Lots of bluster, little rain except at Sutherland Heights where 0.39 inches fell last evening

Another day with hours of thunder, but with those high and cold cloud bases, not much rain reached the ground. Also hurting the rain situation, too much ice.  An afternoon sprinkle, a very close, rogue lightning strike, followed by an early nighttime “chaser” storm that, with all of its bluster, wind and vivid lightning, produced only 0.02 inches here, but a lot more at Sutherland Heights, a robust 0.39 inches (new knowledge, gained after dip sticking gage up there at around 7:30 AM)  To see how remarkable that Sutherland Heights rain amount is, go here to the U of AZ rainlog network.

Here’s a smaller, but typical example of yesterday’s generally “low output” Cumulonimbus clouds:

5:24 PM. Starting to let go.
5:32 PM  Maximum strength.
5:45 PM Almost gone.







Here’s another quite bad cloud (shown below), though it was good one one hand, because it was an early afternoon, frequently thundering cloud which gave promise of rain later in the day. But that rainshaft?  Pitiful.

1:55 PM. At least some rain is getting to the ground amid all the thundery bluster by this cloud, thunder heard about once a minute at its peak output.
1:47 PM. Small, former Cumulus congestus dissipates into an icy mass, no shaft was ever visible. Poor cloud.









It was also a forerunner of the kinds of storms we would have.  Again, with high and cold bases (and oddly to me), there seemed to be an awful lot of lightning for the size of the Cumulonimbus cloud at 1:55 PM, much of it in vivid cloud to ground strokes.  You may have seen a another example of that last evening around 9 PM on the Catalinas when there were a series of frequent and spectacular cloud-to- ground strokes, but little rain.  The most that fell up there was 0.28 inches at Oracle Ridge. Map here.  BTW, you can see the “1:55 PM”
Cb in the U of AZ time lapse movie at the far left beginning around 1:40 PM.

Well, how high were cloud bases?  Rendered by the Cowboys, this 5 PM sounding for Tucson:
Reading this sounding, it makes bases appear to be around 16,000 feet Above Sea Level (subtract our elevation for above ground level) and a few degrees C below freezing.  With bases that high and cold, the amount of water condensing at the bottom of the cloud is less than on days with bases, say, at 5 C and at 10,000 feet ASL.
So, less condensed water input means less rain coming out the bottom later.
If there is “too much ice” for the amount of water coming into the bottom of the cloud as we saw yesterday, its like a glass of water filled with ice cubes in which only a tablespoon of liquid water can be contained in it.  The analogy is only somewhat representative since with “too many ice crystals” competing for the available water vapor, you end up with high concentrations of smaller crystals that hang in the sky rather than fall out.
So you get big anvils and debris clouds with little rain to the ground even in the peak stage of the storm.
Since the best rains in the shafts we see are due to melted graupel and hail, icy particles that generally start as an ice crystal at high elevations in the cloud, if there is little “supercooled” water there isn’t much graupel or hail, the type of precip that can make it to the ground from high bases (melting snowflakes wouldn’t from bases as high as we had yesterday because they’re essentially like Rice Krispies, there’s not much mass in them).

Well, this is pretty boring, so will end here with a sunset photo from last evening:


The U of AZ WRF-GFS rendering of rain in the State of AZ sees early afternoon Cumulonimbus clouds breaking out over the Cat Mountains today.

Why not?

Starting out with pretty similar sounding this morning, but a bit more moist than last evenings above 600 millibars (about 14,000 feet ASL).

Longer view?

Hector marches slowly toward the Southwest (Canadian model outputs), promising an enhancement of August’s meager rains so far in southern AZ.

The End.






1Reminded one of summers in Durango, Colorado, where high, cold cloud bases and “too much ice” is normal.