May 2015

[vc_row row_type=”row” use_row_as_full_screen_section=”no” type=”full_width” text_align=”left” css_animation=””][vc_column][vc_column_text]

A Supercool Cloud

Low clouds like Cumulus tend to consist of water droplets. High ones like Cirrus are made of ice crystals. Mid-level clouds, like this Altocumulus we’ve chosen for May’s Cloud of the Month, often contain ‘supercooled’ water. The water is in liquid droplets, but it’s so cold that it can freeze at any moment setting off a chain reaction of freezing, which can result in a hole in the cloud layer like this one spotted by Craig Pledger over Key West, Florida, US.

It is known as a ‘fallstreak hole’, and it looks as if someone has taken an enormous cookie cutter to a cloud layer. Some people call it a ‘hole-punch cloud’. There is often a streak of cloud trailing beneath the hole. The formation is caused by the freezing of droplets in