Crazy over pileus

Lost control for awhile yesterday evening at sunset as pretty little pileus caps formed repeatedly on top of new Cumulus congestus/Cumulonimbus turrets to the west.  It like an entomologist seeing a spotted owl, or some other rare bird like that.  You don’t see pileus caps that often, and when you do, you’d better have your camera ready because they only last seconds.  Nice sunset color along with them, too. Some nice lightning over that way later, too.

If you were in a research aircraft and wanted to find the most liquid water around at a particular flight level, a pileus cap on a Cumulus turret at that level is a good sign that that’s where it will be compared to other clouds. But don’t  sample too close to cloud top, maybe 100 m below since dry, ambient air is being mixed into the extreme top and you MIGHT not measure the most liquid water there, especially if the top looks a little “frizzy.” .  Its fun to see how much you can hit with an airplane; see what the instruments do.

The rest of the day was very nice before this pretty much replicated the day before in virtually every detail;   several Cumulonimbus clouds arose on Ms. Lemmon beginning in mid-afternoon, anvils trailed over Oro Valley, and there were again a number of distant Cumulonimbus clouds to the NW-NE scattered over the high terrain way up that way.  There were  also Cumulonimbus far to the S-SW toward Mexico, as well as an active cluster to the west at sunset that generated so many pileus clouds.  Here is your cloud diary day in photos:

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6:36 PM. First, before the pileus shots, the overall scene to the southwest and west, and also why telephone poles and overground wiring, relics of the past, are offensive and need to be removed; those wires put under ground. Don’t blow down that way, either.  I’d like to start digging right now!  Hope I’m not upsetting you too much with this scene.  As a CM Jr., , overground wires are the bane of civilization.
5:58 PM. Grouping of Cumuloni,bus and Cumulus congestus clouds distant west, ones with repeated pileus caps as new turrets surged upward through a thin moist layer, also shoved up due to the approaching rising air in the turret.
5:58 PM. Grouping of Cumuloni,bus and Cumulus congestus clouds distant west, ones with repeated pileus caps as new turrets surged upward through a thin moist layer, also shoved up due to the approaching rising air in the turret.
6:56 PM. Yet another pileus cap formed, but this time, is above the top of the surging Cumulonimbus calvus (its got rain coming out of it) top.
6:56 PM. Yet another pileus cap formed, but this time, is above the top of the surging Cumulonimbus calvus top. (Its got rain coming out of it, so its that bit better to call it that instead of just a Cumulus congestus.)

 

The clouds prior to the pileus eruptions were these ones:

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2:42 PM. Just a pretty picture looking NW across Saddlebrooke with Cumulus humilis and Cu fractus in the foreground and scattered Cumulonimbus and Cumulus congestus on the horizon.
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11:45 AM. A good sign of an interesting day ahead, that Cumulus sprout over Ms. Lemmon that indicates there is a lot instability (the decline in temperature with increasing height is pretty large) and that further heating will likely lead to deep clouds.
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4:26 PM. A sight very reminiscent of the previous day, a narrow Cumulonimbus shoots up off the Catalinas. This was the second one in a row like this. Kind of blew up into something considerably larger than the one around 3 PM, with this one’s vast anvil eventually overspreading Catalina and Oro Valley.  Here, playfully, it appears to be in the shape of an alien with two arms reaching out, a fibrous, icy one on the left, and a fragmented, droplet cloud one on the right, with a big head between them.

 

5:19 PM. Pretty much all over here, just a big anvil as bottom got rained out with no more surges of Cumulus to keep feeding it.
5:19 PM. Pretty much all over here, just a big anvil as bottom got rained out with no more good surges of Cumulus to keep feeding it.  Just getting too cool up there.

Want to get one more thing in here, in case you haven’t paid attention to all the rain that’s been falling in Arizona, particularly in the NW part, SE CA, and southern Nevada. They are having a spell that is just incredible. Here, from WSI Intellicast, the 7-day rainfall totals for the US, which highlights how well those areas are doing compared to the rest of the county even. This is an amazing graphic, and so pleasing since all this rain in the Southwest has been falling on very drought-impacted areas.

The seven day, radar-derived precipitation totals for the US. Mountains, of course, interfere with radar beams that do this, and so in mountainous regions these estimates are likely too low, or can be missing altogether.
The seven day, radar-derived precipitation totals for the US. Mountains, of course, interfere with radar beams that do this, and so in mountainous regions these estimates are likely too low, or can be missing altogether.

Summer rain season set to sputter along today and for the foreseeable future. Looks like there will be a few more thunderheads around today compared to yesterday, a bit more instability today, too, this from a 2 min look at model outputs as choke time approaches. If you want a good forecast, you should see Bob’s writeup. I like Bob. Plus, he’s a stupendous expert on convection!

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.