11 (hundredths)

While we would have liked to have had our rain amplifier turned up to more than 11, as Nigel Tufnel might say, but we got this amount out of an unusual situation in which you often miss rain.  The cloud that did it formed virtually overhead and rained itself out without moving.  Best dump of the day was a bit S of this place toward Cat State Park.  But… let us not get greedy.   Our summer vegetation is looking stressed, and so yesterday’s odd situation of virtually no movement of rain/thunderstorm cells meant that a cloud had to build right over us to get any rain.  And that’s what happened when we got almost all of our 0.11 inches yesterday.  The first shot, looking straight up just before it began, with these eyes detecting some evidence of ice in the top of the cloud overhead and getting excited, since that would mean there would be a rainshaft soon.  In these kinds of overhead shots, as I have mentioned before, you will have to raise the monitor over your head to really get this first photo correctly.  Maybe count to 10 or 12 so it counts as some form of exercise.  Would be good for you, that’s for sure.

Went outside at this time to wait for the first drops, hoping I would see those silver dollar-sized ones that fall out first through the updraft1.   It took a few minutes, and I did not see those giants.  Still, the drops were big enough and numerous enough to produce 0.07 inches in about 5 minutes.  Nice.

With no wind “up top”, it was a bit odd to see that this cloud that had rained itself out, still virtually overhead 40 min later as a patch of Cirrus (spissatus cumulonimbogenitus) if you want something to choke on so early in the morning.  See the very upper left hand corner of the second shot:

In the meantime, Cumulus werer lining up and boiling upward just S of us, and eventually went on to produce much heavier rains on the west side of the Cat mountains and into Oro Valley.  Also nice.

Here’s that sequence to the S, beginning with a promising line of Cumulus bases:





Interesting, perhaps, historical note below, he sez, re raindrops


1Mr. Cloud Maven person has the undistinguished, perhaps embarrassing note of sharing with his lead professor, the late Peter V. Hobbs,  the Guinness world record for measured raindrop size (see below).  So, Mr. Cloud Maven person knows something about where those giants (about 1 cm in diameter) fall out.  BTW, a bigger drop was recorded by researchers in Hawaii (Prof. Ken Beard, personal communication) AFTER some global publicity about our record went out.  But, Dr. Professor Ken Beard, did not publish his drop.  So, does a tree fall in the forest if you haven’t published anything about it?  I don’t think so.

BTW2, it was thought via experiments and theory, still prevalent in most textbooks, that rain drops larger than about 5 mm in diameter could not exist, so the finding of drops perhaps as large as a cm in diameter (10 mm, or close to half an inch) as we reported (Hobbs and Rangno, 2004:  Super-Large Raindrops, Geophys. Res. Letts.) was controversial.  I guess the clouds don’t read the textbooks.

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.