Pretty cloud day yesterday; storms dead ahead and ahead

In case you missed the pretty sights of yesterday:

7:05 AM.  Sunrise on the Altocumulus.
7:05 AM. Sunrise on the Altocumulus.  Two layers are evident.
8:42 AM. Kind of blasé except for the rarely-seen-in-AZ (faint) halo. Altocumulus with Cirrostratus above.
3:30 PM.  Pretty patterns; Altocumulus perlucidus.
3:30 PM. Pretty patterns; Altocumulus perlucidus.


4:45 PM.  Cirrus uncinus and Altocumulus (clouds with shading).
4:45 PM. Cirrus fibratus (not hooked or tufted at top) and Altocumulus (droplet clouds at right with darker shading). Lower gray portions beyond Pusch Ridge and extending to the horizon is probably best termed Altostratus.
4:56 PM.  Nice lighting effects on Samaniego Ridge.
4:56 PM. Nice lighting on Samaniego Ridge.
5:21 PM.  Your sunset.  Nice underlit virga from patchy ice clouds.  Could be termed Cirrus spissatus or Altostratus, if you care.
5:21 PM. Your sunset. Nice underlit virga (light snow fallout, likely single ice crystals, not flakes) from patchy ice clouds. Could be termed Cirrus spissatus or Altostratus, if you care.  What kind of crystals, you ask or didn’t?  Bullet rosettes.








































 The clouds and weather just ahead

Expect more Altocumulus, Cirrus, and Altostratus today, patchy and gorgeous.  Would expect some nice Ac castellanus (one with spires) as an upper level low off Baja starts to move toward us.  Some measurable rain likely tomorrow in the area, but probably barely measurable, maybe a tenth at most since it will fall from middle clouds with a lot of dry air underneath them.  (Enviro Can mod still sees rain around here tomorrow.)

Middle clouds might get large enough to call the (small) Cumulonimbus clouds, with a slight chance of lightning tomorrow, Thursday,  as this low moves up and over us.

So both today and tomorrow will have some great clouds!

WAY ahead; watch out!

 After a quiescent period of gorgeous, misleading days, where the temperatures gradually recover to normal values and you’re gloating over the nice weather you’re experiencing by coming to Arizona from Michigan, blammo, the whole thing caves in with strong storms and very cold air heading this way.   Yesterday’s 18 Z WRF-GOOFUS model run for 500 millibars (rendered by IPS MeteoStar), was, if you like HEAVY precipitation throughout Arizona, well, truly”orgasmic.”  You just cannot have a better map at 500 mb for Arizona than this one from that run.  That low center over California, should this verify, would be filled with extremely cold air from the ground on up, cold enough that snow in Catalina would be expected as it goes by.  So, there’s even a prospect of a white Christmas holiday season.  Imagine.

Valid 264 h from 11 AM AST yesterday morning, or for 11 AM AST, Saturday, beginning of football bowl season I think, which last until February I think.
Valid 264 h from 11 AM AST yesterday morning, or for 11 AM AST, Saturday, beginning of football bowl season, which last until February I think.

Now will this verify exactly like this? Nope, not a chance. But, spaghetti tells us we’re going to be in the Trough Bowl, filled with cold air and passing storms beginning in 8-10 days from now. How much precip and how cold exactly it gets is unknown because these progs will flop around in positioning the troughs that head our way. There will be major troughs passing through, so while the amount of precip is questionable, the cold air intrusion is not. It was just so neat, exciting, mind-blowing to see that such a gargantuan storm has been put on the table for us in that 18 Z run.

Most likely subsequent model runs will take this exact map away, but then put something like it back, until we get much closer to verification day, the 21st. May even shift around on which day is the doozy, too, by a couple of days either side. Still, a really exciting period of weather is ahead.

This may seem odd, but one of the keys to our storms way ahead is the eruption of a huge storm in the western Pacific (and that storm is shown developing in the last day (144 h panel) of the Enviro Can mod.

———–dense reading below————-

That erupting, giant low pressure center will shoot gigantic amounts of warm air from the tropical ocean far to the north ahead of it in the central Pacific.  That warm air shooting north, in turn, causes a bugle to the north in the jet stream, a ridge, which deflects the jet toward the north toward the Arctic.  As the jet stream does that, there is almost an immediate response downstream from the ridge; the jet stream begins to turn to the south, developing a bigger an bigger bulge, or trough to the south.  So, a jet stream running on a straight west to east path across the Pacific can be totally discombobulated when a giant storm at the surface arises and shoots heat in the form of clouds and warm air northward1.  In this case, all of this takes place beginning in the Pacific in about 6 days, so that a sudden southward bulge, a buckling of the jet stream, due to that giant low in the western Pacific 8, 000 miles away,  happens over the western US.   And  voila, our big cold and maybe our big storms, too. then.

————end of lead-filled text———

The End.


1First noted by much-honored meteorologist, Jerome Namias, who did not have the Ph. D. but was great anyway, in the early 1950s.

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.