1st March 2004: 00UTC
In the initial stage of the case study the cloud system under consideration is still seen far in the North. The main feature in the surface chart (Height of 1000 hPa) is the deep low over N-Scandinavia and Finland which accompanies a synoptic scale cloud spiral. However, the isolines indicate already at this point of time a secondary minimum within the large low center being close to the cold air cloudiness and which will become effective during the next two days.
1st March 2004: 06UTC
The main low center is the same as 6 hours before but has moved somewhat eastward. The secondary low which has already shown up 6 hours before has widened.
1st March 2004: 12UTC
During the last 6 hours the process described before is continued. In the center of the secondary low a mesoscale cloud spiral is now better visible.
1st March 2004: 18UTC
While the primary low center observed during the whole day is still distinct but nevertheless somewhat decaying. The secondary low center is deepening. It has now a closed circulation center and it is very clearly related to a comma cloud spiral which is immediately west of the Norwegian coast.
2nd March 2004: 00UTC
The comma observed 6 hours before has moved into Norway and is now connected to a very pronounced small scale surface low which has deepened as a secondary maximum within a rather more extended surface low. There is a very high and sharp gradient to the SW of this low center.
2nd March 2004: 06UTC
Although the center of the small scale low is not deepening it is very pronounced and the relation to the comma cloud spiral is very clear.
2nd March 2004: 12UTC
The same as said for the point of time 6 hours before is still true for this time.
2nd March 2004: 18UTC
The impression arises as if the surface low would become cut off in the area of the increased comma.
3rd March 2004: 00UTC
There is indeed a cut off process for the surface low. The whole cloud spiral is within this very pronounced cut off low. This end stage brings again out some differences - mentioned already in the introduction of this case study - between a classical development of an occlusion spiral and the development from a comma features taking place here. It is especially the much smaller size of the cloud system as well as of the closed surface low center ; conseqeuntly the whole cloud spiral encloses the surface low.
