• The satellite image shows in the initial stage a cyclonically curved Comma feature (see Comma ) which is situated within the cold air mass behind a Cold Front; during the further development the Comma increases in size until in the mature stage a synoptic scale spiral is reached.
• In general the cloud spiral in the IR and VIS images has a white and structured appearance indicating multi-level cloudiness with embedded Cbs (see Meteorological physical background and Weather events ).
• In the inital stage a southward continuation of the Comma Tail can be observed in the form of more or less continuous cloud patches in the lower level cloudiness.
• The WV image is characterized by grey to white pixel values according to the appearance in the IR image. On the rear side of the Comma structure the WV image is characterized by a sharp gradient and a black stripe indicating dry air.
• Especially in the initial stages of development the brightest grey shades can be observed within the Comma tail, which is situated within the area of the left exit region of a jet streak (see Front Intensification By Jet Crossing ).

The satellite image for 06.00 UTC shows a Comma configuration extending from Belgium to England with high cellular cloud tops and the continuation of the Comma tail above north France consisting of low cloudiness. The dark stripe in the WV image on the rear side of the Comma is well developed. The coldest cloud tops can be found above Belgium which is within the centre of a PVA maximum at 300 hPa, being connected with the left exit region of a jet streak. At 12.00 UTC the comma extends from the North Sea into Germany. The biggest developments during the last 6 hours can be seen in the southern part of the Comma tail. This area is also characterized in the VIS image by bright grey shades. In the WV image not only at the rear side but also at the front side, very dry air can be noticed. The latter develops during the life cycle and may indicate a splitting of the jet axis as well as the possibility of unstable developments. At 18.00 UTC the cloud spiral extends from north Germany across Poland to north Italy. Two things happen: intensification of the cloud tops in the IR as well as the development of a black stripe on the leading side in the WV image. As will be discussed in the chapter of weather events and within the meteorological physical background, a lot of thunderstorms develop in the area of the Czech Republic and Slovakia.