1st July 2004: 06UTC
Concentrating on the features belonging to the Cold Front under discussion, the most striking feature at this point of time is the intensive surface trough which accompanies the North-South orientated part of the Cold Front. The West-East orientated cloud band which will approach and merge later does not show any surface trough
1st July 2004: 12UTC
The correspondence between the frontal cloud, especially the Western intensified cloud part and the surface trough, is much better now. It seems as if the physical state reflects the mergence of the two frontal cloud parts. However, the surface trough has still a North-South orientation. The pronounced small scale trough over Northern-Italy might be in accordance with the developing thunderstorm there
1st July 2004: 18UTC
At this timestep the first Wave (marked by '1') is recognised for the first time. Indeed there is a pronounced surface (1000 hPa ) trough in the area of the cloud bulge, but the surface trough accompanies the biggest part of the rear side of the cloud band.
2nd July 2004: 00UTC
The relation between the Wave areas '1' and '2' and the surface trough is similar to the situation 6 hours before. A very distinct surface (1000 hPa) trough contains a high curvature vorticity. This is again an explanation for the Wave bulges. However, these parameters are not yet enough for deciding about a further development of the Waves.
2nd July 2004: 06UTC
Now the development of Wave '2' and the very distinct trough in this area give enhanced indication to a further development of the Wave.
2nd July 2004: 12UTC
There is still a surface trough in the area of wave '2'. However, the distinct cyclonic spiral which has developed during the last 3 hours is not reflected by a more cyclonic surface trough. This is in accordance to the fact that the cloud feature seems to be an upper air comma feature which developed behind and merged with the wave area in the frontal cloud band.
The second wave for which the first indications can be seen around '3' is not at all accompanied by a surface trough but on the contrary appears in an area of a surface ridge!
2nd July 2004: 18UTC
The situation in the surface pressure field cannot explain the mesoscalic features observed in the satellite image. Other relevant parameters have to be inspected, which will be done in following chapters.
3rd July 2004: 00UTC
As before the geopotential height field at 1000 hPa shows a trough in the area of wave ‘2’ but is not very indicative to explain the mesoscalic features and developments. The new wave, marked as '3a' is not at all visible in this height field.
3rd July 2004: 06UTC
At this timestep, for the very first time, the surface trough (Hgt 1000 hPa.) indicates the development of a secondary low in the area of the first Northern Wave '2a'. This is the development of an occluding stage.
The Wave '3a' being in development according to the satellite images is not at all represented by the surface (1000 hPa) field.
3rd July 2004: 12UTC
The situation has not changed during the last 6 hours. In the area of Wave '2a' a secondary surface low exists, while '3a' is still not reflected in the 1000 hPa field.
3rd July 2004: 18UTC
Still no signal in the surface (1000 hPa) field in Wave '3a' is observed; there is a very flat distribution there. The development seen in the clouds must be related to other processes, very likely to processes in the upper levels.
4th July 2004: 00UTC
As before, there is no distinct sign of a developing Wave visible in the Hgt 1000 hPa chart. However, a new orientation of the 120 isohypse line in the area of the already fast developing Wave indicates a lower pressure in the Ukrain close to the Krim.
4th July 2004: 06UTC
The fast development of Wave '3a' is now reflected in the 1000 field; there is a large scale low center at 1000 hPa. Meanwhile the cloudspiral of the first Wave development (marked as '2a') is now within an extended low center.
4th July 2004: 12UTC
At this point in time a small closed surface low also appears in the charts over the area of the second Wave '3a'.
4th July 2004: 18UTC
The surface low around '3a' does not deepen but it is much more pronounced in the configurations of the isohypsen now.
