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).

UFO Clouds

 I received a half-dozen emails this week about some strange clouds visible on Wednesday. 

  A few asked (perhaps in jest) whether they were connected to UFOs or some paranormal phenomena.

Picture by James Robers

Picture by Kathleen Millen

They are not natural.  Something artificial caused these strange cloud holes.

Aircraft.

These features have several names:  hole-punch clouds, fallstreak holes, and punch hole clouds are some examples.

They are generally associated with a middle-level cloud deck, such as an altocumulus layer, in which the clouds are supercooled, which means liquid water clouds below freezing. 

 Typically, supercooled cloud water can occur when the air temperature is between 0C and -15C (32F to 5F).

Here is a satellite picture around the same time as the first picture was taken....you can see the extensive cloud layer.

It is fascinating that clouds can be made of liquid water that is below freezing.  

However, things can change fast if such a cloud deck is disturbed by an aircraft that is either ascending or descending through it. Such aircraft passages can cause some of the supercooled liquid water to freeze.  How?

One way is that the wings can cause pressure to fall, and that leads to cooling, cooling the air enough so that the water freezes.

Once one gets some ice, water vapor rapidly moves to the ice crystals causing them to grow and fall out.

This is a very fast process that quickly causes the liquid water droplets to evaporate and ice crystals to fall out.

A cloud hole is born!

You can often see the ice crystals falling out, and that is why they are called fallstreaks.

Don't like this explanation.  Don't worry....there is another one.....

Dramatic Display in the Northwest Skies Today: Super Contrails and Hole-Punch Clouds

I got nearly a dozen emails this afternoon with pictures, mainly from folks around Anacortes and north Whidbey Island to Bellingham, of some very strange cloud formations--namely weird holes in a large deck of clouds.   Here are some examples:

 Courtesy of Tony Bigge

 Courtesy of the Stringmans of North Whidbey Is.

Courtesy of Jason Reid of Bellingham

No...these were not alien incursions into WA air space, but the impact of aircraft passing through a cloud deck of supercooled water (liquid water at 32F or below).   The planes climbing or descending through the clouds caused the supercooled water to turn to ice crystals and fall out, living a circular hole.  These features are also known as "punch hole" clouds and often form in mid-level altocumulus cloud decks.

Now what really got me excited is that the new high-resolution GOES-17 weather satellite actually viewed these from space!  Don's believe me?  Then take a look below!  Absolutely amazing.

But the fun today didn't end there.  We had one of the most amazing contrail days, with huge numbers of them filling the skies..... check out these NASA MODIS images from around 1 PM.  See all the little lines?  Those are contrails in a high deck of cirrus clouds.

 The air was at or close to saturation and the addition of moisture and particles from jet engines produced the multitude of cloud lines.

A picture from the Seattle PanoCam at 8:10 AM this morning said it all:  contrails, low clouds, and a wonderful sunrise--with Mt. Rainier in the distance.  What could be better?

Strange Holes in Clouds Explained

On Wednesday, I received nearly a dozen emails with pictures of strange circular holes in the cloud deck around Seattle.  Here are a few samples:

 Courtesy of Lawrence Wallman

  Courtesy of Lawrence Wallman

Courtesy of Justin Green

These strange features, known as hole-punch clouds...among other names, are caused by the penetration of aircraft through a cloud deck made of supercooled liquid water.  

Believe it or not, many middle-level clouds are below freezing but are still made  of liquid water.  Turns out that clean water can take its time to freeze when temperatures are below 0C.   

We had a cloud deck over Seattle around 3 PM Wednesday that was made up of such supercooled water.  A vertical sounding (vertical ascent from a weather balloon) at Quillayute on the WA coast at 4 PM suggested that the cloud was at roughly 450 hPa pressure or around 6600 m (22,000 ft) and a temperature around -22C (-8F).

We were dealing with an altocumulus or cirrocumulus clouds of liquid water.  A past colleague of mine, Peter Hobbs, and one of his past associates (Art Rangno) studied this situation and called the holes APIPS (Aircraft Produced Ice Particles).   Let me tell you why.

Look closely at the picture shown above (repeated below).  Do you see the fibrous looking material in the middle of the hole. Those are ice crystals! You can tell because they have a wispy, less distinct look to them.  

But what caused the transition between liquid water clouds (with much sharper edge  to ice clouds?   The passage of an aircraft!

When air goes across the wings of an aircraft the air is speed up and that causes pressure to fall on the upper side of the wing (that is what keeps a plane in the air!).  When air parcels experience lower pressure they expand and cool (this is called adiabatic cooling).  

Now clouds can be comprised of liquid water at -10C to around -22C, but if temperatures drop further, it is harder to remain liquid.  Also air can become saturated when it cools on the air frame and go directly to ice if the air is cold enough (-30C to -40C).

It turns out that ice and liquid water find it difficult to be in the same environment, water vapor leaves the liquid water and heads over to the ice crystals (this is often called the Bergeron process).  The ice crystals grow rapidly, become heavy, and fall out of the cloud, producing the hole.  You can see that happening in the cloud picture above.

Mystery solved....

Newest Cloud Types Seen in the Pacific Northwest

In  March 2017, an updated International Cloud Atlas was released and several new clouds were added. 

One new cloud is Asperitas, characterized by a complex wave-like base.   This week (January 17th), James Dearman sent me this wonderful shot of an Asperitas cloud that he took near Vancouver, Washington (see below). 

Pretty amazing cloud, with undulations looking like a sea surface turned upside down.

Here is another example from Virginia:

These clouds result from wave-like motions in the atmosphere that distort a pre-existing cloud deck.   Such waves can be initiated by fronts, thunderstorms, or some other type of atmospheric disturbance.  Generally no precipitation or severe weather with these clouds--but they do look scary.

Folks normally don't think about it, but the atmosphere is full of waves.    Generally, the atmosphere is stable, meaning if you push an air parcel upward, it will want to return to where it started.  But like a swing set, the air parcel tends to overshoot and goes into an oscillation.  A pendulum is another example.

Another new cloud is one we have talked about in this blog:  Cavum, or the hole punch cloud (see below).   These "holes" are produced when an aircraft goes through a cloud made of supercooled water (liquid water below freezing).  The passage of the aircraft through the cloud causes a transition to ice crystals, which subsequently fall out, leaving a hole.