A banner cloud is a type of cloud formation characterized by a long, horizontal, and narrow shape that resembles a flag or banner floating in the wind. It typically develops due to specific atmospheric conditions, such as stable air layers over mountainous terrain or strong winds interacting with obstacles like mountain ridges or tall buildings.
These cloud formations often occur when the wind encounters an obstruction, causing the air to flow upwards and create areas of uplift. As the air rises, it cools and condenses at higher altitudes, forming a narrow cloud formation that stretches parallel to the obstacle causing the uplift. This cloud appears elongated and flat, with distinct edges resembling the outline of a banner.
Banner clouds are usually located on the leeward side of the obstacle where the air flow is forced to rise. They can vary in size and shape, depending on the strength and direction of the wind, as well as the size and shape of the obstacle. In some cases, banner clouds may extend for several kilometers, while in others, they may only be a few hundred meters long.
Banner clouds are often observed in mountainous regions, coastal areas, or places with tall buildings. Their unique and eye-catching appearance makes them a subject of admiration for photographers and nature enthusiasts.
The term "banner cloud" does not have a specific etymology as it is a compound term derived from two separate words: "banner" and "cloud". Here is the etymology of each word:
1. Banner: The word "banner" originated from the Old French term "banere", which referred to a piece of cloth or flag used for displaying a device or symbol. It was used as a military standard or a sign of identification. The Old French word is derived from the Late Latin word "bandum", meaning "standard" or "flag".
2. Cloud: The word "cloud" can be traced back to the Middle English term "cloude" and the Old English word "clūd", both meaning "mass of cloud".