• In the satellite images an MCS looks like a mesoscale cloud cluster, which has a circular or oval shape depending on upper level wind strength.
• In IR, WV and VIS images MCS are characterized by high pixel values (white) in the active part, indicating cloudiness which extends through the whole troposphere.
• The upstream edges of the cloud cluster are generally very sharp. In situations with high upper level winds, the high cloud is transported downstream leading to an extended white cloud shield in the IR but a fibrous grey texture in the VIS image. The brightest grey shades can be found in the active part upstream.

• Very often the surrounding atmosphere is characterized by the development of other convective cells (see Meteorological physical background).
• In the case of MCSs consisting of several independent sub-storms, the cloud patches have more irregular appearance and distribution of cloud top height. In such cases VIS images show a lumpy appearance.

The artificially coloured IR image (above left) shows a number of cells over northern Italy which are characterized by high pixel values (green and cyan). The cloud edges are very sharp around the whole cluster.
In the VIS image (above right) a more structured appearance can be observed. While in the IR image the whole area is characterized by high pixel values due to Ci clouds, in the VIS image only the active part has high pixel values (multi-level cloudiness). The area of the Ci cloudiness of the anvil has a grey, fibrous and translucent appearance in the VIS image.

The images and image loop below show the development of MCSs from the stage where a cloud top temperature threshold of -30°C is reached for the first time up to the stage of huge meso-scale MCS cells with several areas of cold tops.

Appearance in AVHRR imagery

• AVHRR imagery can help in visualizing the growth of, initially, smaller-scale Cb cells and the growth and eventual merging of Cb clusters into larger-scale MCS. The best channel combination is NOAA 1, 2 and 4 (124), as this gives a very good contrast between the upper thinner cirrus clouds and thick convective cores.
• Daytime NOAA channels 3, 4 and 5 (345) show less contrast but, on the other hand, the most thin cirrus anvils that are hard to see in NOAA 124 imagery are easier to find in NOAA 345 images.
• In NOAA 124 images the most striking feature of mature MCS is the intense very white colour of the inner parts and their round or oval shape. In early stages, MCS cores are very bright, and a good contrast is provided by the bluish anvils surrounding the core. If upper level winds are relatively weak, Ci anvils spread out in all directions, otherwise they spread downwind, steered by the upper level flow. Ci anvils can, in later stages of development, become the dominating feature in imagery.
• A dissipating MCS loses its brightness in the core region, as the convective updrafts weaken. Bluish Ci anvils become the dominating feature at this stage.

The afternoon channel 2 and channel 4 images above show several MCS, which developed over western Russia on 11 June 1999. The huge, round shape of most of the MCS is clearly seen, together with the spreading cirrus anvils. NOAA 124 images are better for detecting these cirrus anvils, while the NOAA 345 images are more saturated with a mixture of white cold cloud tops and Cb cloud cells.