Polar vortex weakens unusually early, but Germany's winter may still stay mild

Wind speeds fall sharply high above the Arctic

The polar vortex, a band of fast westerly winds that circles the North Pole in winter and holds cold Arctic air in place, is weakening earlier than in any previous year on record. Wind readings about 30 kilometres up fell from roughly 22 metres per second (around 80 km/h) on 25 October to 0.3 metres per second (about 1 km/h) on 5 November, according to NASA analysis cited by the German forecasting portal wetter.net. Winds at this time of year usually reach 90 to 100 km/h. Since 1 November every daily value has been below the lowest previous figure for its date, and models calculate a brief reversal to easterly winds. The Deutsche Wetterdienst (DWD) confirms the vortex was as weak in early November as it has ever been at this season. Tagesspiegel reports that the westerlies are forecast to drop temporarily below zero between 11 and 14 November, which would reverse the direction of the flow.

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22 m/s

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0.3 m/s

Data from the article text

Vortex split and displacement

Focus reports that the vortex has split into two parts, a strong main vortex over Siberia and a smaller one over North America, while warm air has spread over the North Pole. Tagesspiegel adds that warm air high over Siberia is pushing the vortex away from its usual place above the pole toward the southwest, between North America and northern Europe. Experts describe a rapid and marked disruption and slowing of the stratospheric vortex. Forecast models of the European medium-range centre, cited by Süddeutsche Zeitung, suggest the vortex could reverse its direction around Wednesday, 11 November. According to NOAA the vortex sits roughly 16 to 48 kilometres above the pole, so these changes are taking place in the stratosphere, where the weather we feel does not form.

Why it is happening and what it means for winter

The DWD's Helge Tuschy says the exact cause of the early weakening is not known. Such weakening is usually linked to high-pressure systems that block atmospheric currents, and he pointed to a possible blocking pattern over the Aleutians in Alaska combined with one over the Ural region of western Russia. He explained the mechanism in a direct statement.

“If we have a blocking pattern over the Aleutians in Alaska and at the same time in the Ural region, then disruptive currents toward the stratosphere become possible.”

Tuschy added that El Niño may be an indirect factor and that the winter could turn out milder than extremely icy, while stressing that it cannot be forecast precisely. Thomas Birner of Ludwig-Maximilians-Universität München said the current timing lies far outside the expected range, based on NASA data starting in 1978/79. NOAA notes that the vortex normally weakens for good at the end of winter, usually peaking in January, and that cold outbreaks typically occur between January and March. N-tv reports that the DWD gives a cautious all-clear for the coming months, even as something is brewing toward Scandinavia.

Cold air this weekend is not an Arctic effect

The cold arriving this weekend has a different cause. The polar air flowing in until Friday comes with an ordinary northwest weather pattern, and the DWD expects 4 to 9 degrees at the weekend with night frost. Meteorologist Jan Schenk says in a weather video that the high-altitude disturbance has nothing to do with this cold and that an early winter is not likely for now. Focus also says the frost and slippery roads expected at the weekend are not caused by the split. The official trend from 18 November shows rain and storms with comparatively mild air.

When the cold could arrive

DWD meteorologist Helge Tuschy told the German Press Agency that the disturbance must first work its way down into the layer where weather forms. That could take one to three weeks, but it does not have to. Counted from 11 November, that span runs from 18 November to 2 December. The British Met Office gives a longer window of two to six weeks, which would reach shortly before Christmas Eve. Focus notes that the warm air above the pole is sinking slowly but is not yet deep enough to push out the cold air at ground level.