Clouds and tropical storms

The USA! models continue, in run and after run, to revert back to the serious rains in Arizona that they had foretold a few days ago for the 28th-29th of the month.  But then after that show of huge rains in SE AZ, and as I blabbed about yesterday, they took it away, but the chaos of the situation didn’t mean it was gone forever.

Sure enough, those heavy AZ rains have been back now for a couple of more runs including the one from last night’s 5 PM AST global data.

This is really exciting to see it come back.  But, those “rainful” runs could be heartbreakers just like people are in real life when they don’t live up to your expectations, real or magical ones; the steering situation is just too weak to have a lot confidence in where tropical storm Miriam will end up, the one whose remnants bring AZ so much rain in the model projection below.

Remnants of tropical storm Miriam are predicted to enter Arizona SW of Catalina on Saturday morning, September 29th.











Here’s another HUGE problem:  our friends to the north don’t think much of the chance of rain here; in their numerical model outputs, a form of the one used by the Europeans, poor Miriam dies in the eastern Pacific, her rains fall in the ocean somewhere, not where they are really needed, like at my house.

While the Canadian model can be considered quite bad because of this, you have to give it some respect anyway.  I guess we’ll know in a few more days.

In the Canadian 4-panel model, Muriam’s position, some 1000 miles different than in the US model, is marked by an arrow.  Note in the panel below where the arrrow one is, NO RAIN at all is predicted for Arizona!!!

So, confidence has to be low for rain at the end of the month.


Yesterday’s clouds

With the temperature running toward 100 F, and Cumulus clouds popping up after the morning Altocumulus went away, it sure seemed like a summer rain season day.  Cloud bottoms were too high, somewhere close to EIGHTEEN thousand feet above sea level (15,000 feet above Catalina) for much of a chance for virga to reach the ground.  There was a considerable amount of virga as the capped cloud tops reached -15 C (5 F) and lots of snow formed in them.  Looked like some rain reached the ground toward the border yesterday afternoon (where cloud bases would have been somewhat lower).  Here’s a brief pictorial for yesterday.  More can be see, of course, in the U of A timelapse here, always a fascinating study.  You will see our ice producing Cumulus moving from the SE as they usually do in the summer, but the Cirrus

Tucson sounding for 5 PM AST yesterday afternoon.
11:43 AM. After the Altocumulus with virga dissipated and moved away, a summer-like scene of baby Cumulus developed. Too bad there was a strong inversion (temperature reversal with increasing height) to cap them at -15 C or so, cold enough for decent amounts of ice formation and snow fallout (virga).
12:29 PM. Many more little Cumulus have formed, some starting to show virga, but due to that stable layer at their tops, they can’t grow much farther and become pancake-like.
3:18 PM. Downstream from the Catalina Mountains was this complex that may have been large and deep enough for a couple of drops (from melted snow) to reach the ground later.  Nothing here though.