Big fat Cumulus day

4 AM to 4 AM 24 h totals ending today, ones that catch that morning rain (except where noted):

2.12 inches near Chrysotile, AZ, NE of Globe.

2.06 inches Wet Beaver Creek, Oak Creek Canyon area.

1.85 White Tail, just west of Palisade RS off Catalina Highway.

1.39 Oracle Ridge near Oracle in Cat Mountains

PHX set daily record ending at midnight last night, 0.80 inches.

Here’s the AZ radar-derived rain from 5 AM to 5 AM from WSI Intellicast:

Catalina?  A crummy 0.07 inches.  Well, no rain is technically “crummy”.

Good chance that some or all of that rain yesterday morning fell from clouds not having any ice in them, that is, formed rain due to the “warm rain” process, a rarity in AZ.  But, without an aircraft, its a dicey call.

1 PM Catalina temperature and dewpoint:  86 F and 73 F.  Miami, FL, at the same time:  90 F, 72 F. Warmer and dryer in Miami at the same hour. Our dewpoint was higher here than in Miami, quite something.  Our high dewpoints were helped by all the rain water evaporating yesterday against a background of already very moist tropical air.

The air was extremely humid here, but not hazy like back East on humid days. Interpretation? The air was very clean.

Its not the end of summer rain season even though a few dry days are ahead after today.

Cloud bases in the morning clouds were running 16-17 C, about 62-64 F, which means those clouds had about as much water condensed in them near their tops as any cloud could possibly have here.

AZ mod (here) thinks it can rain here in the late afternoon today.  Excellent.

Some of my big fat Cumulus cloud shots from yesterday, ones that were just like ones in Florida and Gulf Coast this time of year.

7:24 AM. Warm-based Stratocumulus clouds with embedded Cumulus build ups produce intermittent rain along the Catalina Mountains.
9:36 AM. As the Stratocumulus layer dissipates, gigantic, low-based, Florida-style Cumulus clouds begin arising NW of Catalina.
9:48 AM. I can hardly speak, these clouds are so HUGE! How many inches of rain might fall from them? Note glaciated tower protruding above the mass; top, right of center.
10:04 AM. Larger yet! Note low scud clouds, seemingly just above Saddlebroke rooftops.
10:09 AM. While these were wonderfully tall and low-based Cumulus congestus clouds, something was going wrong. Why weren’t there Cumulonimbus clouds, anvils scattered here and there to the SW-W?
11:15 AM. It was getting worse. It was clear that drier air was moving in aloft and dessicating growing clouds. Cumulonimbus were still peppering the area just NW of Catalina, but they were shrinking in size as cloud bases rose.
1:23 PM. The Cumulus congestus clouds lined the tops of the Catalinas, and occasionally produced a glaciated turret, but nothing gigantic as had been expected earlier in the morning.
1:32 PM. Glaciated turret (center) pokes up behind Cu congestus tops over the Catalinas. Would have been raining like “heck” under it.
2:26 PM. Though a big rain did not come through as I thought it might, it was a fabulously photogenic day with scenes of our now green desert topped by those puffy, roiling Cumulus clouds dotting the sky, ones providing thoughts of rain.

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.