Extreme Dutch Weather: 10-5-2012 Tornadic supercell

On thursday 10 th of May 2012 there was potential for extreme weather in the SE edge of Holland. The situation already for days showed up in the weathermaps. My chase target was eastern Brabant/ northern Limburg where from late afternoon there was a chance for supercells, which might even become tornadic. The late afternoon still nothing interesting had happened..... Temperature in Limburg rised to 26 degrees C at 17Z, where eg. Rotterdam had 19 degr. C. In the beginning of the evening things somewhat surprisingly started firing up in the western part of Belgium; producing a first tornadic supercell. This cell also probably splitted above the Netherlands. From now on more smaller cells formed and after discussing the situation with a fellow storm chaser we decided to position in northern Limburg. During the drive on the 'A73' I thought to see a wall cloud at the SE end of the large thunderstorm in front of us. I'm still not sure but it probably belonged to the split of the old cell. And so at the end a so called 'bust' was prevented and I was able to see 'the storm' of the evening. It was a beautiful supercell near Venray that produced several funnels and even at least a short tornado near 'Vierlingsbeek' (which we ourselves did not see.... :( ). We stood near the 'N270' closeby Venray. Some technical background information: Estofex first gave a 'Level 1' but eventualy upgraded to a level 2. Estofex: The Benelux countries, north-eastern France, north-western and northern Germany An upgrade to level 2 is issued for the Benelux countries. Latest observations indicate that the boundary-layer moisture has further increased to about 11 g/kg. The temperature has increased to about 23°C over northern France, and latest satellite image indicates the chance of some further insolation during the next hours. Although the elevated mixed layer air will likely remain across central and southern France, instability will be likely over northern France and Benelux given the rich low-level moisture and diurnal heating. Current scenario is that storms will develop in the late afternoon hours across southern Belgium. The absence of widespread forcing may result in a couple of cells that remain rather isolated for quite a while. Given the strong 20 m/s 0-3 km and 25 m/s 0-6 km bulk shear and about 100 J/kg 0-3 km SRH, these storms will likely evolve into supercells. These may be capable of producing tornadoes given 10 m/s 0-1 km bulk shear that will even increase in the evening hours as a strong WSWerly low-level jet is expected. Given the strong vertical wind shear, strong tornadoes are not ruled out. The main uncertainty is the backing of low-level winds. Latest observations indicate southerly low-level winds across northern France that may lead to favorable veering profiles, confirming the latest scenario. The storms will likely move north-east in the evening hours. Despite the tornado risk, locally large hail, severe wind gusts and excessive precipitation is forecast. After some time, storms may merge into clusters what will reduce the potential of severe weather except for high winds given the strong 850 hPa winds. However, isolated cells will be capable of producing severe weather including tornadoes in the evening and night hours across northern Germany, though.