The conveyor belts involved in a CF in CA show some deviations from the situation of classical Cold Fronts (see Cold Front - Meteorological physical background ). The relative streams show, in the majority of the cases, a warm conveyor belt in lower layers at the leading part of the Cold Front. But the most typical feature in many cases is a sinking dry intrusion from behind which is split in two branches over the rearward and middle part of the cloud band of the CF in CA: one branch is oriented to the south, southwest and the other branch to the north - east/west. The southern part is sinking from high levels to middle or even low levels whereas the northern part does not show strong vertical displacement. (This is an obvious difference to the "Cold Front in Warm Advection", where such a distribution never occurs; see Cold Front In Warm Advection - Meteorological physical background ). The sinking and splitting of the dry intrusion is in good agreement with the low cloud tops seen at a Cold Front in Cold Advection. The following images show the relative streams when there is a split dry intrusion. In the area of the CF in CA over France and N. Spain relative streams from the NW can be observed which are sinking from about 400 - 500 hPa down to about 600 hPa in the area of the cloud band and splitting. This is the part with the low cloud tops (grey in IR). The leading part of the frontal cloud band over S. France and the Pyrenees is accompanied by higher cloud fibres (white in IR); this is the area of the rising warm conveyor belt. The limiting stream line is very close to the transition between low and high cloud elements. On the lowest isentropic surface (300K), the warm conveyor belt extends more into the cloud band than on the higher surfaces.

In those cases where only parts of a Cold Front cloud band are under CA (most often the part of the CF which is closest to the point of Occlusion) a pronounced Warm Conveyor Belt exists in any case. But there is a tendency that the part of the CF in CA is connected to that area of the Warm Conveyor Belt which does not rise but is rather parallel to the isobars.

The next example from 29 April 1999 is a special situation which shows some interesting features already mentioned in the two previous cases. On the lower isentropic surface (300K) a heavily sinking dry intrusion appears in the area of the CF in CA. Above, at 306K, a pronounced warm conveyor belt exists but the cloudiness of the CF in CA is associated with the area of the sinking branch. As a consequence of this strong sinking in a thick layer, cloud tops of this case are very low. The overrunning sinking dry intrusion just discussed is the reason for the low cloud tops and the activity of the cloud bands of CF in CA. When compared to classical Cold Fronts the Cold Fronts in Cold Advection do not very often show further development but remain the same or even decay.

Results of investigation of CF in CA at ZAMG (46 cases)

intensifying fronts	9%
fronts remaining the same	39%
weakening fronts	52%

In this respect CF in CA show a similar behaviour as Cold Fronts in Warm Advection. (see Cold Front In Warm Advection - Meteorological physical background ), whereas classical Cold Fronts are characterised by a much higher percentage of strengthening fronts.

Parameters that determine the further evolution of these fronts are discussed in the sub-chapter Typical appearance in vertical cross sections.

Sometimes in summer these Cold Fronts are accompanied by the development of convective cloudiness at the leading edge of the cloud band. Typically such a situation is associated with an unstable stratification of the relative streams with a warm conveyor belt at lower levels and a dry stream at higher levels (see Convective Cloud Features In Typical Synoptic Environments: At The Leading Edge Of Frontal Cloud Bands - Meteorological physical background ). Such a configuration of relative streams also exists in the cases of CF in CA described earlier. MCS developments at the leading edge of frontal cloud bands seem to regularly occur in the area of the northern Adriatic Sea and surrounding regions: the topographic conditions in this area might, therefore, also contribute to instability.

The importance of the sinking dry intrusion in middle and high levels for the development of MCS is confirmed by the fact that convective cloudiness is found less frequently with Cold Fronts in Warm Advection