DISCUSSION: Over the course of the last 24 to 36 hours, a weak area of low-pressure gradually made its way across portions of western Europe. As it did so, a substantial amount of warm, moist air was able to make its way northward from the western Mediterranean Sea. As this unfolded, this facilitated a notable increase in the degree of convective instability across the region due to substantially increased buoyancy being in place across portions of western and northwestern Europe. In addition, the increased southerly flow towards the surface coupled with stronger westerly winds aloft induced a stronger clockwise turning of the winds with height. This combination of increased convective instability along with increased vertical wind shear allowed for a greater propensity for deep-layer rotation which is conducive for the development of supercell thunderstorms capable of producing tornadoes. In the footage above, note how towards the bottom-left part of the frame you can see a lowering of the cloud base which is referred to as a wall cloud. This is most commonly found at the base of supercell thunderstorms during the processes which precede the occasional occurrence of tornado formation since there is a lowering of the cloud base via increased sinking motion associated with the main updraft.
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©2017 Meteorologist Jordan Rabinowitz