It has been an early and quite vicious start to the winter in parts of Eastern Europe. From the Baltic Sea states of Latvia, Lithuania and Estonia in the west; to Russia’s Siberia in the east; and the Caucuses in the south; the end of October and early November have seen marked changes in weather patterns.

Cold air has been pushing southwards across Eastern Europe and much of northern Asia in recent days. Many climatologists believe this is a sign that changes in the polar vortex are likely to lead to a cold winter ahead.

The polar vortex is an area of low pressure, high up in the atmosphere. It is at its most intense during the winter months. There have been signs in recent years that it is beginning to weaken, and predictions for the coming winter suggest it will weaken significantly.

This weakening is likely to be the result of climate change, being linked to the decrease of Arctic sea ice in recent years.

When this happens, this mass of air buckles and folds. It can make inroads into normally temperate areas of the northern hemisphere.

In the past few weeks there has been significant cold weather and snow across much of Russia, certainly more than we would normally expect at this time of the year.

For example, Perm in central European Russia can expect temperatures to vary between freezing and -5C during early November. Instead, temperatures are between -5C and -15C. Temperatures have been below freezing since 26 October.

This situation has been made worse in the past few days by the development of a deep area of low pressure which has moved in from the North Atlantic and brought wet, stormy weather to southern Scandinavia and the Baltic States.

As this system ran into the really cold air further east, it turned readily to snow. Significant accumulations of 20cm or more have been reported in Belarus, Ukraine and western Russia.

More than half a metre of snow is expected in some areas in the coming days.

Moscow is expected to see cold weather continuing for the foreseeable future, with temperatures at or below freezing, and perhaps another 20cm of snow by the end of the weekend.