Monthly weather forecast for the UK
Dry but often cloudy, average temperatures
December 2013 is expected to be a drier-than-average month with high pressure in control of the weather for most of the time. Unsettled periods are likely around the 13th-17th and again near the end of the month.
December will commence with extensive high pressure to the south of the British Isles which will bring dry weather but it will be quite cloudy in central and northern parts of the country. On the 3rd and 4th a weakening rain belt will move slowly south-eastwards through the country but rainfall amounts in central and southern parts of England and Wales are expected to be derisory. A more active weather system will bring rain southwards on the 5th, followed by a brief northerly with a mix of sunny intervals and snow showers. Most of the snow showers will be concentrated over northern Ulster, Wales, the Cheshire Gap, northeast Scotland and northeast Norfolk, but there will be a limited "window" for these showers (overnight 5th/6th, perhaps until midday on the 6th) as high pressure will soon return from the west and kill off the showers.
High pressure will move slowly eastwards over central and southern parts of the British Isles between the 7th and 10th which will bring bright cold weather initially on the 7th, and a sharp frost is expected in most places overnight 6th/7th. However, as mild, moist air moves around the northern flank of the high from the North Atlantic Ocean, it will become mostly cloudy with temperatures recovering to near-normal values, with some light rain or drizzle likely for the north and west of Scotland and Cumbria.
A brief unsettled interlude is likely around midmonth as high pressure will retreat into eastern parts of Europe between the 11th and 14th and this will allow low pressure to head in from the Atlantic, with accompanying weather fronts, and some brighter showery weather in between the rain belts. It won't last, though, as another quiet spell is expected around the 20th as high pressure will again build from the west, probably resulting in a cold dry bright interlude.
The last third of the month is likely to see high pressure close by for most of the time, and the Christmas period is likely to be cold and dry, but sunshine amounts are uncertain. The month is likely to end rather less settled with low pressure heading in from the north-west.
December 2013 will produce close to or slightly above average temperatures in many parts of the country and I predict a Central England Temperature of 5.3C. Relative to the 1981-2010 reference period, temperatures are likely to be 0.5-1.0C above average in many northern and western parts of Britain but much of East Anglia and south-east England will be 0.5-1.0C below average.
Rainfall totals will be well below the long-term average with most regions of the UK having deficits in the region of 40-60%. The largest deficits are likely to be found in south-west England and south Wales where there may be less than 20% of the normal rainfall locally.
However, the inverse association between sunshine and rainfall tends to be somewhat weaker in the winter months than it is in summer, and thanks to moist air masses circulating around the periphery of our anticyclones, many parts of the UK will have a cloudy month. Sunshine totals may be 20-30% above normal in eastern Scotland, East Anglia and south-east England, but most central and western parts of the country will have deficits of between 20 and 40%, and averaged nationally sunshine will be slightly below average.
Forecast issued by Ian Simpson (aka TWS) on the 2nd December 2013.
Monthly weather forecast
This long range forecast is updated at the beginning every month. As with any forecast at longer range, it's not possible to go into much detail and accuracy can tend to drop off toward the end of the period but it can still act as a very good guide to the weather during the upcoming month.