Extreme Dutch Weather: Low topped supercells in November (11-3-2013)

Monday, 4 November 2013

Low topped supercells in November (11-3-2013)

A couple of low topped supercells in the late afternoon produced several damaging tornado's. The cells managed to evolve in a low Cape - high shear environment. The cells I observed more westward surely had some potential as well, but probably the better low level shear with more 'backing winds' was further eastwards. At the end of the chase I saw a (most likely) spout type funnel cloud (not photographed).

For video's of the events follow the link: Link showing several tornadovideo' s

Some explanation.....

When a thunderstorm has a longer living rotating updraft (mesocyclone) we call it a 'supercell'. A supercell is a relatively rare appearence in Holland; only on a few days a year one or more can be spotted. They can only exist under specific wind conditions. The top of the storm is often not that heigh as that of their bigger brothers in eg. the US. They often bring extreme weather with large hail and even tornado's being possible. A so called 'wallcloud' is a lowering under the stormcloud out of which a tornado can form. The last photo from the 1st of October 2006 shows a wall cloud.

Another type of tornado is not associated with a mesocyclone. It can appear below a stormbase when there are less windy conditions. Although relatively seldom they appear more often than the 'real' tornado. I prefer to call them 'spouts'.

Other weatherphenomena I'm interested in are 'shelfclouds' and 'mammatus' clouds.