This year winter arrived early in the UK, with temperatures plunging well below freezing before November was even out. So is an extra cold winter on the cards?
Forecasting months ahead is fraught with difficulty, but some scientists believe that the warm autumn in the Arctic may portend a cold winter for North America and northern Europe.
As summer came to a close, Arctic sea-ice melted to its second lowest extent on record, allowing ocean waters to release more heat to the atmosphere. By November temperatures in the Arctic had rocketed to a staggering 20 degrees higher than average.
Much of that heat has raised temperatures in the stratosphere, and this is likely to weaken the Arctic polar vortex – the large low pressure region over the north pole.
Research by climate scientists Judah Cohen from the Massachusetts Institute of Technology (MIT) and Jennifer Francis from Rutgers University, indicate that a weakened polar vortex leads to a weakened jet stream – the fast, high-level westerly winds that bring storms to the UK. And when the jet stream weakens it becomes more wavy, and prone to getting stuck in position, bringing long periods of similar weather.
Already we’ve started off with unusually cold temperatures and heavy snowfall over Eurasia, and weirdly warm temperatures over north America. Previously Cohen has shown that heavy Siberian snowfall in October is often linked to colder than normal winters in Europe and the northeastern US.
This year there is the exceptional 2016 El Nino to add to the mix, but Cohen is tentatively forecasting something similar to the severe winter of 2009/10.
