Fog and Cumulus; Mr. Frosty ahead?

An unusual sight yesterday:  bulging dawn Cumulus fronted by fog.  These Cumulus (not spawned by ground currents) suggest instability aloft, a rapid decline in temperatures with increasing height, which allows the buoyancy of “warmish air” in-cloud  surrounded by cooler air to go up,  whilst fog1 suggests the opposite; cold, damp, heavy air that can’t go anywhere but down, slip sliding away as it did yesterday because its topped by warmer air, a atmospheric “glass ceiling”.  Ground fog like this is colder air that you can see.

7:21 AM. Looking NW from Equestrian Trail Road across Oro Valley.

7:19 AM. Odd multiple layers of ground fog (lowest) and Stratus clouds (“clouds” because they’re not on the ground) with shreds of Cumulus fractus above Samaniego Ridge.

7:07 AM. As above, suggesting a very fine layering of moist air with little temperature caps.

Here in Catalinaland, this kind of layering of cold air, as most of you know, is endemic on clear nights.  Those who drive down across the CDO wash from Sutherland Heights or along Lago del Oro from the surrounding higher terrain know.  Because of the stupefying amounts of rain in the past three days, the air is damp enough at ground level to form fog and you can see whose colder at night than you are IF you are above it.  Also, anyone who walks their dog in the morning passed innocuous looking gullies, is aware of how cold air flows downhill and collects in low places.

The lack of density of this fog indicated that it formed in real clean air, air that didn’t have a lot of junk in it (which would also contain a lot of CCN, cloud condensation nuclei.  Pretty hard to get fogs like we had in Bakersfield, CA.

Once things warmed up some, and with Arctic like air up top, Cumulus arose, a couple of which sprouted icy tops and shafts, namely, became small Cumulonimbus clouds, tops around 20-25 kft.  Along with these clouds, there was a treasure of sunny highlights and shadows moving across the Catalinas.  Here you go:

10:49 AM.  Small Cumulus humilis begin forming as temperature warms up to 50 F (egad).
10:49 AM. Small Cumulus humilis, mediocris begin forming as temperature “warms up” to 50 F (egad).


11:13 AM.  There's water on them rocks!  Not enough to get water into the CDO locally, but the Sutherland Wash developed a trickle.  Just too much dry ground up there for much runoff.
11:13 AM. There’s water (glinting) on them rocks!  One of the prettiest sights we get to see on the Catalinas after some rain.  Not enough water was dumped on the mountains during our drought-denting storm to get water into the CDO Wash locally, but the Sutherland Wash developed a trickle. Just too much dry ground up there for much runoff with the relatively steady rains that we had.


12:10 PM.  Small Cumulonimbus clouds erupt just north of Saddlebrooke. Thought I heard thunder from this complex later.
12:10 PM. Small Cumulonimbus clouds erupt just north of Saddlebrooke. Thought I heard thunder from this complex later.

2:50 PM. While small Cbs developed to the north, the Cat Mountains were only able to produce Cumulus congestus (“heavy Cu”).  Didn’t see any ice; neither did you, or there’s something wrong.  But, if you go here (U of AZ time lapse), you WILL see some forming in the downstream portions of clouds over the Catalinas.  Sometimes not seeing ice is because the tops are blowing off away from you before they show it, especially when there isn’t a lot.
3:48 PM. Last gasp Cu congestus. Will highest turret form ice?
3:49 PM.   Ice starting to show!
3:53 PM.  Droplet cloud completely gone.   No question now, nice ice plume. You want to target aircraft into densest portions of this ghostly veil of ice; will correlate with densest portions of liquid cloud. Not enough ice for a shaft below the cloud, but someone felt a few drops below it!































































Below, one of the attributes of our partly cloudy days and low near-winter sun angle; pretty lighting:

5:19 PM.
5:06 PM.
3:54 PM.







The weather way ahead, first week in December.

Pile of cold air to drive into West Coast and Rockies during the first week in December.  Snow even possible here, the air is that cold, but mainly the cold air will likely lead to the first cold spell where temps drop significantly below freezing.  The worst days look like the 5th and 6th right now, after the threat of rain and or snow pass.  So, if you have an evap cooler, you’ll definitely want to have it drained before then if you haven’t already taken care of it (like me).

Rain threat at the end of the month/first day or so in December is fading some in mods, but I refuse to give up on it!

The End.








1Fog is “gof” spelled backwards, BTW.  Has a lot of meanings and I avoided the obvious juvenile approach (today), “Think I’ll go goffing today” which I wouldn’t say anyway because I don’t play gof.