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 I.D.: P.4.6
CL = 0, CM = 8, CH = 0
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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 a smooth typical roll cloud look on the western end, turreted castellanus growth in the middle where the bases are becoming ragged and turreted castellanus growth with common base on the eastern end.
A layer of Altocumulus stratiformis translucidus perlucidus is above the 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.
Pressure gradient was tightening as a fast moving but fairly weak cold front approached from the west.
Very shallow PBL due overnight readiation inversion; lapse rate close to dry adiabatic from top of PBL to 719 hPa.