Fractus

Fractus clouds are small and irregular and are usually found in an environment near the base of a larger cloud. They form or detach from this cloud, and are usually cut by high winds, giving them an uneven, frayed appearance.

They change constantly, often forming and rapidly dissipating. They have no clearly defined bases and are sometimes persistent and form very close to the surface.

Fractus are attached clouds, named after the source cloud type. The two main forms are Cumulus fractus (or fractocumulus) and Stratus fractus (or fractostratus), but they may also appear as a Cumulonimbus, Nimbostratus and Altostratus.

Fractus may develop in Cumulus if the ground warms up sufficiently to begin convection, or it may also originate from the dissipation of a Cumulus, appearing in this case as irregular white clouds located at significant distances from each other.

Masses of multiple fractus clouds, located under a main cloud, are called pannus.

Fractonimbus is a form of Stratus fractus, developing under clouds of precipitation due to turbulent air movement. They are dark gray and irregular in appearance. Fractonimbus exist only under precipitation clouds (Nimbostratus, Altostratus or Cumulonimbus), and do not produce precipitation per se.

When formed into Cumulonimbus clouds, fractus clouds are sometimes called a scud or shield, depending on their behavior and origin.