HONOLULU --

This is KITV4's Amber-Lynn Hyden. I received a lot of questions about a peculiar cloud formation spotted over Mauna Kea on the Big Island recently. You can clearly see a large hole in the clouds. I talked to Derek Wroe, the lead forecaster at the National Weather Service in Honolulu. Here's what he had to say:

Hi Amber-Lynn,

Thanks for sending the very interesting picture, and I think that we may have an answer for you. We believe that the phenomenon captured is called a "hole punch" for obvious reasons. The reason for its existence is not so obvious!

The cloud deck over the Big Island that morning was an altocumulus field. This thin cloud field looks to be several thousand feet above Mauna Kea...somewhere around 20,000 feet or so. A look back at the Hilo sounding from that night reveals that the temperature in this layer was approximately -8 to -12 C. This is important, because water in the atmosphere can remain remain unfrozen at these temperatures, in a state that we call "supercooled", and we believe that this altocumulus field was probably made up of supercooled water. This state is tenuous, since the introduction of ice to supercooled water would cause any supercooled water nearby to freeze on contact, then fall out as light snow. This could leave a hole in the cloud, but the question remaining is: "How did this particular phenomenon occur?"

We can't be sure exactly how this one formed, but we've got an idea. One possibility is that the layer of air aloft was disturbed by the presence of the mountain, causing a small area of lift directly over Mauna Kea. This lift could have caused additional cooling in the cloud layer, which then produced some ice in the cloud layer. Once the ice formed, the supercooled water nearby quickly froze, forming snow which then fell out. The lucky viewer then could have seen the resulting hole. The other explanation could be that an airplane flew through the cloud layer, leading to the same process of ice formation. That's where the "hole punch" phenomenon got its name. However, we feel that this probably isn't the case here, since that would be an odd route for an aircraft.

I hope that this explanation makes sense and was helpful. Thanks for the inquiry!

Aloha,
Derek Wroe
Lead Forecaster