BBC monthly outlook
Monday 6 November—Sunday 12 November
Wet and windy at times
The working week will get off to a very cold start across many parts of England, Wales and eastern Scotland with clear skies and a widespread frost on Monday. The remainder of the day will be dry with pleasant sunny spells. Further to the northwest though, an Atlantic weather front will bring rain that will occasionally turn heavy, particularly across northwest Scotland, where the rain will also turn wintry over the mountain tops. Through Tuesday, the aforementioned weather front and its accompanying rain will drift slowly and erratically east across all parts of the UK but will weaken in the process. Winds will also strengthen for a time, with gales along exposed southern and western coasts of the UK. As the rain band clears east, a cool and showery airstream will edge in from the Atlantic.
By the middle of the week, it looks likely that a transitory spells of drier and brighter weather will affect all parts of the UK, at least for a time, as a ridge of high pressure traverses from west to east. across the country. The quieter weather will increase the risk of cold nights and patchy fog though, but at least there should be some fine and dry weather during the daylight hours for most. As we approach the end of the week and move into the weekend, it looks as if the jet stream will realign to push potentially relatively deep Atlantic low pressure systems across northern areas of the UK, bringing rain and hill-snow to northern areas of the UK, with some strong to gales force winds. Further south though, the influence of high pressure centred further to the southwest of the UK should permit drier and brighter days, but cold overnight periods.
Monday 13 November—Sunday 19 November
A similar autumnal theme, but settling down later?
At time of writing, the variety of forecasting tools and computer models at forecasters' disposal suggest that this period will begin on a very similar theme to that of the previous week. A relatively potent jet stream looks as if it will be aligned to drive Atlantic low pressure systems across or close to the north of the UK at times. Associated weather fronts will then most likely bring a good deal of wet and, at times, very windy weather to northern districts of the UK, with high pressure at more southern climbs maintaining a drier and brighter theme across the southern half of the UK, but with cold and potentially foggy nights. That said, the Atlantic weather systems could occasionally stray south too, so all areas will see rain at times. Between Atlantic weather systems, we anticipate cooler, showery interludes with sunny spells by day.
Any such showers present the threat of some wintry conditions over the highest ground across northwestern and northern parts of the UK. By the end of this period, there are strengthening signals from the computer forecasting models that suggest the high pressure centred to the south and west of the UK will start to drift further north and east. Such an eventuality could mean that the frequency at which Atlantic weather systems impinge on the UK will diminish significantly, resulting in a prevalence of drier, brighter days, and colder, foggier nights.
All in all, another spell of typically autumnal weather.
Monday 20 November—Sunday 3 December
A potentially cold start to winter?
The latest range of computer forecasting model data shows little consensus for the last few days of the climatological autumn and first few days of winter. In addition to the model uncertainty, some of the global climate systems that are known to affect weather conditions closer to home (such as the Madden Julian Oscillation) are also entering weak phases of their cycles, thus offering little steer on the sort of weather conditions we should expect during the period. Of the range of potential forecasts solutions though, those that develop slow moving areas of high pressure in the vicinity of the UK are currently favoured, which would likely mean an increasing chance of dry and relatively chilly weather, with sunny spells by day and the risk of fog by night.
Just to highlight the level of uncertainty in this period, it is worth noting that recent output from computer models that forecast the strength of the meteorological phenomenon called the stratospheric polar vortex show this feature strengthening during this period. Such a strengthening process would favour the return of wet and windy weather to the UK into the start of December. For the moment, on balance it looks as if winter will start on a cold, dry and potentially foggy theme, but as is so often the case with longer range forecasting, we await further information to firm up on our ideas for early winter.
Next week
Check out next week's monthly outlook as we start to firm up on the details for the start of winter!
http://www.bbc.co.uk/weather/2635167#outlook