Isolated Frost

Really? One set of 12zs (all very cold after D4)- provide no snow for much of England and Wales (at least until D6), and it's 'goodbye another week of winter'.

Utter tsk tsk. Complete rubbish.

GFS moves the low into the nation, and the Scandinavian high sinks- optimistic mid-atlantic ridging, plenty of new solutions to come.

I disagree Ian. The 12z's are not 'big'- they will be different again for the 00zs and no matter what the 00z suite does, the 12z tomorrow will be 'big'. Expect many big differences and erratic modelling. Stratospheric modelling shifts the polar high into Greenland whilst maintaining a weak vortex over Hudson Bay and Scandinavia. We'll work from that.

I agree but what we usually see is people saying 'it could easily go wrong' without any charts, or back up for their statements at all. The polar high seems to extend into Greenland in later modelling with Hudson Bay and eastern Scandinavia holding the stratospheric polar vortex. The NOAA 500mb anomaly charts highlight this well- there is also a split forecasted after the original displacement (the secondary warming affecting Siberia, and then Baffin Island and western Greenland. There is much reason to be optimistic. Take the MJO charts signalling movement into a more phase 7 type shape (I don't have the composite on me but it's cracking)- Very exciting times when it comes to the current nwp predictions, with colder air likely to dig in from first a continental source, with the potential for east or north-east winds increasing as we move past d8.

wow!

Okay.. the point in question that a ) is stopping the movement of a seperate PV lobe into Scandinavia b ) stopping the amplified arctic ridge move southward into Iceland and Scandinavia c ) is therefore giving Britain a mean chance of a more S/W flow as the high progresses into central Europe or southern Scandinavia. is this: A small feature generally to the NE of Norway (best spotted at D7 atm), which extends from a low pressure system in the Atlantic, it stops the PV lobe (in purple) from transferring energy into Scandinavia, instead it directs it back into Greenland. The less amplified flow due to the shortwave mean that the jet can then run on top of the high pressure successfully, and build high pressure in Europe. The 06z GEFS isn't all that bad, but includes that crucial feature that it did not include on it's 00z suite. Above is what happens when the low becomes part of the circulation. An amplified polar high, suitable flow for a PV lobe in Scandinavia and a strong chance of Scandinavian or Arctic winds across the UK.

us insomniacs will be bloody pleased with that !!

Definitely

At 192, the GFS ENS has 850 temps of: 18/20 runs with 0c over part of the nation. 4/20 with 0c all over the nation. 8/20 runs with -4c over part of the nation. 1/20 with -4c all over the nation. 2/20 runs with -8c over part of the nation. 0/20 with -8c all over the nation. At 240, the GFS ENS has 850 temps of: 19/20 runs with 0c over part of the nation. 6/20 with 0c all over the nation. 12/20 runs with -4c over part of the nation. 2/20 with -4c all over the nation. 3/20 runs with -8c over part of the nation. 0/20 with -8c all over the nation. At 288, the GFS ENS has 850 temps of: 19/20 runs with 0c over part of the nation. 8/20 with 0c all over the nation. 13/20 runs with -4c over part of the nation. 5/20 with -4c all over the nation. 7/20 runs with -8c over part of the nation. 2/20 with -8c all over the nation. Phew. Hope that helps anyone. You can see the trend for more extreme solutions after D10, but these solutions veer of to the side of cold as temperatures look like going below average again after the upcoming week.

Here's the d11 GFS hemispherical view. 508dm, 532dm, 556dm and 580dm shown (edited on paint, so sorry!) Vortex destroyed, polar high ridging in and disturbing the longwave flow majorly across 70-90N. If you see zonal, I see madness... this looks a very ingrained pattern where we will get reloads whether we hit or miss. Took a while, it's pretty shoddy but I'm distracted by Football Manager... who needs the models when you're transforming an Icelandic second division side into world-beaters?! Mon Por Akureyri!!

The chart shown would indeed be very dry for the UK (very cold though), but the hemispherical pattern is the one to look for at this juncture, and it is looking very interesting.

The vortex has truly been torn apart. D11 and it's on it's knees. No sub 496dm in the northern hemisphere! The details of the run is a strong signal for a large Arctic ridge to dominate, with HP nearby. Retrogression, PV into Scandi, Icelandic High, Scandi High all very much on the table. Exciting times.

It's the energy from the trough in N Norway that is stopping the arctic high from ridging southwards, though it is a superb run

Take him to Siberia's strat... positively balmy!! Suncream and shades at 30,000m!

Run sharpens up and de-zonalises the arctic upper high... look at the energy settling into Scandi- superb start

A little animation about the relative destruction of the vortex (this at 100hpa) A combination of the fantastic NW Extra and some fab paint skills

GP touched on 1979, 1982 and 1987, a lot to note, but also a tad on the extensive warmings, and the relevance in the polar high dynamics for the year below the relevance in the current tropospheric modelling also lies to a certain extent with 1985, an extensive polar high with cold in the UK mid-month.. and the polar vortex goes off on one, record breaker- Sub 492dm in NE US, sub -30c 850s over much of the NE US.. a polar vortex displacement to an incredible extent

Mind my language but FN HELL! !

With the strat warming now beginning to be shown in the latest tropo charts, I was wondering about the effects of the 1-wave, 2-wave pattern and the general effects of Rossby waves. First let us look at the current scenario. (excuse my paint skills!!) note: the line holding the 'purple' is sub 512, the line holding the 'blue' is sub 544, and the line holding the 'green/yellow' is sub 576- everything above that (in red and orange) is over 576dm note2: this is not a complete representation of the tropospherical shape atm- just values at 32dm margins that might show things more easily The current flow shows a surging polar vortex- in a 'C' shape from Siberia, into Canada and out of Greenland- though it is not completely dominant as you can see an upper air polar high extending into the North Pole, with 540dm values.. this disrupts the general flow in the arctic, and the upcoming stratospheric warmings will most likely do more to it note also the polar vortex segment by Newfoundland, though this can disrupt the flow, it is relatively small and intense, giving much of eastern Canada cold weather, though the attention must be paid to the eastern seaboard of the US, zonal as can be. Another note is the little disruption near the UK, that is the subtropical ridge, which is normally positioned at 30N, this will be giving us rather mild weather this upcoming week- if you have a look at the 576dm line across the hemisphere, it is very zonal, and so we have got unlucky (or lucky) with it extending across only in our locale Here is the GFS for d8 (11 Jan)- the polar vortex has been completely taken out by the polar high (see the small green segments and the light blue which is surrounded by the purples and dark blues)- the vortex has one segment over NE Canada, N Russia and N Japan- all of them relatively weak and meridional. The polar high is probably undermined by my drawing as you can see the long light blue ridge across the arctic... this is very positive and the perfect 'block' to begin with note this time the 544dm (anything blue) line, it is very disturbed with a big drop in the mid-west of the USA, a big drop just to the west of the UK, and a big drop across central/eastern Europe- this is what we want to see The 576dm line is nearly completely zonal, but this time the pacific high (part of the subtropical ridge) extends into the west of the US, instead of the UK/w Europe. Here is a superb snapshot of a brilliant pattern.. the polar vortex (sub 512dm in this case) is extremely weak and split around, whilst if you look at the 544dm line, it is completely disturbed around the atlantic/europe- with a huge ridge built in the atlantic from Greenland, and a big drop of sub 544dm air across Europe... it is anything but zonal and the hemispherical pattern is disturbed... here's hoping for a similar scenario from the upcoming strat warming that are disturbing that 500mb pattern already

I was thinking, with indications of a pattern change and high-latitude blocking (with the signal for a Scandinavia/nordic high becoming more prominent before d15), whether they are the holy grail in Scotland and the NE of England, as well as the south-east. I'm pretty young, and wasn't here for the Scandi highs of 1991, and those prior to that- but in recent years, the dominant cold spell 'starter' is the Greenland high, with troughing towards Scandinavia, allowing north to north-easterly flows to dominate. The December 17 - January 12 2009-2010 period gave me 34cm of lying snow at one point, with record low temperatures of -11c. The November 24 - December 7 2010 spell gave me 42cm of lying snow at one point, with new record low temperatures of -12c. The dominance of low pressure towards Scandinavia and Central Europe, with the upper high towards Greenland, ridging south and east towards Iceland and Svalbard, generally gave an unstable arctic continental flow, with heavy snow from the NE. However, the Scandinavian high of February 2012. Gave me a grand total of 1cm of lying snow (though it was extremely cold), whilst those further south-east (more prone to the continental flow, and closer to the upper air cold pool), received over 10cm, and even 15cm. I also recall this: In which it was very cold here, but there was no snow, whilst the south-east (in particular London) was receiving a fair amount of snow. So, I was wondering, does the Scandinavian high deliver for the NE and Scotland? Maybe the instances I have experienced were not 'true' Scandi highs (I mean, the spells shown below show the surface heights peak in the Kola Peninsula and Norway respectively). Are there any major instances of Scandinavian highs delivering similar snow totals or any major snow totals for those further north?

My note was the pattern change was more hemispherical. And in my opinion, no matter how fleeting it may be, a change from +10c uppers to -10c uppers on UK shores is quite notable. Indeed the likelyhood is not for anything large scale in the next 10 days, but the wider picture shows huge hemispherical fluctuations this month.

Interesting picture of the UK on the 15th, and saying we are searching for the elusive pattern change. When this on the 13th shows a very cold easterly flow over the UK. And the 'elusive pattern change' comes in the next 10 days if you look at the hemispherical charts. With warmings down the line that could further interest the situation. Interesting post PE.

Difference between the operationals in the arctic region (tropospherically) is the transported pv segment that travels from Canada into Russia (and then Scandi on the GFS) is based on a meridional polar high- whilst the energy directed eastwards from Baffin Island on the ECM creates an upper trough in which the polar vortex circulates in with, to strengthen the canadian sector vortex- the GFS/EC stratospheric vortex placements (Hudson Bay or Baffin Island) will be vital in the direction of the upcoming weeks as not only does it affect the polar high circulation, but it significantly alters the shape and dynamics of the tropospheric polar vortex's eastern segment (Siberia or Scandinavia)- Note the 544 dm over the North Pole and 492 dm nr Novaya Zemlya- and the extensive upper air ridge into Svalbard.. a very conductive set-up

About sums it up.