|Route:||Soest - Almere - Markermeerdijk - Kampen - Terwolde - Deventer - Eemmeer - Nijkerk - Elspeet - Apeldoorn - Deventer|
|During the beginning of the week, GFS charts showed a nice chance of
possible convection over Holland, so I made a date with Ben Lankamp as I had
the day off from work and Ben has vacation from school.
Ben arrived during the early afternoon, when storms had already fired up
over NW-Holland and Belgium. These ones became electrically active pretty
soon and the storm over Belgium produced hail as well. We decided to stay home
and wait for convection development nearby, as the most unstable air had still to form
(CAPE>1000 J/kg at 18Z according to GFS charts). We watched some video of US
storms to kill time.|
Just before 15 LT (13Z) storms formed over Utrecht and near Amsterdam, so we decided to go north and chase convection over Flevoland. We soon noticed a storm to our west, while driving on highway A27. The storm was located west of Almere, so we went to Almere Buiten to take a closer look. A nice downdraft region was present, with a lowering behind it and nice CG's in the precipitation area. We took some photo's. The line of storms stayed west of us and moved north, so the only way to intercept them was driving towards Lelystad and then on the dyke crossing Lake IJsselmeer.
We got confused as latest radar images on my i-mode cell-phone showed that the line was weakening and a more active line was present to our east. We still decided to chase the line to our west and drove to a parking spot halfway the dyke. Well the storm was OK, but not spectacular.
Radar images showed an active squall to our east, so we drove off again. We stopped to take pictures of the updraft towers of our western storm system, but drove east again pretty soon. We were in doubts again as we saw a new cell explode to our north and the eastern squall seemed unreachable, but we still decided to drive east. There we got delayed by road constructions near Terwolde, so the eastern line was no target anymore.
In the early evening we drove west as new storms showed up in the Rotterdam-area which looked quite active with some sort of bow-echoe on radar. At first we were bound to drive towards SW-Utrecht, but this system was moving pretty fast, so we had to seek a more northerly location for intercept. Of course, Flevoland was the best choice again, so we stopped just west of Zeewolde, with a view over Lake Eemmeer.
Surface winds were blowing from the NE at this point and above 850 hPa strong SW-winds were present, creating an amazing wind shear environment. The first approaching storm was relatively weak and showed a small and high based shelf (or was it an inflow band or forming roll cloud?). The other system directly behind it was more active with a dense precipitation region and also a rain free base! In front of our eyes a lowering formed at about 20.42 LT. It was not well defined, but it had a tail cloud pointing towards the downdraft region. Soon thereafter the lowering became lower and more organized. The lower part of the updraft was visible as well, showing great organisation. Rotation was pretty evident with the lowering and the updraft as a whole. At about 20.52 the wall cloud got undercut by outflow and at 20.55 the wall cloud dissipated.
We went east again as the storm seemed to be right moving (radar showed N-NE storm-movement). We stopped just west of Nijkerk to watch the approaching outflow where a great shelf cloud was forming. Many lightning strikes were visible, often purple ones. The storm was moving at high speed, so we had to drive east again pretty soon. Driving east had some disadvantages though, as Hollands largest forest, the Veluwe, was in our way. We decided we had no other choice, so we proceeded. Ben shouted that he saw an amazing shelf cloud once in while, but I had to be alert for traffic and road options and missed a lot of this spectacle. In the middle of the forest we drove to a house with a field in front of it and manages to take some pictures of the menacing looking shelf, which showed multiple layers. It was too close and it was too dark for very clear pictures, but it we succeeded somewhat.
We continued east and noticed that one cloud got loose from the storm and moved east very fast. It took us at least half an hour to catch up and pass. It was a roll cloud with clear rotation! From behind (the west side) it looked black, but in front it was bright white and it was visible over the entire horizon. We took some pictures east of Deventer and saw more, smaller, roll clouds behind the main one. The sun had already set, so it was quite dark for photography. Also lightning activity had ceased, so it was time to return home at about 23 LT.
What a great chase this was! I want to thank Ben for navigating again...so helpful! Looking forward to our next chase :)
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© 2004 Bernard Hulshof