Mysterious Holes In the Sky

During the past weeks, several of you have sent me pictures of strange holes in the clouds above our region.   Scary-looking pictures.

For example, one was taken by Paul Spring in Bellingham on Friday at about noon.

Two holes in mid-level clouds.

Pretty wild.  

Alien visitations?  Secret defense department project?  Nope.

Such "hole punch" clouds are not rare and were first explained by Research Scientist Art Rangno and Professor Peter Hobbs of  the University of Washington in a paper published in 1983 (see below)

They found that such holes were caused by aircraft flying through clouds made of supercooled water: liquid water droplets that are below freezing.

Yes, water can exist in a liquid state even at temperatures below freezing!  Many clouds have significant areas of supercooled water.

When an aircraft disturbs such supercooled clouds they rapidly turn to ice crystals that fall to earth.   

The UW team had another name for this situation:  Aircraft Produced Ice Particles (APIPs) 

In fact, one of the pictures provided by Paul Spring showed the transition to ice crystals (see below).  

Water clouds have relatively sharp edges while ice clouds have fuzzy edges.  Look closely and you can see the ice crystals in the center of the "hole" falling towards the earth and being pushed by differing winds below, resulting in a bend in the falling ice.

Can we see the hole-punch clouds in weather satellite imagery?

You bet!

Here is a  GOES visible satellite images from just before noon on Friday, centered on the area around Bellingham.  Do you see the nearly circular "holes" in the clouds?   Those are the features in question!

Aircraft had a lot of impacts on clouds on Friday, with several jet contrails (thin white lines, indicated by red arrow) over Puget Sound, while all the "hole punching" was occurring around Bellingham (blue arrow).