The first image shows a strong upper air trough with the cold front in front of the trough's axis.
The trough extended more to the South and moved fast to the East. The connected frontal cloud band extended from West Norway over the North Sea to Northern England.
The trough's axis is connected to the faster-propagating comma cloudiness behind the cold front.
A separate upper air low developed in the cold air mass behind the front. The positions of the cloud spiral's centre and of the upper air low show a clear vertical tilting of the low's axis. A further intensification of the low is likely.
The low revealed still a strong tilting axis (compare with 1000 hPa). Comma and cold front merged.
The low's axis became perpendicular (compare with the spiral's centre over the German-Dutch border and the geopotential of 1000 hPa). That is a hint to the beginning of the decaying phase.
A geopotential height less than 5080 gpm can be seen which is quite unusual for end of November in this area. Around the low's centre the image reveals high extending clouds. Over Northern France and the Western parts of the British Isles high extending cold air convection can be seen.
Ongoing decay of the low is indicated by dissipation of cloudiness and the vertical low's axis.
The upper air low still existed but ongoing dissipation of clouds indicates the end of the critical situation.