The main reason for the development of convective Convergence Lines is the wind field pattern produced by changing thermodynamical situations in an orographic region during daytime.

The convergence in these areas can be explained by two different effects:

1. A typical synoptic situation showing a large scale wind field in low and middle levels with wind directions more or less parallel to the mountain chain. For the four mountain chains studied (Greek mountains, Carpathians, west Alps, Massif Central (France)) this means a synoptic-scale northerly flow.
2. The orography changes the wind field in direction as well as in speed. During the morning, in mountainous areas, there is a flow around an obstacle; during day the wind develops a component towards the mountains. The speed is quite low and there is a flow up the slopes. This can be explained by diabatic heating by the mountainous surface during day. (In the study made by ZAMG, cases from June to September were chosen since during the summer the Convergence Lines are better developed due to higher levels of solar radiation). The wind up the slopes is determined by the topographic features like slope angle and friction. The curvature of a slope also induces some vertical motion. This wind field results in convergence directly over the mountain chains or sometimes slightly shifted to the leeward side. Upward motions can be found in the regions of convergence.

The Greek and the French mountain Convergence Lines show very similar properties regarding the meteorological situation: A northerly synoptic-scale flow and the development of convective Convergence Lines over the mountain ranges.

The Convergence Line forming over the Carpathian mountains indicates a more complicated physical background: There are two "branches" of mountain chains. In case of northerly synoptic scale wind flow, the Eastern Carpathians are orientated in the same direction as the wind whereas the Southern Carpathians are more or less perpendicular to it. Therefore the convective cloudiness along the southern Carpathians cannot be explained by the same theory. As described in more detail in the chapter "key parameters" (see Key parameters ), a flow around the two mountain ranges as well as a small scale cyclonic rotation only at low levels can be observed in the majority of cases; this might be an explanation for a component towards the Southern Carpathians. At the transition between the Eastern and the Southern Carpathians (the "corner"), cloudiness is weakest. This is in accordance with an area where convergence is low or even divergence may be occuring. Full answers for these features are yet to be found.

The Transylvanian mountains also influence the wind field. There is a flow around them in the morning and a flow over them at noon.