Summer thunderama returns to Catalina for a day

Against the deepening blue skies over us as the sun continues its descent to overhead of the Equator, coming right up (September 22nd, AZ time), our late summer Cumulus and thunderheads become even more spectacular. You can see the whole cloud day here, courtesy of the University of Arizona, if you would like to avoid the tedium of examining photos and captions by yours truly.

I got very excited about a small thunderstorm that took shape almost overhead of Sutherland Heights, and you know what that means.  Yes, too many photos of almost the same thing!  See below.  Captured it, too, BEFORE it even started to rain, or even thought about it.  Produced a large number of cloud-to-ground strikes in the vicinity, too, more that you would expect from such a small storm.  Also, if you could see them, you saw repeated split strikes, ones in the core of the rain, and at the same time a branch in clear air to the north, a mile or two quite a ways from the rain shaft.  I had not seen that before happen over and over again.  Samaniego Peak reported the only rain, 0.28 inches, in the ALERT Catalina Mountain gauges, like twice that in the core of the shaft.

Then, of course, we had a lot of LTG in the early evening and nighttime hours to the NE-S-SW as storms marched across Tucson, Marana and Oro Valley.  Missed us, though.  A place in Avra Valley got an inch.

That’s pretty much it for your cloud and weather day yesterday.  Farther below, the details….

Mods see nothing for a couple of days, until Monday, when the moisture from now Hurricane Odile begins to work its way into AZ.

Yesterday’s clouds

10:30 AM. After a completely clear morning, Cu began to pop up around 9:30 AM. This size by 10:30 AM gave hope that the day would have full Cumulonimbus clouds later on.



3:26 PM. Just a pretty scene. Note the contrast between the blue sky and the white glaciated top of this Cumulonimbus calvus. Note too, that there is only a faint rain shaft underneath (behind ridge top, that smoother area).



3:48 PM. Here’s where you and me saw a lot of rain promise in this developing cloud base on our nearby mountains. Almost every cloud that had this much base or a bit more, eventually rained. Maybe it would explode into something really big with powerful winds! Well, “really big” didn’t happen, but it did do its job with nice, but small rain shaft a little later.




4:01 PM. Excitement builds as base grows a little wider; rain excitement is now guaranteed. I can only imagine what you were thinking when you saw this, and how happy you were since it could lead to a nice rain on you. LTG and wind, just ahead.



Ann DSC_0038-2

4:05 PM. Bottom beginning to drop out now!



4:06 PM. Graupel and/or large drop strand (center)  just began to appear (look hard).   This was taken just after the first cloud-to-ground strike near Samaniego Peak (center).



4:11 PM. The gush reaches the ground amid frequent split cloud-to-ground LTG strikes, ones near or in the core, and repeated strikes a mile or two to the right in clear air.



4:17 PM. Our little rain shaft offered up a lot of wind, probably in the neighborhood of 50 mph, judging by the spread of the rain “plume” on the ground to the right. Some drops and gusty winds of 20-30 mph reached Sutherland Heights soon after this, making for an especially pleasant evening outside.



5:42 PM. An isolated thunderstorm, rumbling to the west of the Tortolitas yesterday evening , offered up this dramatic shadow scene.Its remnant providing a sunset highlight.



5:48 PM. Trying its best to rain.



6:37 PM. The remains of the thunderstorm shown in the photo above provided a nice sunset highlight as they so often do.


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.