Again, accumulations of 25 liters per square meter, with potentially peaks exceeding 50 liters per square meter in 24 hours in some places. The Belgians will have to pull their heads into their necks again 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 furrow. However, it could be that the activity spills over into the center and that we also experience 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 lies with a “cold drop”, also called “polar drop”, which was located 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 sort of wave, a wave, which will hit Belgium on Saturday. Indeed our regions, like last week, will once again find themselves on a long dividing line separating a warm air mass and a cold air mass, in conflict. These “fronts” can be covered by small undulations; Each time a wave forms and propagates, rainstorm activity intensifies in that location. This line of demarcation currently continues as far as Spain. The upward movements caused by the altitude depression on this line will create a wave in the south of France, a wave which will therefore reach us tomorrow and induce significant precipitation. In Belgium, if we take the entire episode (including a second less active burst on Sunday evening) we could reach 80 L/m2 in certain places, according to the most pessimistic scenarios. For comparison, it normally falls 78.2 L/m2 for the entire month of June in Uccle.
It should be noted that, in addition, the water on the surface of the Mediterranean is currently showing temperatures of 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”, judges Fabian Debal who therefore invites the population to follow the updates from the IRM.
