What To Know
- “The peak of activity should rather be reached in the evening and at night and it is the south-eastern half of the country that should be affected, certainly the region south of the Sambre and Meuse valley.
- It is possible that the activity spills over into the centre and that we also experience precipitation in Hainaut, the two Brabants or Limburg but probably less than in the south-eastern provinces”, summarises Fabian Debal, meteorologist at the IRM.
- 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 induce significant precipitation.
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 that should be affected, certainly the region south of the Sambre and Meuse valley. However, it is possible that the activity spills over into the centre and that we also experience precipitation in Hainaut, the two Brabants or Limburg but probably less than in the south-eastern provinces”, summarises Fabian Debal, meteorologist at the IRM.Already damage across the country last Wednesday The fault of a “cold drop”, also called “polar stall“, which was located this Friday afternoon over Spain, where it is already creating showers and thunderstorms in the Iberian Peninsula. “A cold drop is a pocket of cold air at altitude, an altitude depression, with winds that turn on themselves, explains Fabian Debal. It is sometimes called a polar stall, because this structure is isolated from the rest of the general atmospheric circulation. It therefore often remains in place and moves very slowly. The precipitation can then cause 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 induce significant precipitation. In Belgium, if we take the entire episode (including a second, less active salvo on Sunday evening) we could reach 80 L/m2 in some places, according to the most pessimistic scenarios. For comparison, 78.2 L/m2 normally falls for the whole month of June in Uccle. It should be noted that, in addition, the water on the surface of 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”, judges Fabian Debal, who therefore invites the population to follow the updates of the IRM.
