The fractus species designates irregular, torn cloud fragments with rapidly changing outlines. It applies to cumulus (Cu fra) and stratus (St fra). Cumulus fractus frequently appears beneath cumulonimbus and nimbostratus during rainfall.
Bad-weather clouds
Stratus fractus beneath precipitating clouds are informally called scud. They form when moist air below the rain base saturates through evaporation of falling drops, creating small, chaotic clouds that move rapidly with the wind. Their presence indicates high low-level humidity and usually accompanies persistent rain or storms.