What an awful past 24 h here in “Catland”! We’ve not only had low, perhaps, unprecedented low temperatures for a day with full sun, but also a noxious 15-30 mph north wind. (Why didn’t we retire to Kauai where we would never be this cold????!!! Just kidding, sort of.)
In some quarters(such as in a recent commentary by Al Gore), it has been reported that we should expect colder winters as it gets warmer due to global warming (I am not kidding here-check the last paragraph here).
If this is the case, and our current godawful cold spell here in AZ has been enhanced by GW, then we had better reconsider where we grow citrus crops! South Florida just had a record cold December. Perhaps Florida is too far north for citrus crops as global warming proceeds and winters get colder, or at least cold spells more severe. California, Arizona, are you listening?
Now, for a diatribe on clouds, about which Mr. Cloud-Maven person, me, is an expert (he sez).
If you saw the few small clouds we had yesterday, you saw something extraordinary for SE AZ. Why? Because of all the ice crystals that formed in such tiny clouds (ones called, cumulus fractus).
Below is a photo of cumulus fractus clouds forming lots of ice from yesterday afternoon. The top most cloud is a pure cumulus fractus cloud, not yet showing ice. But beyond that cloud, farther to the east, are similar clouds spewing forth a large plume of ice crystals, seen as the wispy, semi-transparent cloud downwind toward the right half of this photo. Cu fra forming ice are common in the high elevation areas of the Rockies, but not here because our lower clouds that are small are almost never as cold as those, even in the wintertime. Our clouds, according to the NWS sounding launched from Tucson around 5 PM LST yesterday were about -25 C, an extraordinarily low temperature for clouds not having any depth to speak of. And, due to that low temperature, voila, ice forms!
So, a good eye with a little knowledge about ice formation could have guessed that these little clouds would have to be colder than about -20 C to have been so prolific in ice production, those veils seen downwind of them. Ice forming in such shallow clouds are too small to fall out as precip as a rule, though some “virga” or flurries were observed here and there in SE AZ, such as at Stafford yesterday afternooon and west of Wilcox as well. (Of course, I had hoped a couple of days ago that we here in Catalina would see a flurry. Still, with flurries at Stafford, it was a damn close call, astronomically speaking, so I don’t feel that bad for getting a little too excited about the possibility of snow here a couple of days ago. Besides, it was a “learning experience” as well….)
Amaze your friends with such trivia!!!
However, it will be a long time before you see such clouds, as low and small as these were, produce ice like this. Well, we hope so anyway, or we are moving to Costa Rica where I will not have to experience even one second of being too cold! If you want a really good look at what they were doing, go to the U of A’s timelapse for yesterday (here). (Forgot to point this out until now…darn.)