Category Archives: Generating cells

Pretty skies; pretty Cirrus

Here are some shots:

Cirrus fibratus, straightish fibers of CIrrus lacking a tuft or hook at the top, in this case toward the left. For fussy folks who detect a slight hook, Cirrus uncinus would be OK, too. Not really too important to differentiate between these species. Just shows its moist up there, and, like yesterday, there was a trough going by;  air sliding up ahead of it, going down and clearing things off behind it (as happened late yesterday).
Cirrus uncinus (tuft, center, with dangling strands of snow), something like the tops of deep storms on a rainy day. These little guys are also sometimes called “generating cells.” Vertically-pointed radars during storms show that those dangling strands of ice can make it all the way to the ground, the head, or cell, dozens of miles downwind by the time that happens since the wind is so strong at the tops of storms.
Cirrus fibratus (foreground) and Cirrus spissatus where shading of the underside begins to occur in the distance.
The rarely seen Cirrus castellanus, center, a cloud that can resemble the top of a Cumulonimbus calvus before it crumples back down into a flat fluff of ice.


The weather ahead

Tried to find some rain for you in the models, but only one had rain, and that was the low resolution (big grid spacing) Canadian GEM model posted here.  It had the  rainy panel (lower right) for SE Arizona calculated from last evening’s global data:

Valid for Wednesday morning, 5 AM, October 30th.  The colored areas in the lower right panel are those ones where the model thinks it should have rained in the prior 12 h.  Note heavier, red-blobs in AZ!  How great would that be?
Valid for Wednesday morning, 5 AM, October 30th. The colored areas in the lower right panel are those ones where the model thinks it should have rained in the prior 12 h. Note heavier, red-blobs in AZ! How great would that be?  Again this rain is the result of a westerly trough grabbing the moisture out of a tropical storm off Baja, a very “iffy” situation, to quote a term oft used by the much honored, late atmos sci Professor Richard Reed of the U of WA1.














Also, I am really learning about how much the WRF-GFS model likes to bring hurricanes and tropical storms into the Southwest.  Yesterday’s model run at 11 AM AST, had another doozie coming up the coast in two weeks still having tropical storm strength and its about to pounce on northern Baja, southern Cal, and maybe AZ.  Here is that depiction for your amusement, valid at 11 AM, Saturday NCAA football day, November 9th.

the stuff of dreams for Saturday, November 9th, 11 AM AST.

ann Sat November 9th 2013102418_CON_GFS_SFC_SLP_THK_PRECIP_WINDS_384








The late Richard Reed, a man that did not mince his words.  The nicest thing he ever said to me was, "Those guys have gotta be stopped."
The late Richard Reed, a man that did not mince his words. The nicest thing he ever said to me was, “Those guys have gotta be stopped.”

Some more of that Catalina climo

Here is a 35 year record showing what days have had measurable rain in January.  Sometimes “singularities” in weather show up in these kinds of charts of tempearture or precipitation, such as the “January thaw” that seems to occur with some regularity in the East but is “unexplained.”  You would be looking at our chart for Catalina for example,  a cluster of days with higher or lower precipitation and it MIGHT be a singularity, something that Nature likes to do at that time of the year rather than a statistical fluke that represents nothingness.  Here’s January, a month that averages 1.65 inches in Catalina.  These data are almost totally due to the careful measurements made at Our Garden organic orchard here in Catalina–only the last few years here are from measurements on East Wilds Road.

Not much to see here.  That peak on the 6th looks more like a fluke rather than a singularity.  You would never say that one day represents a singularity, but maybe 5-10 days.

The reason why I wanted to see this was because of the striking changes that were foretold by the “WRF-GFS” model 36 h ago and were shown here yesterday.  Was there a singularity that might support a greater chance of rain in SE AZ in mid-January, and therefore, cast that bit more credibility on such a huge model change?

I would have to say “no.”  And, not surprisingly, that huge change has gone bye-bye in the models.  Nothing like it is shown now, though they do have a rain situation developing for here by the end of the 15 day run (around January 20th and beyond).    But this rain comes out of the lower latitudes of the Pacific, a completely different direction than was shown just yesterday, and if the models are correct in this pattern breakdown, it means flooding in California as the flow breaks through to the coast from the Pacific.

Below, what the models came up with based on last night’s global data, again, from IPS Meteostar, whose renderings I favor.

These are exciting times for those of us who peruse the models.


These vast changes indicate that there is something far, far upwind, perhaps a data sparse zone, errors in reported measurements that is causing a problem for the models and that more changes in their outputs may come down the line until that problem is better “resolved.”  (They are never perfectly resolved.)

So, every 6 h update of the models is a “must see”, with the persuser (me) holding his breath with excitement.  In these cases, its all “good” because a rain situation is foretold for us.  Take a look at where the jet stream is compared to where it is now, up around British Columbia.   You can see it barging into southern California and major rains ALWAYS accompany this pattern.  Also, you can probably count on at least two storms breaking through before this pattern changes much.   The reservoirists in Cal will be very excited to see this pattern develop since most of their holdings have much below capacity.  And these kinds of storms usually produce significant rain in Arizona, too, though here we would be a little far south to get the brunt of those storms in this scenario.

Pretty clouds yesterday

Can’t leave without a little cloud excitement.  I wonder how many looked up and saw this little beauty go by (shown below)?  So pretty and delicate-looking, as unusually thick virga (snow) fell from this little cluster.  It would be called, “Cirrus uncinus” at this stage.

That snowfall probably began developing one-two hours before it came over us, and the cloud patch would likely have been fluffed up on top that bit and as a mostly liquid water cloud, that is, an “Altocumulus castellanus” before becoming this “uncinus.”

Below we saw the dying remnants of that patch, the snow to finally stop falling out with the parent cloud mostly gone, and that snow continuing to dry up on the way down.  Lots of nice cloud sights yesterday, in fact.







Cirrus uncinus display; the tops of storms made visible

First, some instructional material:  You should be looking for your camera now, as seen in the first shot! Those Cirrus clouds to the SW are moving at you rapidly (95 kts, 115 mph at 30-35 Kft ASL!), and so there’s not much time!  In this first shot you can already detect some Cirrus uncinus, Cirrus clouds with hooked, or tufted tops in the center, with long icy strands trailing to the left. At this point perspective makes them bunch together so that they may not appear that “photogenic.”  However, just wait!  And, it was worth waiting just a few minutes for.

Take a lot at which they looked like passing overhead in the second and third shots, only about 7 minutes later. Just magnificent, some of the best Cirrus uncinus examples I have seen.

What is interesting about these clouds is that you are getting a glimpse of the structure of “stratiform”–that is, steady rain and snow storms that happen every day around the world, except that here in these photos,  you are only seeing examples of the very tops of them. Those widespread rainy/snowy storms are usually packed with thousands of these kinds of clouds in a solid overcast up there, each “cell” shedding tiny ice crystals which then waft their way down, growing, perhaps merging into “aggregates” of ice crystals we call snowflakes, and, that most of the time except in Wisconsin in the winter, melt into raindrops as they fall below the melting level.  Chances are, our little snowstorm of a few days ago had tops just like this.

Sometimes, clouds like these, and returns from vertically-pointed radars that can detect clouds like these, are referred to as “generating cells”, for obvious reasons.  The trails you see here are clearly visible on very sensitive “cloud sensing” radars–they are not visible on “First Alert” Doppler style radars and such used by the NWS because the ice crystals are too small at this point to produce a return on “normal” radars.  These cells form in a relatively shallow layer that usually lacks wind shear, likely mixed out by the little up and downdrafts in it.  Its only after the crystals fallout that they encounter wind shear and end up being stretched out into “tails” as here.

Falling from heights of 30,000 feet takes a long time, for an ice crystal falling at only around 0.5 meters per second or around 1.5  ft a second or even less.  It will take  LONG time for anything to reach the ground, perhaps 2-3 hours to reach the melting level.  So the little generating cell that produced a ice crystals at the top of major storms that grow and merge into snowflakes is likely over Alamosa, CO, and points northeastward by the time that flake landed on you at the ground with upper level winds such as we had yesterday.

I think its kind of interesting, but I may be the only one!

The end.