Sky Holes!

"Sky holes", also known more formally as "Hole Punch Clouds" or "Punch Hole Clouds", are not some secret Government experiment, nor Alien cloaked spacecraft.  They are instead, holes that form in thin, puffy cloud layers. 

There are many hypothesis for what causes them:  jet planes passing through the cloud layer, wind, and others.  But they remain an enigmatic example of mother nature's incredibly complex weather processes.

The prevailing theory is that Cirrocumulus clouds contain both ice crystals, and supercooled water droplets. The introduction of the extra water from the jet exhaust causes a rapid increase in the rate of crystallization, and all the water turns to ice as the ice crystals get larger. This rapidly desaturates the air, which then pulls in moisture from the air around it, thus spreading the hole. The larger ice crystals then drift downwards (as virga), since they are heavier, resulting in the characteristic “V” or “wing” cross-section of the central cirrus uncinus cloud, which looks a bit like a bird or an angel, if you are imaginative enough.

Punch Hole Cloud Occurrences:

Tampa Florida November 2008

The odd cloud formation seen around the Tampa Bay area on Monday morning initially caused some head scratching around here, but it turns out to have been a rare formation but one documented before. Meteorologists call it a "hole-punch cloud", a nontechnical but accurate name for the formation that looks like a hole was punched in a layer of clouds. St. Pete Beach resident Gwen Swinburne was kind enough to send us a photo, and observant reader Rex Chivers wrote to say he saw two about 8 a.m. Monday, one near Tampa, the other toward Pinellas and likely the one Swinburne photographed. Apparently, a number of conditions can cause the formation. On Tuesday, there was a layer of clouds high enough to be mostly ice crystals instead of simply condensed water. The air was highly stable, so the clouds were fairly uniform. A pocket of cold air, which sinks toward the ground, "punched" the hole in the clouds and created the circular opening. That's what the meteorologists at News Channel 8 say. Sometimes rising air can cause the same effect. These cloud formations have been observed before but are rare enough to catch the attention of the weather service.
	Tampa Hole Punch Clouds November 24 2008

Mobile Alabama 2003

From NOAA:  During the early afternoon of Wednesday, 11 December 2003, a strange and unusual cloud formation occurred over the Mobile, Alabama area. The name..."Hole Punch Clouds".

A quick internet search quickly reveals a few strikingly similar past photos that were taken in south Florida, the Carolinas and even Australia and Canada. Therefore one can conclude that the phenomena has happened before, but on a relatively infrequent basis.

A regional sounding (meteorological instrumentation that shows how temperature and moisture vary with height) taken near Valparaiso, Florida reveals a cloud layer between approximately 25,000 and 27,000 feet. The cloud layer was likely a few thousand feet lower according to a sounding taken further west over Slidell Louisiana near the time of sunset (not shown). Meteorologists refer to clouds at this level as 'cirro-form' clouds. Generically, these are termed 'high clouds.' However, the white puffy-like texture in the cloud deck that surrounds the "hole" possesses traits of both cirroform and cumulo-form clouds (which form at much lower altitudes). Cirroform clouds with a cumulus-like appearance are termed 'cirrocumulus' clouds.

What was the weather pattern that day ? - Although a large scale high pressure system was building in at the surface with northerly winds in progress, the "hole punch clouds" occurred at a much higher level in the atmosphere. Just above the cloud layer and at about 32,000 feet above ground level, the high level winds were blowing was from west to east over much of the US Deep South. The clouds were aligned along this rapidly flowing stream of air, known as the jet stream.

How does the hole occur in the clouds ? - the puffy clouds were likely composed of ice crystals and very small super-cooled liquid water droplets. Studies have shown that very small supercooled liquid water droplets can exist well below freezing (as low as -40 degrees (C, or Centrigrade) ). The temperature in the cloud layer was around -24 deg (C) at the time of occurrence. Sometimes...when ice and the supercooled liquid droplets coexist within a cloud...a process occurs whereby ice crystals grow at the expense of the droplets. If the mixed cloud is agitated...the supercooled droplets freeze instantaneously. It is understood through microphysical arguments that water vapor must evaporate from the surrounding supercooled droplets and flow towards the ice crystals. This would start a cycle whereby newly formed ice crystals cause the surrounding droplet to evaporate...resulting in a circular form void of clouds with a mass of crystals in the center. Many photos taken that day seem to represent this process.

What caused the disturbance to begin ? One possible explanation is a jet plane. Visible satellite imagery that day suggested several "hole punch" clouds over both southern Mississippi and Alabama. These coincided with jet contrails. Click here and you will see a photo of "hole punch" clouds taken in Australia with an airplane contrail nearby. An airplane passing through the mixed cloud layer while ascending or descending would likely disrupt the delicate coexistence between the ice crystals and the supercooled liquid water droplets. A second possible explanation is that small scale atmospheric vertical motions (both up and down) related to the jet stream brought ice crystals downward into the moist cloud layer, thus effectively 'setting off' the cyclic process described above.

One thing is for sure... Without an ability to directly measure these small scale vertical motions and the quantities of temperature and moisture directly within and adjacent to the actual clouds, we can only speculate on what caused this common but relatively infrequent awesome phenomena to occur !...

photo courtesy of: Gary Beeler, Warning Coordination Meteorologist, National Weather Service Mobile, Alabama

Wisconsin 2006

During the afternoon of November 15, 2006, an unusual cloud formation was seen across central Wisconsin.  Known as "hole punch clouds,"  the holes develop as ice crystals above the main cloud layer fall through the clouds, causing the super-cooled water droplets to evaporate.  The result is a circular form void of clouds, with a mass of crystals in the center. The photo was taken by Samantha Weise in Stevens Point.

Louisiana 2007

On January 29, 2007, inhabitants of Acadiana, the Cajun heartland in southern Louisiana, saw unusual looking cloud formations. These “hole punch” clouds were just as apparent from above as they were from below. This pair of images shows the hole-punch clouds captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite (top) and from the ground (bottom). The MODIS image shows a number of round holes in a blanket of cloud cover over Oklahoma, Arkansas, Louisiana, and Texas. A few of the “holes” are elongated, with what appear to be smaller clouds inside them.

2007/029 - 01/29 at 17 :05 UTC Aircraft dissipation trails over southern United States

This strange phenomenon resulted from a combination of cold temperatures, air traffic, and perhaps unusual atmospheric stability. The cloud blanket on January 29 consisted of supercooled clouds. Supercooled clouds contain water droplets that remain liquid even though the temperature is well below freezing, and such clouds are not unusual. According to the Cooperative Institute for Meteorological Satellite Studies (CIMSS) Satellite Blog, cloud-top temperatures ranged from �20 to �35 degrees Celsius. As aircraft from the Dallas-Fort Worth airport passed through these clouds, tiny particles in the exhaust came into contact with the supercooled water droplets, which froze instantly. The larger ice crystals fell out of the cloud deck, leaving behind the “holes,” while the tiniest ice particles in the center remained aloft.

The people on the ground watching the show these clouds made didn’t have to worry about getting wet or being showered with ice. When the general atmospheric conditions aren’t favorable for rain, the falling ice crystals sublimate—change state directly from a solid to a gas—as they pass through warmer layers of the atmosphere.

Melbourne Florida 2000

“Hole Punch Clouds” in Melbourne, Florida – Nov. 12, 2000 By David Larimer FLORIDA TODAY weather columnist A unusual cloud formation appeared in skies over the Space Coast on Thursday caused by ice crystals and enhanced by the jet stream. There is no scientific term for the cloud display you see above. The National Weather Service calls the formation "hole-punch" clouds because of the oval-shaped opening. The image was captured by meteorologists Matt Bragaw and Peter Blottman at the weather service office in Melbourne on Thursday morning. The display is rare but has occurred in Melbourne skies in years past. In 1993, the weather service's Dennis Decker photographed a similar display. His dramatic photo was published in a national weather magazine. Randy Lascody, a senior meteorologist at the weather service office, explained the conditions that led to the striking formation: "The atmosphere on Thursday was very dry from about 5000 to 28,000 feet. There was a rather extensive deck of cirrocumulus (mixture of 'super cooled' water droplets and ice crystals) invading the sky associated with strong westerly jet stream winds. "However, the 'hole-punch' features were aligned north/south. This suggests that there was some sort of 'wave' in the atmosphere that was causing rising/sinking air couplets. "This would cause ice crystals in the descending portion of the wave to fall into the super cooled (liquid) cloud layer. When this occurs, the ice crystals grow (at the expense of the liquid droplets). Therefore, a hole opened in the deck of cirrocumulus. "This process is similar to the principle used in cloud seeding to make cloud particles larger and produce precipitation. In this case, the precipitation aloft (meteorological term is 'virga') descended into the dry air below 28,000 feet and evaporated (actually, the proper term for this process is 'sublimated'). "The virga is evident in a few of the pictures descending from the center of the hole in the clouds. This resulted in a cone-shaped cloud high in the atmosphere that I'm sure a few people thought was a funnel cloud."

Punch Hole (Hole Punch) Cloud Gallery:

France
Gunnison Valley in Colorado November 2007	Gunnison Valley in Colorado November 2007
Alai-Minar India	December 2007.
Upstate NY	Upstate NY
Elongated Hole Punch Clouds	Elongated Hole Punch Clouds
Los Angeles August 2007	Los Angeles August 2007
	A Hole Punch Cloud forming (viewed from above) - notice the standing waves.  This is over Poland
Over Stafford, UK	Punch Hole Clouds Over McLeans Ridges, NSW, Australia
	Punch Hole Clouds Over McLeans Ridges, NSW, Australia
Seen from above

Irregular Punch Hole Clouds:

Irregular Punch Hole Cloud Videos:

Hole Punch Clouds Forming in Europe 2007 - Part 1

Hole Punch Clouds Forming in Europe 2007 - Part 2

Cotton Ball Clouds:

Is there an opposite to a Hole Punch Cloud?  These spherical dense opaque clouds, floating alone in clear space seem to be the opposite of Punch Hole Clouds!

Also see:  Planetary Boundary Layer: Turbulence

Project HAARP?  Link1 : Link2 : Link3