The initial formation of a local cumulus cloud known as cumulus mediocris because of its moderate height extension. Notice that even at this stage, the cloud looks quite different from a typical fair-weather cloud which has a more flattened base. This is shown in the first thumbnail. However, not all such cumulus cloud develop into thunderstorm cloud without the correct weather conditions. In this case, the cloud continued to grow within the next several minutes to eventually become a cumulonimbus cloud producing heavy squalls of rain which flooded the Mriehel region. However, officially only 10mm were recorded as such clouds produce showers over very short distances, in some case being even around the size of a football ground.

The weather situation on the day was a very light NE wind due to a broad upper-level trough as indicated in the second thumbnail. Combined with the presence of a cold pool of air at 850mb, the sea breezes that were intiated by the strong June sunshine quickly rose higher into the atmosphere helping to create a local thunderstorm which benfitted from lots of precipitable water due to the warm Ionian seas from where the wind was originating. Click here for further explanation of the thunderstorm cloud that formed on the day.