photo #6076106

Larry Smith (Member 57,002) spotted a bright hole over the pine tree in the delicately textured cloud above his home in Plaquemine, Louisiana, US. It wasn’t the pine tree that made the hole. Most likely, it was caused by an aircraft climbing or descending through this Altocumulus stratiformis cloud which would have been made of supercooled water droplets. These are droplets that are so cold in the frigid temperatures of this mid-level cloud that they’re just waiting to freeze. All they need is a little more cooling, and a chain reaction of freezing begins. The cooling of the air in the low pressure around an aircraft’s wings can be just enough to get things started. Ice crystals form, and they in turn encourage the nearby droplets to freeze too. Like toppling dominoes, the effect spreads, and the hole grows larger and larger. As they form, the ice crystals become large enough to fall, appearing as a streak that looks like a Cirrus cloud. The official name for this distinctive cloud feature is cavum, Latin for a ‘cavity’ or ‘hole’, but many know it as a fallstreak hole or a hole-punch cloud.