photo #6217244

Erika Bourne (Member 60,953) was already running late to pick up her daughter when she spotted this Altocumulus fluctus formation over Waltham, Massachusetts, US. Even though she was under time pressure, Erika knew she still had to stop the car to truly appreciate the moment. Fluctus are curling features that are also known as Kelvin-Helmholtz clouds, a name taken from two physicists who made waves in the field of fluid instability. Prized by cloudspotters, the breaking-wave formation develops when cloud forms at the boundary between two layers of air, the upper of which is moving distinctly faster than the lower. The wind-shear effect of these differing airflows can create a succession of rolling vortices across the top edge of the cloud.Despite being short on time, Erika stopped to watch the fluctus clouds because she knew formations like these are rare and fleeting, their distinctive curls lasting just a couple of minutes before dissipating away. ‘I considered these clouds a reminder to savor the upcoming time with my family,’ she told us. ‘Because, just like the clouds, and just like waves, nothing is permanent. If you are not present, you can miss the magic.’