Polar vortex and stratospheric warming in France, Digi Mart USA News (France): The phrase “polar vortex” has been appearing in headlines in recent days, often evoking images of extreme cold. According to François Jobard, a forecaster at Météo-France, its consequences for everyday weather are “very limited and hypothetical,” as reported by 20 Minutes.
The polar vortex is a ring of strong winds that forms each cold season over the polar regions, in the stratosphere, between 10 and 50 km altitude. Everyday weather, by contrast, unfolds in the troposphere, the first 10 to 15 kilometers of the atmosphere.
What has drawn renewed attention is a more technical term, “stratospheric warming.” Romain Weber of Lyon Météo says some models forecast a potential stratospheric warming that could be one of the earliest ever recorded, potentially disturbing the polar vortex toward late November and early December.
Such events can sharply raise stratospheric temperatures, which normally range between -170 and -80 °C, by 50 to 60 °C in a short time. These disturbances can sometimes lead to cold air descending to mid-latitudes, but Jobard stresses that the polar vortex is not the jet stream and that the connection is not always present.
Jobard summed up the point with a remark: “Sometimes too, what happens in the stratosphere stays in the stratosphere.” In other words, a stratospheric warming guarantees nothing at ground level. A cold wave can also occur without any stratospheric disturbance, since the troposphere can produce cold spells on its own.
For the coming days, Météo-France sees no notable weather phenomenon for France. Temperatures this week are expected to remain a few degrees below normal, in a fairly typical way for November, with a warming expected early next week.
The more pressing concern is a Mediterranean weather episode to watch over Languedoc, arriving as soils are already very wet or saturated in places, while much of the country remains extremely dry. Jobard warned that rain is needed now, because groundwater tables are not refilling.
Weber described October rainfall in Lyon as still well insufficient and expects November to be rather wet and fairly mild overall.
