Australians on Wednesday were treated to a bizarre sight in the sky: a fallstreak hole, which forms from droplets in the cloud that are below freezing, but haven't yet frozen.
Here's how NOAA explains the formation: "These 'supercooled' water droplets need a 'reason' to freeze, which usually comes in the form of ice crystals. Planes passing through the cloud layer can bring these ice crystals. Once the ice crystals are introduced, the water droplets quickly freeze, grow and start to fall. A hole is left behind, which will start to expand outward as neighboring droplets start to freeze." - Discovery Channel
"Clouds are made of water droplets, and hole punch clouds—also known as fallstreak hole clouds—occur when part of that cloud falls out, leaving behind a hole. That opening in the cloud is the result of an extremely localized snowfall.
Usually, atmospheric water droplets latch on to particles in order to form ice crystals, or snow. This happens on a massive scale during snowstorms. The only way water droplets can spontaneously form ice crystals without those particles is if temperatures fall to roughly -40°F (-40°C). " from National Geographic
Just got this sent in from Geocaching Melbourne. Did you see the weird rainbow thing in the sky over Wonthaggi? pic.twitter.com/RGWLAUJpwM
— Star FM Gippsland (@StarFMGippsland) November 3, 2014
View images of the rare cloud formation known as a Fallstreak Hole http://t.co/OETopnQPIe | @abcnews pic.twitter.com/PaUG1832QZ
— ABC Australia (@ABCaustralia) November 3, 2014
One more photo of the incredible skies over eastern Victoria today, this one from Tamara at Korumburra. pic.twitter.com/r1vsY2eb4e
— 3AW Melbourne (@3AW693) November 3, 2014
Fallstreak hole near Clear Lake, IA evident on #MODIS Visible Satellite. Image via @UWSSEC @NASA #iawx pic.twitter.com/ddfrtyI54k
— NWS Des Moines (@NWSDesMoines) November 1, 2014
Top photo: A fallstreak hole appears over Victoria, Australia, on Nov. 3. Credit: JasonPrekop/YouTube screen capture