Last chance for August rain?

An unusually strong “trough” (a bend in the winds that points to the Equator) aloft will be moving across our region today, and as it does, it will be clustering storms, much like they were bunched together two days ago.   Remember that those bunched thunderheads came through in a band about mid-day.  Something similar is foretold for today, except a little later.  We hope that it takes a little longer than about 25 minutes to go through today, too.  Violent weather is expected in AZ today, too, with the PHX NWS office particularly worked up by this possibility and that office has already issued public advisories about frequent lightning, terrific winds, and huge dumps of rain.

Dry and fall like days will follow today…..meaning morning low temperatures will probably drop into the 60s here as the dry invading air moves over us.  With the lower sun angle these days leading to deeper blue skies overhead, the lower morning temperatures, you will definitely be thinking about college fubball in the days ahead.

Pay especial attention to what Bob has to say, our premier senior heavy weather forecaster, and your NWS for watches and warnings.  Mike at the U of AZ will be weighing in as well later this morning.  Could it be a tube day, too, somewhere?  Will be watching.

Not very certain there will be any more August rain here after this, a very dark thought.  As you know the chances of rain start to decline at this time of year.

Catalina summer rain frequency chart
Looks like it needs to be updated…..

 

Yesterday’s clouds (not in chronological order, just because…)

Maybe I make it too easy for you every day…

Ice  developed early and often in those morning Cumulus as they transitioned to weak Cumulonimbus clouds with tops that weren’t so high, but considering how early that happened, it led someone to think that it might be a really good thunderstorm day.    But then the air aloft dried out and those Cumulus tops couldn’t reach the ice-forming level by afternoon, which was quite a disappointment for someone.

Here are some pretty cloud scenes for you:

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11:01 AM.  Ice is obvious here. But, what kind of ice? If you look closely you can see that the ice crystals in this glaciated turret are comprised of hollow sheaths and needles, since the top of this cloud modest;  not that high and cold.  Well, that’s what I thought, anyway, just something about the texture…. Those kinds of crystals form at temperatures higher than -10 C (14 F), which is an unusual occurrence in Arizona. Happened yesterday because cloud bases were warm to start the day (about 10 C, or 50 F). Huh? Seems like a non-sequitur. “Strangely believe it”, as we like to say here, ice forms at higher temperatures as the bases of the clouds get warmer because ice formation is tied to drop sizes. The warmer the bases, the larger the drops reaching the freezing level in Cumulus turrets, and those  larger drops freeze at higher the temperatures.
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6:27 PM.  A parheila or sun dog, or mock sun in Altostratus cumulonimbogentius (of course). Caused by ice crystals falling flat on their face, hexagonal plates, pristine ones,  without any riming (cloud drops that have bumped into them and froze)
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7:02 PM.  Evening Cumulonimbus with a nice rain shaft; sent a few bolts “down” which is technically incorrect since the most luminous thing you see is called the “return stroke” and actually is going from the earth to the cloud.)
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11:01 AM.  Small Cumulonimbus forms over the Catalina Mountains. The turret on the left side is still mostly water, but would have a lot of small ice crystals in it. The center of the photo turret has glaciated, few or no liquid droplets exist.
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6:26 PM.  Cumulus highlighted by the setting sun under Altostratus or Cirrostratus (take your choice–Cs can have shading late in the day, otherwise, no shading for Cs. So pretty a scene.
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Just a nice closeup of a Cumulus turret. The variation in shading displays the complicated arrangement of liquid water content in the cloud, those darker areas having more.
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9:43 AM.  Going up? The Cumulus began forming on the Catalinas about 9 AM, a pretty early start, and that, a good sign of Cumulonimbi in our future.
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5:24 PM.  Just another just a pretty scene with Cumulus humilis and congestus.

The End.