1st July 2004: 06UTC
This is the initial stage of the case study. No Waves have been recognised in the satellite images, nor in the geopotential height at the surface. The isolines of the temperature advection (TA) follows the rear side of the North-South oriented part of the Cold Front cloud band, while the West-East oriented part, merging with Cold Front at a later stage, is mainly under CA. An interesting area is the WA maximum found over the border between France and Germany. It demonstrates a typical Wave situation.
1st July 2004: 12UTC
Six hours later the indication of a Wave (seen previously over the Elzas) has dissapeared. A large area of WA accompanies the warm sector of the frontal system while CA is found over a large part of the cold front cloud band.
1st July 2004: 18UTC
At this timestep the first signs of a probable wave development can be observed. There is not yet a (distinct) WA maximum in the area of the bulge. The zero-line of TA, however, is within the frontal cloudband and a further development of a WA max has to be observed.
2nd July 2004: 00UTC
At this point of time a doublestructure of waves '1' and '2' can be observed in the satellite image. As before, the zero-line of TA extends through the frontal cloudband but there are not yet WA maxima in the area of the cloud bulges. Especially the CA maximum behind Wave '2' is remarkable.
2nd July 2004: 06UTC
At this step in time the intensification of Wave '2' from satellite imagery is very likely. Still a WA maximum is not dominant, but from the configuration of the zeroline a maximum can be thought to be over Latvia and Estonia. The CA max is still distinct and accompanies the cold air cloudiness.
2nd July 2004: 12UTC
As before, the configuration of the zeroline of TA indicates a weak WA maximum close to the wave bulge '2'. But much more distinct is the CA connected to the comma development.
Very strong is also the gradient of TA in the West-East orientated part over Austria. The cold air moves against a very warm air mass in the south.
2nd July 2004: 18UTC
A WA maximum in the Northern Wave area '2' is still not distinct and it cannot help in explaining the double structure of the wave there.
The Wave areas '3' and '3a' are also connected to distinct features in the TA field. While the bulge '3' is under CA, a distinct separation of WA - CA is observed in Wave '3a'
3rd July 2004: 00UTC
This is the point in time where the wave bulge at '3a' develops a well organised configuration. However, the distribution of WA and CA in the TA field is not supporting a wave development there; intensive CA is dominating!
3rd July 2004: 06UTC
Now the Wave structure at '3a' is very distinct. But again, no WA maximum exists; the wave bulge is under CA. Thinking back on the distribution of the geopotential height at the surface there was no cyclonic circulation in the lower layers which could lead to a distribution of WA and CA maxima which are classical for a wave
3rd July 2004: 12UTC
Similar as it was with Wave '2a', but much more distinct, a WA maximum appears now over the Black Sea which is the leading part of the cloud bulge of the wave '3a'. But there is also a second maximum in the cloud bulge more to the North at the Ukraine-Russian border. The cloud bulge structure has already 6 - 9 hours before this point of time suggested a possible Wave development.
3rd July 2004: 18UTC
Now the devlopment of the Wave '3a' is accompanied by an intensification of the southern WA maximum. But as before, there is also a weaker one to the North.
4th July 2004: 00UTC
The process of wave development and intensification of the WA maxima has continued over the past 6 hours. Now the northern WA maximum has strengthened and is found in the region of the cloud bulge.
4th July 2004: 06UTC
This image, but also the next few slides reveal a clear intensification of the WA maxima connected with an occlusion process.
4th July 2004: 12UTC
The Wave has transformed into an Occlusion. A clear intensification of WA is observed.
4th July 2004: 18UTC
The Wave has transformed into an Occlusion. A clear intensification of WA is observed.
