BBC monthly outlook
Summary
A colder, slightly wet outlook for November.
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Saturday 30 October to – Sunday 7 November
Drier and colder next working week for a time.
A very wet weekend is in store for much of the country as heavy rain sweeps across the UK. Low pressure is expected to remain nearby through much of the next week, but high pressure will also build to the west. This will cause winds to shift to the north and bring in some noticeably colder air, causing temperatures to dip below average through the working week. The nearby low will keep shower chances high for northern and eastern areas, but many will have a dry midweek. By next weekend, however, unsettled weather will likely return, bringing milder, wetter days.
Monday 8 November to – Sunday 14 November
Unsettled and changeable week, but often cool.
Heading into the middle of November, our confidence in the forecast has dropped a bit as computer models are really struggling with how strong high pressure will be. It is looking more likely now that we will see highs remain in Southwest Europe or the Mediterranean, keeping low pressure to the north of the UK and a cool, wet, and breezy pattern for us.
However, it will probably be quiet a changeable week due to the nearby high pressure. These pressure zones tend to dominate the weather patterns and push low pressure out of their way, so it is very likely we will see some occasional ridges of high pressure extend in from the south. This will bring some dry but colder spells as the ridges shift winds to the north. Dry spells should only last for a few days at a time though.
The risk to this forecast is that these ridges do not move away and instead build in and remain. This is a drier, cooler, less changeable outlook, as winds will tend to be out of the northwest and bring in colder air from Iceland. There is perhaps a 30% chance of this pattern developing instead, so confidence is a bit low. We do, however, have medium to high confidence that it will often be cooler than normal.
Monday 15 November to – Sunday 28 November
An often wet and cold second half of November.
Confidence has also dropped for the second half of November. Again, the computer models are really struggling with the large-scale pattern. In these situations, we can turn to our historical analogues for some additional guidance. These are models where we look at years since 1950 that saw similar weather patterns to those we are observing at the moment. One big signal is coming from a pattern called La Nina, which is cooler than normal ocean temperatures in the eastern Pacific Ocean near the equator.
Although far away from the UK, this trend can set up the large-scale weather pattern from North America stretching across the Atlantic and into Europe. Usually in November, we see high pressure near Iceland and Greenland, extending north of Europe into West Russia with a weak area of low pressure near the UK. We are expecting this to be the case for the second half of November this year, and there are signals in a few computer models that support this. This would be a colder than normal and slightly wet outlook for the UK with weak weather fronts often bringing outbreaks of rain.
The alternate scenario, which has some strong support in the computer models, is for high pressure to build overhead and remain in place, keeping things slightly cooler than normal but dry. The temperatures would be sensitive to the position of the high in this pattern, and the further east the high is the milder it will be. There is a roughly 35% chance of this developing instead, but we have higher confidence that in either pattern temperatures will tend to be on a cooler side of average.
Further ahead
Hopefully we can increase the confidence in the forecast with fresh data. We will also look at the risk for a potential cold outbreak of Arctic air in late November.
https://www.bbc.co.uk/weather/outlook