In a clear lable atmosphere (ECMWF depicted Showalterindeces under 0!) and under influence of daytime convection several cells quickly emerged on May 29th 2005.
An analysis of the enhanced infrared images showed cloudtops reaching -70 degrees Celsius. More important however was that the cells all developed on WV boundaries. These WV dark stripes where already recognised at a very early stage of the case study.
Studying the severe convection RGB the physical contents of the cells could be explained, where at the initial stages the cell consisted of small iceparticles it slowly changed to large iceparticles as the cells reached their adult status.
Development of cells on WV boundaries is a common thing in Europe during summer as they are often seen as the initiator of convective development. The theory behind this lets itself best be described by the "Loaded Gun theory". The theory describes how convective developments can overcome a capped inversion.
The devastating effects of the severe convection of that day are well seen in the set of radar-images provided from the Thessalonica region. The dBz values reaching over 50, a clear indication to the severity of the convection and raising the assumption of associated hail. The hail in this case caused severe damage to the agricultural areas in Greece as it devastated the crops.
The second convective development happened in the leading edge of a large north-south aligned frontal system covering western Europe. In the morning hours of the 30th of May convection starts over the Austrian Alps. The convection is soon followed by cells emerging over the Czech Republic and Poland. In all the described satellite images the rapid development of the convective cells was well witnessed. Again most cells emerged on WV boundaries.
A study of the accompanying radarimages also showed the serverity of the case. Numerous hail-warning were set out as it brought great damage to the agriculture in Central Europe.
The convective events of this day were also investigated using nowcasting methods. Using the SAI product developed by the Nowcasting SAF the case was analysed half hourly. It was only at one hour before the event started that signs could be seen for the onset of convection. A second similar product is the GII. It benefitted as it gave already preconvective signs 2 hours before the convection started. Downfall was that some areas (Bavaria) where wrongly depicted as being unstable and potential for convective development due to a strong capped inversion.