It’s December. Why is it so warm?
Here we are, less than two weeks before Christmas and it’s been feeling more like spring than early winter across much of the UK lately.
Granted, Northern Ireland, northern England and Scotland saw some snow last weekend, but it’s been a cold blip in what has been a pool of warmth.
November was the third warmest on record for the UK as whole, with mean temperatures (an average of day and night temperatures) 2C above normal.
People on social media have been telling me that they’ve been walking around outdoors in t-shirts and shoots have been growing from the ground in their gardens!
Why is it so warm?
The maximum temperature has reached at least 13C somewhere in the UK for the past week, with some days seeing 15C – around 7C above normal for the time of year.
It’s been so exceptionally mild across the UK thanks to a warm, moist tropical maritime air mass spreading in from the south west.
The air has often been travelling from the Azores, but occasionally from as far afield as the Caribbean – laden with not just warmth, but also an abundance of moisture, which played a major role in making the intense rainfall that caused the Cumbrian floods.
— NWS OPC (@NWSOPC) December 5, 2015
Role of the jet stream
The jet stream has played a significant part in the significant warmth, because it is not only responsible for spawning and moving around weather systems, it also shifts around huge masses of cold and warm air at the surface.
Recently, and indeed for the near future, the jet stream is not only moving swiftly, but its waving motion in the atmosphere is reaching further north and south than normal.
When it reaches northwards, it scoops up cold air and drags is south and when it reaches southwards, it scoops up warm air and drags it north.
Where these scoops of warm and cold air end up significantly influence the temperatures that different places experience, relative to normal.
— Mark Griffiths (@The_Grifter) December 6, 2015
In the case of the UK, it just happens that we are getting plenty of scoops of warm air at the moment and will continue to do so this week.
How warm will it get?
Whilst the rest of the week is looking very mild across the UK, with temperatures well above normal, there are a few days when we’ll bathed in notable warmth.
The image below, from Wetterzentrale, shows a plume of warm air (shown in orange) spreading across all areas on Thursday.
Temperatures are widely expected to reach 12-16C, but some parts of eastern England could reach 17C and possibly a bit higher.
The highest temperature on record for the UK in December is 18.3C, recorded at Achnashellach in the Scottish Highlands on 2 December 1948.
At moment, I don’t think that record will be broken, but it’s not completely out of the question if the sun manages to break through for any length of time.
If you’re hoping for a white Christmas, well, don’t get your hopes up. The latest forecast suggests a mild, wet and windy theme through Christmas week.