Cumulonimbi sightings; can rain be far behind?


Yesterday saw a gorgeous sight after our long cloudless spell; Cumulonimbus anvils approaching from the south-southeast in the later afternoon, our summer friends with their winds and rain squalls.  The bottom of those thunderheads disappeared before they arrived over Catalina, and were just anvils, that icy portion above 30,000 feet or so, but they harbinger a great rainfull day today as degree of moisture improves.  The dewpoint in Tucson was only 39 F yesterday at this time, and is now a robust 58 F!  Welcome water molecules!  This means that if you condensed all the water out of a cubic meter of air today you would get  about 8 grams while yesterday you would have only gotten about 4.5 grams, so almost a doubling of water content in the air swirling around us.

And with this, instead of having cloud bases at 14,000-15,000 feet above sea level (about 11- 12 KFT above us) as we did yesterday, they’ll be closer to 10-11 KFT above sea level, or 7-8 KFT above us (maybe even topping Ms. Lemmon).  This will mean that less of the precious rain falling out of those Cumulonimbus clouds today will evaporate before it reaches the ground.   And with that, some very dramatic skies later today.

Check the U of A local model here to see what the great “Beowulf Cluster” is thinking about rain today in AZ.  Looks good.  Note some favored areas just to the SW of us might get an inch of rain today! (But, don’t count on the EXACT placement of those strong rain areas; they’re often off by many miles.  Its just a good indicator of strong showers very near us today.)

The past two days have seen some rain fall in SE AZ, but the cloud bases were so high, not much reached the ground.  So, the chances of a significant rain here in Catalina this afternoon and evening are good, indeed.

Farther ahead…and remembering 1955.

The models are still making it look like a normal uptick in rain chances around the 4-5th of July, pretty usual for us here in Catalina, with a bit of a dry spell before that uptick in rain chances.

One interesting facet of the weather pattern these days is how a cold spring and summer in the Pacfic NW in 1955 translated into a bountiful summer rain season here.  This June will be one of the coldest/wettest ever in Washington State.  Many of you out there probably remember the great summer rains of 1955 and those string of hits by The Platters.  While weather never quite repeats itself, and there hasn’t been a group like The Platters back either,  its something to hope for, that is, that the cold in the NW, wet in AZ pattern will recur this summer.

Lots of complainers now in the Pac NW these days with the continuing rains and cool weather there as the longest day of the year has passed, the days beginning to shorten, with no sign of summer yet.

Here are a few shots of those approaching Cumulonimbus clouds from yesterday:

First Cumulus over Ms. Lemmon about 1 PM AST.
Just after 3 PM, first Cumulonimbus sighting, and its moving this way!
5:22 PM: Cumulonimbus complex moving this way, but looking like too much anvil cloud, not enough connecting clouds.
6:24 PM: Its gone, faded away as the afternoon heating faded and all the lower Cumulus were gone. Just an icy mass drifting toward us.
7:36 PM: a nice ice cloud sunset, but no chance of rain.