... E-France, Belgium, the Netherlands, Luxembourg and the S-North Sea ...
Despite weak signals of northward traveling short-waves along the eastern fringe of the trough, no synoptic scale forcing mechanisms are expected. A departing wind maximum at 500hPa over the western North Sea places the area under the right entrance region although divergence values remain slim during the day. Therefore thunderstorm development will be tied to orographic support, surface convergence zones and boundary layer moisture dispersal mainly over E-France and extreme W-Switzerland. Furthermore GFS backed off the eastward progress of the trough during the past few runs, which shifted focus for initiation to W-Switzerland and N-Belgium/Netherlands.
The surface features dewpoints of 9-12°C which is already enough for daytime driven initiation despite weak lapse rates throughout the atmosphere. WRF and GFS have most robust MLCAPE release over Benelux with up to 500J/kg, decreasing rapidly towards the south/east.
Although thunderstorm initiation can be anywhere in this broad area, extreme W/NW Switzerland and Benelux northwards have the most promising conditions for initiation. Shear at all levels is weak at best, so strong wind gusts and marginal hail are possible. A very isolated large hail risk over Benelux can't be ruled out if CAPE release indeed approaches the optimistic GFS output, but confidence in that scenario is too low for a level-1. Thunderstorms move northwards over the North Sea, decreasing in coverage/intensity after sunset.
Despite weak signals of northward traveling short-waves along the eastern fringe of the trough, no synoptic scale forcing mechanisms are expected. A departing wind maximum at 500hPa over the western North Sea places the area under the right entrance region although divergence values remain slim during the day. Therefore thunderstorm development will be tied to orographic support, surface convergence zones and boundary layer moisture dispersal mainly over E-France and extreme W-Switzerland. Furthermore GFS backed off the eastward progress of the trough during the past few runs, which shifted focus for initiation to W-Switzerland and N-Belgium/Netherlands.
The surface features dewpoints of 9-12°C which is already enough for daytime driven initiation despite weak lapse rates throughout the atmosphere. WRF and GFS have most robust MLCAPE release over Benelux with up to 500J/kg, decreasing rapidly towards the south/east.
Although thunderstorm initiation can be anywhere in this broad area, extreme W/NW Switzerland and Benelux northwards have the most promising conditions for initiation. Shear at all levels is weak at best, so strong wind gusts and marginal hail are possible. A very isolated large hail risk over Benelux can't be ruled out if CAPE release indeed approaches the optimistic GFS output, but confidence in that scenario is too low for a level-1. Thunderstorms move northwards over the North Sea, decreasing in coverage/intensity after sunset.
