© Frank Le Blancq
La Pulente, St Brelade, Jersey
Latitude: 49° 11' 18'' N
Longitude: 2° 13' 33'' W
25 November 2012 1626 (Local Time)
Camera direction: towards SW
Image P/S code: P.4.1
Image I.D.: 5479
CL = 0, CM = 3, CH = 0
The cloud is an extensive thin sheet (species stratiformis) with merged cloud elements arranged in broadly parallel lines (variety undulatus). The sky is easily visible through the layer, identifying the variety translucidus. The blue of the sky can also be seen in the spaces between the lines of merged elements (variety perlucidus). The colour is predominantly white, with some light grey colouration near the back edge due to the cloud being thicker and to the low angle of the Sun.
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Low pressure of 994 hPa was centred over Ireland. A warm front was moving north-east over the eastern English Channel with a cold front moving east over the western English Channel. The photo was taken in the weak warm sector, where the cloud was well broken, revealing the Altocumulus cloud layer.
This thin, high layer of Altocumulus covers a large area of sky and is the species stratiformis. It is thin enough throughout to reveal the position of the sun (variety translucidus) and gaps between the cloud elements permit the sky to be seen (variety perlucidus). The presence of enlongated elements, almost parallel to one another, indicates the variety undulatus.
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This layer of Altocumulus (species stratiformis) is clearly translucent (variety translucidus) and gaps between the elements permit the sky to be seen (variety perlucidus)(2). The elongated elements, almost parallel to one another indicate the variety undulatus(4). The layer was invading the sky.
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In this night-time image, the thin layer of medium-level cloud through which the moon is visible is Altocumulus stratiformis translucidus. On the left edge, there are gaps between the cloud elements, making this also the variety perlucidus. The optical phenomenon surrounding the moon is the aureole of a lunar corona.
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This layer of medium-level cloud is Altocumulus. Its rounded masses and rolls have an apparent width of between 1° and 5° and there is some shading. The specific species of this Altocumulus is classified as stratiformis, due to the cloud’s extensive coverage of the sky. The sheet of cloud is sufficiently translucent to reveal the position of the Sun, and so it is also of the variety translucidus. In places there are spaces between the cloud elements, which also indicates the variety perlucidus, and the enlongated and broadly parallel rolls indicate that the variety undulatus also applies.
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The photo shows a layer of Altocumulus stratiformis undulatus perlucidus, viewed from an aircraft at an altitude of approximately 1 1000 m over the Italian Alps. At the lower right of the picture, some Cumulus clouds can be seen over the mountains.
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A sheet of lightly shaded white to dark-grey elements, showing the chief characteristics of Altocumulus: regularly arranged laminae, merged at 1, detached at 2, ragged at 3. The layer is of variety translucidus as one may assume that it would be possible to determine the position of the sun through most of it. The clouds were not progressively invading the sky and the coding is therefore CM = 3 rather than CM = 5. A disturbance was centred off Ireland and the station was about 300 km ahead of its warm front, which was undergoing rapid frontolysis.
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