Meteosat-8 WV 6.2μm

1st March 2004: 00UTC
In the WV image the same as well as additional structures, compared to the IR image, can be observed. It follows that: there is a westerly-oriented cloud band structure which can also be seen as a white band in the WV image. But north to this band there are some additional band structures which cannot be seen in the IR image as they are not cloud but WV structures:

• There is a narrow dark stripe along the cloud band just mentioned and then there is another narrow white band which leads into a wave structure at 75N between 0 and 10E. In this area some white (cold) cloud could also be seen in the IR image representing a part of the high WV band which is already condensed.
• To the north and of crucial importance for the further development is the dark (dry) area around 75N and 15 – 20 W.

1st March 2004: 01UTC
Between 00 and 06 UTC the dark area in the WV image representing dry air is widening and approaching E-ward. Thereby it is overrunning the lower cloud shield discussed in the sequence of IR images.

1st March 2004: 02UTC
Between 00 and 06 UTC the dark area in the WV image representing dry air is widening and approaching E-ward. Thereby it is overrunning the lower cloud shield discussed in the sequence of IR images.

1st March 2004: 03UTC
Between 00 and 06 UTC the dark area in the WV image representing dry air is widening and approaching E-ward. Thereby it is overrunning the lower cloud shield discussed in the sequence of IR images.

1st March 2004: 04UTC
Between 00 and 06 UTC the dark area in the WV image representing dry air is widening and approaching E-ward. Thereby it is overrunning the lower cloud shield discussed in the sequence of IR images.

1st March 2004: 05UTC
Between 00 and 06 UTC the dark area in the WV image representing dry air is widening and approaching E-ward. Thereby it is overrunning the lower cloud shield discussed in the sequence of IR images.

1st March 2004: 06UTC
Between 00 and 06 UTC the dark area in the WV image representing dry air is widening and approaching E-ward. Thereby it is overrunning the lower cloud shield discussed in the sequence of IR images.

Up to this point of time the first curl has developed at the western boundary of the cloud area in the center of the dry air above.

Such dry air quite often is a sign for a PV anomaly which is stratospheric air penetrating downward into the troposphere. As a consequence of this process the rotation becomes quite high and influences also deeper cloud layers which could be an explanation for the development of the curls.

1st March 2004: 07UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 08UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 09UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 10UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 11UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 12UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 13UTC
In the period from 07 to 13 UTC the development and intensification of the cloud spiral can be seen also in the WV image and the effect of the cyclonic rotation in the dry air (PV anomaly) is quite evident.

1st March 2004: 14UTC
From 13 to about 18 UTC the main process of the development of cloud curls and spirals at the boundary of the dry air in the WV goes on. But additionally, in the WV small scale dry centers are seen very well. In this type of image at least two dry spots indicate new developments of curls at 70N/10E.

1st March 2004: 15UTC
From 13 to about 18 UTC the main process of the development of cloud curls and spirals at the boundary of the dry air in the WV goes on. But additionally, in the WV small scale dry centers are seen very well. In this type of image at least two dry spots indicate new developments of curls at 70N/10E.

1st March 2004: 16UTC
From 13 to about 18 UTC the main process of the development of cloud curls and spirals at the boundary of the dry air in the WV goes on. But additionally, in the WV small scale dry centers are seen very well. In this type of image at least two dry spots indicate new developments of curls at 70N/10E.

1st March 2004: 17UTC
From 13 to about 18 UTC the main process of the development of cloud curls and spirals at the boundary of the dry air in the WV goes on. But additionally, in the WV small scale dry centers are seen very well. In this type of image at least two dry spots indicate new developments of curls at 70N/10E.

1st March 2004: 18UTC
The WV image very clearly shows a double structure in the comma cloud spiral with two black spots. At the same time in the IR image the decay of the head of the spiral was mentioned. Consequently the formation of a new spiral will take place in the area of the second (more southern) dark spot.

1st March 2004: 20UTC
In the period from 20 to 23 UTC the structure in WV shows the two dark spots and the development of brighter grey shades (cloudiness) around the southern dark spot.

1st March 2004: 23UTC
At 23 UTC the new comma spiral and it WV environment is fully developed over N-Sweden. Over N-Norway the decay of the former spiral is still visible.

2nd March 2004: 03UTC
From 03 to 06 UTC the WV image shows some additional features compared to the IR image: the dry air is streaming over the lower cloud of the frontal band and there is a fibre visible in WV.

2nd March 2004: 06UTC
From 03 to 06 UTC the WV image shows some additional features compared to the IR imgage: the dry air is streaming over the lower cloud of the frontal band and there is a fibre visible in the WV

2nd March 2004: 09UTC
From 09 to 18 UTC the most interesting phenomenon in the WV image is that the dry air is streaming over the frontal cloud band and as a consequence a configuration typical for a split front arises. This has also been mentioned in the sequence of IR images. Besides relevant numerical parameters, the WV image can explain the double structure partly by the overflow of dry air on the rearward side of the cloud band

2nd March 2004: 12UTC
The process of development of a synoptic scale cloud spiral is going on; in the WV image the most interesting phenomenon are the two black areas which are partly above the cloud band and partly behind. They represent dry air in upper levels with a high degree of cyclonic rotation

2nd March 2004: 15UTC
The process of development of a synoptic scale cloud spiral is going on; in the WV image the most interesting phenomenon are the two black areas which are partly above the cloud band and partly behind. They represent dry air in upper levels with a high degree of cyclonic rotation

2nd March 2004: 18UTC
The process of development of a synoptic scale cloud spiral is going on; in the WV image the most interesting phenomenon are the two black areas which are partly above the cloud band and partly behind. They represent dry air in upper levels with a high degree of cyclonic rotation