WARM FRONT BAND - CLOUD STRUCTURE IN SATELLITE IMAGES
- The satellite image shows an anticyclonically curved synoptic scale cloud band which is connected with a Cold Front cloud band.
- In ideal cases:
- in the VIS image the grey shades are generally white at the rear edge becoming gradually more and more grey towards the
- in the IR image the grey shades of the cloud band are grey to white, where the brighter values appear in the ideal case
towards the forward and downstream cloud edge.
- In reality:
- very often no continuous cloud band exists but rather several cloud layers with broken cloudiness, or sometimes even only
- in the IR image several white cloud areas are superimposed on grey lower cloud layers (see Meteorological physical
- High bright WV pixel values can be observed in the area of the frontal cloud band.
- At the leading edge of the cloud band the WV image shows in connection with the jet axis a sharp gradient from white to black
indicating dry air at the cyclonic jet side.
- In contrast to the Warm Front Shield (see Warm Front Shield), the warm sector of the Warm Front Band is usually cloudless, except in winter
and spring time when extended fields of fog and low level clouds can exist which relate to processes in the lowest layers (see Fog and Stratus).
10 January 1995/06.00 UTC - Meteosat IR image
10 January 1995/06.00 UTC - Meteosat WV image
This case has an appearance very close to the classical description.
The Warm Front cloud band can be observed on the Atlantic (east of approximately 25W) extending to Scotland and Northern Ireland. Several features mentioned above can be observed:
- the gradual increase of cloud top temperatures from the rear to the leading edge (in IR image);
- the distinct leading boundary of the cloud band (in IR and WV images);
- the Dark Stripe (in WV image) at the cyclonic side of the above-mentioned cloud edge;
- the cloudless warm sector.
Also the relation of the cloud band and the key parameters is very close to the ideal case (see Key parameters
01 March 1995/06.00 UTC - Meteosat IR image
01 March 1995/06.00 UTC - Meteosat WV image
This case shows some deviations from the ideal cases.
The cloud band of the Warm Front can be located in the IR and WV images from the south-eastern part of Sweden across the Baltic Sea and the Baltic countries to the Ukraine. In the IR image it consists of several high, i.e. cold, cloud areas and cloud lines superimposed on dark grey, i.e. warmer, cloud tops. In the WV image a broad white band in the area of the Warm Front indicates high water vapour content which is bounded by dark stripes on the northern as well as the southern edges. The northern stripe represents the dry air on the cyclonic side of the jet. The dark grey area extending from the Benelux countries across Germany and Denmark to Poland is an area of Fog and Stratus cloudiness.