General Assembly TWITPIC Timelapse: Undulatus asperatus Posted by Thunder Pig Monday, February 21, 2011 Undulatus asperatus  (or alternately,  asperatus ) is a rare, newly recognized  cloud  formation, that was proposed in 2009 as the first cloud formation added since  cirrus intortus  in 1951 to the  International Cloud Atlas  of the  World