Pretty scenes and a little ice

6:43 PM. Trailing raindrops.
6:43 PM. Trailing raindrops.  The lack of visible ice at cloud top indicates low updrafts, and marginal ice formation, tops just barely reaching the temperature level where ice forms.  That level tends to change some each day due to different aerosol and droplet concentrations, but is generally near the -10 C to -12 C level in Arizona.   In oceanic regions, where clouds have larger drops and form drizzle and rain before reaching the freezing level, ice first forms in clouds closer to the -5 C level.
2:09 PM.
2:09 PM.  No ice or virga present.

“So what gives Mr. Weatherblogperson? Most clouds had no ice and a very, very few did, ones that had some rain fall out of them. Below I have handcrafted a diagram with too many arrows and text on it, just for you, my friend, to help explain the  mystery of yesterday’s clouds.  I think, or rather hope, the excess text and arrowing will be self-explanatory…..

The balloon sounding data from Tucson yesterday afternoon at 5 PM AST (launched around 3:30 PM, actually).
The balloon sounding data from Tucson yesterday afternoon at 5 PM AST (launched around 3:30 PM, actually).

Overhsooting tops? Here’s the biggest one of the day yesterday.  Most however, because they are colder than the environment, collapse quickly and as is often the case in days like yesterday, there is NO overshooting top by the time the ice and rain start to fall out the bottom of the cloud.  But, you can bet before that happened there was one.

3:21 PM. Looking SSW toward Tucson at light rainshower with an overshooting top above most tops.
3:21 PM. Looking SSW toward Tucson at light rainshower with an overshooting top above most tops.  Need a fatter arrow.  That top is above and beyond the slope down part of Pusch Ridge.
7:01 PM.
7:01 PM.  The large patch in the distance would be Stratocumulus formed by the spreading out of Cumulus cloiuds.

Author: 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.