Fractus (pannus) / scud

Pannus or scud clouds are a type of fractus clouds, found on thunderstorms. They appear as ragged cloud shreds at low altitude above the ground and detached from beneath the thunderstorm base.

  • Ragged and wispy in appearance.
  • Often along the gust front on a thunderstorm.
  • They form by forced lift along the gust front and mixing (entrainment) of cooled outflow air.
  • May also form in the inflow region of the storm by mixing (entrainment) of cooled outflow air. Pannus (scud) clouds in this region may form a wall cloud and/or inflow tail.