Polar vortex winds reverse in earliest November breakdown on record

The stratospheric polar-vortex winds reversed on November 10, in what a Met Office scientist described as the earliest November breakdown since weather-balloon records began in the 1950s. Scientists say the unusual timing does not establish what caused the disruption or how strongly it will affect winter weather.

The polar vortex is a belt of strong winds high above the Arctic that helps keep cold air near the North Pole. When the winds weaken or reverse, the circulation can become distorted, and changes in the stratosphere may influence the jet stream and weather patterns farther south. Such disruptions can raise the chance of cold outbreaks, but they do not guarantee severe or snowy conditions in any particular region.

Adam Scaife, a Met Office scientist, said the November 10 reversal was the earliest in the balloon-record era. He said a very strong El Niño may have contributed to the weakening, but that link has not been established. El Niño, a warming of surface waters in the tropical Pacific, can affect atmospheric circulation, including the jet stream.

Andrew Charlton-Perez, a University of Reading scientist, urged caution about attributing the event to El Niño. He said a...