Watching rain come out of the Arizona summer sky

Here is a sequence of photos showing the development of a rainshaft from a prior “doing nothing” cloud base.  For a long time, it appeared that these dark clouds, bottoms of Cumulus clouds, were too raggedy, not contiguous enough in a nice, large and dark region indicating a wide updraft, one  that might push cloud tops to the “glaciation” level where ice forms magically and spreads throughout the cloud top.   Our Cumulus clouds,  at this warm time of the year,  must climb to about 20,000 feet or more above sea level, or to the -10 C (14 F) level,  before the liquid cloud drops in them will freeze to ice, and then only some cloud drops do.   Those first ice particles, surrounded by drops that have not yet frozen,  become hail or “graupel” (aka, “soft hail” you can mash between your fingers) as they collide with those unfrozen drops as they begin to fall out.

So, no rainshaft, no tops to 20,000 feet or more, no matter how dark the clouds may look.   At least for a long time yesterday, they did nothing.  You’re thinking, “What a waste!”  and, “So close!” (to precipitating).  I did, for sure,  as I thought a chance for rain in the area was going to be missed.

But then, there it was (look hard, straight above the tree near the middle of the 2nd photo) !  A thin strand of rain dropping out of those dark bases, a strand that quickly became a downspout, then a huge rainshaft clobbering,  maybe Saddlebrooke!  Very nice, dramatic to see.

Here’s the main sequence of that.  First the line of non-raining cloud bases is shown, and then the cloud base area where the shaft began to fall out.  After that, it lengthened, broadened into a full rainshaft.  Notice the curvature to the left as it went down toward the ground, showing the N wind underneath cloud base.  This is SUCH an exciting time because you’ve been waiting and waiting for something to happen and begin to wonder whether it will at all.

We only got a trace, a few drops.  But the air cooled nicely, followed by another fabulous Arizona sunset producing that little bit of paradise.











Why was there a line of clouds like that shown over Cat land yesterday evening?

Clash of the “outflow” winds from thunderstorms in the area, that were meeting below that line of cloud bases.  That wind clash passed through this location at 6 PM LST when the wind shifted from the southwest to the north.   Above these kinds of clashes, the air is forced to rise and enhanced clouds, or a line of clouds forms. Some areas got over 2 inches yesterday between Colossal Cave and Benson.  Check these amounts out here.

Here’s one of last evening’s sunset, for a little color,  “Arizona gold” in here to break up all the gray: