Waves In The Sky

Cloud ripples 12 hours before the cold front (photo by Kate St. John)

10 September 2014

What does it mean when there are waves in the sky?

These altocumulus undulatus clouds form at mid height at the spot where moisture meets wind shear.  Straight above my camera the wind abruptly changed direction and speed.  The long lines are perpendicular to the strongest wind, just like waves on a lake.

Altocumulus undulatus are typically only 300 feet wide so the wind shear here is a narrow zone.  If you flew through these clouds you’d probably feel a bump.

The waves might mean something big is about to happen … or not.  If they thicken over time, they indicate that moisture is building ahead of an approaching front 100 to 200 miles away.  If they cover only a small part of the sky, they merely mean that something’s going on right there.

Keep looking up.

(photo by Kate St. John)

3 thoughts on “Waves In The Sky

  1. Thanks for the post! I saw a somewhat similar phenomenon in the sky above me and searched it via Google Lens and your blog was the only result that properly explained it!

    1. No. There are no thoughts about Schumann Resonances, which are electromagnetic. Here’s what causes these clouds, per Wikipedia at https://en.wikipedia.org/wiki/Altocumulus_undulatus_cloud: “As with other altocumulus, the undulatus variety can form in all seasons, announcing an approaching system within the general area (about 100 – 200 mi or 160 – 322 km). They result from wind shear (an abrupt speed or directional shifting in the wind, acutely changing with height).”

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