BBC monthly outlook
Unsettled and very wet at times, but drier later
Wednesday 2 October – Sunday 6 October
A dry cold snap midweek, then turning mild and wet
After a cold start, Wednesday is expected to be a mostly dry and sunny day but with temperatures falling several degrees below average. This will make things feel noticeably colder than recent days, especially at night with calm, clear skies. Temperatures will plummet widely in the low single figures, and some places in northern England and Scotland will see some air frosts bringing a slight glaze onto cars, buildings, and plants.
Thursday will continue with the cold snap, although it should be just a touch less cold than Wednesday morning. However, the remnants of Hurricane Lorenzo will be moving towards Ireland from the southwest, and this will send a warm front into the UK from the west later in the day. This front will bring plenty of rain, with a few bands of heavy rain, as well as some much warmer air from the southwest. Temperatures overnight into Friday are expected to recover and return to near average.
Meanwhile the remnants of Lorenzo will move near the west coast of Ireland and Northern Ireland, bringing a risk of some severe gales and very high surf on the coast. Overnight into Friday morning strong winds may spread into West Scotland, where a further risk of gales is expected on the coast. A strong high pressure centre to the northeast will prevent Lorenzo from continuing northwards and instead the low is expected to make a right-hand turn and track into Britain. However, as it does this is will rapidly weaken, so while heavy rain is likely, strong winds are not.
A brief break in the rain on Saturday in the wake of Lorenzo will lead a return of active Atlantic fronts sweeping in from the west by Sunday.
Monday 7 October – Sunday 13 October
Unsettled weather to continue but feeling mild.
Heading into the first full week of October, the weather pattern is expected to keep things unsettled across the UK with low pressure tracks moving overhead or just to the north. It looks like low pressure will tend to remain near or over Scandinavia through the week, bringing frontal systems into the UK from the northwest. This will lead to a cooler picture for Scotland and Northern Ireland, but nearby high pressure to the south and southwest will tend to keep things a bit milder in the South and West.
It will likely remain rather unsettled across the country as frontal systems are expected to be frequent. Northerly or north-westerly winds will bring in cooler air, but there are no strong signals at this time for any wintry precipitation anywhere - it just won't quite be cold enough yet. With high pressure nearby, a few drier interludes are likely between fronts, and these may be accompanied by a brief cold snap with more northerly winds, although these will be dry and sunny.
Confidence is a bit lower than normal for this range, as there is still a lot of uncertainty on how the atmosphere will react to the remnants of Hurricane Lorenzo in the previous week (which is helping to drive low pressure into Scandinavia). There is a 30% risk that the jet stream may not strengthen much as Lorenzo weakens, which will keep high pressure ridging stronger into Northwest Europe and the UK. This will push active frontal systems off to the north and low pressure into Scandinavia, leading to an overall drier but colder picture.
Monday 14 October – Sunday 27 October
Gradual shift into a more settled, warmer pattern.
Unfortunately, due to Atlantic hurricanes and a few other tropical weather patterns, forecast confidence for mid-to-late October remains rather low at the moment. We currently expect that the more active low pressure tracks across the UK from earlier in the month will gradually get pushed out of the area by encroaching high pressure as we head into the second half of the month. This will likely be a gradual shift that takes place for several days as opposed to a more abrupt change.
As Atlantic hurricane season winds down deeper into autumn, some tropical weather patterns favour a building ridge of high pressure in North Europe, which we expected to end up near Scandinavia. This should bring a break in the unsettled and very wet weather across the UK, although some occasional rain may reach western areas at times. High pressure in Scandinavia will favour easterly winds through Central Europe, and while we do expect East Europe and Germany to turn a bit colder, the UK should remain relatively mild.
However, this comes with a rather large caveat that Atlantic hurricane season may not wind down. The typical Atlantic hurricane season lasts until November 1st, so we may well see further strong hurricanes develop. These storms can strongly influence the weather patterns even thousands of miles away over Europe and will tend to wreck long-term forecasts as the large scale computer models can struggle to forecast them in advance. Therefore, there is currently a quite high risk (40%) that low pressure tracks will remain over the UK and things will stay more unsettled for the rest of the month.
We will take a closer look as the potential for some cold snaps through October and see if our milder pattern shift will hold.