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Offline Global Warming  
#1 Posted : 29 December 2018 22:11:53(UTC)
Global Warming

Rank: Advanced Member

Joined: 07/10/2006(UTC)
Posts: 6,714
United Kingdom
Location: Chineham, Basingstoke

This thread is for all comments, discussion and analysis of temperatures in the UK during January, with particular emphasis on the Central England Temperature (CET), for the simple reason that it is the longest running temperature series in the world with over 360 years of data. But you can comment on any interesting temperature statistics or data from across the UK, including your own back yard.


This month the big question is will we see an impact in the UK from the Sudden Stratospheric Warming? If we do it may not arrive until mid month. So it could be a month of two halves temperature wise. That said it looks like high pressure may dominate the early part of the month which could also bring cold conditions to some. The closing days of December are seeing high pressure but a cloudy high with winds from the SW or W so relatively mild. Predicting temperatures in the winter under high pressure can be very challenging as the position of the high and the amount of cloud that gets trapped in it is critical. Don't rely on 850hPa temperatures to predict surface conditions as inversions are common under high pressure at this time of year.


To make things a little more fun we also run a competition in this thread throughout the year. This is by no means the only focus of the thread and you don't need to participate in the competition to post here. But it is a bit of fun which many of us enjoy.


The competition is run on a monthly basis and you can participate in just one or two or all of the months. For those who do take part throughout the year there is an annual competition which runs alongside the monthly competition. Full details below.


For those taking part in the competition all CET predictions for January should be sent directly to me via the forum private message system. Do not post them directly into the thread. You can also send me predictions for the average CET for 2019 as a whole if you wish.


The deadline for predictions this month is 2359 on Wednesday evening (2 January). 


To keep things simple there will be no late submission penalty system as such going forward (I haven't actually applied any penalties for the past couple of years). The hard deadline for submissions will be the second of the month every month but you can make your prediction at any time before that. You can adjust your prediction once only each month prior to the deadline. Entries after 2359 on the 2nd of the month will only be accepted at my discretion if I consider there is a reasonable excuse.


Here is a reminder of how the CET competitions work for the benefit of everyone but also anyone who would like to join in for the first time. All are welcome to participate.


How do the competitions work?


Each month a new thread is opened a few days in advance of the start of a new month. Your challenge is to predict the mean Central England Temperature (CET) for the following month. The CET is the longest running temperature series and goes back to the mid 1600's. Each month I post some statistics about the CET for that month in recent years as well as a summary of some of the latest model output and long range forecasts to provide some context to assist you in making your prediction.


Predictions can be made either to one or two decimals (the actual data is published to two decimals). The closest person or persons to the final figure at the end of the month are declared the winner for that month. There are no prizes. This competition is just a bit of fun and the chance to amaze your fellow posters with your skill and foresight in predicting the weather (or you can just make a random guess!).


We use the Hadley data for the purposes of this competition which is maintained by the Met Office. Provisional figures are published daily with a final adjusted number usually issued on the first day of the following month.


In addition to the monthly competition there is an annual competition which runs throughout the year. The annual competition keeps a running total of the cumulative prediction errors from each month for each person. Absolute differences are used so it makes no difference if you overpredict or underpredict the CET in any given month. At the end of the year the person with the lowest cumulative prediction error after totalling each of the 12 months is declared the winner for the year. This is always a hard fought contest and requires a consistency of good predictions in order to win.


Summary of important points


- Predictions can be made up to 23:59 on the 2nd day of the month to which the prediction relates. No entries will generally be accepted after this time unless I am late in opening up the thread.


- All predictions should be made by private message to me. 


- Once you have sent your prediction you are only permitted to change it once prior to the deadline. Any subsequent amendments will be ignored. 


- You may make a prediction to either one or two decimals. You can predict the same figure as someone else.


- Where two members have the same cumulative prediction error for the year at the end of any month, the order of ranking in the competition table will be determined by which person has had the closest prediction to the actual CET in any month. If there is a still a tie I then look to the second closest prediction for each person and so on until the tie is broken. If the tie cannot be broken (very unlikely by December but can happen in the first couple of months of the year) then each person impacted is awarded the same position in the table.


Missed predictions


If a person participating in the annual CET competition does not make a prediction in any one month (including January) their prediction error for that month will be calculated as follows:


- the upper quartile (75th percentile) of the prediction errors of all the people in the annual competition who did make a prediction for that month will be calculated at the end of the month;


The result of the above calculation will be used as the CET prediction error for any person who misses a prediction in a particular month subject to one further point:


- If, for any person, their average monthly prediction error for all the previous months in the year to date is higher than the 75th percentile of errors (for those that did make a prediction) in the month the person in question made no prediction, then the average prediction error will be substituted instead of the 75th percentile figure. This override is only likely to apply to those people towards the foot of the table who have very made very large errors in previous months.


One final important point. If you want to be included in the year long competition you may not miss more than two predictions during a calendar year. If a third prediction is missed that person will be eliminated from the annual competition (otherwise it would mean 25% or more of the annual error being calculated on non-existent predictions which would reduce the credibility of the competition too much). However, that person can continue to make predictions for the purpose of the monthly competition.


Now on to some data for January:


Historic CET summary for January


1971-2000 4.2C (30 years)


1981-2010 4.4C (30 years)


1999-2018 4.7C (last 20 years)


We have not had a cold January since 2013 and that was only 0.7C below the 1971-2000 mean. There have been three years above 5C recently - 2014, 2016 and 2018. Last very cold January was 2010 with 1.4C.


Here is a chart of the January CET for all years since 1961:


Direct link to larger version of the chart CHART



Current model output (at 12z 29 Dec)


GFS (12z) - most ENS members suggesting generally above average 850 conditions for the first week of Jan apart from a dip on the 2nd. After that a bit of a spaghetti mess.


http://www.wetterzentrale.de/de/show_diagrams.php?model=gfs&var=2&geoid=49069&lid=ENS&bw=


GEM (12z) - similar to GFS


http://www.wetterzentrale.de/de/show_diagrams.php?model=gem&var=2&geoid=49069&lid=ENS&bw=


Multi Op - fairly good agreement from all the models


http://www.wetterzentrale.de/de/show_diagrams.php?model=multi&var=2&geoid=49069&lid=OP&bw=


The ECM ENS T2m temperatures for De Bilt look very consistent and mild for the first 2 weeks of Jan


http://cdn.knmi.nl/knmi/map/page/weer/waarschuwingen_verwachtingen/ensemble/detail/ensemble-verwachtingen-detail10.png


Met Office contingency planners outlook 


Temperature Summary


A higher than average probability of colder conditions 


Temperature analogues


If we look at years with Nov CET close to 8C and Dec CET close to 7C we have the following matches:


2006 and 1953. Not surprising as very few Decembers close to 7C. Early 2007 was very mild while early 1954 was very cold. So no pattern there.


Widening the net to all years since 1950 with generally warm Novembers and Decembers we can add the following years to the mix:


1983, 1986, 1994, 1997, 2003, 2011, 2015


Apart from early 1987 (cold) and 1984 (cool) all of these years had a mild or very mild Jan / Feb following them.


So based purely on Nov / Dec temps the past would indicate that we could be in for a mild rest of the winter. But of course it is not as simple as that. Looking at broader conditions and I have said elsewhere, 1953 is currently an excellent match for 2018. That year saw conditions turn very cold in early 1954.


First look at January temperature tracker



Edited by moderator 02 March 2019 11:11:05(UTC)  | Reason: Not specified

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Offline Whether Idle  
#2 Posted : 30 December 2018 16:53:33(UTC)
Whether Idle

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Joined: 03/09/2006(UTC)
Posts: 9,191
Man
Location: Dover

Thanks GW for this thorough explanation of the nature and rules of this competition. I hope we see many lurkers and posters having a go this year.
Dover, 5m asl. Half a mile from the south coast.
Online Bolty  
#3 Posted : 30 December 2018 21:49:26(UTC)
Bolty

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Location: Blackrod, near Chorley, Lancs - alt: 156m

January isn't really looking like the Siberian Express that certain people were spouting just a week ago. In fact, now it looks like its going to be nothing special.

My guess is for quite an anticyclonic month with high pressure drifting around the UK. On some occasions it may sit over Europe, keeping the UK fairly mild, before allowing the odd "toppler" through to give a colder few days. CET-wise, I'm going for near average.

Edited by user 30 December 2018 21:54:46(UTC)  | Reason: Not specified

Scott
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Offline Caz  
#4 Posted : 31 December 2018 09:35:08(UTC)
Caz

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Joined: 28/10/2008(UTC)
Posts: 23,908
Woman
United Kingdom
Location: Market Warsop, Nottinghamshire, East Midlands

Thank you for the very comprehensive explanation of the competition GW!  Perhaps we should link every new month to this one, so the rules are always to hand for anyone new to read!  


Good luck everyone!  

Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition. Discuss monthly temperatures and records.CET competition
Offline Bertwhistle  
#5 Posted : 31 December 2018 09:57:06(UTC)
Bertwhistle

Rank: Advanced Member

Joined: 20/11/2015(UTC)
Posts: 6,868
Location: Central Southern England

Originally Posted by: Caz Go to Quoted Post


Thank you for the very comprehensive explanation of the competition GW!  Perhaps we should link every new month to this one, so the rules are always to hand for anyone new to read!  


Good luck everyone!  



And great advertising on the MOD Caz! I nearly echoed your marketing but following Brian's suggestion of deleting accounts on Boxing Day, I was too scared to post off topic!


GW- can I PM you a January and whole-year one together?


Cheers.


Edit: apols; just read your intro post again Simon.

Edited by user 31 December 2018 09:58:45(UTC)  | Reason: Not specified

Bertie, Itchen Valley.
August 2020: best heatwave since '95
Offline Caz  
#6 Posted : 31 December 2018 13:08:39(UTC)
Caz

Rank: Advanced Member

Joined: 28/10/2008(UTC)
Posts: 23,908
Woman
United Kingdom
Location: Market Warsop, Nottinghamshire, East Midlands

Originally Posted by: Bertwhistle Go to Quoted Post


 


And great advertising on the MOD Caz! I nearly echoed your marketing but following Brian's suggestion of deleting accounts on Boxing Day, I was too scared to post off topic!


GW- can I PM you a January and whole-year one together?


Cheers.


Edit: apols; just read your intro post again Simon.


 I didn’t think about getting my account deleted!  I intend posting again on the MOD but I’ll add a disclaimer next time!  Watch that space!  

Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition. Discuss monthly temperatures and records.CET competition
Offline johncs2016  
#7 Posted : 31 December 2018 13:20:53(UTC)
johncs2016

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Joined: 13/06/2016(UTC)
Posts: 8,657
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Location: The NW of Edinburgh

Originally Posted by: Caz Go to Quoted Post


Thank you for the very comprehensive explanation of the competition GW!  Perhaps we should link every new month to this one, so the rules are always to hand for anyone new to read!  


Good luck everyone!  



I have noticed that you have linked to that in your signature as well, which is a very good idea since this will now direct people to there from wherever you have posted on this forum (or other forums on this site such as the FA forum) even from locations such as one of your early morning posts in the daily CC threads.


That is something which I will probably soon get around to doing myself, since it is probably time to give my own signature a bit of a sprucing up for the New Year as just about everyone should know by now, where my three local stations here in Edinburgh are located.


EDIT


I'm sure that Brian wouldn't have deleted your account anyway even if you had posted something on the MOD thread which is off-topic, as long as you have stated quite a good reason there for doing so.


 


 

Edited by user 31 December 2018 13:24:31(UTC)  | Reason: Not specified

The north of Edinburgh, usually always missing out on snow events which occur not just within the rest of Scotland or the UK, but also within the rest of Edinburgh.
Offline Caz  
#8 Posted : 31 December 2018 14:26:31(UTC)
Caz

Rank: Advanced Member

Joined: 28/10/2008(UTC)
Posts: 23,908
Woman
United Kingdom
Location: Market Warsop, Nottinghamshire, East Midlands

Originally Posted by: johncs2016 Go to Quoted Post


 


I have noticed that you have linked to that in your signature as well, which is a very good idea since this will now direct people to there from wherever you have posted on this forum (or other forums on this site such as the FA forum) even from locations such as one of your early morning posts in the daily CC threads.


That is something which I will probably soon get around to doing myself, since it is probably time to give my own signature a bit of a sprucing up for the New Year as just about everyone should know by now, where my three local stations here in Edinburgh are located.


EDIT


I'm sure that Brian wouldn't have deleted your account anyway even if you had posted something on the MOD thread which is off-topic, as long as you have stated quite a good reason there for doing so.


 


 


Thanks for the reassurance and vote of confidence John!  I think Everyone, including Brian, knows my intentions are generally well meant!  

Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition. Discuss monthly temperatures and records.CET competition
Offline Stormchaser  
#9 Posted : 31 December 2018 14:58:23(UTC)
Stormchaser

Rank: Advanced Member

Joined: 24/10/2008(UTC)
Posts: 12,076
Man
Location: West Hants

The major determining factor for how the 2nd half of this month pans out will be the propagation rate of the MJO across the Pacific Ocean.


You see, not only does this encourage colder weather patterns for us by itself, but it also drives strong poleward ridging in the right place for 'lending a hand' to an anomalous ridge that will be in place above the N. Atlantic during at least the first half of Jan. In doing so, it may provide a means for connecting an east-based -ve NAO pattern in the troposphere to one in the stratosphere, locking in a prolonged period of anomalously cold conditions across the UK.


BUT


This interaction is dependant on whether the MJO propagates quickly enough across to phases 7-8-1; if it's too slow, the stratospheric ridge will have declined too far by the time the MJO forcing makes itself known from below; the Canadian vortex will be on its way across to merge with the Siberian one and it will be hard to stop once it builds up some inertia.



This brings me around to a serious problem that's been plaguing long-range forecast efforts in recent months; the tropical cycles haven't been behaving as would usually be expected for the El Nino base state, despite the ocean SST anomalies having a clear El Nino configuration. 


The latest cycle is proving to be one of the most unusual of all; it achieved exceptional amplitude and slow propagation speed across the Maritime Continent during the 2nd half of Dec, well beyond (or rather below, speed-wise) the expectations of most, perhaps even all experts in the field. This has allowed ridging to centre itself over or just south of the UK rather than a little to the W or NW as was the general consensus expectation based on a low amplitude MJO heading swiftly into the Pacific.


Having already been very unlucky with the cut-off trough positioning during the mid-month blocked interlude (it stopped the high from taking on a much better orientation for bringing properly cold air across the UK), this was a harsh follow-up kick to the nether regions for those seeking wintry conditions arriving within the first half of the winter season.


This odd MJO behaviour appears linked to climate change and an expansion of the Hadley Cell. There may also be an extra contribution from a strong stratospheric warming event in the S. Hemisphere for the current cycle, increasing the deviation from norm.


 


So now there's this huge conundrum at large; will the tropical cycle continue to be so much slower than would normally be expected that it will miss the boat, so to speak, leaving us looking to tropical forcing alone which would likely mean the rest of winter seeing a few 'waves' of cold rather than something sustained?


One could simply anticipate a continuation of recent trends due to climate change and the S. Hem stratospheric warming, but there's only so much that the MJO movement can physically be slowed while it's active; something's got to give. 


 


As fascinating as the processes at play are, it's a dark time for long-range weather guidance efforts. Anyone trying to estimate the CET using scientific methods, I wish you the best of luck! I'm just going to go with 'the feeling in my bones' or whatever. Trying to do otherwise has only led to frustration, although it did go surprisingly well March-July last year. There's still hope, if these climate change influences can be factored in more reliably.


Best wishes to you all in the year of 2019 .

If you have any problems or queries relating to TWO you can Email twomoderationteam@gmail.com :)
Homeland: Rural Mid-West Hants nearly 10 miles S of Salisbury (near Fordingbridge). More insights: https://twitter.com/peacockreports
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Offline Caz  
#10 Posted : 01 January 2019 07:56:48(UTC)
Caz

Rank: Advanced Member

Joined: 28/10/2008(UTC)
Posts: 23,908
Woman
United Kingdom
Location: Market Warsop, Nottinghamshire, East Midlands

A very Happy New Year to all CET predictors and guessers!  


Let’s hope the 2019 weather is as interesting as last year and the competition as exciting! 

Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition. Discuss monthly temperatures and records.CET competition
Offline Gusty  
#11 Posted : 01 January 2019 10:27:33(UTC)
Gusty

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Location: Folkestone

Happy New Year all 

Steve - Folkestone, Kent
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Offline ARTzeman  
#12 Posted : 02 January 2019 13:09:05(UTC)
ARTzeman

Rank: Advanced Member

Joined: 14/07/2012(UTC)
Posts: 30,212
Man
Location: Peasedown St John. N.E. Sommerset

Met Office Hadley         8.0c.      Anomaly      4.4c. Provisional to 1st.


Metcheck                      5.51c     Anomaly      1.34c


Netweather                   7.72c     Anomaly      3.53c


Bordon                         4.1c       Anomaly      -2.96c


Darwen                        4.0c       Anomaly      -1.22c


Forest Town Mansfield   7.3c       Anomaly       2.8c


Peasedown St John       9.1c      Anomaly        3.39c.


 


Mean of my 10 watched stations 6.56c. Anomaly 1.05c.              



Some people walk in the rain.
Others just get wet.
I Just Blow my horn or trumpet
Offline Bertwhistle  
#13 Posted : 02 January 2019 19:20:32(UTC)
Bertwhistle

Rank: Advanced Member

Joined: 20/11/2015(UTC)
Posts: 6,868
Location: Central Southern England

The MOD thread is definitely the place to market this thread. 28 members viewing at the mo'.

Bertie, Itchen Valley.
August 2020: best heatwave since '95
Offline Bertwhistle  
#14 Posted : 02 January 2019 19:28:51(UTC)
Bertwhistle

Rank: Advanced Member

Joined: 20/11/2015(UTC)
Posts: 6,868
Location: Central Southern England

Originally Posted by: Stormchaser Go to Quoted Post


The major determining factor for how the 2nd half of this month pans out will be the propagation rate of the MJO across the Pacific Ocean.


You see, not only does this encourage colder weather patterns for us by itself, but it also drives strong poleward ridging in the right place for 'lending a hand' to an anomalous ridge that will be in place above the N. Atlantic during at least the first half of Jan. In doing so, it may provide a means for connecting an east-based -ve NAO pattern in the troposphere to one in the stratosphere, locking in a prolonged period of anomalously cold conditions across the UK.


BUT


This interaction is dependant on whether the MJO propagates quickly enough across to phases 7-8-1; if it's too slow, the stratospheric ridge will have declined too far by the time the MJO forcing makes itself known from below; the Canadian vortex will be on its way across to merge with the Siberian one and it will be hard to stop once it builds up some inertia.



This brings me around to a serious problem that's been plaguing long-range forecast efforts in recent months; the tropical cycles haven't been behaving as would usually be expected for the El Nino base state, despite the ocean SST anomalies having a clear El Nino configuration. 


The latest cycle is proving to be one of the most unusual of all; it achieved exceptional amplitude and slow propagation speed across the Maritime Continent during the 2nd half of Dec, well beyond (or rather below, speed-wise) the expectations of most, perhaps even all experts in the field. This has allowed ridging to centre itself over or just south of the UK rather than a little to the W or NW as was the general consensus expectation based on a low amplitude MJO heading swiftly into the Pacific.


Having already been very unlucky with the cut-off trough positioning during the mid-month blocked interlude (it stopped the high from taking on a much better orientation for bringing properly cold air across the UK), this was a harsh follow-up kick to the nether regions for those seeking wintry conditions arriving within the first half of the winter season.


This odd MJO behaviour appears linked to climate change and an expansion of the Hadley Cell. There may also be an extra contribution from a strong stratospheric warming event in the S. Hemisphere for the current cycle, increasing the deviation from norm.


 


So now there's this huge conundrum at large; will the tropical cycle continue to be so much slower than would normally be expected that it will miss the boat, so to speak, leaving us looking to tropical forcing alone which would likely mean the rest of winter seeing a few 'waves' of cold rather than something sustained?


One could simply anticipate a continuation of recent trends due to climate change and the S. Hem stratospheric warming, but there's only so much that the MJO movement can physically be slowed while it's active; something's got to give. 


 


As fascinating as the processes at play are, it's a dark time for long-range weather guidance efforts. Anyone trying to estimate the CET using scientific methods, I wish you the best of luck! I'm just going to go with 'the feeling in my bones' or whatever. Trying to do otherwise has only led to frustration, although it did go surprisingly well March-July last year. There's still hope, if these climate change influences can be factored in more reliably.


Best wishes to you all in the year of 2019 .



Best wishes to you to SC- Happy New Year and thanks for your ongoing insights.


I am particularly interested in the bit in your first paragraph where you talked about a trop-strat. connection of -ve NAO patterns. Can you elucidate how this could create prolonged anomalous cold hereabouts- is that like strat-trop propagation of the SSW effects?

Bertie, Itchen Valley.
August 2020: best heatwave since '95
Offline Caz  
#15 Posted : 02 January 2019 19:38:40(UTC)
Caz

Rank: Advanced Member

Joined: 28/10/2008(UTC)
Posts: 23,908
Woman
United Kingdom
Location: Market Warsop, Nottinghamshire, East Midlands

Originally Posted by: Bertwhistle Go to Quoted Post


The MOD thread is definitely the place to market this thread. 28 members viewing at the mo'.


  Done it!  

Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition. Discuss monthly temperatures and records.CET competition
Offline Caz  
#16 Posted : 02 January 2019 19:42:00(UTC)
Caz

Rank: Advanced Member

Joined: 28/10/2008(UTC)
Posts: 23,908
Woman
United Kingdom
Location: Market Warsop, Nottinghamshire, East Midlands

Originally Posted by: ARTzeman Go to Quoted Post


Met Office Hadley         8.0c.      Anomaly      4.4c. Provisional to 1st.


Metcheck                      5.51c     Anomaly      1.34c


Netweather                   7.72c     Anomaly      3.53c


Bordon                         4.1c       Anomaly      -2.96c


Darwen                        4.0c       Anomaly      -1.22c


Forest Town Mansfield   7.3c       Anomaly       2.8c


Peasedown St John       9.1c      Anomaly        3.39c.


 


Mean of my 10 watched stations 6.56c. Anomaly 1.05c.              


Thank you Art!  I look forward to your daily updates. You’re another great contributor to this thread who deserves credit!  

Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition. Discuss monthly temperatures and records.CET competition
Offline Bertwhistle  
#17 Posted : 02 January 2019 20:25:52(UTC)
Bertwhistle

Rank: Advanced Member

Joined: 20/11/2015(UTC)
Posts: 6,868
Location: Central Southern England

Originally Posted by: Caz Go to Quoted Post


Thank you Art!  I look forward to your daily updates. You’re another great contributor to this thread who deserves credit!  



Agreed- although I don't post that often Art, love to compare the different stations you collect the data from.


Back to the big issue, I can't wait to see the prediction spread for January- I think I've done a Dev this month and hedged for a safe medial guess. Too much variability in the models.


 

Edited by user 02 January 2019 20:28:08(UTC)  | Reason: Not specified

Bertie, Itchen Valley.
August 2020: best heatwave since '95
Offline Stormchaser  
#18 Posted : 02 January 2019 20:58:19(UTC)
Stormchaser

Rank: Advanced Member

Joined: 24/10/2008(UTC)
Posts: 12,076
Man
Location: West Hants

Originally Posted by: Bertwhistle Go to Quoted Post


Best wishes to you to SC- Happy New Year and thanks for your ongoing insights.


I am particularly interested in the bit in your first paragraph where you talked about a trop-strat. connection of -ve NAO patterns. Can you elucidate how this could create prolonged anomalous cold hereabouts- is that like strat-trop propagation of the SSW effects?



Thanks Bertie 


The idea is that we should have a stratospheric setup featuring a vortex over Canada and a vortex over Siberia with a ridge over the N. Atlantic for mid-month, at which point the movement of an active MJO looks to encourage ridges to build well north across the N. Atlantic in the troposphere. In theory, these two can align and reinforce one another, locking in a negative NAO pattern for an extended period.


 


Things rarely plan out so cleanly, though. Case in point - since my last post, it's become clear that the split of the vortex won't initially place the residual vortexes far enough apart to be of much use to us; one will be over the far-western N. Atlantic instead of Canada. However, between approx. 10th and 14th Jan, the lagged effect of the current MJO movement across the W. Pacific (troposphere-stratosphere wave breaking) looks likely to make itself known in the lower and mid-stratosphere, serving to widen the split and shift that N. Atlantic vortex west across N. America.


This is the 'lending a hand to an anomalous ridge that will be in place above the N. Atlantic' that I mentioned in that earlier post.


 


Obs data suggests things are progressing nicely toward a mid-month change, but EPS keep killing off the MJO unreasonably quickly, leading to a longer struggle to get the vortex split to do much of use for us, and this has been enough for the Met Office to lose confidence in a mid-month change despite the obs being contradictory.


It serves to add even more uncertainty to this month's CET estimates - and it's not like the coming 10 days are all that clear to begin with; ECM's a fair bit colder than GFS this evening! 

If you have any problems or queries relating to TWO you can Email twomoderationteam@gmail.com :)
Homeland: Rural Mid-West Hants nearly 10 miles S of Salisbury (near Fordingbridge). More insights: https://twitter.com/peacockreports
2021's Homeland Extremes:
T-Max: 30.4°C 21st Jul | T-Min: -6.8°C New Years Day! | Wettest Day: 34.1mm 2nd Oct | Ice Days: 2 (27th Jan & 8th Feb)
Keep Calm and Forecast On
Offline Bertwhistle  
#19 Posted : 02 January 2019 21:38:56(UTC)
Bertwhistle

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Originally Posted by: Stormchaser Go to Quoted Post


 


Thanks Bertie 


The idea is that we should have a stratospheric setup featuring a vortex over Canada and a vortex over Siberia with a ridge over the N. Atlantic for mid-month, at which point the movement of an active MJO looks to encourage ridges to build well north across the N. Atlantic in the troposphere. In theory, these two can align and reinforce one another, locking in a negative NAO pattern for an extended period.


 


Things rarely plan out so cleanly, though. Case in point - since my last post, it's become clear that the split of the vortex won't initially place the residual vortexes far enough apart to be of much use to us; one will be over the far-western N. Atlantic instead of Canada. However, between approx. 10th and 14th Jan, the lagged effect of the current MJO movement across the W. Pacific (troposphere-stratosphere wave breaking) looks likely to make itself known in the lower and mid-stratosphere, serving to widen the split and shift that N. Atlantic vortex west across N. America.


This is the 'lending a hand to an anomalous ridge that will be in place above the N. Atlantic' that I mentioned in that earlier post.


 


Obs data suggests things are progressing nicely toward a mid-month change, but EPS keep killing off the MJO unreasonably quickly, leading to a longer struggle to get the vortex split to do much of use for us, and this has been enough for the Met Office to lose confidence in a mid-month change despite the obs being contradictory.


It serves to add even more uncertainty to this month's CET estimates - and it's not like the coming 10 days are all that clear to begin with; ECM's a fair bit colder than GFS this evening! 



Thanks SC; the trop-strat wave breaking- is that linked to Rossby waves?

Bertie, Itchen Valley.
August 2020: best heatwave since '95
Offline Global Warming  
#20 Posted : 02 January 2019 22:09:42(UTC)
Global Warming

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Location: Chineham, Basingstoke

I have 48 CET predictions so far for January. Just under 2 hours to go before the deadline. Hopefully we can make it over 50.

Chineham, Basingstoke, Hampshire, 89m asl
Live weather data: https://www.weatherlink....2-4760-be27-6cc9a5a1fc4c
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