How can such a large difference in temperature be explained?

Unusual temperature difference? For 19 consecutive days (November 30 to December 18), the National Heat Index has remained below the 1991-2020 averages. In particular, there was a cold peak on December 17th, when it reached -19°C in the early morning in the Lorraine countryside. We had to go back to 2010 to find such a cold month of December. Indeed, the -5°C recorded in Paris on Sunday morning had not occurred since December 1996. In question, an anticyclone over Scandinavia that was drawing a northeasterly wind was positioned at the origin of this mass of cold air from Russia. .

But on Monday, December 19th, France found very fair weather, due to a change in the meteorological composition. The anticyclone retreated towards Central Europe. This caused a depression to occur over the nearby Atlantic Ocean. It drove, this time, strong southwesterly winds carrying a very light air mass from the Canary Islands and Morocco, where the temperature was 25 degrees Celsius in the afternoon of Monday, December 19th.

Significant temperature differences were recorded in December 2022.
Credits: Meteo France.

Read also: Weather: Why the sharp drop in temperatures this week?

Noticeably fast thawing of ice

The rise in mercury has been impressive in places. Such is the case in Epinal, where only -12°C was measured on Sunday, December 18th at 8am and where the temperature already reached 8°C on Monday at 1am, more than 20°C in less than 24 hours. During the day, the temperature continued to rise, reaching nearly a maximum of 13°C.

In Paris, from -5°C on Sunday morning, the temperature practically did not stop rising, reaching nearly 12°C this afternoon. The extremes rose places 10 degrees above average for the season.

Also, the equinox will be especially noticeable at the beginning of the week in the southwest. Temperatures there are already over 20 degrees at the foot of the Pyrenees. We also recorded 9°C in Lille, 12°C in Paris, 14°C in Rennes, 15°C in Lyon and 17°C in Bordeaux, Toulouse and Biarritz.

Only northern Alsace still recorded lower-than-normal maximum temperatures on Monday.

The temperature difference is not exceptional

There is nothing exceptional or abnormal about this temperature difference According to Meteo France. It was the period of extreme cold in these recent days that particularly surprised me. This phenomenon is becoming increasingly rare in the context of global warming. Cold days like the one I’ve had for the past two weeks have become more and more exceptional over the past 10 years. However, it may still occur in the future.

Moreover, after October with the temperature records being brokenAnd a mild November, too, made this winter sequence even more surprising. Just like the sudden rise in mercury, a situation we almost lost habit of.

However, this meteorological inversion is itself relatively classic in its pattern. In spite of everything, it is not necessarily so in its timing, especially the accelerated, which is already more unusual.

A very sweet birthday coming up

This wonderful melt will continue all week, right up to the Christmas weekend with wet weather. A parade of turbulence is to be expected, with rainy lanes to the north: humid, ambient air.

In the next few days, temperatures will be about 5°C higher than the national averages, and at times 8°C in the southwest. We mustn’t hit December’s sweetness records. Temperatures were 17°C in Paris, 20°C in Lyon, and 22°C in Clermont-Ferrand in 1989, for example.

Thus, the opening of gifts this Sunday should take place in fairly quiet and calm conditions. There should be veiled to cloudy weather, awaiting fresh disturbances that will arrive from the northwest towards the end of the day. Likewise, the entrances to the sea will return to the Mediterranean Sea. It will be accompanied by a stream, which must be directed from south to southeast.

It seems that the trend for the next week is gradually becoming more reliable. There should now be the majority of favorable scenarios for continued relatively mild weather. However, others, who are a minority, see a possible change in the weather after December 28th. The anticyclone will swell over Scandinavia and cold air can descend toward northern France. Follow.