A taste of spring.
This Thursday, February 15, the whole of France is entitled to particularly high temperatures for the month of February with temperatures between 15 and 20°C over most of the territory.
A mercury well above seasonal norms due to the arrival of subtropical air over France coming directly from northwest Africa.
In the Pyrenees, temperatures even go well beyond 20°C with 23°C expected in Biarritz and “possibly 25/26°C locally” in the surrounding area, according to Keraunos, the storms and tornadoes observatory.
Summer temperatures are expected tomorrow Thursday in the southwest with the Foehn effect.
Possibly more than 25/26°C locally.
The 20°C mark should be crossed in the center of the country on February 15.
pic.twitter.com/cnccRB4ukv
— Keraunos (@KeraunosObs) February 14, 2024
These abnormally high temperatures in the South-West are linked to the foehn effect, a meteorological event little known to the general public which nevertheless occurs regularly in France, particularly in mountainous areas.
This phenomenon is generated by the meeting of atmospheric circulation and relief when a prevailing wind meets an assembly line.
This mass of air then crosses this obstacle by flowing over it before descending on the other side of the mountain.
The Pyrenees often affected
When these air parcels rise, they are subject to a drop in pressure and cool.
“When humidity and cooling are sufficient, their temperature reaches that of the condensation point where clouds form,” explains Météo France.
It is then that part of the water vapor takes a liquid or solid form, then once the peak is crossed, the air undergoes an increase in pressure, making it less humid and heats it, leading to a rise temperatures.
Seen from the sky, the Foehn effect can be easily discerned with a cloud cluster on the windward side of the slopes, "while the leeward slope benefits from a very large sunny gap characteristic of the Foehn effect", specifies the specialized site Météo Contact.
As indicated by the two weather forecast sites, this effect is often felt at the foot of the Pyrenees by southerly current, as is the case this Thursday with a southerly wind blowing up to 80 km/h rising up the relief on the Spanish.