Any cloud that is produced by the forced uplift that occurs when air passes over hills or mountains. The exact type of cloud depends on prevailing conditions, particularly the stability, but because of the localized nature of the uplift the clouds tend to remain in one place. When conditions are unstable and cumulonimbus clouds form, these may give rise to extremely long-lasting showers with large amounts of precipitation that may lead to flash floods. Under stable conditions, stratiform clouds often occur, frequently in the form of wave clouds. Banner clouds are also of orographic origin.
Subjects: Meteorology and Climatology.