It is not uncommon to observe this type of horizontal clouds guarding the tops of the mountains, because their formation is associated with the orography of the terrain .
When a mass of hot and humid air meets a steep slope in its path, the air is forced to rise to cooler layers; then, the water vapor condenses and gives rise to these formations that usually last a few hours. The top of Everest or the Matterhorn are almost always adorned by one of these orographic flag-shaped clouds .
They are also very common in the southern Andes, when there are westerly winds from the Pacific Ocean. They also occur often in the northwestern United States (Oregon and Washington states), and in the Canadian province of British Columbia, with winds that come from the north of the Pacific Ocean. Coastal places with mountains can have 2,500 mm of precipitation per year . The localities next to the mountains in the passage of the storm systems, receive the humidity in the form of liquid water or snow.
The orographic clouds remain attached to the peaks where they originate, and their arrangement and size vary from small plumes at the top or above it to large mantles that cover the entire elevation like a waterfall. They are usually flattened, although with strong wind they can appear turbulent and swirling, especially in very high areas.
