Long-range predictions have given good indications of global average temperature so far this year. 2016 is running at record levels of global warmth, as predicted. However, these global figures don’t necessarily mean the UK will be warm. It’s never as simple as taking global information and applying it to a UK regional scale.
So, what are the latest indications for the coming winter? Professor Adam Scaife, head of long-range prediction at the Met Office Hadley Centre, explains: “The risk of a cold start to winter has increased to 30% this year. Statistically, however, it is still more likely that the UK will experience a normal start to winter, but there is an increased risk of cold snaps between now and Christmas.”
Adam added: “Several factors, including tropical rainfall, are known to drive UK and European winter conditions: following a strong El Niño last year, the tropics are now influenced by a weak La Niña and unusual rainfall conditions in the Indian Ocean.”
However, prospects for winter in the UK aren’t governed solely by tropical rainfall, there are other influences too. For example, the Quasi-Biennial Oscillation (QBO) experienced an unprecedented flip in February and is now back to westerlies this year. And although it is not the main factor, the westerly phase of the QBO is associated with milder wetter winters. Finally, the winds high in the stratosphere, circling the Arctic – around what is known as the Polar Vortex – are disturbed and weak at the moment. Although these winds are many kilometres above the surface, they can influence the strength and position of the jet stream, and this is helping to increase the risk of cold snaps in the UK.
Adam added: “Historical weather observations and our latest computer model simulations agree that these factors are increasing the risk of a cold start to winter for the UK, but this is unlikely to persist through winter as a whole.”
The record of recent winter outlooks has been encouraging, and the Met Office outlook has given good advice in recent winters for the UK as a whole. For example, last winter the mild wet stormy December and drier, cooler end to winter was picked up more than a month ahead.
It is too early to make definitive forecasts of how wet, cold, snowy or stormy this winter will be and we will continue to assess the how the weather will develop through our regular monthly outlooks and shorter-term forecasts.