This is the outlook using the Japanese Met Agency model the JMA. It is not meant to be a forecast but an outlook, it was Issued on the 7th of December. I have added the 3 images together rotated them and added a red line so you can see the UK. Blue colours are low pressure trough areas and Orange’s high pressure ridge area.
Week 1 8th December to 14th.
This period higher pressure will be over the UK. But due to the centre position of the high pressure it looks like we will be drawing up Southerly warm but moist air. So temperatures will be a 2-3 centigrade above average for this time of year. We will see some dry spells and other days some showers or longer spells of rain.
Week 2 15th December to 21st
This period looks like seeing high pressure over the UK bringing overall dry condition with temperature around normal but if anything just slightly above average for mid December.
Week 3-4 22nd December to 4th January.
This is a two week period over Christmas and into the New Year. Average pressure with low pressure trough to the South West of the UK. This looks like around average rainfall and temperature a little below average for the end of December. I cannot say this looks good for wintery weather lovers.