punch hole cloud

punch hole cloudPunch Hole Cloud.  photo:  pixdaus.com

Did you hear this story on NPR yesterday?  Yeah, me too.   It got me damn curious how this all works and what a punch hole cloud looks like.  Turns out the dynamics of this phenomenon are interesting, the resulting snowfall is minimal, and the punch hole clouds are glorious.

punch hole cloudPunch Hole Cloud.  photo:  livescience.com

A new study done by a team of researchers from the National Center for Atmospheric Research in Boulder, CO, the NASA Langley Research Center in Hampton, VA, and the University of Wyoming in Laramie just came out attempting to explain these phenomenons.  The conditions that have to be met for these occurrences to perform are very rare, but they happen.

canal cloudCanal Cloud.  Same as punch hole cloud, but different shape.  photo:  sacramentofordemocracy.com

Planes Trigger Snow:

– Water does not have to freeze until -40C (which happens to also be exactly -40F)

– Supercooled water (H2O that is below freezing but not frozen) has to be in clouds.  Example: cloud with liquid water in it at -22C

– Plane propeller  creates expansion of the air which further cools air and water in that air potentially to -40C

– Jet wings create cooling and a drop in pressure as the air passes over their wings also allowing a drop in temp potentially to -40C

– Now, this water freezes and creates a chain reaction that compels the cloud’s water to turn to ice and begin to precipitate out of the cloud

– The snowfall generated from these events is very small

“The [clouds] don’t have a strong predilection toward precipitation, but they are close enough that a nudge will push them into precipitating,” says cloud physicist Patrick Chuang of the University of California, Santa Cruz, who did not contribute to the new study. – scientificamerican.com

punch hole cloud2 Punch Hole Clouds.  photo:  abovetopsecret.com

Hole Punch Clouds:

– Same as above conditions:  supercooled water, plane cools water to freezing, ice precipitates out

– This generally happens in a thin planar cloud as show in all the pics in this post

– the “hole” formed in the cloud happens exactly where the plane passed thru the cloud

– Often thought to be holes in clouds from UFOs passing through them

Hole-punch and canal clouds form when the cloud layer is in a so-called supercooled state, in which the water droplets are below the point of freezing but have not yet crystallized into a solid. With a little encouragement—by providing a solid nucleus for ice to grow on, as in cloud seeding with silver iodide, or by cooling the cloud further, to about –40 degrees C, which forces the freezing process—the somewhat fragile supercooled state collapses, and water in the cloud begins to freeze.  – scientificamerican.com

The airplane-induced freezing works by the forced-cooling process. If a cloud’s supercooled water is at temperatures of –20 degrees C, for instance, the passage of a propeller plane or jet can drop temperatures enough to reach the spontaneous freezing threshold of –40 degrees C. – scientificamerican.com

I’ve never seen a punch hold cloud, but you can bet your life I’ll be looking all over for them now. This one of the most interesting cloud phenomenons I’ve ever heard of. The plane thing is kinda cool, but I don’t think it’ll have much impact.  What’s more interesting is how the mean temperature went up in USA during the stoppage of flights after 9-11:  Jet Contrails decrease temperature of Earth.

Video below = cool demo of hot water vaporizing and turning to snow instantly.

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