BBC monthly outlook
Summary
Signs of a colder November on the horizon
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Wednesday 3 November to – Sunday 7 November
Cooler through the end of the week
As high pressure builds to the southwest, northerly winds will usher in a burst of below normal temperatures to the UK for much of this week. Low pressure to the north and east may allow spells of showers to occur the latter half of the week across northern and eastern areas while largely dry conditions develop across the south. A more potent low pressure system should pass between Scotland and Iceland this weekend. This will bring a wave of wet conditions to Scotland and Northern Ireland, along with increased winds and a return to milder weather.
Monday 8 November to – Sunday 14 November
An unsettled pattern returns for mid-November
The early part of the week should see milder air being drawn in across the UK from the southwest as high pressure shifts towards Central Europe. Multiple low pressure systems are expected to pass over or just to the north of the UK during the week. This will provide for periods of wet weather to develop along with breezy winds, especially across the north and west.
Later in the week a cold front is likely to move through, which will spread wet and windy conditions across the UK. In the wake of the front, high pressure will develop late next weekend allowing for drier and calmer conditions to return, but will cause temperatures to cool down. It is not likely to be anomalously cold though.
The main risk to the forecast for this week is that the ridge of high pressure in Central Europe becomes weaker and allows for the trough of low pressure in Scandinavia to extend southward across Western Europe.
This would result in colder northerly winds to become more entrenched across the UK, especially over the latter half of the week. This would also likely promote a drier pattern as the more active storm track shifts away from the UK and instead would favour Western and Central Europe. There is about a 25% chance of this pattern developing.
Monday 15 November to – Sunday 28 November
Late November cold
Moving into the second half of November, we should see an overall colder pattern begin to take shape. Model guidance continues to struggle with the large-scale pattern, so we have turned to our historical analogues to delve into what had occurred in similar situations in years past.
One important signal to consider is the La Nina that is currently developing. La Nina events occur when cooler than average ocean temperatures develop along the equator in the eastern Pacific Ocean. While far away from the UK, La Nina is an important driver in setting up the large-scale weather pattern across North America towards the Atlantic and Europe. With a La Nina occurring in November, one common feature is high pressure forming near Greenland while a weak area of low pressure develops in Western Europe.
This is the pattern that is expected to take hold over the second half of November. The high pressure near Greenland will help direct colder air from the north towards the UK, leading to a period of below normal temperatures. As the Greenland high becomes more entrenched and occasionally extend towards Northern Europe, winds are likely to diminish. With low pressure still expected to be close by, this doesn't appear to be a dry pattern, but it is also unlikely to be an extremely wet pattern. A few of the computer models are beginning to support the solution indicated by the historical analogues.
The other scenario which has support in the computer models would be for high pressure to be more prevalent across Western Europe. This would still favour a cooler pattern, but temperatures would be more sensitive to the position of the high with a few brief shots of milder air possible. An overall drier pattern would also develop. There is about a 35% chance that this pattern ultimately prevails. Confidence is higher, however, regarding temperatures for the period falling on the colder side of normal.
Further ahead
We will continue to monitor the risk for a potential outbreak of cold Arctic air to develop late in November.
https://www.bbc.co.uk/weather/outlook