WARM FRONT SHIELD - CLOUD STRUCTURE IN SATELLITE IMAGES
- The satellite image shows a synoptic scale cloud shield which is in front of a Cold Front comprising the area of the Warm Front and the
- In the VIS image the grey shades in a well developed case are generally white within the warm sector and near to the surface Warm Front,
while the grey shades become gradually more and more grey towards the forward cloud edge (see Warm Front Band).
- In the IR image the grey shades of the cloud shield are usually white indicating cold cloud tops, but very often they show
substructures differing from case to case.
- The pixel values in the WV image within the area of the cloud shield are high and bright.
- At the leading edge of the cloud shield 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 (see Warm Front Band).
- In contrast to the Warm Front Band,(see
Warm Front Band - Cloud structure in satellite image
) the warm sector of the Warm Front Shield is overcast with cloudiness developed within the ascending Warm Conveyor Belt, which can
in a well developed case extend through a rather deep layer of the troposphere.
27 January 1995/00.30 UTC - Meteosat IR image
27 January 1995/00.30 UTC - Meteosat WV image
27 January 1995/12.00 UTC - Meteosat VIS image
The IR as well as the WV image of 00.00 UTC show a cloud shield of a Warm Front extending from the Atlantic (east of approximately 20W) across Ireland to the Bay of Biscay. The VIS image from 12.00 UTC shows an eastward propagation of this shield as far as the Benelux countries and west Germany.
Several features mentioned above can be observed:
- bright grey shades in the centre of the cloud shield in the IR and WV images;
- high albedo values in the VIS image in the centre of the cloud shield and gradually decreasing values to the forward edge;
- the black area in the WV imagery in front of the leading edge of the cloud shield in accordance with the cyclonic jet side;
- the cloud shield encompasses the warm sector and the Warm Front area, which is in contrast to the band-formed Warm Front.