last call for Cumulus clouds today, maybe a distant Cumulonimbus top off to the north.  Then one of those long clear and dry spells of fall gets underway….


The End

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.


  1. A cloud like the one in your first photograph developed here yesterday morning and gave me a good soaking while I was biking, but since then it’s been mainly sunny. However, it appears our first significant rain since mid-June is coming this Sunday. We need it.

  2. Must have been a nice sight, Roland. Glad to hear a substantial rain is on the way. I heard that about SEA, too.


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