undular bores are a type of atmospheric gravity wave that cause wave-like disturbances to propagate through different mediums, creating striking visual patterns.

These disturbances are triggered by disturbances like a cold front or thunderstorm outflow, causing a series of atmospheric waves to move through a stable layer of the atmosphere.

These clouds form at altitudes above 7,000 meters when undular bores affect upper atmospheric layers, causing ice crystals to align in wave patterns.