© Michael Bruhn

Broadmeadows VIC 3047, Australia

Latitude: 37° 41' 24'' S

Longitude: 144° 56' 50'' E

02 August 2011 0819 (Local Time)
Camera direction: towards NNE

Image P/S code: P.4.6

Image I.D.: 5930

C_L = 0, C_M = 8, C_H = 0

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  Altocumulus volutus

  This is a rare example of the new species volutus occurring within the genus Altocumulus. Volutus, commonly known as a “roll cloud”, is a long, horizontal, detached, tube-shaped cloud mass, often appearing to roll slowly about a horizontal axis. It usually occurs as a single line and seldom extends from horizon to horizon.

  This example has the look of a smooth, typical roll cloud on the western end; turreted castellanus growth in the middle where the bases are becoming ragged; and turreted castellanus growth with a common base on the eastern end.

  A layer of Altocumulus stratiformis translucidus perlucidus is above the volutus on the eastern end and slightly superposed on the western end. Some Altocumulus lenticularis, at the same base as the volutus, is low on the right-hand side.

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  © Michael Bruhn
  Broadmeadows VIC 3047, Australia
  Latitude: 37° 41' 24'' S
  Longitude: 144° 56' 50'' E
  02 August 2011 0819 (Local Time)
  
  
  Camera direction: towards NNE
  C_L = 0, C_M = 8, C_H = 0
  Image P/S code: P.4.6
  Image I.D.: 5930
• 

  The pressure gradient was tightening as a fast-moving but fairly weak cold front approached from the west.

  © Commonwealth of Australia 2011, Bureau of Meteorology
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  Very shallow planetary boundary layer due to overnight radiation inversion and lapse rate close to dry adiabatic from top of planetary boundary layer to 719 hPa 

  © University of Wyoming