Extreme Dutch Weather: 7-7-2011 Nice little arcus, followed by real shelf cloud

Tuesday, 19 July 2011

7-7-2011 Nice little arcus, followed by real shelf cloud

This Thursdayevening the radar showed some convective weather crossing the SW part of the Netherlands. After a nice little arcus with some little gusts late in the evening a very beautiful once in a 2-3 year multilayer shelf came nearby. Even very close...

een filmpje: www.youtube.com/watch?v=fewlAeSq71w

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.