Stratwarms and cold weather
 

http://www.metoffice.gov.uk/news/rel...inter-guidance
http://metofficenews.wordpress.com/2...pe-and-the-uk/

http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Stratwarms and cold weather
 

On Sunday, December 16, 2012 1:43:48 PM UTC, wrote:
http://www.metoffice.gov.uk/news/rel...inter-guidance

http://metofficenews.wordpress.com/2...pe-and-the-uk/



http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm

Will Hand (Haytor, Devon, 1017 feet asl)

---------------------------------------------

thanks you Will. After reading and learning from these, I doubt you will be as willing to draw such strong links to SSW's and especially to very weak ones, ("stratwarm" is a term used nowhere in the article, or the blog). I could be wrong on that, of course.

If you wish me to post the same papers again that I've linked to before, explaining SSW's and their effects on surface conditions in more detail, to help you, I'm willing to do so. They are easily researched.

Stratwarms and cold weather
 

thanks you Will. After reading and learning from these, I doubt you will be as willing to draw such strong links to SSW's and especially to very weak ones, ("stratwarm" is a term used nowhere in the article, or the blog). I could be wrong on that, of course.


In the 1st link that Will provided by the Met Office:

The new model, dubbed the "high top" system, is different from the previous system as it takes into account something known as sudden stratospheric warming's (SSWs) - which have previously been shown to be responsible for cold conditions at ground level.

SSWs happen when the usual westerly winds in the stratosphere, between 10km and 50km up, break down and ultimately reverse.

---------------------------------------------------------------------------

Maybe dear pupil you should read the detail before lecturing & trying to offer the teacher advice.

Stratwarms and cold weather
 

On Sun, 16 Dec 2012 13:43:48 -0000
"Eskimo Will" wrote:

http://www.metoffice.gov.uk/news/rel...inter-guidance
http://metofficenews.wordpress.com/2...pe-and-the-uk/

http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------


And here's one that appeared a few days before the "beast from the
east."

http://metofficenews.wordpress.com/2...er-atmosphere/


--
Graham P Davis, Bracknell, Berks.
Time flies like an arrow but fruit flies like a banana. [Marx]

Stratwarms and cold weather
 

On Sunday, December 16, 2012 6:39:36 PM UTC, Teignmouth wrote:


thanks you Will. After reading and learning from these, I doubt you will be as willing to draw such strong links to SSW's and especially to very weak ones, ("stratwarm" is a term used nowhere in the article, or the blog).. I could be wrong on that, of course.





In the 1st link that Will provided by the Met Office:



The new model, dubbed the "high top" system, is different from the previous system as it takes into account something known as sudden stratospheric warming's (SSWs) - which have previously been shown to be responsible for cold conditions at ground level.



SSWs happen when the usual westerly winds in the stratosphere, between 10km and 50km up, break down and ultimately reverse.


Errrrrr yes. We all know the atmospheric signatures of strong SSWs. We also know that the MetO have changed their models and incorporated strong SSWs in their forecasting. So your point is about the effects of the weak SSW that Will got hopelessly wrong? Will understands exactly what I mean. A pity you don't.

Stratwarms and cold weather
 

Graham P Davis wrote:
On Sun, 16 Dec 2012 13:43:48 -0000
"Eskimo Will" wrote:

http://www.metoffice.gov.uk/news/rel...inter-guidance
http://metofficenews.wordpress.com/2...pe-and-the-uk/

http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------


And here's one that appeared a few days before the "beast from the
east."

http://metofficenews.wordpress.com/2...er-atmosphere/


---------------------------------
Well if it does help cold spells develop it either wasn't there this
time or had the complete opposite effect on our weather. Or - is it
responsible for the HP and cold over Europe only?
Dave

Stratwarms and cold weather
 

"Dawlish" wrote in message
...
On Sunday, December 16, 2012 6:39:36 PM UTC, Teignmouth wrote:


thanks you Will. After reading and learning from these, I doubt you will
be as willing to draw such strong links to SSW's and especially to very
weak ones, ("stratwarm" is a term used nowhere in the article, or the
blog). I could be wrong on that, of course.





In the 1st link that Will provided by the Met Office:



The new model, dubbed the "high top" system, is different from the
previous system as it takes into account something known as sudden
stratospheric warming's (SSWs) - which have previously been shown to be
responsible for cold conditions at ground level.



SSWs happen when the usual westerly winds in the stratosphere, between
10km and 50km up, break down and ultimately reverse.


Errrrrr yes. We all know the atmospheric signatures of strong SSWs. We also
know that the MetO have changed their models and incorporated strong SSWs in
their forecasting. So your point is about the effects of the weak SSW that
Will got hopelessly wrong? Will understands exactly what I mean. A pity you
don't.

==========================

The point is, is that even relatively weak or shortlived warmings will
decrease the zonal wind and if there is an existing block that will help
prolong it. It is no coincidence that the last block retreated eastwards in
the models when the stratwarm ceased.

Will
--

Stratwarms and cold weather
 

"Dave Cornwell" wrote in message
...
Graham P Davis wrote:
On Sun, 16 Dec 2012 13:43:48 -0000
"Eskimo Will" wrote:

http://www.metoffice.gov.uk/news/rel...inter-guidance
http://metofficenews.wordpress.com/2...pe-and-the-uk/

http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------


And here's one that appeared a few days before the "beast from the
east."

http://metofficenews.wordpress.com/2...er-atmosphere/


---------------------------------
Well if it does help cold spells develop it either wasn't there this time
or had the complete opposite effect on our weather. Or - is it responsible
for the HP and cold over Europe only?
Dave

See my last reply Dave.

Will
--

Stratwarms and cold weather
 

On Sunday, 16 December 2012 17:10:32 UTC, Dawlish wrote:

If you wish me to post the same papers again that I've linked to before, explaining SSW's and their effects on surface conditions in more detail, to help you, I'm willing to do so. They are easily researched.

Dear Dave,

I am not anti Dawlish and you do come up with valid points. But I am finding this continual snipping at Will both disrespectful and unnecessary. I have been following this newsgroup for around 15 years and have learnt huge amounts from the various professional and other contributors to this group. Will is unique in his attitude of sharing any unusual and potentially dangerous weather events that appear on the horizon. Most forecasters are reluctant to post, fearing ridicule if they do not materialise. To loose Will on here would mean the demise of "on the edge" knowledgeable warnings and discussions. I always take a squint at Darren Prescotts excellent 7 day summary of the charts. There are other retired meteorologists on here who pop by with their input. I am still trying to fathom the earthquake/weather connection with weatherlawyers ramblings (often to himself it seems), but worth a read. Lawrence keeps his head down these days, but he has relevant views. I remember some time ago there was some sort of expose on you that seemed to suggest that you are a school teacher in Dawlish, which I have no problem with. I am just interested about your meteorological background so that when you post your comments on here, that give the impression that you have or have had some meteorology training. It would just help me in evaluating your replies to Will's and other posts. I just find it incredibly tedious when it all starts getting personnel and ranty, so hopefully this won't happen this time.

Yours respectively,

Mike McMillan

Stratwarms and cold weather
 

On 16/12/12 19:14, Dave Cornwell wrote:
Graham P Davis wrote:
On Sun, 16 Dec 2012 13:43:48 -0000
"Eskimo Will" wrote:

http://www.metoffice.gov.uk/news/rel...inter-guidance

http://metofficenews.wordpress.com/2...pe-and-the-uk/


http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

And here's one that appeared a few days before the "beast from the
east."

http://metofficenews.wordpress.com/2...er-atmosphere/



---------------------------------
Well if it does help cold spells develop it either wasn't there this
time or had the complete opposite effect on our weather. Or - is it
responsible for the HP and cold over Europe only?
Dave

It was pretty cold last week, I think on Wednesday it didn't get above
freezing in my location.

Stratwarms and cold weather
 

On Sunday, December 16, 2012 7:29:28 PM UTC, wrote:
"Dawlish" wrote in message

...

On Sunday, December 16, 2012 6:39:36 PM UTC, Teignmouth wrote:





thanks you Will. After reading and learning from these, I doubt you will

be as willing to draw such strong links to SSW's and especially to very

weak ones, ("stratwarm" is a term used nowhere in the article, or the

blog). I could be wrong on that, of course.











In the 1st link that Will provided by the Met Office:







The new model, dubbed the "high top" system, is different from the

previous system as it takes into account something known as sudden

stratospheric warming's (SSWs) - which have previously been shown to be

responsible for cold conditions at ground level.







SSWs happen when the usual westerly winds in the stratosphere, between

10km and 50km up, break down and ultimately reverse.





Errrrrr yes. We all know the atmospheric signatures of strong SSWs. We also

know that the MetO have changed their models and incorporated strong SSWs in

their forecasting. So your point is about the effects of the weak SSW that

Will got hopelessly wrong? Will understands exactly what I mean. A pity you

don't.



==========================



The point is, is that even relatively weak or shortlived warmings will

decrease the zonal wind and if there is an existing block that will help

prolong it. It is no coincidence that the last block retreated eastwards in

the models when the stratwarm ceased.



Will

--

Show us the research that shows that a very weak event (the SSW last week was exactly that), which does not actually propagate to the surface (it didn't), produces an enhanced effect to a surface block.

Stratwarms and cold weather
 

On Sunday, December 16, 2012 7:14:01 PM UTC, Dave Cornwell wrote:
Graham P Davis wrote:

On Sun, 16 Dec 2012 13:43:48 -0000

"Eskimo Will" wrote:



http://www.metoffice.gov.uk/news/rel...inter-guidance

http://metofficenews.wordpress.com/2...pe-and-the-uk/



http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm

Will Hand (Haytor, Devon, 1017 feet asl)

---------------------------------------------





And here's one that appeared a few days before the "beast from the

east."



http://metofficenews.wordpress.com/2...er-atmosphere/





---------------------------------

Well if it does help cold spells develop it either wasn't there this

time or had the complete opposite effect on our weather. Or - is it

responsible for the HP and cold over Europe only?

Dave

It didn't develop further than reversing the winds in the stratosphere for no more than 3 days from 13-15 Dec. Here's the eveidence:

http://wekuw.met.fu-berlin.de/~Aktue...w/wdiag/ts.php

It probably didn't have any effect on our weather. The present state of SSW research cannot say whether it would, or it wouldn't, according to the MetO, but such a weak event?? The research which has been produced before shows no such link between weak SSW events and surface blocking. To say that any SSW will enhance surface blocking really is ridiculous and cannot be supported by current research.

If it isn't; someone please show where and I will accept your evidence willingly.

If not; it's time to speak out and say to Will that he is simply ramping cold with no evidence.

Stratwarms and cold weather
 

On Sunday, December 16, 2012 7:29:28 PM UTC, wrote:
"Dawlish" wrote in message

...

On Sunday, December 16, 2012 6:39:36 PM UTC, Teignmouth wrote:





thanks you Will. After reading and learning from these, I doubt you will

be as willing to draw such strong links to SSW's and especially to very

weak ones, ("stratwarm" is a term used nowhere in the article, or the

blog). I could be wrong on that, of course.











In the 1st link that Will provided by the Met Office:







The new model, dubbed the "high top" system, is different from the

previous system as it takes into account something known as sudden

stratospheric warming's (SSWs) - which have previously been shown to be

responsible for cold conditions at ground level.







SSWs happen when the usual westerly winds in the stratosphere, between

10km and 50km up, break down and ultimately reverse.





Errrrrr yes. We all know the atmospheric signatures of strong SSWs. We also

know that the MetO have changed their models and incorporated strong SSWs in

their forecasting. So your point is about the effects of the weak SSW that

Will got hopelessly wrong? Will understands exactly what I mean. A pity you

don't.



==========================



The point is, is that even relatively weak or shortlived warmings will

decrease the zonal wind and if there is an existing block that will help

prolong it. It is no coincidence that the last block retreated eastwards in

the models when the stratwarm ceased.



Will

--

Is it "no coincidence" Will? Do; "relatively weak or shortlived warmings will

decrease the zonal wind and if there is an existing block that will help

prolong it".

Where are you getting these "facts" from? Surely you must have evidence to back this up?

Stratwarms and cold weather
 

On Sun, 16 Dec 2012 19:14:01 +0000
Dave Cornwell wrote:

Graham P Davis wrote:
On Sun, 16 Dec 2012 13:43:48 -0000
"Eskimo Will" wrote:

http://www.metoffice.gov.uk/news/rel...inter-guidance
http://metofficenews.wordpress.com/2...pe-and-the-uk/

http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------


And here's one that appeared a few days before the "beast from the
east."

http://metofficenews.wordpress.com/2...er-atmosphere/


---------------------------------
Well if it does help cold spells develop it either wasn't there this
time or had the complete opposite effect on our weather. Or - is it
responsible for the HP and cold over Europe only?
Dave

I think the link I provided gives the answer:

"The more significant the SSW, the more likely it is to have an impact at the surface and also the greater the potential impact.

"Met Office observation systems have picked up a *minor* SSW in the
stratosphere over the past few days"

--
Graham P Davis, Bracknell, Berks.
Time flies like an arrow but fruit flies like a banana. [Marx]

Stratwarms and cold weather
 

"Dawlish" wrote in message
...
On Sunday, December 16, 2012 7:29:28 PM UTC,
wrote:
"Dawlish" wrote in message

...

On Sunday, December 16, 2012 6:39:36 PM UTC, Teignmouth wrote:





thanks you Will. After reading and learning from these, I doubt you
will

be as willing to draw such strong links to SSW's and especially to
very

weak ones, ("stratwarm" is a term used nowhere in the article, or
the

blog). I could be wrong on that, of course.











In the 1st link that Will provided by the Met Office:







The new model, dubbed the "high top" system, is different from the

previous system as it takes into account something known as sudden

stratospheric warming's (SSWs) - which have previously been shown to be

responsible for cold conditions at ground level.







SSWs happen when the usual westerly winds in the stratosphere, between

10km and 50km up, break down and ultimately reverse.





Errrrrr yes. We all know the atmospheric signatures of strong SSWs. We
also

know that the MetO have changed their models and incorporated strong SSWs
in

their forecasting. So your point is about the effects of the weak SSW
that

Will got hopelessly wrong? Will understands exactly what I mean. A pity
you

don't.



==========================



The point is, is that even relatively weak or shortlived warmings will

decrease the zonal wind and if there is an existing block that will help

prolong it. It is no coincidence that the last block retreated eastwards
in

the models when the stratwarm ceased.



Will

--

Show us the research that shows that a very weak event (the SSW last week
was exactly that), which does not actually propagate to the surface (it
didn't), produces an enhanced effect to a surface block.

It's common sense, a bit of understanding of what blocking is (not actually
an entirely surface feature at all) and an understanding of atmospheric
dynamics is all that's needed to understand that. Reducing the zonal wind
speed will er lead to less mobility and hence de facto an increase in
tendency for the atmosphere to block. Surely you can understand that? If
not, please go back to lurking properly and read some meteorology text
books, there are plenty around.

Will
--

Stratwarms and cold weather
 

Mike McMillan wrote:
On Sunday, 16 December 2012 17:10:32 UTC, Dawlish wrote:

If you wish me to post the same papers again that I've linked to before, explaining SSW's and their effects on surface conditions in more detail, to help you, I'm willing to do so. They are easily researched.

Dear Dave,

I am not anti Dawlish and you do come up with valid points. But I am finding this continual snipping at Will both disrespectful and unnecessary. I have been following this newsgroup for around 15 years and have learnt huge amounts from the various professional and other contributors to this group. Will is unique in his attitude of sharing any unusual and potentially dangerous weather events that appear on the horizon. Most forecasters are reluctant to post, fearing ridicule if they do not materialise. To loose Will on here would mean the demise of "on the edge" knowledgeable warnings and discussions. I always take a squint at Darren Prescotts excellent 7 day summary of the charts. There are other retired meteorologists on here who pop by with their input. I am still trying to fathom the earthquake/weather connection with weatherlawyers ramblings (often to himself it seems), but worth a read. Lawrence keeps his head down these days, but he has relevant views. I remember som
e time ago there was some sort of expose on you that seemed to suggest that you are a school teacher in Dawlish, which I have no problem with. I am just interested about your meteorological background so that when you post your comments on here, that give the impression that you have or have had some meteorology training. It would just help me in evaluating your replies to Will's and other posts. I just find it incredibly tedious when it all starts getting personnel and ranty, so hopefully this won't happen this time.

Yours respectively,

Mike McMillan
------------------------------------
Hopefully that was meant to say "Dear Paul" !!

Stratwarms and cold weather
 

On Sunday, December 16, 2012 11:13:37 PM UTC, wrote:


[...] a bit of understanding of what blocking is (not actually

an entirely surface feature at all)

=======

Exactly. And although the UK, being peripheral, got just a few days of extremely cold weather, such blocking as there has been has produced a lengthy period of below average (and at times far below average) temperatures over Scandinavia and NE Europe, and indeed Germany and Poland (not just cold but snowy).

Woolings et al 2010 links SSWs and tropospheric blocking for one. And researching into the December 2009 cold, Lin Wang and Wen Chen (Geophysical Research Letters) note this: "Another interesting point is that in previous studies, the downward propagation is usually documented for extreme strong stratospheric anomalies such as major warming or strong vortex intensification [e.g., Baldwin and Dunkerton, 2001; Limpasuvan et al., 2005]. However, the
warmings in this case even do not meet the criteria for minor warming defined by World Meteorological Organization. *It suggests that in addition to extreme strong events, some weaker stratospheric anomalies can also propagate downward and influence the troposphere.*"

("Downward Arctic Oscillation signal associated with moderate weak stratospheric polar vortex and the cold December 2009." Lin Wang and Wen Chen, GRL 11 May 2010.)

It is quite in order to suggest *a greater likelihood* of tropospheric blocking even during a weak stratospheric warming event.

Stephen.

Stratwarms and cold weather
 

On Sunday, December 16, 2012 11:07:27 PM UTC, Graham P Davis wrote:
On Sun, 16 Dec 2012 19:14:01 +0000

Dave Cornwell wrote:



Graham P Davis wrote:

On Sun, 16 Dec 2012 13:43:48 -0000

"Eskimo Will" wrote:



http://www.metoffice.gov.uk/news/rel...inter-guidance

http://metofficenews.wordpress.com/2...pe-and-the-uk/



http://www.lyneside.demon.co.uk/Hayt...ntage_Pro..htm

Will Hand (Haytor, Devon, 1017 feet asl)

---------------------------------------------





And here's one that appeared a few days before the "beast from the

east."



http://metofficenews.wordpress.com/2...er-atmosphere/





---------------------------------

Well if it does help cold spells develop it either wasn't there this

time or had the complete opposite effect on our weather. Or - is it

responsible for the HP and cold over Europe only?

Dave



I think the link I provided gives the answer:



"The more significant the SSW, the more likely it is to have an impact at the surface and also the greater the potential impact.



"Met Office observation systems have picked up a *minor* SSW in the

stratosphere over the past few days"



--

Graham P Davis, Bracknell, Berks.

Time flies like an arrow but fruit flies like a banana. [Marx]

Indeed. That's what the research shows and if someone wishes to say that minor events *will* contribute to blocking, they are really going to have to produce the research evidence to show that. If they can't; its time to admit that and stop saying that they do.

Stratwarms and cold weather
 

On Dec 16, 8:27*pm, Mike McMillan wrote:
On Sunday, 16 December 2012 17:10:32 UTC, Dawlish *wrote:
If you wish me to post the same papers again that I've linked to before, explaining SSW's *and their effects on surface conditions in more detail, to help you, I'm willing to do so. They are easily researched.

Dear Dave,

To lose Will on here would mean the demise of "on the edge" knowledgeable warnings and discussions. I always take a squint at Darren Prescotts excellent 7 day summary of the charts. There are other retired meteorologists on here who pop by with their input. I am still trying to fathom the earthquake/weather connection with weatherlawyers ramblings (often to himself it seems), but worth a read.

***

Posting this with Windows 7 so I apologise for the crap interface.


How can I be writing to myself if you are reading them?
DO WAKE UP IN THE BACK, THERE!

The fact is I have a Fred Hoyle perspective on modern science.

It doesn't help that I am math blind. But like a colour blind soldier,
I have less chance of getting fooled by camouflage when I am looking
for trouble.

Stratwarms and cold weather
 

A current warming event is occurring across N America and westwards across
the other side of the globe. The changing pattern has led to a move of the
polar vortex (eg at 50hPa) from NE Canada to N Russia about 120 Deg E . The
resulting change over Europe from a W/SW stratospheric flow to a NW flow may
well be implicated in a decline of the Russia area of high pressure. The
reduced or reversed westerly over the USA may be helping with the forecast
block over USA and a colder weather type there.

Could this event also be partially responsible for some of the 1 month and
3 monthly forecast output jumping from a cold to less cold types in output
issued after about 2 Dec depending on the inclusion of stratospheric levels
in the models ?

As far as cold over UK - there is a hint from KMA for an increased incidence
of easterlies (possibly cyclonic) for a week 13th -20 th Jan - KMA got the
change to the cyclonic SW/W type over the UK in December. CFS2 also the last
week UKMO monthly also hint a some temporary ? changes around this time.
Would not bet on this being correct though.

Stratwarms and cold weather
 

On Monday, 17 December 2012 18:08:06 UTC, Weatherlawyer



How can I be writing to myself if you are reading them?

DO WAKE UP IN THE BACK, THERE!

SORRY SIR (I do read them ,onest)



The fact is I have a Fred Hoyle perspective on modern science.



It doesn't help that I am math blind. But like a colour blind soldier,

I have less chance of getting fooled by camouflage when I am looking

for trouble.

Stratwarms and cold weather
 

"Mike.Trigger" wrote in message
...
A current warming event is occurring across N America and westwards across
the other side of the globe. The changing pattern has led to a move of the
polar vortex (eg at 50hPa) from NE Canada to N Russia about 120 Deg E . The
resulting change over Europe from a W/SW stratospheric flow to a NW flow
may well be implicated in a decline of the Russia area of high pressure.
The reduced or reversed westerly over the USA may be helping with the
forecast block over USA and a colder weather type there.

Could this event also be partially responsible for some of the 1 month
and 3 monthly forecast output jumping from a cold to less cold types in
output issued after about 2 Dec depending on the inclusion of
stratospheric levels in the models ?

As far as cold over UK - there is a hint from KMA for an increased
incidence of easterlies (possibly cyclonic) for a week 13th -20 th Jan -
KMA got the change to the cyclonic SW/W type over the UK in December. CFS2
also the last week UKMO monthly also hint a some temporary ? changes
around this time. Would not bet on this being correct though.


Hi Mike, very interesting. I notice that in the fag end of the DT 12Z ECM
run it has a deepening low moving SW from Novoya Zemyla and the Russian high
collapses, presumably in response. Models are not consistent with detail at
shorter range and that may be due to big changes in the stratosphere.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Stratwarms and cold weather
 

On Monday, December 17, 2012 6:36:09 PM UTC, Mike.Trigger wrote:
A current warming event is occurring across N America and westwards across

the other side of the globe. The changing pattern has led to a move of the

polar vortex (eg at 50hPa) from NE Canada to N Russia about 120 Deg E . The

resulting change over Europe from a W/SW stratospheric flow to a NW flow may

well be implicated in a decline of the Russia area of high pressure. The

reduced or reversed westerly over the USA may be helping with the forecast

block over USA and a colder weather type there.



Could this event also be partially responsible for some of the 1 month and

3 monthly forecast output jumping from a cold to less cold types in output

issued after about 2 Dec depending on the inclusion of stratospheric levels

in the models ?



As far as cold over UK - there is a hint from KMA for an increased incidence

of easterlies (possibly cyclonic) for a week 13th -20 th Jan - KMA got the

change to the cyclonic SW/W type over the UK in December. CFS2 also the last

week UKMO monthly also hint a some temporary ? changes around this time.

Would not bet on this being correct though.

I'm interested. Would you post a link to where you've found the information in your first paragraph.