Accessory cloud Accessory cloud An accessory cloud is a cloud which is dependent on a larger cloud system for its development and continuance. It is often an appendage but also can be adjacent to the parent cloud system. The arcus and roll clouds, shelf cloud, wall cloud, and scud are examples of low level or vertical accessory clouds whilst the anvil, and overshooting top, are examples of high level accessory clouds. The condensation funnel of funnel clouds and tornadoes are also accessory clouds. They are associated with deep moist convection and especially cumulonimbus, the primary cloud producing thunderstorms. The pileus and mammatus
Wall cloud warm, moist air rises and converges, overpowering wet, rain-cooled air from the normally downwind downdraft. As the warm air continues to entrain the cooler air, the air temperature drops and the dew point increases (thus the dew point depression decreases). As this air continues to rise, it becomes more saturated with moisture, which results in additional cloud condensation, sometimes in the form of a wall cloud. Wall clouds may form as a descending of the cloud base or may form as rising scud comes together and connects to the storm's cloud base. Wall clouds can be anywhere from a fraction