While crossing the North Atlantic, Robin Severns (Member 65,839) met a procession of Cumulus congestus clouds west of the Azores. Lines of towering cloud like this can form as a result of convergence, when opposing winds blow towards each other from opposing directions and force air upwards along the line where they meet. If the air carries enough moisture, the cooling as it rises can be enough to form clouds capable of heavy, localised precipitation. You can see the showers beneath this line of convergence clouds. These showers are typically only short-lived. Robin’s Cumulus will likely develop no further. They already look to be starting to dissipate as the sun dips in the western sky.