• The satellite image shows within the frontal cloud band of the Cold Front an area of increased cloudiness (vertically as well as horizontally) which is superimposed by a PVA maximum at 300 hPa at least (see Key parameters );
• VIS, IR and WV images show bright grey shades, indicating thick cloudiness (see Typical appearance in vertical cross section );
• the increased cloudiness can appear in two forms:
  • lumpy structure, which indicates embedded CBs
  • Wave - like configuration as a consequence of the formation by cyclonic vorticity;
• this cloud feature is clearly brighter than the surrounding frontal cloudiness (see Key parameters );
• at the rear of the frontal cloud band, WV imagery indicates a jet axis pointing approximately perpendicular to the cloud band by a Black Stripe as well as Cloud Fibres which may be seen also in the IR image.

The cloud band of a Cold Front leads from north Germany across the west Alps to Corsica. The vertically and horizontally increased area can be observed over the west Alps and Italy (around approximately 45N/10E).
The approaching jet can be seen in the IR and WV images by high Cloud Fibres above the Atlantic (from approximately 52N/15W to 49N/07W) as well as along the French west coast (from approximately 48N/07W to 46N/00E). In addition to this the dark area in the WV image from Ireland across France to Corsica indicates dry air on the cyclonic side of the jet axis.

Appearance in AVHRR imagery

• Images from Channel 1 (fourth row, left) and Channel 2 (fourth row, right) show more details in the cloud structure than in Meteosat VIS, but the cloud patterns do not differ significantly from Meteosat-images. Channel 2 images show more contrast between land and sea than Channel 1 or Meteosat images.
• Cloud patterns in images from Channel 4 or Channel 5 (third row, left) are similar in Meteosat IR images, but show more fine structures in the area of front Intensification (FI) by jet crossing.
• RGB-combination of channels (below left, second row) provides a quick overview of cloudiness.
• Channel manipulation (third row, right) highlights cloud patterns, especially the Jet Cloudiness and the Front Intensification.

In the case of the Front Intensification, high and middle clouds are clearly observed in AVHRR satellite images.
The image in the third row right shows the result of substracting: Channel3B from Channel 1-. This artifical image is an effective tool for pattern recognition and shows areas with particle size of >= 10µm. The jet fibres (with ice particles >=10µm) are very pronounced. In the above images, Jet Fibres lie almost parallel to 50N latitude. The polar jet crosses the polar front close to the Isles of Scilly (SW England). Front Intensication over E. Ireland and the Irish Sea is seen as a concave cloud edge. In the above images, Jet Fibres from the Bay of Biscay to Belgium cross the polar jet at 52N/10W (Germany). Front Intensification is occurring over NE Netherlands and sea area German Bight. In the image (above left), middle and high level cloudiness are grey and white area respectively. Low level cloudiness as well as land is dark grey or black. In the image above right the grey and white areas respresent either ice crystals (Jet Fibres from Bay of Biscay to Belgium) or areas with high risk of precipitation. Frontal cloudiness over the North Sea, Germany and France and showers over the north of Great Britain are clear to be seen in this channel manipulation. The Front Intensification shows as a white bulge over sea area German Bight. In the upper right corner of these images, twilight can be seen. The frontal zone, jet fibres and the Front Intensification by Jet (FI) are light grey to white with quite remarkable shadows produced by the high clouds lying over lower clouds. The contrast between land/sea is best seen in Channel 2, the image above right.