A Cloud-Edge Dynamics for the Holepunch Phenomenon

A holepunch cloud is a curious phenomenon where an aircraft penetrates a thin cloud layer and leaves behind a growing circular hole of clear air. Observed since the early days of aviation, only very recently has the holepunch feature been simulated in a full-physics numerical weather model. Although the initiation process has been clearly attributed to ice crystal formation, we explain that the continued expansion of the hole is a travelling front between two phases of moist air --- unsaturated and weakly-stratified (clear) intruding into saturated and moist-neutral (cloudy). The motion of this front is governed by differences in the speed of gravity wave propagation in clear and cloudy conditions.