© Markéta Augustinová
Zálší, Czech Republic
Latitude: 49° 13' 2'' N
Longitude: 14° 35' 53'' E
30 December 2014 1126 (Local Time)
Camera direction: towards SSE
Image I.D.: P.2.9
CL = 0, CM = 0, CH = 9
Links in the image description will highlight features on the image. Mouse over the features for more detail.
The thin layer of white, high cloud with small cloud elements (less than 1 degree apparent width) is Cirrocumulus stratiformis; and variety undulatus due to the undulations orientated top left to bottom right. There is a suggestion of a lower Cirrocumulus layer (duplicatus) on the left of the image, with larger undulations orientated from left towards the top right. The detail of this, however, is rather obscured by a lower layer of Cirrus at 4 and 5, evident particularly in the top left of the picture and down the left side.
Clearly though, the main feature of the picture is the large hole in the top middle of the image, below which there is as a bright white fallstreak of ice crystals. The hole is the supplementary feature cavum, popularly known as a fallstreak hole or hole-punch cloud.
The supplementary feature cavum is formed when glaciation occurs in a thin cloud layer consisting of supercooled water droplets, in a liquid state, at a temperature below 0°C. As the supercooled water drops glaciate, the resulting ice crystals fall from the cloud layer to a lower level as virga or fallstreaks. The resulting cloud hole typically grows larger with time while the glaciation process continues.
The location was under influence of decreasing ridge of high pressure. A warm front was coming from the northwest.
The photograph shows an extensive white patch of Cirrocumulus. It is composed of very small elements without shading, in the form of grains and ripples which have an apparent width of less than one degree. The image contains examples of species stratiformis and floccus and variety lacunosis. Towards the bottom of the image is supplementary feature cavum in the form of a distrail, most likely formed by an aircraft flying through the cloud layer.