As already mentioned in the general remarks the cloud band of the Occlusion described in this chapter develops in the area of a wave (see Wave ) but shows, in contrast to the Occlusion of the Warm Conveyor Belt type (see Occlusion: Warm Conveyor Belt Type ), clearly different cloud layers.

In a fully developed stage the satellite image shows two synoptic scale cloud bands:

• a multilayered frontal cloud band of a Cold Front
• a lower cloud spiral which seems to penetrate from below the higher cloud band
• both cloud bands seem to be uncoupled

• In the VIS image the cloud spiral is white indicating deep cloudiness with high albedo.
• In the IR image the grey shades of a cold conveyor belt cloud band are spoken rather grey but with some increased white areas superimposed. The following points can be summarized:
  • At the transition between the cloud band of the Cold and Warm Front (oriented south-west to north-east) and the cloudiness of the cold conveyor belt type, a distinct gradient from white to (dark) grey can be observed. After some distance from the transition zone often cloud tops gradually become higher (whiter) followed again by a decrease of cloud tops within the innermost part of the cloud spiral. Such a cloud structure can be explained quite well with the conveyor belt theory (see Meteorological physical background ).
  • During the later stages of development, also high cloudiness can develop leading to a similar appearance to the Warm Conveyor Belt type of the Occlusion (see Meteorological physical background ).
• In the WV image the two cloud bands with different cloud types are seen even more distinctly. A black stripe characterizing the dry air on the cyclonic side of the jet axis extends parallel to the higher cloud band and crosses the cold conveyor belt cloudiness immediately at the transition zone. This effect cannot be detected in the case of an Occlusion of the Warm Conveyor Belt type. The driest air represented by very black pixel values is included in the spiral development. This fact can be observed in both types of Occlusion (see Occlusion: Warm Conveyor Belt Type ). During the later stages of development high and bright pixel values can be observed within the whole area of the cloud spiral which means that the crossing black stripe vanishes.

The penetration of the cloud band of the cold conveyor belt cloudiness from beneath the south-west to east-north-east oriented frontal cloud band is well developed and can be seen at 01.00 UTC above the North Sea at approximately 55N/04E. The transition zone between the cloud band of the Cold and Warm Front and the developing cloud spiral of the cold conveyor belt is situatedfrom the North Sea at approximately 54N/04E to north Denmark at approximately 57N/09E.
The enhanced images at 06.00 and 12.00 UTC clearly indicate the different height and orientation of the two cloud bands. At 06.00 UTC the cloud spiral extends from north-east Poland at approximately 54N/19E across the Baltic Sea to north-east Germany at approximately 54N/11E. At 12.00 UTC the cloud spiral has further developed and extends from White Russia at approximately 52N/28E across Lithuania to Poland at approximately 52N/18E.
The fully developed stage contains a lot of the mentioned features: two differently oriented cloud bands, lower cloud tops of the cold conveyor belt in the area of the transition zone close to the frontal cloud band; higher cloud tops downstream above the Baltic States and White Russia; again decreasing cloud tops towards the spiral centre. The cold cloud tops above Lithuania are situated within the area of the left exit region of a jet streak. Six hours later the cold conveyor belt cloud band shows up as a multilevel structured cloud band without any differentiation from the cloud band of the Cold Front.