|After a rather long period with normal or below normal temperatures in The Netherlands a southern flow brought warmer air. Air-mass was moist and moderately unstable as well with CAPE-values rising up to 1500+ J/Kg in eastern parts of the country. This should be enough for producing a couple of nice air-mass thunderstorms with the chance of large hail. Tornado chances were poor due to lack of wind shear.|
During the early afternoon my chase partner Ben Lankamp arrived at my place, where we waited for storm development. Already there were storms over Western Germany and Southeast England and near my place many types of Altocumulus clouds were present, indicating unstable air at midlevels of the atmosphere. At 15 LT first storms popped up over Eastern Holland and the complex over England was exploding and backbuilding towards Northwest France at that moment. We decided to go in search of the air-mass storms over Eastern Holland first. Soon we saw the massive storm towers to our southeast, but we got fooled by estimating the distance to the storms not correctly. Because of this we lost precious time and found the storm when it was in it's decaying phase. Outflow winds were pretty strong near Arnhem and we did see a hail core. Radarimages on my cell phone (i-mode) indicated that the storm had lost much of it's activity. Another to it's southwest was still active, but when we found this one, it died as well.
The active complex over Eastern England had grown into a linear complex, crossing the North Sea. The southwest of the country soon had to deal with this active looking squall line.
We soon got convinced we had to drive southwest and wait for the squall to appear at the horizon. Towards the evening hour we arrived near Hoornaar where we had a great view over the western horizon. Soon a low hanging shelf cloud was visible, approaching at great speed. Once in a while a CG struck behind the shelf, but lightning activity didn't seem high. We made lots of photographs of the shelf cloud, which came closer and closer by the minute. After 20 minutes or so, the shelf cloud got so close, we decided it was time to leave. Our goal was staying ahead of this convective line as long as possible, so we could shoot many pictures. We made a wrong decission by driving northeast instead of east, as the storm was moving east pretty fast. After 30 minutes we couldn't stay in front of it and we let the storm pass in southern Flevoland. There we harvested moderate to heavy rain with quite a lot of CC and IC lightning strikes.
As I had to do night shifts later that evening, we couldn't go further east and we decided to end the chase. It was evident it became quite a succes again! Soon we found out that the squall line covered the entire Low Countries and even beyond and that almost every location in Holland had seen a shelf cloud. Further east the shelf cloud was even more spectacular!