code oranje
...northwestern Europe...
The GFS model gives indications of marginal instability over France, Belgium, Netherlands and the Wrn/Srn UK and later also over Germany.
CAPE fields (especially 0-3 km integrated) show slight instability over the ocean, Srn UK and English Channel and into Belgium during the early evening, at the cold side of the occlusion. However, 2000-4000m lapse rates reveal that this CAPE is present under a subsidence inversion, allowing not very deep convection.
The strip of poor mid level lapse rates in the wake of the occlusion can be tracked nicely and probably corresponds with descending air, so any chances of strong convection would be at the occlusion and cold front itself, where lift, very moist and likely neutral profiles should be present or perhaps a narrow fringe zone where deep instability can be released. Convective precipitation is produced in GFS.
A PV anomaly is missing, and so the faith in a convective touch to this front is low. However, if any sustained convection develops it may impose a threat of tornadoes besides strong/marginally severe gusts (bowing lines), because of the 15-20 m/s low level shear, 60 m/s deep layer shear and >300 m2/s2 0-3 km SREH capable of inducing brief mesocyclones in storms. It was chosen to indicate a large, rather conditional level 1 area for this reason.
The second wave gives a small convective signal over Belgium at the end of the period and, if realized, may induce similar conditions as described before.
The cold front is likely to become more active during the early Wednesday hours, when CAPE is predicted along it between Bretagne and central Germany - especially after 06Z during the next period. Isolated thunderstorms may occur then and shear conditions (as described above) are still favorable for tornadogenesis.
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