Before the rain: a LOT of clouds, some smoke

Got pretty upset later yesterday afternoon when I saw these scenes off to the south through west, creating a little “sky rage”:

4 PM.  View to the southwest toward Twin Peaks.
4 PM. View to the southwest toward Twin Peaks.
4:58 PM. Vierw toward the west and southern part of Tortolita Mountains.
4:58 PM. View toward the west and southern part of Tortolita Mountains.

Its not CIrrus or Cirrostratus you see, my friend, though as a nascent cloud expert, a CMJ, you may well have told a neighbor at the time of these photos, “Look, here comes the lead Cirrostratus undulatus (its had waves in it) clouds  that precede our rain in a couple of days.”

You might even have gone on quite a bit about it, but you’d have been so WRONG and had to have apologized to your neighbor the next day,  “after further review.”

What did you review?

The satellite infrared (IR) imagery, locally available.  What would have been the obvious problem with your pseudo-astute cloud discussion?

If there is no cloud indicated in the IR imagery and KNOWING that if it IS Cirrostratus, no matter how thin, if its pretty widespread, as it is in these images, it WILL be detected in the satellite IR images1.

Let’s check if there is a cold cloud encroaching on Catalina around the time of these photos:

4:15 PM AST.  Cold-topped clouds not even close, though they are moving this way fast.  Maybe we'll see some lead clouds on the horizon at sunset...  Post event thought.  See 3rd photo.
4:15 PM AST. Cold-topped clouds not even close to Catalina.  What were you thinking, saying you saw some Cirrostratus? However,  those high and cold-topped clouds ARE moving this way fast. Maybe we’ll see some lead Cirrus clouds on the horizon at sunset… Post event thought. See photo below.




5:56 PM.  Note thin linear shadows in front of Cirrus clouds.
5:56 PM. Note thin linear shadows in front of Cirrus clouds.

Let’s also check, too, with our AOD (Aerosol Optical Depth) sensor on a satellite to see if it has any smog in it around here (below).  Now this image below is an integrated view all the way to the ground, and so it can’t tell you what height smog is at.  But, from the ground yesterday afternoon,  we could “fill in that blank” by seeing that its way up there, probably at or above 20, 000 feet above sea level.

Below:   valid at 3:15 PM. Shows region of thin smog clockwise, south through west through NW of Catalina toward where the first two photos were taken.

ann AOD_2215_US



Next, after you’ve apologized to your neighbor, he might well ask of you, “Where did it come from, if that’s a smog layer up there?”

To prepare for such a query after you had learned that it was not a CLOUD,  but rather smog, you would have used an estimate of its height (say, 7 km above sea level as a starter value), and gone to NOAA’s Air Resources Laboratory’s HYSPLIT model and prepared a few back trajectories for a few days, ones that end at Tucson, or even our exact lat and long.  If you had done that, here’s what you would have seen this morning for a back trajectory for FOUR days, ending over Tucson at 5 PM AST yesterday for 6000 meters above sea level:

The star is the end point for 5 days of model calculated backward air trajectory for that air over Tucson at about 7500 meters above sea level, about 5000 meters above the ground.
The star is the end point for 5 days of model calculated backward air trajectory for that air over Tucson at about 6500 meters above ground level, a first guess (not really) for the height of the smog layer in the photos.  Other levels above this level look pretty much the same.    Each fat triangle is a day.  I put a LOT of writing on this, I HOPE it helps, but not sure.  These graphs should have the start point for the vertical cross section at the bottom on the other side!

So, it would appear that our smog layer may have originated as part of something coming across the Pacific from Asia.  There are no fires in Canada and in the Rockies that could have lofted a smoke layer like the one we saw yesterday.  Confidence level? Moderate at best since the height of the layer had to be estimated by eyeball.  You can go HERE to make your own plots like these, that is, to the Air Resources Laboratory of NOAA.

Clouds?  Must talk about clouds.

There’s a lot of them headed our way. Check this annotated gif with writing on it from a couple of hours ago:

At 3:30 AM AST.
At 3:30 AM AST.  I’ve written some things on it, and since we know from recent educational attainment studies that US students lack much geographical knowledge, like where the Pacific Ocean is, I thought I would see if anybody notices a problem here.


Big Pac IR loop from the U of WA Huskies Weather Department here.  I had to use these images for the whole western Pacific down to the Equator so that you could see the whole of the cloud system that is now impinging on the West Coast of North America,  from Manzanillo, MX, to Alaska.  Pretty cool, huh?

Of course, as we know, the first of these clouds coming toward us, and for the next couple of days, will be high and middle clouds like Cirrus, a lot of Altostratus, and some Altocumulus.  Might see, as happened yesterday afternoon, a Cu fra over the high terrain.  (There is a little moist layer around 10,000 feet above sea level, according to this morning’s Tucson sounding.)

The rain gets here, the mods say, finally on Saturday morning, the 26th.  There will be breaks in these high and middle clouds, and with luck, one or more super-spectacular sunsets/sunrises in the next three days.

Enough! Quitting…..TE.


1Itty-bitty patches of Cirrus won’t be detected in the IR imagery.  Its has to be a couple of square kilometers  to be detected by the NOAA GOES satellites, the kind from which most weather imagery originates. Usually though, when Cirrus clouds occur, its detected because there are many larger patches besides the tiny ones.  Tiny ones in isolation are rare, often associated with contrails.