There has been some references to the potential for a switch to colder weather as we go towards the middle of December but what can we expect to see?
Weather models have been extremely volatile in the last week or so constantly flipping backwards and forwards between different solutions but I think things are now becoming a little clearer with the day 10 ECM clusters showing a way forward.
The chart above shows two clusters in 10 days time. The first cluster and currently the one most supported within the 51 ECMWF ensemble suite shows high pressure building across the UK and up towards Scandinavia. This will turn our weather increasingly settled but also likely colder as winds switch around to the East.
The second cluster shows a similar pattern, high pressure in charge extending towards Scandinavia but in slightly different positions.
So, we can be fairly confident that in around 10 days time high pressure will build across the UK.
Beyond that is when the uncertainty begins to grow.
The chart above might look like a mess of squiggly lines but there’s a logic, I’ll draw your attention to the parts important to this discussion.
The red line is the average UK temperature for the time of year (note, this is for roughly 1000 feet up in the air) currently (left side of the image, the further right you go the further ahead in time you go, the dates are along the bottom) we are above average but towards the middle of December we see strong support for a plunge in temperatures into below average territory.
The further ahead you go, the further the lines drift apart and the less confidence you can have. There’s no strong signal for deep cold or a repeat of “the Beast from the East” just yet, but signs of things turning colder are now starting to show.
After quite an unsettled week this week with areas of low pressure bringing strong winds and heavy rain, high pressure is expected to build across the UK in the 7-10 day range turning things largely settled. We’re likely to see a return to fog and night time frosts as colder air slowly moves in across the UK.
Further ahead into the second part of the month, there is a possibility of deeper cold moving Westwards out of Europe and bringing an enhanced snowfall risk, but at this early stage it remains a lower probability.