Regularly updated news and views from Brian Gaze, TWO's founder. Follow @TWOweather to keep up to date with Brian on Twitter.
The next few days will bring milder and more changeable conditions than we've had recently as a southwesterly flow develops across the UK. By the start of next week high pressure may become more influential once again but will it be cold or mild?
The medium range computer models have been showing two basic scenarios for the middle of December and beyond:
1) A changeable west to southwesterly flow persists. This keeps it mild and all regions have rain at times but also drier periods
2) High pressure builds back and settled conditions return. This outcome brings a much greater likelihood of cold weather but it doesn't guarantee it.
In recent days I thought the balance had tipped just in favour of option 1, but the latest computer model output casts doubt on that. The overnight GFS00z run shows high pressure building over the continent by +192 hours. Later in the week it becomes centred over the UK with colder conditions returning.
The ECM00z shows a similar set-up at +192 hours but it looks potentially cloudier and less cold, although by +240 hours pressure is rising across the UK.
The GEFS00z ensemble at +240 hours shows quite a lot of support for high pressure to be centred close to the UK. A few of the perturbations have the high pressure centred farther northwest. This would allow much colder air (and possibly wintry showers) to start being drawn towards the UK from the north or east. However, most of the perturbations don't so show this so probability of this outcome is quite low.
Developments next week and beyond remain uncertain. The latest computer model runs show a good chance of high pressure bringing settled weather but a changeable and wetter outcome is still possible. If high pressure returns temperatures are likely to fall again, particularly in the south east where it could become quite raw.
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