Punch Cloud: the Uncloud.
A “Hole Punch” cloud is a
non-technical name given to a
from an aircraft dissipation hole or trail. They are also called "Punch
Hole" clouds. Rather than extending as a
line, Hole Punch clouds appear as a circular or oval hole in a deck or
thin layer of supercooled water clouds. They are not uncommon where jet
flight paths intersect altocumulus layers. What is
is when they form in a perfect circle that persists for a length of
to be widely observed.
On December 11, 2003 that’s exactly what
Gulf Coast. A remarkably circular and persistent Hole Punch cloud
over Mobile, Alabama at lunchtime. Numerous curious people photographed
it. The event was so much a topic of conversation that it was the top
news story of the day.
Education section you'll find a Hole
Punch article with background and pictures. Also check the
of the Mobile office of the National Weather Service for an extensive
article with links to the synoptic
charts of the day. The University of Wisconsin gives a
space perspective from the NASA AQUA satellite.
Hole punch clouds are not new but scientists are getting a better understanding lately. They've been seen
the world and more
pictures are on the website for Project Atmosphere Australia.
image of this
hole punch cloud for personal use only.
Now here's the "Hole Story", Copyright, Alan Sealls
December 11, 2003. It's a crisp fall day in southern Alabama. Clear
sapphire skies and light wind create a carpet of dew by sunrise. I wait
until mid morning to tackle my task of cutting down a small tree in my
front yard. The day is perfect. Temperatures top 50 degrees by eleven
a.m., and my wife is not home to protest the demise of the tree. It
really was dead anyway.
Knowing the fickle nature of falling trees I secure a guide rope, and
the aid of my neighbor, Bob. I figure that if Bob could take down a
full-sized tree that was ten feet from his house, my tree would be no
As we sling the rope up and around the treetop, I glance south toward
the Gulf of Mexico. Cirrus and Altocumulus clouds are appearing in the
southern sky, along with a distinct contrail. This pattern is common in
the winter when there’s surface high pressure centered to our
north, and a westerly upper air flow along the Gulf Coast. With added
vapor and condensation nuclei from a few high-flying jets, contrails
seem to appear as frequently as natural clouds.
I crank the gas chainsaw. The wail of the engine summons my neighbor Ed
to lend a hand. There’s something about chainsaws and men…
The sawdust flies, mimicking a mini snow squall. It settles around the
trunk like a dusting of flurries. With the usual notching, cutting, and
tugging, the tree responds; first a crackle of splintering wood, then
the thud of thunder. The tree meets the lawn. Thanks Bob. Thanks Ed.
Now it’s noon. I look up again to the south. Perfectly framed
between two stands of tall trees is a circle in the clouds. A hole! I
had seen a few of these dissipation holes before but never one so
perfect or large. Without hesitation I dash into the house and return
with my SLR camera and video camera. I rush to get the video camera on
the tripod and hit record. Once that’s set I attempt to take
still photographs. One problem; my SLR battery is dead and I
don’t have a spare.
Again, I run into the house and return now with a plastic
point-and-shoot 35mm camera. I manage to capture a few good shots on
color negative as I lament not having my other camera with fine grain
film and a full suite of lenses.
For the next 20 minutes the hole grows and drifts eastward. I
watch and surmise that a jet flew through the Altocumulus deck at a
steep angle, delivering condensation nuclei and water vapor.
These holes are not too unusual when supercooled water droplets form
into ice crystals and then fall as Virga. Ice crystals rob neighboring
supercooled water droplets of vapor to further their own growth,
working outward in a circle. The end result is a feathery Cirrus
precipitation in the middle of a Altocumulus or Cirrocumulus layer.
Dissipation holes are nicknamed “hole punch clouds.”
Similar ones have been photographed around the world but this one is
unique for its size and symmetry.
The combination of the size of the hole, longevity, and the fact that
it happened at lunchtime make it the top local news story of the day. I
know. I’m the Chief Meteorologist at the CBS television station
in Mobile. By the time I arrive at work two hours later there are
numerous emailed digital pictures from our viewers. Public interest in
the strange cloud is so great that we post a special page on our
website with viewer photos of it.
Some people think it looks like an angel, while others joke about a similarity with a scene in the movie Independence Day.
To confirm my suspicions of the cause of the cloud, I go to the
University of Wisconsin at Madison website for high resolution images
from NASA’s AQUA satellite. I find a beautiful illustrative image
that I share with my viewers. Taken around 12:30 p.m. local time, the
picture clearly shows the patch of Cirrus clouds centered in the hole
over southern Mobile County. Not only are there several well-defined
contrails to the west, but what is even more interesting is a long
dissipation trail in southern Mississippi, along with other holes in
the clouds there.
A dissipation trail is the cousin of a condensation trail. This type of
clearing line is often caused from a jet flying in the Altocumulus or
Cirrocumulus layer. The vapor trail causes supercooled water droplets
to freeze into ice crystals and fall as Cirrus streaks, eating away the
cloud deck in a straight line!
What I learned: A little hole can become a big deal. Look up, and make
sure you have good batteries in your camera! …and that’s
the hole story.