Unusual cloud formation over the Azores today.

[gkr1959]

Can anyone explain what this is?

[idefix37]

@gkr1959
This cloud pattern is the phenomenon called gravity waves as explained here:
https://www.weather.gov/source/zhu/ZHU_Training_Page/Miscellaneous/gravity_wave/gravity_wave.html
with many examples:
https://svs.gsfc.nasa.gov/14445/

These atmospheric waves appear when wind aloft flow over a mountain. In your screenshot you see these waves spreading as a plume on the leeward side of the mountainous Azores islands.