The Hong Kong Observatory revealed that a rare fluctus cloud formation, which resembles breaking waves, was spotted in the sky over the city on June 17. The meteorological department shared an image of the phenomenon as seen over Victoria Harbour.
According to a Facebook post by the Hong Kong Observatory, a fluctus cloud is formed due to the Kelvin-Helmholtz instability, which is when two different layers of air with different temperatures and speeds come together.
This causes the upper layer to ripple and curl like waves, forming a series of vortices that create the crashing-wave appearance. The formation typically lasts only a minute or two, which makes it difficult to spot.
Header image credits: Hong Kong Observatory via Facebook