Definition:A shelf cloud is a low, horizontal, wedge-shaped arcus cloud which is attached to the base of the parent cloud, which is usually a thunderstorm, but could form on any type of convective clouds.
It is also called as arcus or arc cloud.
Rising cloud motion often can be seen in the leading or outer part of the shelf cloud, while the underside often appears turbulent and wind-torn.
People seeing a shelf cloud may believe they have seen a wall cloud since an approaching shelf cloud appears to form a wall made of cloud.
A shelf cloud usually appears on the leading edge of a storm.A sharp, strong gust front will cause the lowest part of the leading edge of a shelf cloud to be ragged and lined with rising fractus clouds.
A very low shelf cloud accompanied by these signs is the best indicator that a potentially violent wind squall is approaching.