© Michael Bruhn
Richmond near Hobart. Tasmania, Australia
Latitude: 42° 44' 2'' S
Longitude: 147° 26' 24'' E
21 August 2009 1212 (Local Time)
Camera direction: towards N
Image P/S code: P.5.1
Image I.D.: 5869
CL = 7, CM = 1, CH = /
Altostratus is a greyish or bluish cloud sheet or layer of striated, fibrous or uniform appearance, totally or partly covering the sky. In this image, the grey cloud is fairly uniform. The base lifted and thinned sufficiently to become semi-transparent over most parts and reveal the position of the Sun as if through ground glass, which indicates the variety translucidus. On this occasion, the Altostratus evolved through the thinning and lifting of Nimbostratus and may therefore be designated Altostratus nimbostratomutatus.
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The pressure chart from 0900 hours local time shows a low centre of 974 hPa south-south-west of Tasmania, Australia. The associated cold front over western Tasmania was moving east towards the location of the photograph (indicated by the red arrow).
The Hobart Airport, Tasmania, Australia (WMO 94975) sounding from 0000 UTC shows a moist troposphere from the surface to the tropopause. It is particularly moist at medium levels, associated with the nearby cold front.
The major part of this layer of Altostratus is sufficiently thin to reveal the position of the sun (variety translucidus). An occlusion was present 150 km to the west, moving eastwards in a general westerly flow.
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