What does CBMAM indicate in a METAR?

CBMAM in a METAR refers to Cumulonimbus Mammatus Clouds. This specific cloud type is significant in weather reports because it indicates the presence of severe weather conditions. The term "Mammatus" describes a particular anatomical structure of the clouds, characterized by their pouch-like formations hanging from the base of the larger cumulonimbus clouds. These features can suggest instability in the atmosphere and are often associated with thunderstorms, severe turbulence, and potential severe weather phenomena.

Recognizing CBMAM in METARs is crucial for pilots and air traffic controllers as it provides important information about potential turbulence and severe weather conditions in the vicinity of the airport. Understanding this notation helps in preparing for possible deviations during flight or for adjustments in schedule and safety measures.

The other options, while related to cloud types, do not accurately describe the notation CBMAM in the context of METAR reporting. Cumulonimbus clouds are specifically dramatic and often associated with thunderstorm activity, making their identification vital in understanding and anticipating weather-related challenges in aviation.