“Pretty in Pink”

Well, “tending” toward pink, anyway…  But who remembers the Psychedelic Furs and what their song title alluded  anyway?  Of course, no one.  But I liked its dark sound.   Oh, well.

But here it is, that “pretty in pink” sky (2 shots) from yesterday evening in case you missed it.  Again these are Cirrus and Altostratus ice clouds with an isolated exception of Altocumulus lenticularis (just above horizon in the second shot), which is composed of droplets.  The second photo is a zoomed shot of the stack (several pancakes on top of one another) of a lenticular cloud off to the NW of Catalina.

Those lenticular clouds should always bring some excitement that things are changing, maybe heading toward a rain situation.   Rain did fall in the northern third of AZ when these Ac len clouds were present yesterday evening.

Why the excitement?

While these clouds don’t rain themselves, they are usually precursors of rain situations in the region because they illustrate that the winds aloft are relatively strong, the air in the “mid-levels” (roughly 10 to 20 thousand feet above the ground) has some moisture, and they indicate the kind of “stable” conditions in the mid-levels in their flatness, “pancaked-ness”, that precedes fronts.  Of course, we also had those moderate SW winds yesterday that also indicates that “something is going on”.

And something was going on as a cold front traversed the Great Basin yesterday.  Even this morning there is still precip in NW New Mexico as of 6:30 AM LST this morning.

And how do we know a new air mass came by?

The temperature change over the last 24 hours, from yesterday at this time to today at this time is one of the best ways of keeping track of fronts and changes in air masses.   Here is a plot of that 24 h change.  As you can see, the drop in temperature, while it has occurred at my gravel driveway (-5 F) is not quite here in Catalina (though it really is) according to the venerable The Weather Channel’s data which does not have my data (or pressure trace which has the usual sharp rise following a cold front–that heavier, denser, cold air is pushing down on all of us this morning and on my aneroid (not a body part, but a name for a barometer, BTW.)

The last shot here is what the clouds looked like before sunset.  Lots of gray indicating they are quite thick and fall into the Altostratus category even though they are very high.  Cirrus, by definition, cannot have this much grayness.  But, when you see this kind of  late afternoon sky, you can almost always count on a great evening scene, that sky especially “pretty in pink.”

Don’t see too many misspelled words, bad sentence structure and other grammatical lapses so will post this now…











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.