With no weather in view for the next week or so, and with June being “dust devil” month in Arizona, it seemed appropriate to reference the work of Dr. Peter C. Sinclair, University of Arizona, Institute of Atmospheric Physics, 1960s. Read all of his journal articles because I liked dust devils myself…. Don’t we all like to see them, are fascinated by them, when we don’t have a jumping castle about to be tipped over by one?
I know a lot of you out there, too, are fascinated by dust devils and even while driving, take snapshots of dust devils you’re particularly fond of. The photo below is from a friend who’s particularly fond of dust devils, as an example.
Dr. Sinclair put stuff on his car, the kind of stuff shown in this article above, and drive into dust devils, getting measurements of the temperature, pressure and winds inside them. He was the first person to do that, to get measurements inside them, and so was making a real contribution. He was kind of a hero of mine since I, too, had a fascination with dust devils, though of a more visceral nature; I just jumped into them sans instrumentation when they crossed our San Fernando Valley school yard. Its a gritty experience. Hair gets messed up, too, but who cared about girls then?
Here’s a post-dust devil kid shot, entitled, “little Artie’s hair” for some reason. (I hope it was a post dust-devil shot! I always laugh when I see this photo and hope you do, too.)
Note that in the article referenced above, Dr. Sinclair, shown standing next to his equipment, has hair that is perfectly in place. I don’t think he jumped into them, to really KNOW them, like I did…
Plenty of sun all day, high sun angle, with resulting surface temperatures that could melt lead leads to tremendous instability at the ground and “superadiabatic” lapse rates here in Arizona. In these situations, the air right at ground level, within inches, might be 120 F, and the air just above, “only” 100 F.
The atmosphere gets rid of that excess heat at the ground via thermals, bubbles of warm air that lift off and is replaced by cooler air overhead. Our afternoon winds, ones that come up suddenly, then die out, and repeat that sequence over and over again, are evidence of those thermals. Leads to a very bumpy temperature trace since its warmer, then cooler, warmer, then cooler, etc.
Sometimes, when the bubble lifts off, perhaps suddenly, air swirls in to take its place, and by conserving its angular momentum, develops a tube as the air spins more rapidly as it approaches the the central lift off point. A more recent explanation is that small volumes of air already have rotation and become tilted upward over hot surfaces, as shown here.
The weather ahead…
Man, the models of late have come up with an exceptional trough in the West. While no rain is expected here, it is quite extraordinary, and is pretty much supported by the ensemble plots (aka, spaghetti plots). Here is the upper air anomaly plot showing how extraordinary this forecast for the heights of the 500 millibar surface are for June 17th, ten days from now. This would mean exceptionally cool air over southern California and Nevada, and some cooling here, though not so much is indicated for us at this time since the low stays west of us. Inside the strongest winds around this low at this level would be the areas having precip, or in Nevada and central California only.
At this time of year, we need a tropical fetch for us to get rain, and that isn’t forecast right now. But the models are having a hard time with this situation, and it may be that some tropical air can be caught up on the faouter boundary of this low if it moves off to the west. Such moist air is already foretold to invade over New Mexico and west Texas, lucky guys.