James Peacock
@peacockreports.bsky.social
Head Meteorologist at MetSwift, working to revolutionise delivery of weather information.
LinkedIn: https://t.co/pUCAQfAfRP
LinkedIn: https://t.co/pUCAQfAfRP
It's a weather pattern that can deliver some of the most widespread 50+ mm totals to western Europe.
Where the westerlies hit the mountainous terrain in northernmost Iberia, some pretty immense rainfall totals can occur.
In short, this scenario is one to watch out for.
Where the westerlies hit the mountainous terrain in northernmost Iberia, some pretty immense rainfall totals can occur.
In short, this scenario is one to watch out for.
November 29, 2025 at 4:36 PM
It's a weather pattern that can deliver some of the most widespread 50+ mm totals to western Europe.
Where the westerlies hit the mountainous terrain in northernmost Iberia, some pretty immense rainfall totals can occur.
In short, this scenario is one to watch out for.
Where the westerlies hit the mountainous terrain in northernmost Iberia, some pretty immense rainfall totals can occur.
In short, this scenario is one to watch out for.
One possible result of weather patterns being simultaneously pushed toward blocking highs in the Arctic & an enhanced jet stream is a succession of lows racing into Europe, bringing bouts of wet & windy weather in the 1st half of December.
Not a scenario I'm keen to experience.
Not a scenario I'm keen to experience.
November 29, 2025 at 4:33 PM
One possible result of weather patterns being simultaneously pushed toward blocking highs in the Arctic & an enhanced jet stream is a succession of lows racing into Europe, bringing bouts of wet & windy weather in the 1st half of December.
Not a scenario I'm keen to experience.
Not a scenario I'm keen to experience.
With 42.2 hours in the past 10 days, November 2025 has managed to claw its back back to the long-term average for sunshine to-date here in NE Dorset.
It's also managed to be very near the long-term average for rainfall.
Seems only the temperatures will be noteworthy this month.
It's also managed to be very near the long-term average for rainfall.
Seems only the temperatures will be noteworthy this month.
November 27, 2025 at 10:29 AM
With 42.2 hours in the past 10 days, November 2025 has managed to claw its back back to the long-term average for sunshine to-date here in NE Dorset.
It's also managed to be very near the long-term average for rainfall.
Seems only the temperatures will be noteworthy this month.
It's also managed to be very near the long-term average for rainfall.
Seems only the temperatures will be noteworthy this month.
Granted, the ECMWF ensemble is still heavily weighted toward those brisk westerlies, but I know from experience that whole ensemble sets can lean the wrong way when key complications aren't well resolved at the nearer timeframes.
So, I'm wary of presuming mostly mild & windy.
So, I'm wary of presuming mostly mild & windy.
November 27, 2025 at 9:23 AM
Granted, the ECMWF ensemble is still heavily weighted toward those brisk westerlies, but I know from experience that whole ensemble sets can lean the wrong way when key complications aren't well resolved at the nearer timeframes.
So, I'm wary of presuming mostly mild & windy.
So, I'm wary of presuming mostly mild & windy.
Sometimes forecast modelling diverge as point in time draws closer, due to complicating features being picked up more.
Case in point with the middle stages of next week. The 'big Atlantic low' scenario is still there, but no longer a clear favourite.
Case in point with the middle stages of next week. The 'big Atlantic low' scenario is still there, but no longer a clear favourite.
November 27, 2025 at 9:11 AM
Sometimes forecast modelling diverge as point in time draws closer, due to complicating features being picked up more.
Case in point with the middle stages of next week. The 'big Atlantic low' scenario is still there, but no longer a clear favourite.
Case in point with the middle stages of next week. The 'big Atlantic low' scenario is still there, but no longer a clear favourite.
If energy waves then continued to be absorbed by the polar vortex, we'd see the NAM index head negative across the 1000 to 200 hPa pressure levels late Nov into Dec.
Instead, those waves are forecast to be reflected, resulting in a mixed NAM response.
Instead, those waves are forecast to be reflected, resulting in a mixed NAM response.
November 26, 2025 at 1:40 PM
If energy waves then continued to be absorbed by the polar vortex, we'd see the NAM index head negative across the 1000 to 200 hPa pressure levels late Nov into Dec.
Instead, those waves are forecast to be reflected, resulting in a mixed NAM response.
Instead, those waves are forecast to be reflected, resulting in a mixed NAM response.
See how the polar vortex (marked 'L') is displaced toward Eurasia by an anomalous anticyclonic circulation (marked 'H').
As I mentioned in my latest blog published yesterday (www.metswift.com/2025/11/24/s...), this is a common layout for a displacement type event.
As I mentioned in my latest blog published yesterday (www.metswift.com/2025/11/24/s...), this is a common layout for a displacement type event.
November 26, 2025 at 1:32 PM
See how the polar vortex (marked 'L') is displaced toward Eurasia by an anomalous anticyclonic circulation (marked 'H').
As I mentioned in my latest blog published yesterday (www.metswift.com/2025/11/24/s...), this is a common layout for a displacement type event.
As I mentioned in my latest blog published yesterday (www.metswift.com/2025/11/24/s...), this is a common layout for a displacement type event.
28th Nov looks to be when we might briefly see the zonal mean zonal wind at 60N, 10 hPa pressure level become negative.
Uncertain whether it will remain so long enough for the daily mean to be below zero, which is required for a technical major sudden stratospheric warming event.
Uncertain whether it will remain so long enough for the daily mean to be below zero, which is required for a technical major sudden stratospheric warming event.
November 26, 2025 at 1:27 PM
28th Nov looks to be when we might briefly see the zonal mean zonal wind at 60N, 10 hPa pressure level become negative.
Uncertain whether it will remain so long enough for the daily mean to be below zero, which is required for a technical major sudden stratospheric warming event.
Uncertain whether it will remain so long enough for the daily mean to be below zero, which is required for a technical major sudden stratospheric warming event.
IMO there's a good chance that the change in 7-day rolling mean temperature between mid- & late November 2025 is among the largest on record for my local area.
Dropping by 9.2°C in 8 days, it went from 5°C above the 1991-2020 average on 15th to 3.3°C below it on 23rd.
Dropping by 9.2°C in 8 days, it went from 5°C above the 1991-2020 average on 15th to 3.3°C below it on 23rd.
November 26, 2025 at 11:30 AM
IMO there's a good chance that the change in 7-day rolling mean temperature between mid- & late November 2025 is among the largest on record for my local area.
Dropping by 9.2°C in 8 days, it went from 5°C above the 1991-2020 average on 15th to 3.3°C below it on 23rd.
Dropping by 9.2°C in 8 days, it went from 5°C above the 1991-2020 average on 15th to 3.3°C below it on 23rd.
...with the signal for a rapidly recovering polar vortex holding fairly steady through 23rd, before being toned down a bit in the updates of 24th then 25th.
Yesterday's set began to hint that the polar vortex might weaken again in the 3rd week of December.
Yesterday's set began to hint that the polar vortex might weaken again in the 3rd week of December.
November 26, 2025 at 9:15 AM
...with the signal for a rapidly recovering polar vortex holding fairly steady through 23rd, before being toned down a bit in the updates of 24th then 25th.
Yesterday's set began to hint that the polar vortex might weaken again in the 3rd week of December.
Yesterday's set began to hint that the polar vortex might weaken again in the 3rd week of December.
The past month's extended ECMWF ensemble sets for the (60N) zonal mean zonal wind at 10 hPa in late November through December.
The signal for a major sudden stratospheric warming event strengthens through 12th Nov, then abruptly takes on a 'reflective' appearance on 19th Nov...
The signal for a major sudden stratospheric warming event strengthens through 12th Nov, then abruptly takes on a 'reflective' appearance on 19th Nov...
November 26, 2025 at 9:13 AM
The past month's extended ECMWF ensemble sets for the (60N) zonal mean zonal wind at 10 hPa in late November through December.
The signal for a major sudden stratospheric warming event strengthens through 12th Nov, then abruptly takes on a 'reflective' appearance on 19th Nov...
The signal for a major sudden stratospheric warming event strengthens through 12th Nov, then abruptly takes on a 'reflective' appearance on 19th Nov...
The trend in the ECMWF ensemble has me wondering how much we can trust the recent consensus for predominantly mild weather to persist across northern Europe beyond next ~Friday.
Note the trough digging down across western Europe more, with higher SLP to the north.
Note the trough digging down across western Europe more, with higher SLP to the north.
November 26, 2025 at 8:58 AM
The trend in the ECMWF ensemble has me wondering how much we can trust the recent consensus for predominantly mild weather to persist across northern Europe beyond next ~Friday.
Note the trough digging down across western Europe more, with higher SLP to the north.
Note the trough digging down across western Europe more, with higher SLP to the north.
November 2025's tremendous temperature tumble continues, with the Hadley CET to-date down to 14th warmest on record as of 24th.
With temperatures varying around the 1991-2020 average for the rest of it, the final CET will likely be around 19th warmest & about 1°C above average.
With temperatures varying around the 1991-2020 average for the rest of it, the final CET will likely be around 19th warmest & about 1°C above average.
November 25, 2025 at 2:08 PM
November 2025's tremendous temperature tumble continues, with the Hadley CET to-date down to 14th warmest on record as of 24th.
With temperatures varying around the 1991-2020 average for the rest of it, the final CET will likely be around 19th warmest & about 1°C above average.
With temperatures varying around the 1991-2020 average for the rest of it, the final CET will likely be around 19th warmest & about 1°C above average.
Are global mean temperatures in 2025 being pushed down by La Niña?
I've seen this notion doing the rounds but...
2025's mean ONI is on track to be near -0.3, while 2024's was +0.35. Historical correlation suggests this has little net effect on global mean temperature in 2025.
I've seen this notion doing the rounds but...
2025's mean ONI is on track to be near -0.3, while 2024's was +0.35. Historical correlation suggests this has little net effect on global mean temperature in 2025.
November 24, 2025 at 3:22 PM
Are global mean temperatures in 2025 being pushed down by La Niña?
I've seen this notion doing the rounds but...
2025's mean ONI is on track to be near -0.3, while 2024's was +0.35. Historical correlation suggests this has little net effect on global mean temperature in 2025.
I've seen this notion doing the rounds but...
2025's mean ONI is on track to be near -0.3, while 2024's was +0.35. Historical correlation suggests this has little net effect on global mean temperature in 2025.
Beyond 7th December, the 'window of opportunity' for a pattern change that I've mentioned before continues to feature in the ECMWF ensemble.
~40% of the set develops high pressure either north of Europe (~30%) or right over Europe (~10%).
Just something to keep an eye on.
~40% of the set develops high pressure either north of Europe (~30%) or right over Europe (~10%).
Just something to keep an eye on.
November 24, 2025 at 10:01 AM
Beyond 7th December, the 'window of opportunity' for a pattern change that I've mentioned before continues to feature in the ECMWF ensemble.
~40% of the set develops high pressure either north of Europe (~30%) or right over Europe (~10%).
Just something to keep an eye on.
~40% of the set develops high pressure either north of Europe (~30%) or right over Europe (~10%).
Just something to keep an eye on.
There continues to be strong cross-model agreement on the opening week of December being generally mild in most of Europe, with wet & windy weather focused on the northwest.
Some uncertainty how far SE the wet & windy weather tends to reach, ECMWF's ensemble the more aggressive.
Some uncertainty how far SE the wet & windy weather tends to reach, ECMWF's ensemble the more aggressive.
November 24, 2025 at 9:56 AM
There continues to be strong cross-model agreement on the opening week of December being generally mild in most of Europe, with wet & windy weather focused on the northwest.
Some uncertainty how far SE the wet & windy weather tends to reach, ECMWF's ensemble the more aggressive.
Some uncertainty how far SE the wet & windy weather tends to reach, ECMWF's ensemble the more aggressive.
Looking back at satellite imagery from noon today, I can see the shadow cast by cirrostratus which was keeping the sunshine hazy where I was even as the sky became clear overhead.
This is with the sun at its highest point of the day. Low rider!
This is with the sun at its highest point of the day. Low rider!
November 23, 2025 at 6:42 PM
Looking back at satellite imagery from noon today, I can see the shadow cast by cirrostratus which was keeping the sunshine hazy where I was even as the sky became clear overhead.
This is with the sun at its highest point of the day. Low rider!
This is with the sun at its highest point of the day. Low rider!
There's growing confidence that ~29th Nov will see a major sudden stratospheric warming event, but one where reflection of wave activity in the stratosphere allows the polar vortex to quickly rebound.
OTOH, most runs still have it anomalously weak in the 2nd week of Dec.
OTOH, most runs still have it anomalously weak in the 2nd week of Dec.
November 22, 2025 at 8:40 PM
There's growing confidence that ~29th Nov will see a major sudden stratospheric warming event, but one where reflection of wave activity in the stratosphere allows the polar vortex to quickly rebound.
OTOH, most runs still have it anomalously weak in the 2nd week of Dec.
OTOH, most runs still have it anomalously weak in the 2nd week of Dec.
To visualise the effect of El Niño & La Niña, I decided to try applying a linear detrend to the ERA5 global mean temperature dataset, then plotting it against the annual mean Oceanic Niño Index.
The result is an astonishingly good fit to a polynomial with 3 degrees of freedom.
The result is an astonishingly good fit to a polynomial with 3 degrees of freedom.
November 22, 2025 at 6:16 PM
To visualise the effect of El Niño & La Niña, I decided to try applying a linear detrend to the ERA5 global mean temperature dataset, then plotting it against the annual mean Oceanic Niño Index.
The result is an astonishingly good fit to a polynomial with 3 degrees of freedom.
The result is an astonishingly good fit to a polynomial with 3 degrees of freedom.
There was quite the jump in temperature at Bournemouth Airport between 2 am & 3 am last night. 8.7°C in the space of an hour!
November 22, 2025 at 5:08 PM
There was quite the jump in temperature at Bournemouth Airport between 2 am & 3 am last night. 8.7°C in the space of an hour!
...which makes it difficult for the high pressure to move northward much. The result is an anomalously dry pattern for much of Europe, potentially very mild in the north.
Then, in the 2nd ~week of December, there will probably be some changes afoot...
Then, in the 2nd ~week of December, there will probably be some changes afoot...
November 21, 2025 at 10:12 AM
...which makes it difficult for the high pressure to move northward much. The result is an anomalously dry pattern for much of Europe, potentially very mild in the north.
Then, in the 2nd ~week of December, there will probably be some changes afoot...
Then, in the 2nd ~week of December, there will probably be some changes afoot...
My current thoughts on the first ~week of December in Europe.
Events in the tropics look to drive a build of high pressure across Europe, then try to shift that northward.
Meanwhile, events in the stratosphere will probably favour low pressure in the Greenland-Iceland area...
Events in the tropics look to drive a build of high pressure across Europe, then try to shift that northward.
Meanwhile, events in the stratosphere will probably favour low pressure in the Greenland-Iceland area...
November 21, 2025 at 10:10 AM
My current thoughts on the first ~week of December in Europe.
Events in the tropics look to drive a build of high pressure across Europe, then try to shift that northward.
Meanwhile, events in the stratosphere will probably favour low pressure in the Greenland-Iceland area...
Events in the tropics look to drive a build of high pressure across Europe, then try to shift that northward.
Meanwhile, events in the stratosphere will probably favour low pressure in the Greenland-Iceland area...
With the much colder weather of late, November's Hadley mean central England temperature to-date has begun to nosedive & is down from 1st to 5th warmest on record as of 19th.
Signs are it could drop to around 14th before a possible late recovery via an onset of milder weather.
Signs are it could drop to around 14th before a possible late recovery via an onset of milder weather.
November 20, 2025 at 2:28 PM
With the much colder weather of late, November's Hadley mean central England temperature to-date has begun to nosedive & is down from 1st to 5th warmest on record as of 19th.
Signs are it could drop to around 14th before a possible late recovery via an onset of milder weather.
Signs are it could drop to around 14th before a possible late recovery via an onset of milder weather.
The criteria 'reversal of zonal mean zonal wind at 60 deg N at 10 hPa' strikes a good balance between event detection & the significance of those events in terms of subsequent polar vortex disruption.
A score of 1 indicates an optimal value for the given property of a SSW event.
A score of 1 indicates an optimal value for the given property of a SSW event.
November 20, 2025 at 10:48 AM
The criteria 'reversal of zonal mean zonal wind at 60 deg N at 10 hPa' strikes a good balance between event detection & the significance of those events in terms of subsequent polar vortex disruption.
A score of 1 indicates an optimal value for the given property of a SSW event.
A score of 1 indicates an optimal value for the given property of a SSW event.
With all the "will it, won't it" talk regarding a possible major sudden stratospheric warming event late this month, this seems a good time to highlight this excerpt from A. H. Butler & E. P. Gerber 's 2018 paper on the definition of such events.
journals.ametsoc.org/view/journal...
journals.ametsoc.org/view/journal...
November 20, 2025 at 10:42 AM
With all the "will it, won't it" talk regarding a possible major sudden stratospheric warming event late this month, this seems a good time to highlight this excerpt from A. H. Butler & E. P. Gerber 's 2018 paper on the definition of such events.
journals.ametsoc.org/view/journal...
journals.ametsoc.org/view/journal...