Possibility of a nice little cold snap middle of next week perhaps, may as well make the most of the scraps that comes our way I suppose.

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Crikey, I hadn’t looked at the models for a couple of days, then just loaded up the GEFS spaghetti plot and thought I must be looking at a cached one from a couple of weeks ago. Where did all those colder runs come from? I thought we were locked into mildness until mid Jan at least.

That only serves to further hlighlight the volatility in the output there has been recently and continues to be in the model output, Rob.

The one almost constant theme of much of the output this month is that FI has tended to start at a rather early stage, and that still seems to be the case just now. It seems that virtually nothing can be ruled in or out at the moment for the period after the end of the festive season.

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That only serves to further hlighlight the volatility in the output there has been recently and continues to be in the model output, Rob.

The one almost constant theme of much of the output this month is that FI has tended to start at a rather early stage, and that still seems to be the case just now. It seems that virtually nothing can be ruled in or out at the moment for the period after the end of the festive season.

It seems the lessons of the limits of model reliability and the similar limits regarding the ensemble suites might need to be revisited.

It might also be worth puncturing the myth that when the models show an extended mild period they’re invariably right; clearly they’re just as prone to error as any other long-range outlook.

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Couple of tasty perts for next week

 

It seems the lessons of the limits of model reliability and the similar limits regarding the ensemble suites might need to be revisited.

It might also be worth puncturing the myth that when the models show an extended mild period they’re invariably right; clearly they’re just as prone to error as any other long-range outlook.

Good point well made: however, looking at the historic charts for the 60s, 70s and 80s, the one thing that has struck me is that these charts were less volatile than today. That is to say - weather systems seemed to me to move about more slowly. Toppler’s were 2-3 day affairs, and today a toppler seems to come and go in 1 to 1.5 days, just for example... To prove this, there would have to be an awful lot of sampling studies undertaken. It’s just a hypothesis from how it looks to the lay observer.

Obviously, if this theory has any legs (or at least others have observed the same), then any such theory needs to consider the cause of any speeding up of passage of weather systems in our latitude and location. The obvious culprit is the increase of circa 1 degree in global temperature since the 60s. To my eyes - as a life-time weather observer, high pressure systems in winter just do not hang about for as long as they did in those (my formative) 3 decades. - and whilst this is true (to my eye) of Scandi’ highs, it seems true for where ever they are centred. May be this is the reason why ‘the winter easterly wind’ seems to have become such a rare phenomenon. Frosty blocking highs need to settle for the air to get cold enough to become a solid and immovable force - as it became in 1963 and many times in the 60s - up to 1970 and then again in the 80s too, but less so since.

Anyone agree, disagree - or have a comment?

 

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Wx summary - mild for W Europe week 1, but cold air advances from the east week 2. Atlantic coasts and Baltic still above 0C though cooler but C Europe back to freezing (just) and the Scottish highlands also get their 'blob of blue'. Pptn broadly across Europe week1 retreats to NW Atlantic week 2 so drier than yesterday.

Jet across the N of UK to Sat 1st, then to the S for a few days, after which loops keep changing the direction for the UK but with trend to come from N/NW after Sat 8th

GFS op shows LP on Atlantic and HP over France giving mild SW-lies to Sat 1st before LP moves to the N and then NE of UK with brief N-ly spell from Tue 4th. HP cell then moves E-ward across UK 1035mb Fri 7th, pushed out of the way by LP from NW 975mb Orkney Wed 12th with air from NW/N to end of run Fri 14th

GEFS v mild dropping sharply back to norm Mon 3rd and mean staying there to Fri 14th though op & control suggesting something cooler around Thu 6th and again at end. Dry spells now and around 6th , small amounts at other times in S; Scotland and N England rather different with wet spell now and damp most of the time afterwards - dividing line somewhere around Liverpool - Leeds. Snow row figures rising for Inverness

ECM similar to GFS but the HP cell moves through more quickly and cold air looks poised to come S Sat 8th

 

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Good point well made: however, looking at the historic charts for the 60s, 70s and 80s, the one thing that has struck me is that these charts were less volatile than today. That is to say - weather systems seemed to me to move about more slowly. Toppler’s were 2-3 day affairs, and today a toppler seems to come and go in 1 to 1.5 days, just for example... To prove this, there would have to be an awful lot of sampling studies undertaken. It’s just a hypothesis from how it looks to the lay observer. 

Very appropriate for the modern era. Perhaps they should be renamed "Twittlers". 

PS: There were major upstream problems with the GFS/GEFS data sets yesterday. However, things have normalised in the last 12 hours or so and the current plots (on TWO and elsewhere) are valid.

 

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 To my eyes - as a life-time weather observer, high pressure systems in winter just do not hang about for as long as they did in those (my formative) 3 decades. - and whilst this is true (to my eye) of Scandi’ highs, it seems true for where ever they are centred. May be this is the reason why ‘the winter easterly wind’ seems to have become such a rare phenomenon. Frosty blocking highs need to settle for the air to get cold enough to become a solid and immovable force - as it became in 1963 and many times in the 60s - up to 1970 and then again in the 80s too, but less so since.

Anyone agree, disagree - or have a comment?

 

Memory plays tricks in remembering only the more dramatic weather examples but I too would have said that through the 1950s to the 1970s a lasting frosty or foggy high was commonplace in Dec or Jan - not every year, perhaps 1 in 3, but common enough to be expected.

However, there are examples of decade-long shifts in climate without the need to invoke global warming so caution is needed there. I'm thinking of the Dust Bowl in Oklahoma in the 1920s where farmers who had come to rely on regular rainfall were ruined by a decade of drought - and a recent programme on PBS suggested that decadal swings of this type in that area had occurred previously

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2022 "getting in there early" with the first plume of the year (LOL) set for January 1st.  It would not surprise me to see somewhere reach towards the record max.  

https://www.meteociel.fr/modeles/arpege.php?ech=84&mode=16&map=300

 

 

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2022 "getting in there early" with the first plume of the year (LOL) set for January 1st.  It would not surprise me to see somewhere reach towards the record max.  

https://www.meteociel.fr/modeles/arpege.php?ech=84&mode=16&map=300

 

 

And in contrast we seem to be converging on some cross model support for an arctic pulse at +144. The solution varies as usual with some GEFS members looking quite potent. Nothing more of a ‘snap’ at this stage but in line with the ‘current’ thinking of the theme going into January. The UKM text has again undergone subtle changes and is hinting at something more substantial at some point.

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And in contrast we seem to be converging on some cross model support for an arctic pulse at +144. The solution varies as usual with some GEFS members looking quite potent. Nothing more of a ‘snap’ at this stage but in line with the ‘current’ thinking of the theme going into January. The UKM text has again undergone subtle changes and is hinting at something more substantial at some point.

I’ve been keeping an eye on next week and the GFS ensemble suite has trended colder and gradually more and more perturbations have moved towards a colder interlude. As can be seen in the table, there’s a general trend currently for cooler to cold conditions beyond; here’s the London picture of the 00z

https://www.meteociel.fr/modeles/gefs_table.php?ext=1&x=&lat=51.5085&lon=-0.12574&ville=Londres

 

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I'd be surprised if next week's northerly plunge inconveniences those of us in the south too much, although we may need to switch the central heating back on for a day or two. However, it should have more bite in the north but even there I would expect the snow risk to be mainly over high ground. The whole episode is shunted through too quickly for it to be significant to most of the UK population. 

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Good point well made: however, looking at the historic charts for the 60s, 70s and 80s, the one thing that has struck me is that these charts were less volatile than today. That is to say - weather systems seemed to me to move about more slowly. Toppler’s were 2-3 day affairs, and today a toppler seems to come and go in 1 to 1.5 days, just for example... To prove this, there would have to be an awful lot of sampling studies undertaken. It’s just a hypothesis from how it looks to the lay observer. 

 

Agreed, I have had similar thoughts myself.  We talk about the modern winter, maybe we should be using the term 100 mph or express train winter. In the past we used to generate cold snaps purely through air stagnation.  On some occasions these days we see high pressure cells sprinting across the UK as quickly as some of our more mobile depressions do. As you say it would be interesting to hear the scientific view.

On the current models there seems to be a general consensus for what is virtually a trop split around t+144, unfortunately there is an equally strong signal for the vortex to regroup towards our side of the pole very quickly going forward. At present that seems to mark the beginning of a spell òf cool (maybe at times colder?) zonality.

 

I'd be surprised if next week's northerly plunge inconveniences those of us in the south too much, although we may need to switch the central heating back on for a day or two. However, it should have more bite in the north but even there I would expect the snow risk to be mainly over high ground. The whole episode is shunted through too quickly for it to be significant to most of the UK population. 

Thats where my thinking is at, and the short term focus on the abnormal warmth of the next 3 days is capturing my full attention.

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Northerly topplers in the south very rarely give anything than a cold breeze and a couple of hail showers but wil feel seasonal for a day !!

 

It seems the lessons of the limits of model reliability and the similar limits regarding the ensemble suites might need to be revisited.

It might also be worth puncturing the myth that when the models show an extended mild period they’re invariably right; clearly they’re just as prone to error as any other long-range outlook.

Indeed so, Peter.

Much as GFS FI often cannot be taken that seriously for obvious reasons, there have been a couple of occasions this month when it has been correct in picking up on a trend well in advance:

1. It began to pick up in the rise in pressure over Iberia & North Africa in FI about 10 days ago and then stuck fairly solidly with this thems for days afterwards.

      2. Back in early December, it spotted the trend for pressure to build from the south northwards over the UK just after mid-month with the possibility of it moving towards Greenland/Iceland. This also took place and was responsible for the frenzy of excitement there was in this thread for a time a couple of weeks ago.

It was in trying to pin down what was likely to happen from Christmas Day onwards where it seemed to struggle big time, but there again I think all the models struggled in that respect last week.

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Northerly topplers in the south very rarely give anything than a cold breeze and a couple of hail showers but wil feel seasonal for a day !!

Indeed. A common mistake many people make it to overestimate risk of showers in inland areas during the winter months.  

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Interesting 06z thus far.

https://modeles16.meteociel.fr/modeles/gfs/run/gfsnh-0-138.png?6 

A closed high around Iceland from ridging down from the arctic rather than a transitory Atlantic ridge ...possibly!

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Good point well made: however, looking at the historic charts for the 60s, 70s and 80s, the one thing that has struck me is that these charts were less volatile than today. That is to say - weather systems seemed to me to move about more slowly. Toppler’s were 2-3 day affairs, and today a toppler seems to come and go in 1 to 1.5 days, just for example... To prove this, there would have to be an awful lot of sampling studies undertaken. It’s just a hypothesis from how it looks to the lay observer.

Obviously, if this theory has any legs (or at least others have observed the same), then any such theory needs to consider the cause of any speeding up of passage of weather systems in our latitude and location. The obvious culprit is the increase of circa 1 degree in global temperature since the 60s. To my eyes - as a life-time weather observer, high pressure systems in winter just do not hang about for as long as they did in those (my formative) 3 decades. - and whilst this is true (to my eye) of Scandi’ highs, it seems true for where ever they are centred. May be this is the reason why ‘the winter easterly wind’ seems to have become such a rare phenomenon. Frosty blocking highs need to settle for the air to get cold enough to become a solid and immovable force - as it became in 1963 and many times in the 60s - up to 1970 and then again in the 80s too, but less so since.

Anyone agree, disagree - or have a comment?

 

Well, my formative years were around the same time but my take away is systems either seem to move faster or things grind to a halt. We simply never see the classical Norwegian sequence of cold air before a low, a warm sector and then cold NWlies - it just never happens anymore. What are cold NWlies anyway....

Wrt cold easterlies, well often there is no cold air to our east, and even though it is cold over Scandinavia this year sea ice there is barely at normal. We get cold winters from the east when its a cold winter to the east - that hardly ever happens now.

I also see synoptics as a symptom not a cause - because they are being driven by that reality highlighted.

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Indeed. A common mistake many people make it to overestimate risk of showers in inland areas during the winter months.  

In general this is a fair assessment, but as we’ve seen on occasions minor troughs can deliver snow widely even in a 36hr ‘toppler’ set up.

 

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