Between Iceland and Scotland an violet area with some convective clouds can be seen. The transition zone to the blueish colours indicates tropospheric cold air and marks the position of the jet stream.
Note: You can always click on the to bring up the RGB-key.
With the Airmass RGB the position of the jet can be traced as well as the influence of dry stratospheric air on the development.
The cellular cloudiness in the cold air behind the cold front is superimposed by stratospheric dry air. This is in good correspondence with the conceptual model of an instant occlusion.
The development of cellular cloudiness in the area of stratospheric upper air can be followed. The comma clouds are situated at the left exit region of the jet streak. That is a hint that PVA superimposed the comma structure yielding its intensification.
The blueish areas of cold air merge more and more with the reddish areas of stratospheric air. That happens due to the increasing amount on cold tropospheric air. The comma clouds east of the Scotish and English coast intensified. This was triggered by PVA in the left exit region of the jet stream or by a PV-anomaly (both processes will be considered in detail later on).
The area of comma cloudiness are clearly superimposed by stratospheric air.
The jet is coming from behind the front in W-E direction. The whole development took place in the left exit region of a jet streak and near a PV anomaly. This will be shown later.
The comma was just about to merge with the cold front. Stratospheric air reached to the spiral.
Comma and preceeding cold front merged. The cloud spiral and the surface low's centre are clearly to be seen. The surface low will move only slightly during the next about 18 hours.
The life-cycle of the cloud spiral and the air mass flow can be followed till the end of time period. Now significant changes happened during the last 3 hours.
High extending clouds superimposed by stratospheric air influenced parts of the Netherlands and West Germany.
The surfacew low's position and cloud spiral remained almost stationary.
The clouds over parts of the Netherlands and West Germany continued rotating.
Now significant changes happened.
The surface low and the connected cloud spiral started moving slowly to the West.
The high extending clouds over the Netherlands moved to the South and the cloud spiral started decaying. Cloud dissipation as already seen in IR and WV images marks the end of critical weather situation.
Dissolution of cloudiness marks the end of this unusual snow fall situation.