Clouds Formation

Another group of supplementary features are cloud formations that are associated mainly with cumuliform clouds of free convection. Pileus is a cap cloud that can form over a cumulonimbus or large cumulus cloud, while a velum feature is a thin horizontal sheet that sometime forms around the middle or in front of the parent cloud. A tuba feature is a cloud column that may hang from the bottom of a cumulus or cumulonimbus. An arcus feature is a roll or shelf cloud that forms along the leading edge of a squall line or thunderstorm outflow. Some arcus clouds form as a consequence of interactions with specific geographical features. Perhaps the strangest geographically specific arcus cloud in the world is the Morning Glory, a rolling cylindrical cloud which appears unpredictably over the Gulf of Carpentaria in Northern Australia. Associated with a powerful "ripple" in the atmosphere, the cloud may be "surfed" in glider aircraft. Mamma (sometimes known informally as mammatus) form on the bases of clouds as downward facing bubble-like protuberances caused by localized downdrafts within the cloud. The best known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus. Incus is the most type-specific supplementary feature, seen only with cumulonimbus of the species capillatus. A cumulonimbus incus cloud top is one that has spread out into a clear anvil shape as a result of rising air currents hitting the stability layer at the tropopause where the air no longer continues to get colder with increasing altitude.
• Stratocumulus fields
Stratocumulus clouds can be organized into 'fields' that take on certain specially classified shapes and characteristics. They can often be found in the following forms:
- Actinoform, which resembles a leaf or a spoked wheel.