Interactive overlays: 24 Nov 2005, 00 UTC

In the first IR image we see a broad cold front band extending from Scotland to Norway. Behind this cold front, cold air masses with cellular cloudiness can be noticed.

The cold front stretches from Great Britain to Norway and is also revealed by the WV image. Behind the front a distinct and broad dark area exists, indicating cold and sinking air in the upper troposphere. Between Iceland and Great Britain a sharp transition zone of brightness values can be noticed. The jet stream can be located in this zone. The dark area is situated on its cyclonic side.

The high-reaching and compact frontal cloud band of the cold front is in connection with a surface trough.

The first image shows a strong upper air trough with the cold front in its forefield.

The first image shows a pronounced upper jet from NW direction behind the front. The area of the instant occlusion is situated in the left exit region of the jet streak. Strong maxima of PVA coincide with the cold front as well as with the cellular cloudiness behind the front.

PVA at 500 hPA is connected with the cold front as well as with the cellular cloudiness behind the front.

A maximum of the thermal front parameter can be found at the leading edge of the cold front as well as in wide parts of the frontal clouds. The cellular clouds in the cold air masses behind the front coincide with a trough of equivalent thickness.

In the conceptual model of an instant occlusion PV=2 is not assumed as a key parameter. However, it can provide supporting information.
The broad dark area behind the cold front was already described in the WV image and airmass RGB chapters. It was interpreted as stratospheric dry air protruding down to lower levels. Compared with the models fields of PV=2 it gives an excellent fit.

The first image shows a typical situation for a cold front. The zero line of temperature advection is situated at the leading edge of the front.