Seasonal outlook - September 30, 2012
November chill?
December stays cool

Issued: Saturday 29th September 2012
Duty forecasters: Captain Bob



*November*
Into the beginning of November the flow remains westerly so little in the forecast alters, bands of rain followed by showers through the first week, southern England becoming drier as the pattern shifts in emphasis during the second.
Here it looks as if pressure will be rising a large anticyclone setting over the UK to provide the whole country with a dry, chilly and fine spell of weather through to mid-month, overnight frosts, fog and misty inland where skies clear, sunny by day and pleasantly very mild, chillier where this lingers for any length of time. Southern Britain seems favoured to see the benefits of a persisting ridge of high pressure and some late pleasant autumnal weather, through until around the 21st, more northern areas at risk of cloudier conditions and some rain on a developing westerly to south- westerly flow as the main area of high pressure weakens and slips away southwest.
Late in November all areas see a major 'flip' in conditions as colder weather moves south through the UK on a brisk northerly, low pressure tracking away to the east with a corresponding rise in pressure to the west, frosts overnight where winds fall light inland, wintry showers spreading south and east, especially over higher ground.
Well, here we are at the point where the thoughts turn to the winter ahead of us, there is a great deal to throw into the melting pot this time around, in addition to the usual parameters, we have an interesting sea surface temperature profile, cold PDO, weak El Nino in the central Pacific and a warm AMO, a set up which usually ups the ante in favour of blocking, how strong this'll be is debateable, the whole forecast is weighted towards a colder pattern when compared to the averages?

*December*
Colder conditions already established across the country during the latter stages will linger through the early part of December, the whole UK covered by a northerly flow which will bring a mixture of sunny spells and wintry showers, overnight frosts will be widespread. Through the first week, milder weather will move through north-western Britain as the flow swings around to the west, these cloudier and less cold conditions spreading south and east, southern Britain becoming brighter and drier as a ridge of high pressure builds in from the west.
Through to the middle of the month is looks as if the weather will be mainly unsettled and generally on the mild side, the flow distinctly westerly, occasionally southwest when it'll be feeling mild, some spells of brighter, colder and fresher conditions, when heavy blustery showers will punch their way across all areas.
Around mid-month pressure should begin to rise both to the east and west, the whole pattern becoming much more settled and colder as an anticyclone sits over the UK, perhaps drifting a little more westward with time. Southern Britain is at risk of a developing easterly breeze carrying wintry showers through England and Wales, northern Britain more settled beneath a ridge of high pressure.
During the Christmas period, pressures are expected to remain high across the central swathe of the country, but perhaps the main centre of high pressure moving to the northwest, this redistribution allowing lower pressure developments taking place to the north to swing south into the UK, wintry showers becoming more widespread and a brisk northerly breeze.
Through to New Year, the flow will be maintained for a time from the north to northwest, cold at first then easing to a less chilly regime, low pressure coming in off the Atlantic bringing rather wet and windy weather to all areas, gales expected.

Captain Bob
Email me at simon.keeling@weatheronline.co.uk


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