In Finland the event began with an intensive cold front passage. The cold front was a katatype cold front; a pre-frontal convergence line preceded the actual cold front.
The best this could be seen in the vertical cross sections as a double structure in the convergence and vertical motion fields. The air ahead of the cold front was potentially very unstable. Instability was released quickly in the evening of 9 August over Finland, resulting in heavy thunder and gusts.
In Lithuania the continuous rain and resulting flooding was caused by the occluded front. Since the movement of the low pressure was slow, also the occluded front moved slowly over the area, causing continuous downpour of rain.
The model fields and satellite image analysis show that the occlusion front was quite well developed: the isentropic trough along with moist warm air at the middle and upper tropospheric layers and strong ascending motion caused steady continuous rain within the front.