OPOD - Multiple hole punches

Last updated on September 16, 2023

OPOD - Multiple Hole Punches: A Captivating Atmospheric Phenomenon

Have you ever gazed up at the sky and witnessed a mesmerizing display of multiple hole punches in the clouds? This captivating atmospheric phenomenon, known as multiple hole punches or fall streaks, is a sight to behold. Recently, Gareth Rondel captured this enchanting spectacle on his phone camera in Bedfordshire, England on the morning of November 12th. The photographs he shared reveal at least five elongated hole punches with virga or fall streaks descending from their centers. But what exactly causes these intriguing phenomena? Let's delve into the science behind multiple hole punches and uncover the secrets of their formation.

Unveiling the Mystery of Hole Punches

Hole punches are peculiar circular or elongated holes that appear in clouds, accompanied by ice crystals falling from their centers. These holes are believed to arise from an instability within the cloud layer, causing supercooled droplets to rapidly convert into ice crystals. As the ice crystals grow and descend, they create a less opaque region in the cloud, resulting in the formation of a hole. Interestingly, the presence of a bright sundog shining from a distant hole punch indicates that the virga is composed of ice crystals rather than rain.

Triggers for Hole Punch Formation

Several factors can trigger the formation of hole punches in the clouds. One possible trigger is disturbance by an aircraft passing through the cloud layer. The disturbance caused by the aircraft's movement may induce the supercooled droplets to undergo the transformation into ice crystals. Alternatively, seed crystals, which are ice crystals acting as nuclei, might tumble downwards from higher clouds or contrails, initiating the formation of hole punches.

The Science Behind Supercooled Droplets

The existence of clouds with supercooled droplets can be attributed to a fascinating property of water—it does not always freeze at zero degrees Celsius. When nuclei for ice crystal growth are absent, water droplets in the cloud can remain in a supercooled state and cool to sub-zero temperatures. This condition is known as metastability, where the ice state is more stable than the liquid state. However, introducing sufficient nuclei or disturbing the cloud in some way can rapidly trigger the growth of ice crystals at the expense of the droplets.

The Curious Nature of Hole Punches

While the formation of rain from ice crystals is a normal occurrence, hole punches and similar phenomena exhibit a peculiar characteristic. In these cases, the transformation from supercooled droplets to ice crystals occurs only in small patches, creating the distinct holes we observe. This selective transformation adds to the intrigue surrounding hole punches and highlights the intricacies of atmospheric processes.

Unraveling Elongated Hole Punches

One particularly intriguing aspect of multiple hole punches is the presence of elongated holes in the cloud layer. The elongation suggests the possibility of an aircraft disturbance, either directly or through the precipitation from its contrail. The interaction between an aircraft and the cloud layer can disrupt the supercooled droplets, leading to the formation of elongated hole punches. These elongated holes add an extra layer of complexity to the already captivating atmospheric optics display.

Capturing the Beauty of Multiple Hole Punches

Gareth Rondel's stunning photographs provide us with a glimpse into the enchanting world of multiple hole punches. Through his lens, we can appreciate the delicate interplay between light, clouds, and ice crystals that culminates in this breathtaking phenomenon. It serves as a reminder of the countless wonders that nature has to offer, often hidden in plain sight.

In Conclusion

Multiple hole punches, with their ethereal beauty and intriguing formation process, continue to captivate skygazers worldwide. As we uncover more about these atmospheric optics phenomena, we gain a deeper appreciation for the complex interplay of natural forces that shape our skies. So, the next time you find yourself gazing at the clouds, keep an eye out for the enigmatic allure of multiple hole punches, reminding us of the boundless mysteries that surround us.

Multiple Hole Punches, Fall Streaks & Sundog ~ Caught on a phone camera by Gareth Rondel. Bedfordshire, England on the morning of 12th November.

�Gareth Rondel, shown with permission.

At least five elongated hole punches puncture the clouds. Virga or fall streaks, precipitation that does not reach the ground, trails downwards from their centres. That the virga is composed of ice crystals rather than rain is evidenced by the bright sundog shining from the distant hole punch.

Hole punches are roughly circular or elongated holes in clouds with ice crystals falling out of their centre. They are thought to result from an instability causing supercooled droplets already in the cloud layer to suddenly convert to ice crystals. The ice crystals grow and fall out of the cloud. Areas with large crystals are in any case less opaque than a host of small droplets – we therefore see a hole.

A trigger for the instability might be disturbance by an aircraft. Another trigger could be seed crystals , ice crystals acting as nuclei, tumbling downwards from higher cloud or a contrail.

Clouds with supercooled droplets arise because water does not always freeze at zero degrees Celsius. If no nuclei are present on which ice crystals can grow, the cloud water droplets remain and cool to sub-zero temperatures. The condition is metastable in that ice is the more stable state. Introduce enough nuclei or otherwise disturb the cloud and ice crystals grow very rapidly at the expense of the droplets.

This is a normal condition. Rain can form that way from an initial formation of ice crystals coagulating into larger snowflakes which subsequently melt as they descend. What is strange is that in hole punches and their like, the supercooled droplet to ice transformation takes place only in small patches.

The lower image showing a very elongated hole is suggestive of an aircraft distirbance, either directly or via precipitation from its contrail.

Note: this article has been automatically converted from the old site and may not appear as intended. You can find the original article here.

Reference Atmospheric Optics

If you use any of the definitions, information, or data presented on Atmospheric Optics, please copy the link or reference below to properly credit us as the reference source. Thank you!