Not as good as a rain day with lightning, but yesterday did have its moments in the sky, enough to make the astrologers on Mt. Lemmon jealous with displays of parhelia (“sun dogs”, or “mock suns”), faint haloes, a rare parhelic circle, something you don’t see but once every year or two, and fallstreifen (fall streaks) from Cirrus uncinus clouds going in almost opposite directions, an extremely rare sight.
The rare “parhelic circle” is a local brightening often extending out from a parhelia (sun dog) at a sharp angle, which I just learned about here1. Usually you don’t see a whole circle, just part of one.
These optic displays are caused by ice crystals, of course, ones not too complex, but rather simple ones like prisms, short solid columns, bullets, and hexagonal plates. Some examples of these can be seen here.
The bottom of yesterday’s moist layer was just above 30,000 feet at a temperature of -35° C and extended all the way up to about 40,000 feet above sea level where the temperature were around -65° C.
Some photos documenting the excitement of yesterday
Below, examples of cold Cirrocumulus, ones that quickly transition to Cirrus clouds.