Planes Create Weird Clouds—And Snow, Rain Fall Out. Hole-Punch cloud over Mobile Al.2003

A few years ago scientists were surprised by the sight of two planes carving a hole through a cloud—which then began spewing snow.

A new study spawned by the accidental discovery solves the mystery behind so-called hole-punch clouds and explains how airplanes can change the weather, at least on an extremely local level.

Scientists have studied hole-punch clouds since the 1940s and have long suspected that planes play a role in their formation. (See pictures of a potentially new type of cloud.)

Now, ice microphysicist Andrew Heymsfield and colleagues have found that aircraft really can create the odd clouds. Their research also uncovered something totally new: that aircraft can unleash precipitation by carving the cloud tunnels, which had never before been observed.