The beautiful days are coming back ... much faster than expected.
Temperatures are heating up considerably after the cold snap that swept through France last week.
The high pressure from Scandinavia had caused negative temperatures to be felt down to -13 ° C in Dunkirk or even -18 ° C in Mulhouse.
This Tuesday, the thermometer shows almost spring-like positive values, ranging from 13 ° C in Lyon to 19 ° C in Tarbes.
The phenomenon should increase in the middle of the week and until the weekend, with a thermometer showing Wednesday up to 22 ° C in Pau (Pyrénées-Atlantiques).
The cold snap is now behind us.
But such a difference in temperatures in a few days can be surprising.
How do we explain it?
The Parisian takes stock.
As impressive as it is, a change of this magnitude is hardly surprising.
The phenomenon is primarily meteorological: the cold wave observed last week was due to an anticyclone coming from Northern Europe, especially Russia, specifies Tristan Amm, forecaster at Météo France.
“The wind that blew over the northern half of France was particularly cold and dry.
The high cyclone circled clockwise around France and shifted towards central Europe before reaching southern Europe.
It is now in the Mediterranean ”.
The wind blowing from the southwest is now warmer and wetter.
"It will continue to supply fresh air over most of the country throughout the week," said the forecaster.
A high temperature anomaly
Consequence: there is already an "anomaly" with the high temperature this week in most regions, except the north of the country.
“On average, the temperature in Paris in mid-February is 4 ° C in the morning and 9 ° in the afternoon.
Today (Tuesday Editor's note), we are three degrees above normal for the season.
And these averages will increase further: we are expecting between 16 ° C and 17 ° C degrees this weekend in the capital, ”observes Pascal Scavinier, head of the forecast service at the Weather Channel.
"This episode could be brought to accentuate a little more by next week, even if we remain cautious on our forecasts", adds the meteorologist.
Low pressure over the Atlantic and high pressure over central Europe => SW flow over France this week.
Diving from the thalweg towards Morocco this WE straightens the flow to the S. The overall forecast (Pmer and Extreme Forecast Index) offers remarkably mild T ° this WE (1/2) pic.twitter.com/3JMm8gYpAP
- Alexandre Flouttard (@ stormchaser_a81) February 16, 2021
A peak of hot air should even be observed in the Pyrénées-Atlantiques.
"Not only will the region benefit from the flow of hot air coming from the Maghreb, but temperatures will increase thanks to what is called the foehn effect", adds Alexandre Flouttard, forecaster at Météo France.
“This effect is a meteorological phenomenon in which the wind which crosses a mountain range will force the hot air mass to rise.
This will then condense and lose its moisture on reaching the top of the relief.
Then, when the mass goes down, the air will compress and heat up, causing the mercury to rise, ”he explains.
Temperatures ranging from 19 ° C in Sainte-Colome to 22 ° C in Oloron-Sainte-Marie are thus expected this Wednesday.
A temperature difference caused to recur
If the country's temperate climate and its proximity to the ocean partly justify the sudden temperature changes, such a difference remains uncommon in recent years.
Since 1956, only ten episodes have been observed, during which the temperature difference was more than 10 ° C in February in Paris, according to data from the Orly weather station.
The most recent case dates back to the winter of 1994: at the time, the thermometer read -3.2 ° C on February 21, before climbing to 10.6 ° C on the 26 of the same month, i.e. over 13 degrees. amplitude in a few days.
The most significant difference appeared in Paris in the winter of 1956: in less than a week, the thermometer went from -11.8 ° C on January 31 to 9.3 ° C on February 2, i.e. a difference of 21, 1 ° C.
A record.
READ>
Weather and climate
: why we can no longer speak of "
seasonal norms
"
If such amplitude deviations seem rare enough, they could be caused to recur more frequently, estimates the telephone Hervé Le Treut, climatologist and member of the Academy of Sciences.
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“Abnormal and repeated climatic phenomena can obviously be a reflection of global warming, even if we still need perspective to decipher all of its indirect consequences.
But in general, the increase in our temperatures means that such changes in amplitude are very likely to be repeated, ”concludes the specialist.