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Fractus clouds, also called fractostratus or fractocumulus, are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong , giving them a jagged, shredded appearance. Fractus have irregular patterns, appearing much like torn pieces of cotton candy. They change constantly, often forming and dissipating rapidly. They do not have clearly defined cloud base. Sometimes they are persistent and form very near the surface. Common kinds include and .
Cumulus fractus clouds actually look like ragged cumulus clouds. They may originate from dissipated cumulus clouds, appearing in this case as white ragged clouds located at significant distances from each other. Cumulus fractus in particular form on the leading and trailing edges of summer storms in warm and humid conditions. NOAA Cloud Types - NOAA Chart of Different Cloud Types. Observing fractus gives an indication of wind movements under the parent cloud.
Masses of multiple fractus clouds, located under a main cloud, are called pannus or scud clouds.
Fractonimbus is a form of stratus fractus, developing under precipitation clouds due to turbulent air movement. They are dark-gray and ragged in appearance. Fractonimbus exist only under precipitation clouds (such as nimbostratus, altostratus or cumulonimbus), and don't produce precipitation themselves. Fractonimbus may eventually merge completely with overlying nimbostratus clouds.
Stratus silvagenitus clouds also commonly form as scattered stratus fractus silvagenitus. These clouds can be seen as the occasional ragged tuft of cloud seeming to rise from forests, commonly just after rain or during other periods of high humidity.
In addition to forming in inflow, fractus also forms in the outflow. Scud are very common on the leading edge of a thunderstorm where warm, moist air is lifted by the gust front. Scud are usually found under .
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