1st July 2004: 00UTC
In the satellite image of July 1st: 00UTC, West-Europe is overcasted by a frontal system, dominating the weather. The occlusion cloud spiral of the system is still over the Atlantic and can not be seen in this image. Between Norway and Scotland the onset to a secondary cloud spiral is seen. Its evolution is also nicely pictured in the following images. The Cold Front, on which the 1st Wave will develop, can be seen over Northern France, Belgium and the Netherlands. Over the course of day the Cold Front will see a fast North-Eastward displacement and enhancement. At the time being there seems to be a weaker cloud area like an interruption between a N-S and a W-E oriented part of the cloud band.
1st July 2004: 03UTC
The Cold Front has moved eastward within the last 3 hours and the secondary Occlusion between Norway and Scotland now also becomes better visible. However, the more important feature is that the Cold Front exists of a North-South orientated part, which seems to have a common history, and a West-East orientated part which seems to approach. Derived parameters will help to understand this. On the image a '*' marks the position of the cloud intensification.
1st July 2004: 06UTC
Further intensification of the Cold Front can especially be observed over Germany. It appears brighter in IR imagery and shows a convective structure.
1st July 2004: 09UTC
In this image the Cold Front stretches from Poland and Czech Republic across Germany and Switzerland to France. It intensifies and appears very bright in IR imagery.
1st July 2004: 12UTC
The Cold Front passes the Austrian Alps. The leading edge of the front reveals the development of some thunderstorms, as is typical for such events.
1st July 2004: 15UTC
Over Northern Italy the development of a huge thunderstorm can be seen. In the IR images this Mesoscalic Cloud System can be traced for the next few images. The area of more interest for this case study, however, is seen close to Eastern-Germany and Poland. The enhancement of cloudiness marked here with a '1' gives a first impression of a cloud bulge. This should draw the attention of a Forecaster to watch this area carefully.
1st July 2004: 18UTC
Three hours later the Cold Front moved eastward across the Alps. The MCS over Northern Italy is still active. The possible Wave area over Poland -observed in the previous image- is from cloud configuration still very interesting.
1st July 2004: 21UTC
The Cold Front has moved Eastward over Hungary. The possible Wave area has not increased distinctively, but still the appearance of the frontal rearside from Poland into the Baltic Sea is very indicative for a Wave development.
2nd July 2004: 00UTC
Three hours later, the possible Wave area is much more distinct and 2 cloud bulges can now be identified! A northern over the Baltic Sea (marked with '1') and a new southern one over Eastern Poland (marked with '2'). Since the first recognition of a possible wave development about 15 hours have passed. This is a typical duration for a classical development of a Wave.
2nd July 2004: 03UTC
Looking only into satellite features, the two wave bulges (marked with '1' and '2') show potential for further development.
In the Alpine area over Southern-Germany, Austria and the Czech-Republic cloudiness has developed behind the Cold Front clouds, which is now merging with the Cold Front.
2nd July 2004: 06UTC
At this timestep the southern Wave-like bulge (marked '2') clearly has increased and shows the cyclonic curvature and bulge of a Wave in development. This happened 6 hours after the first recognition in the satellite images. There is pronounced cold air cloudiness behind the wave bulge 2.
Very dominant are now the cloud areas behind the CF over Austria and Hungary, but also the cloud area over Southern Germany.
2nd July 2004: 09UTC
The Wave area (marked with '2') has further developed. A distinct cyclonic rotation center can be observed. Behind the wave bluge intensive cold air can be seen. The cloud fields behind the Cold Front mentioned already in the previous images have merged with the Cold Front and form a distinct band from Hungary to Switzerland.
2nd July 2004: 12UTC
Two phenomenas are very impressive in this image. On the N-S oriented cloud band a rapid development of Wave '2' took place which shows already a light degree of cyclonic rotation. However, the small scale cloud spiral probably is a formation within the cold air cloudines which has merged with the frontal cloud band.
Second, an intensification of cloudiness at the rear of the new Cold Front over Northern-Austria (marked with '3'). At the time being this is not yet a clear indication of a Wave, but still important and should therefore be observed carefully.
Very impressive as well, but not related to the Waves, is the formation of Comma-Clouds over Germany in the cold air behind the Cold Front.
2nd July 2004: 15UTC
Within Wave '2' several substructures (2a, 2b) can be identified. The configuration of these substructures '2a' and '2b' suggests the mergence between the frontal cloud band and a cold air cloud feature, a comma.
The configuration of the W – E oriented part of the CF implements around '3' shows more and more the possible development of a Wave.
Another feature of interest is the intensification of the brightness in the Cold Front marked by '*'. It resembles very much the intensification in the left exit region of a Jet Streak.
2nd July 2004: 18UTC
The cloud features at the rear of the large frontal system reaching from Sweden across the Baltic States into the Ukrain and further westward across Hungary and Austria correspond very clear to conceptual models of Waves ('2' and '2a') and front intensification by Jet Crossing ('*'). The Wave-like features at '3' already recognised 6 hours before, exhibits more and more the features of a Wave. The influence of the Alpine Mountains for the formation of '3a' are thought to be important to further investigate.
3nd July 2004: 21UTC
The Conceptual Models at the rear side of the frontal cloudband develop according to their physical state. In the chapter of derived parameters these will be discussed in more detail. What is especially interesting in this case study is the fact the Waves are splitted during their development into further smaller wave features. It will be very interesting to look into the physics of the derived parameters.
3rd July 2004: 00UTC
Now both Wave areas are very distinct and the main developments are concentrated to '2a' for the already developed Wave (observed for over 24 hours!) and a new still developing Wave '3a', first observed as possible Wave area 12 hours ago.
3rd July 2004: 03UTC
Wave '2a' transforms into an occlusion. The appearance of the Wave '3a' becomes more clear and forms a disctinct synoptic-scale S-feature, characteristic for a Wave.
3rd July 2004: 06UTC
If one now solely concentrates on Wave '3a' one can say that the cloud bulge reveals a rather convective texture and that the cyclonic curvature resembles the ideal configuaration.
3rd July 2004: 09UTC
At this timestep Wave '2a' has evolved into an Occlusion (Southern Finland and Estonia). It could be observed that it took about 33 hours in that the Wave appeared as a substructure to a Cold Front and due to enhancement transformed into an Occlusion. Wave '3a' is found over Romania and the Ukrain.
3rd July 2004: 12UTC
During the last 6 hours the cyclonic bulge of the southern Wave '3a' fluctuated. Now it is very intensive and a comparison with derived parameters will be important.
3rd July 2004: 15UTC
The southern Wave '3a' becomes more pronounced in IR imagery. On the rearside the dissolution of clouds over the Ukrain can be observed.
3rd July 2004: 18UTC
The development of the Wave features has continued. It has to be remarked that this Wave has been observed for 18 to 21 hours since its first recognition.
3rd July 2004: 21UTC
The features and intensification of the Wave are very dictinct. From satellite imagery a fast development into an Occlusion cloudspiral would be expected.
4th July 2004: 00UTC
Indeed, the development can be observed now. On one hand from the feature of a more pronounced and brighter cloud bulge over Russia but much more from the feature of cloud dissolution in the area of '*'. This is very much in accordance with a Wave-type where dry air from above overruns the cloud bulge and dissolve the upper layer clouds. On the other hand this enhances the cyclogenesis (e.g. more deepening) and a rapid further development can be expected
4th July 2004: 03UTC
The feature of cloud dissolution by overrunning dry air can be seen in area '*'. The Development of a cloudspiral is (already) very distinct.
4th July 2004: 06UTC
Although the most part of the Cold Front lies outside the image, both features described before can be observed.
4th July 2004: 09UTC
While the development of a cloud bulge, typical for a Wave, lasted about 24 hours, the development from Wave to Occlusion cloud spiral only took 6 to 9 hours.
4th July 2004: 12UTC
The further development of the Occlusion cloudspiral can be observed.
4th July 2004: 15UTC
The further development of the Occlusion cloudspiral can be observed.
4th July 2004: 18UTC
The further development of the Occlusion cloudspiral can be observed.
4th July 2004: 21UTC
The further development of the Occlusion cloudspiral can be observed.