Sightings; Cumulonimbus clouds and aerosols

4:54 PM. Outstanding sighting, a Cumulonimbus (calvus) top WAY out to the W of Catalina (100 miles or more), at a place where it was not supposed to rain yesterday according to models. Wonderful event since it indicates we are still well within tropical air moist enough for a Cumulonimbus cloud!  If all Cumulonimbi were to the east of us, it would have been a depressing day.


Novella-sized caption below (WP caption function not working again!):
“Educational module:
the air seems clean yesterday but its not.
Those whitish, cloud free areas represent thermals that
have risen from the ground and while cooling and rising,
the relative humidity has been rising to near saturarion.
At the same time, some of the aerosol particles inside
that rising plume, ones called “cloud condensation nuclei,
have been fattening up like a hot dog champion eater with
50 hot dogs in front of him/her because those particles
are “deliquescing”, absorbing water vapor before the actual
saturation point is reached, and water molecules form on
the particle.  This is particularly noticeable when the
humidity rises above 60% in the rising plume.  Those
whitish areas represent ghost clouds, ones about to form,
though they may not quite make it. If you are a glider pilot,
as many of you are out there, you will be heading for these
hazy puffs knowing that they are plumes of rising air that will
keep you afloat.  Is this a caption or a novel?
7:32 PM
Caption:  7:32 PM.  One of the great sights in Arizona at
sunset, a remaining Cumulonimbus (capillatus) cloud
struggling to keep going as the sun disappears over the horizon.
This one was particularly filled with portent since it was
moving in this direction indicating “better” moist air for those
kinds of clouds would be over us tomorrow (today).
Below, taken at 3:46 PM, the “picture of the day” showing the typical non-eventful clouds over the Catalina mountains.  Don’t think today will be this quiet.

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.