Sunday, February 22, 2015

Hole punch clouds

Shortly after sunset on Feb. 19 I saw what looked like a hole-punch cloud, also called a fall streak hole. It looked a bit like a giant space amoeba from Star Trek:

OK. Maybe a lot like one.

I understand these are caused by a domino-like effect where super-cooled water vapor needs a nudge to create a cascading condensation that then falls out of the cloud. One possibility for the source of the nudge is a passing airplane.
I've seen these before and I assumed updrafts from our nearby mountains were the cause, but I don't know.
At least one of my pictures confirms the hole punch occurred near the flight path of planes. The bright line in this photo is a plane:

However, my pet theory that the mountains are creating updrafts that trigger the condensation suggests that there would be more hole punches to coincide with the few peaks in the area, as shown in this photo from a couple years earlier:
Hole punch clouds above the mountains on my western horizon

I looked around for others and did find one, though it was less impressive:

Though less impressive, it did look a little like a giant rabbit in the sky (on its back), something I've been seeing a bit of recently and shared with the Orange County Astronomers last week:

Multiple hole punches does not eliminate planes as the source, so the cause in my region is not settled.

As the hole punch drift east, the sky was dark enough to bring out a few stars: 

Other hole punch clouds:


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