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).

El Nino Weather Ahead

We are in a very strong El Nino and typically its influence on Northern Hemisphere weather circulation increases during December, with the most profound impacts after January 1.

We will get a potent taste of a typical El Nino pattern next week.   

Let me show you.

As I noted in a previous blog, the sea surface temperature of the tropical Pacific has become far warmer than normal (see below).  In fact, the critical El Nino index (region 3.4 sea surface temperatures anomaly from normal) is now about 2°C above normal, resulting in a strong El Nino.

The difference in temperature from normal.

El Ninos tend to produce a certain atmospheric pattern over the eastern Pacific (see below), with a portion of the Pacific Jet Stream heading into California, bringing wetter-than-normal conditions over central and southern California.  In addition, low pressure develops offshore of the West Coast, and warmer than normal temperatures are observed over the western U.S., particularly across the upper plains.

 And a very similar pattern is predicted next week.

The predicted upper-level map (300 hPa pressure level, about 30000 ft)  for Wednesday shows heights (solid lines) and winds (shading), indicating a jet stream (strong winds in knots, reds and orange colors strongest) entering southern California and a low offshore.

The impact on western U.S. precipitation will be profound.  As shown by the cumulative precipitation through next Friday,  California will be far wetter than Oregon and Washington, with San Diego and LA getting 2-3 inches.

The latest NOAA/National Weather Service  6-10 day precipitation outlook predicts drier than normal conditions for the Northwest, but very wet over the southwest. 

Classic El Nino.

Also classic is the very warm conditions prediction for the western U.S., particularly the upper plains.

So those heading south for the holiday season are well advised to take their raincoats and umbrellas.  Northwest weather will move to the Southwest for a while.

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