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The synoptic circulation was quite stationary and characterised with omega pattern over Europe: lows over the Atlantic and the Black Sea area and highs over the Mediterranean and northern parts of the continent. The areas affected by severe convection were located over a strong SW to W flow in mid troposphere and weak winds near the surface. Air mass was unstable with substantial deep layer shear which favoured the formation of supercells and organised convective storms.
A nice animation of satellite images from EUMETSAT can be found here:
3. Predictability
3.1 Data assimilation
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