Again, accumulations of 25 liters per square meter, with potentially peaks in certain places exceeding 50 liters per square meter in 24 hours. The Belgians will still have to hide their heads this weekend, because an episode “rainy-stormy”with some “heavy rainfall and intense thunderstorms”a “replica” of last week according to the MRI, will hit our country again. The yellow alert – or even orange if the areas affected by the 50 L/m2 exceedances expand – should be there this weekend, for an episode that should last from Saturday midday to Sunday midday.
The episode should mainly affect the south-east of Belgium but could spill over into the centre.The peak of activity should rather be reached in the evening and at night and it is the south-eastern half of the country which should be affected, certainly the region south of the Sambre and Meuse valley. It is however possible that the activity spills over into the centre and that there is also precipitation in Hainaut, the two Brabants or Limburg but probably less than in the south-eastern provinces”summarizes Fabian Debal, meteorologist at IRM.
Already damage across the country last Wednesday
The fault is a “cold drop”, also called “polar stall”, which was this Friday afternoon above Spain, where it is already creating showers and storms in the Iberian Peninsula. “A cold drop is a pocket of cold air at altitude, an altitude depression, with rotating windsexplains Fabian Debal. It is sometimes called polar stall, because this structure is isolated from the rest of the general atmospheric circulation. It therefore often stays in place and moves very slowly. Precipitation can then lead to flooding.”
From Spain
This cold drop will not reach our country as such but it will trigger a kind of wave, a surge, which will indeed hit Belgium on Saturday. Indeed, our regions, like last week, will once again be on a long demarcation line separating a mass of warm air and a mass of cold air, in conflict. These “fronts” can be crossed by small undulations; each time a wave forms and propagates, the rain and storm activity intensifies at this location. This demarcation line is currently continuing as far as Spain. The upward movements caused by the high-altitude depression on this line will create a wave in the south of France, a wave which will therefore reach us tomorrow and will therefore induce significant precipitation. If we take the whole episode (including a second less active salvo on Sunday evening) we could reach 80 L/m2 in some places.
It should be noted that the Mediterranean is currently showing temperatures 1 to 2 degrees above normal. The air masses that will pass over it will therefore be more loaded with water vapour, which will contribute, among other factors, to the intensity of the precipitation.This is a delicate episode, potentially problematic, for France and of course for the Benelux”, Fabian Debal still judges, who therefore invites the population to follow the IRM updates.
