Monthly Outlook

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A cold end to September. Changeable in October

The Atlantic has been alive with Tropical Storms and Hurricanes over the past few days.
Warmer than normal sea surface temperatures are helping to fuel these storms.

Even when a major Hurricane is churning away on the other side of the Atlantic, it can still sometimes influence the UK's weather.

For example, Hurricane Teddy will track close to Bermuda and then north towards Nova Scotia over the next 6 days.

As it does so, it will start to manipulate the path of the north Atlantic jet stream, causing a large southwards loop to develop close to western Europe. This will pull in a deep low pressure area and then much colder air across the UK, during mid to late next week.

Dry and sunny giving way to wet, windy and colder

Over the next week or so, we can expect some dramatic changes to occur in the UK's weather.
In recent days, we have been reminded of summer, with prolonged periods of sunshine and some warm temperatures in many areas.

This has been the result of extensive high pressure, developing right over the UK.

Across southern areas, a keen easterly breeze has been developing over the last couple of days.

This will peak during Saturday, before fading in strength during Sunday and Monday, leaving light winds once again.

This easterly wind is being caused by low pressure over Spain and France, nudging northwards and up against our area of high pressure.

However, the high pressure will win this particular battle, and keep much of the UK dry and settled this weekend and on Monday.

A weak front over the English Channel this weekend will bring a bit more cloud and a few showers over southern England.

The best of the sunshine and dry weather with be over central areas.

In the north, a combination of a weak front close to northern Scotland and some low cloud moving in from the North Sea at times, will mean some overcast skies from time to time.

You could see some drizzle, especially over north-east England and eastern Scotland.

Next week, a powerful zone of low pressure over the Atlantic, racing our way from northern Canada, will push our high pressure away.

This will begin on Tuesday, when a spell of increased wind and some rain will sweep across many areas.

Southern and eastern England will have driest weather for longest.

Turning cool and unsettled between Wednesday and next Sunday, as a deep area of low pressure moves in.

This will bring showers or longer spells of rain, with a risk of a few thunderstorms on Thursday.

Colder air from the north-west will arrive by Friday and the weekend.

A few wintry showers in Scotland, Cumbria and over the Pennines, while frost at night becomes likely in parts of the north.

Changeable, but wettest and windiest in north

The end of September and into the start of October is now looking more likely to be influenced by an active low pressure track over the north Atlantic.
Individual low pressure areas running along this track could carry the remnants of ex-Tropical Storms or Hurricanes.

This means there is potential for some heavy bouts of rain, especially across the north and west, along with some brisk winds.

High pressure is expected to be a significant feature over the central and north Atlantic, sometimes extending into western parts of Europe.

For the UK, south and south-western areas will be closest to the high pressure and therefore may be expected to have the best chance of some drier and more settled weather.

This will be similar to the weather pattern in the second week in September.

With winds from a westerly or sometimes north-westerly direction then temperatures will not rise too far above normal.

This is especially true over northern areas, where we will see a few chilly nights, where clearer skies and lighter winds develop, between fronts.

If high pressure is able to establish over northern France for a few days, then some warmer air would make it up into southern England.

Some of the model guidance does still show this outcome, but there is reducing confidence for this to happen now.

High pressure slowly becoming a greater influence

Looking through the first half of October, the forecast becomes a little trickier.
In recent weeks, the computer models have been unusually poor at this range.

This is mainly due to the extremely active Atlantic hurricane season this year, with the hurricanes having erratic but sometimes tangible downstream effects on the weather pattern over Europe.

High pressure over the western side of Europe and the north-eastern Atlantic will become a more significant feature for the UK's weather, building northwards over the UK more often.

Dry weather will become more widespread and frequent, particularly by mid-October, as the low pressure track is steered away from the UK.

A few cool nights, but often quite warm by day.

Low pressure areas and their associated wind and rain will tend to get shifted down over Italy, Greece and eastern Europe more often, as the jet stream dives south from Scandinavia.

But one thing that needs watching out for is the prospect of a rogue ex-hurricane making its way towards the UK, as a potent autumn wind storm. Such systems can introduce severe gales and a spell of heavy rain, especially over northern and western parts of the UK.

We saw this with ex-Hurricane Ophelia in October 2017, which brought very strong and damaging winds to parts of Ireland.

But the balance is fine. If the track of an ex-Hurricane stays a little further out over the Atlantic waters, then it simply serves to reinforce the high pressure ridging overhead the UK.

The will lead to prolonged dry, calm and settled conditions here.

Further ahead

Getting the detail correct for the first half of October will be the biggest challenge, especially determining when high pressure could expand over all of the UK once again. We'll look at the very latest signals for this next Wednesday.