James Peacock

Roughly 3/4 of the ECMWF ensemble supports the ECMWF det. run's idea of breaking down the westerly flow late next week.

Only around 12% resemble the GFS det. run for the week after. Most are either anticyclonic (calm, chilly) or have some form of (weak) easterly in NW Europe.

Which way it goes has a big effect on how mild conditions are in NW Europe during the run-up to Christmas Day.

GFS' take encourages mild or very mild weather, while ECMWF's makes for a much chillier (though not exactly cold) picture.

It's been an oddly long time since there was last a persistent disagreement between the GFS & ECMWF deterministic forecast models to discuss.

The former insists on more westerlies for the UK late next week, while the latter is keen to introduce a flow from the S or SE.

A lone crow watches the sunset 🌅

The best seat in the house. More of Wednesday evening's sunset at the Bull Wall, Clontarf.

Once I was once very surprised when one of those gave chase, albeit in a half-measured manner, while I was cycling. They're usually so very chill, more so than their relatively hairless cousins.

‪For example, at this point in the year this area was largely underwater in 2023 & 2024, while this year the standing water has only recently manifested; within the last week or so.‬

The opening 3rd of December 2025 has been similarly wet to 2023 here in NE Dorset, but since the start of autumn it's been much drier, just a little above the 1991-2020 average.

This is evident by the water table - standing water is far less widespread than in 2023 & 2024.

Forecast modelling hasn't done very well with how far into Europe the anomalously wet weather reaches during the next 7 days.

Since 4th Dec, the ensemble mean has shifted the boundary hundreds of miles north-westward, with SE England & NW France most affected.

On top of wet weather there tomorrow, it looks like rainfall will focus across western UK & Ireland yet again this weekend into next week, as a front stalls within a long-fetch south-westerly flow.

By contrast, parts of south-eastern England could remain dry throughout.

Reading as an example. There are a few runs that have daily max temps drop below 4°C. At the other end of the spectrum there are a few still reaching 10-12°C.

The ensemble mean drops close to the long-term average. The skew is slightly toward below average for 25th-26th.

Importantly, the cold scenarios are nearly all from calm weather allowing a temperature inversion to develop (colder near the surface than higher up).

Which is to say, they don't feature any snowfall - the white Christmas probability currently looks very low.

Increasing signs in forecast ensembles that the weather might at least bring some mainly dry weather to northern Europe this Christmas. 00z ECMWF ensemble ~70% in support.

Temperatures with that anything from cold to mild depending on the position & shape of high pressure.

Overall, I think it's not unreasonable to anticipate temperatures heading closer to the long-term average than of late, i.e. becoming more 'seasonal'.

Unclear whether that's with more wet & windy weather or something drier & calmer.

Forecast modelling tends to be inconsistent when looking over a week ahead (let alone 12 days), but of late it's been even more so than usual for the Atlantic-Europe sector.

A cold runup to Christmas Day in NW Europe seems a long shot, but I'm not certain that it'll be mild.

61.6 mm of rain here in NE Dorset for 1st-9th December 🌧️

Far from the wettest of locations out there in the UK, yet still 277% of the 1991-2020 average for up to this point.

A mere 1.4 hours sunshine in the last 5 days ☁️😣

Thankfully today should deliver around 4 hours ☀️😎

After what will be at least the 3rd day running without any sunshine for many areas, tomorrow will offer a reprieve for much of England & Wales.

Thursday might also deliver some sunshine there.

Staying mainly cloudy in Scotland, which might have to wait until at least Saturday.

Storm Bram will set the rainfall theme for the next week or so in the UK & Ireland: Wettest in the west.

While the already typically wettest areas could see up to 100 mm more than usual, the typically driest east may be close to normal, making for a steepened west-east gradient.

...2019 absolutely obliterated it with 18.0°C on 25th, followed up by 17.8°C the next two days for good measure. One of the most extreme anomalous warmth events on record here.

Since then the closest has been 'only' 15.3°C on 15th in 2024.

Impressively considering the seasonal cooling of the ocean around, January's record highest is on par, 14.9°C set on 9th in 2015.

February has a higher record as soon as 4th (15.1°C in 2004) but doesn't step up much further until 18th (15.7°C in 1945). The monthly record until...

Peaked at 14.3°C here in NE Dorset yesterday - that would be typical in mid-April!

It's not far off the absurdly mild December of 2015's highest, which was 14.8°C on 19th.

The record highest daily max for any point in the month here was set way back in 1979, with 15.0°C on 5th.

Beyond this week, I can see a window of opportunity for a quieter spell of weather to emerge... eventually.

~18% of the 00z ECMWF ensemble gets there on 19th Dec, ~31% on 23rd. The other half of it still has mostly unsettled weather throughout.

In fact, eastern parts of England might only see around 10 mm this week, which is a little less than the long-term average for this time of year.

In the North Atlantic, there's been a trend in forecast modelling to keep low pressure further northwest this week.

As a result, the wet weather in the UK & Ireland now looks more concentrated on western parts, especially near-west of high ground.

Arctic temperatures have since permitted a bit more freezing through November - as you'd expect - but not much more than in the warmest years on record.

The November volume update is awaited with some trepidation.

(zacklabe.com/arctic-tempe...)

Last October, the Arctic sea ice volume was record-low, slightly below that of 2020, while the extent was about a million square km greater - a roughly 17% larger coverage.

This implies record-low sea ice thickness, & by more than a small margin.

(zacklabe.com/archive-2025/)

Still some vibrant splashes of autumn colour to be found.

That would still be some way short of the record warmest to-date, mind. The mean CET record for the first half of Dec has in fact stood for over 100 years now, an impressive 9.13°C in 1898.

Much more recently, 2015 was on 8.88°C, & it went on to take all the to-date records for 16th onward.

Up to 5th, December 2025's Hadley mean Central England Temperature has been just slightly warmer than the 1991-2020 average.

However, the outlook for the next week or so is about as mild as it gets at this time of year, which may lift the CET into the 8s °C by mid-month.

...which would raise the chances of a shift toward a less unsettled, perhaps colder pattern for northern Europe.

This is reflected in the ECMWF ensemble clusters, with ~21% of the set taking that sort of route in the 3rd week of December.