During the evening of 27 June, after a very hot day in Central Europe (up to 35 °C in the Mosel Valley), severe thunderstorms rapidly developed over Switzerland and Germany.
04 May 2023
27 June 2001
Frequent lightning, hail and strong winds causing several fires, flooding and severe damage to trees and buildings accompanied the storms.
The synoptic situation favouring the development of these storms was characterised by an upper-level trough approaching from the west together with hot, moist air at lower levels.
However, not all regions were equally affected; the storms developed mainly in Switzerland, southern Germany (Baden-Württemberg) and northwest Germany (Nordrheinwestfalen and western Niedersachsen).
The Meteosat-7 images show the situation at 17:30 UTC, around the time of maximum convective activity. The convective cells, which have a rather symmetrical structure, cover large parts of the Alps and southern Germany.
Two very large cells are also visible in northern Germany. Shadows cast by the cumulonimbus clouds on the surrounding low-level clouds (see visible image) give an indication of their vertical extent.
The circular structure of the cells would suggest that there was a relatively weak upper-level flow (also clearly seen in the AVHRR image below). This weak upper level wind flow was probably a reason why the storms did not organise themselves into larger storm systems such as mesoscale convective systems (MCS) or supercells.
Download full resolution NOAA-15, AVHRR (visible channel) image (27 June 2001, 18:19 UTC) (Courtesy of Michael Wienzek)