This first weekend in April promises to be particularly hot. Up to 30° degrees expected on Saturday in the South-West. Warm air coming from the Sahara rises towards France. A “Foehn effect” will occur in the South, causing the thermometer to rise. We explain this phenomenon to you.
From this Friday, April 5, 2024 and for the entire weekend, it will be summer before its time at the foot of the Pyrenees and in the Toulouse plain. Météo France is forecasting up to 30° in the South-West and south of the Garonne.
New temperature records are expected at the start of April. A phenomenon which can be explained by a rise of hot air from the Sahara which began to influence France yesterday, Thursday April 4.
According to meteorologists, “the situation will be remarkable”especially on Saturday April 6, 2024. In fact, a very deep depression will circulate towards Ireland (storm Kathleen) which will further propel this hot air from Africa towards France in a “heat pump” process.
This Friday, April 5, the mild weather will spread: 25°C will undoubtedly be reached in the southwest but also in Auvergne-Rhône-Alpes and in the Center-Val de Loire, even in Franche-Comté and Alsace. Near the Pyrenees, the 30°C mark could be reached, with 26 to 27°C south of the Garonne. And temperatures will rise another notch on Saturday, for what appears to be the peak of this hot streak nationally.
Yann Amice, meteorologist
A particularly warm air mass which will create a “Foehn effect” in the South-West. Because the Autan wind (coming from the south-east) will rise in the South-West.
A Foehn effect modeled by Météo France which should occur this weekend of April 6 and 7, 2024 in the southwest of France.
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© Météo France
The Foehn effect is characterized by warming and drying of the air on one side of a mountain barrier, causing temperatures to rise extremely rapidly.
When it occurs, the Foehn causes temperatures to vary, and sometimes even jump, as is likely to be the case this weekend. VShe thermodynamic phenomenon, which owes its name to a local Alpine wind, generates a hot and dry wind when an air mass encounters a more or less extensive relief.
As surprising as it is, on one side of the mountain, it is cool and it can even rain if there is enough water vapor, on the other, it is good, even very hot depending on the season. The Foehn effect has no real limits.
The scientific explanation is rather simple to understand. Facing a relief, “ the air will tend to rise. By rising, it will cool, lose its humidity and therefore dry out, but also relax. “. The atmospheric pressure will be lower and lower as the air rises in altitude. “ It will tend to condense, which will cause precipitation on the side of the mountain exposed to the wind. », saccording to weather forecasters.
Arriving on the other side of the mountain, “ the air will compress since the atmospheric pressure returns, which will heat it up“. This air simply has a greater warm potential than what it had upstream, because it has been emptied of its water.
A heat peak which is generally short-lived. Temperatures are also expected to drop from Sunday with the arrival of a stormy storm.
The month of March which has just ended has already been marked by numerous heat waves all around the planet, particularly notable in Africa, South America and Asia. Heat of course linked to global warming, but which is added to a cyclical element: the El Niño phenomenon.
This regular climatic episode which occurs every 2 to 7 years is characterized by a rise in water temperature on the surface of part of the Pacific Ocean. It results in an increase in the global temperature of the planet, which increases droughts and floods in certain regions of the world. However, it should be completed around June July 2024.
