Eventually the cloud had reached a stable layer at an altitude of 10km and began to grow horizontally as seen in the first thumbnail on the right. Afterwards, parcels of air began to descend back to the ground. The mammatus cloud formation is not very well known hence it is impossible for me to explain exactly how it forms. One theory proposed is that the descending air warms at different speeds due to the moist and dry adiabatic lapse rates. Wind shear was also present. One striking feature was the strange shape of the jet stream around Western Europe which connected to the trough in the Central Mediterranean. `Cu congestus` and `Cb pileus` are also related. This was a brief follow up of a storm cloud development that took place between around 1100 CEST and 1500 CEST.