stodge

Jo, I'd be really concerned about the Severn Valley looking at those numbers - places like Bewdley and Tewkesbury as the water comes off the North Welsh mountains.

I agree but everyone else seems to think it's the worst run that's ever been produced. Both GEM and JMA are interesting tonight and I don't consider either model rubbish - ECM isn't the be-all and end-all of models though again from some you'd think it was the only one worth looking at. At day 10 it has a much weaker Atlantic and clear signs of amplification to the south. We may or may not have 7-10 days of milder weather but that's far from certain. JMA at T+192 just to cheer up a few of the doom-mongers

Evening all Plenty of attention currently on Storm Christoph and rightly so with more rain falling over many areas again this evening. Looking further ahead, a colder weekend followed by a transition to milder weather early next week before, well, it depends. GFS OP last evening was relentlessly mild but other models were showing a change in the pattern to perhaps something more settled as height rises over Scandinavia started to manifest at the beginning of next month. Let's see where this evening's offerings take this - will it be the finest cut for cold fans or scrag end? 12Z GEM: T+120 takes us to next Monday (25th January). The remnants of Christoph are over southern Norway as part of a complex trough extending into south-eastern Europe and western Scandinavia. A ridge of HP approaches from the south west heralding the arrival of milder air with a large LP in mid-Atlantic and heights over the Canaries. 850s between -4 and -8 over the British Isles at this time. The evolution from there to T+180 is more complex than seemed likely yesterday. The energy from the Atlantic trough forms a small LP over the north of Ireland but that slides SE and the next push of energy also disrupts as heights build from the north toward the Faeroes. The LP elongates in the Atlantic with a shallow residual trough to the east and a more significant LP over the Aegean. Milder air has pushed in to southern and western Britain but has stalled across central parts with colder air to the north and east as a SE'ly flow develops in the west and calmer conditions elsewhere. From there, a real stand-off develops. The Atlantic trough continues to disrupt SE while heights develop to the north of the Faeroes with a weak ridge through the north and east of the British Isles. A frigid air mass to the north east over Scandinavia is inching closer with embedded troughs. The 850s reflect a steep temperature gradient with +4 uppers in the far south west and -8 uppers in the north and east. GEM ends with a real battleground and the evolution from there is anybody's guess. 12Z GFS OP - by far the mildest of the output yesterday. At T+120 the remnants of Christoph are closer than was the case on GEM stretching from the Faeroes to the northern North Sea and then down to the Balkans. The ridge is already into southern and western parts with milder air coming. Heights persist over Greenland and the Canaries. Uppers of -4 to -8 across the British Isles at this time. From there, the evolution gets quite complex - the Atlantic trough phases with the residual trough to the north and east and creates a complex elongated feature in which secondary LP run west to east across southern Britain. By T+180, the trough runs from mid-Atlantic to the Norwegian Sea and across Scandinavia with heights to the south. A mild SW'ly flow covers southern Britain with calmer conditions further north. Milder air with positive uppers is across most of the British Isles by this time with any colder air confined to the far north east. Moving on, the pattern continues with Atlantic LP moving east over the British Isles and by T+240 another LPis moving through southern counties with a NE'ly to its northern flank. Heights to the far north east and near the Azores. Still mild across the British Isles with positive uppers for most. A very different evolution to GEM with no sign of heights to the north and a generally mild and unsettled picture. Plenty of rain to come over the next 10 days as well. 12Z Parallel - a very interesting evolution yesterday. at T+120 Christoph is even shallower to the north and east with the main LP now over south-eastern Europe. The ridge is coming into southern and western parts but a hint of height rises to the north west as well? Uppers of -4 to -8 over the British Isles at this time with milder weather approaching from the west. From there, the large Atlantic trough seeks to move east but disrupts and elongates close to the British Isles with small secondary features crossing central parts though a ridge does give a quieter day or two further south. At T+180, a complex shallow trough is just to the west of Ireland with heights to north and south. Winds remain from the SW in the south but variable further north. All parts except the very far north are in positive uppers by T+18- with +4 uppers across southern areas. From there, the pattern remains mobile and unsettled with more LP moving across the British Isles. By T+240, the main Atlantic trough is starting to move towards the British Isles as a complex and vigorous storm system. Mild air with positive uppers over all parts. Both GFS OP and Parallel look mild and very unsettled with plenty of the wet stuff and little of the white stuff. 12Z ECM - by T+120 the remnants of Christoph sit off the Norwegian coast with a light NNW'ly flow over the British Isles. The ridge is approaching the south-west but the Atlantic LP seems weaker and shallower but that may be an optical delusion. Uppers of -4 to -8 over the British Isles at this time. Moving on and the Atlantic-based regime takes over and by T+192 mild or very mild TM air is over all parts with an LP close to north-west Scotland and heights over Iberia. Positive uppers over all parts. As often happens, ECM teases in the last two frames of its output - by T+240, the Atlantic is looking much quieter and heights are building from the spouth toward the British Isles with a clack residual N'ly. Colder air is back into northern Britain but it remains mild further south. ECM joins the evolution to mild next week but the later stages introduce some new variables with a much quieter Atlantic than GFS and the hint of height rises to the south and north-east. In common with all the other models, no sign of a raging zonal Atlantic or a strong PV over Greenland/NE Canada. Looking further ahead, my usual glance at GFS OP and Parallel as we move into the first week of February at T+312 and T+384. Well - both end with -8 uppers covering the British Isles but it's a long way off. It's not an evolution shared by Control which keeps the Atlantic in charge throughout. Interestingly, both OP and Control see the route through Greenland rather than Scandinavia so we'll see. Oddly enough, Control seems to split the PV in early February as does Parallel but OP not so keen. Conclusion: cold fans will be hoping GEM is correct tonight but it looks on its own though JMA has a similar colder evolution by T+192. GFS and ECM nowhere near as keen at this time to go down any other route other than mild and unsettled. Some of the huge rainfall totals have eased off a fraction and both GFS OP and Parallel promise a much colder evolution in far FI as the Atlantic quietens and you'd think ECM might do something similar. The key here seems to be slowing the Atlantic and getting some amplification going - that may be indicative of the MJO moving into more favourable phases or something else. Control isn't interested which is a concern but while we look set for a milder interlude from early next week it's still far from resolved if it's a milder interlude or a more prolonged spell of Atlantic-driven weather.

Evening all As Storm Christoph begins to show its hand, my daily look at the medium to longer term trends. A milder spell early next week is inevitable but out to T+240 there were signs last evening of heights rising and a colder but more settled outlook going into next month. Let's see if this trend is the yellow brick road or the road to nowhere. 12Z GEM: T+120 takes us to Sunday. By then, the remnants of Storm Christoph are to the north east of the British Isles extending to the west of Norway with a second centre over eastern Europe. Small secondary features have moved west to east across the southern flank of the former storm and a new LP is just north of the Azores but there is a break (possibly temporary) between the troughs suggesting a transient ridge. Uppers below -4 across the British Isles at this time. As expected, the troughs soon phase and what's left of Christoph becomes a remnant of a complex trough but the LP to the north west of Ireland is aligned negatively as heights try to push down from Iceland. Heights to the far south over the Straits of Gibraltar and a SW'ly flow over most of the British Isles by T+180 bringing milder air with positive uppers across southern and western Britain with colder air hanging on in the north east. From there, some interesting developments - the LP over the British Isles starts to disrupt to the south and south east as heights try to push down from the north west and a new HP forms over the frigid airmass in Scandinavia. The forming of shallow heights in cold pools is something we see over Greenland most winters but perhaps we are now seeing out over Scandinavia and this is forcing the tough south east into Europe. Mild air remains over southern and western Britain but it remains colder to the north east. GEM ends as a messy battleground of sorts and the "possibilities" from there are varied and many of them would lead to cold. 12Z GFS OP - the T+120 chart isn't hugely different to GEM. I note the more pronounced LP over Italy with a NW'ly flow over the British Isles. Cold at T+120 with uppers of -4 or lower generally. From there, the transition to the milder airflow takes place and by T+180 the controlling Atlantic LP is further north than on GEM but with a secondary LP in advance of the main feature crossing northern Scotland, again further north than on GEM. Generally mild over the British isles with +4 uppers in the south and only slightly negative uppers further north. From there, the mild theme continues with the Atlantic LP building toward Iceland and a SW'ly airflow covering the British Isles with positive uppers over all parts by T+240. The ridge of HP is extending across Europe from the south west re-enforcing the milder regime. The rainfall totals remain worrying - five inches for North Wales, four inches for South Wales in the next 10 days. 12Z Parallel - rumours of Parallel's demise seem exaggerated so we'll go back to it. T+120 and the trough to the east covers most of northern and western Europe with a ridge to the next Atlantic LP upstream. A slack NW'ly flow over the British Isles with 850s below -4 widely. The cold regime persists a little longer than the OP but the ridge duly builds in as heights rise over Europe with the trough in mid-Atlantic extending toward the British Isles and a residual LP over the Norwegian coast. A SW'ly covers the British Isles at T+180 and milder air has reached the west with positive uppers but cooler air hang son in the east and especially the north east. Moving on, the evolution is messy but interesting - heights rise to the north-east clearing the trough mostly out of Scandinavia and the Atlantic troughs disrupt south east over the British Isles. A W'ly over southern parts but a SE'ly over the far north east. Nonetheless, it remains mild for most parts at T+240. GFS OP is awful for cold fans but Parallel ends on an interesting note with a hint of heights rising to the north east though not as distinctive as GEM. 12Z ECM - Knowing this model, it'll be Mr Mild all the way. No great surprises at T+120 with the trough to the east and a NW'ly over the British Isles. Cold air with 850s or -4 or lower over the British isles at this time. From there, as with the other models, it's a transition to something much milder as heights rise to the south and the Atlantic trough phases into the trough over northern Europe to form a complex feature stretching from Scandinavia south west back into the Atlantic by T+192. Positive uppers over southern areas but the last vestiges of colder air hanging on in the north east and northern isles. From there, we get one of the ECM's little teases with an LP crossing the centre of the British Isles at T+216 and moving east allowing a N'ly for T+240. There's a hint of upstream amplification and the Atlantic LP looks weak and disorganised so perhaps an opportunity for the amplification to develop. As you might expect, colder air is heading south at T+240 but positive uppers remain in the far south with -8 850s moving into the north of Scotland. Plenty to consider in the medium to longer term with ECM teasing as always at T+240 and both GEM and Parallel hinting at a change in the pattern while GFS OP is relentlessly mild. Moving on and I'll put up the T+312 and T+384 charts from OP and Parallel to get an early look at the first days of February. Well, OP starts mild but ends with more than a hint of something colder while Parallel is cold until the end when it turns milder as the Scandinavian HP runs out of steam against the Atlantic. Control goes in a very different direction in FI but it's more cold than mild to be honest. Conclusion: after the fun and games of the next few days, there will be a swift transition to milder weather in the middle of next week but by the end of the week that could be derailed by heights rising over Scandinavia forcing the trough to align negatively into Europe. GFS OP wants none of it at this stage and ECM looks to weaken the whole Atlantic profile but both GEM and Parallel (and Control) seem to want to develop the Scandinavian HP into early February so it's one to keep an eye on in the coming days.

The possibility of heights developing over Scandinavia has been on the cards for a few days. As I see it, IF we get the PV back over to the Canadian side, assuming it is still weak from all the warmings and SSW displacements, it won't be enough to prevent Scandinavian height rises and from ther eit can get very interesting. My personal view would be the UK being the battleground between cold and mild airmasses in early February with the cold winning out through the middle of the month.

I fear the Severn Valley is going to have a lot of problems given the large amounts of rain due over north Wales. Accumulated rainfall at T+72 from GFS 12Z OP, WRF NMM and ARPEGE. 4 inches or more for north Wales and an awful lot for north-west England as well.

Evening all A quiet and pleasant day here in lowland East London but last evening's output emphasised the high rainfall totals in the next 10 days and to be fair there was plenty of interest in far FI going into early February what does or does not happen in the stratosphere. Not much interest for southern coldies but plenty of interest further north and particularly for higher ground in Scotland. Let's see where we are this Monday evening: 12Z GEM: T+120 takes us to Saturday and the unsettled theme very much in evidence. One LP sits over the western Norwegian coast with another LP approaching from the south west. Milder air encroaching with it but still 850s of -4 and below for northern and eastern parts. Moving on, the LP to the south west deepens and moves across southern areas as a significant feature but clears away and a NW'ly covers most areas but hints of a ridge at T+180 which has briefly cut the flow in the trough leaving the main Atlantic LP spinning far to the west. Heights persist over Morocco and Greenland. Uppers of -4 to -8 generally by T+180 with the mildest air confined to the south west. From there, some respite in the deluges as heights rise from the north and slip through the British isles to be off the east coast of England as a weak HP centre by T+240. A trough is negatively aligned to the west with heights to north and south as before. Colder air remains in situ and by T+240 it's 850s of zero to -4 with the mildest air held out to the south west. I've added the cumulative precipitation chart and it shows less rain than last evening but still a lot for the west and south-west. An interesting evolution from GEM and again showing what can happen if you aren't dealing with a raging PV and an active jet. 12Z GFS OP - at T+120 there are notable differences between GEM and GFS. The main LP to the north is closer to the British Isles while the LP is already over southern England but as a secondary feature. Uppers of -4 to -8 across all parts so you'd have to wonder whether that secondary feature would be providing some snow to some parts but I'll leave that to much nearer the time and to models such as Euro4 and ARPEGE. From there, the colder regime gradually relaxes as pressure rises from the south and SW'ly winds are over the British Isles by T+180 with a complex Atlantic trough to the west and weak heights over Scandinavia. Positive uppers are moving back in from the south west but colder air remains in northern and eastern parts. From there, an LP crosses the British Isles but then moves SE and the next LP, breaking from the mid-Atlantic trough, takes a more southerly track as heights build from the north and by T+240 a small HP has formed to the north west of the British Isles and there's a slack E'ly flow across the southern and eastern British Isles. I've added the cumulative precipitation chart for the UK to T+240 and again north-west England looks the worst hit with 4 inches of rain expected in the next days and up to five inches in North Wales. Milder air remains in the south west but colder air is spreading from the north and east with some -10 uppers in the far north east of Scotland. As with GEM, GFS OP ends a bit messy with a hint of something settled and colder. On then to the 12Z Control - not hugely different from the OP at T+120 as you might expect. Uppers of -4 to -8 across the British Isles. From there, an attempt to cut the trough line with heights from north to south fails leaving a transient ridge over southern and western Britain by T+180. A shortwave over the Northern Isles keeps a light NW'ly over northern and eastern parts. Otherwise it's still not too different from the OP. Negative uppers remain over the British isles but milder air is approaching from the south west. On to T+240 and after another LP has crossed the British Isles, a slack trough remains over eastern Britain with another weak ridge upstream and a hint of heights over Scandinavia which may or may not be significant. Positive uppers over southern England but colder air further north. Control also ends a bit messy and confusing with an obvious milder synoptic profile to the west and south west but in the absence of a zonal jet it's not making much progress. 12Z ECM: by T+120 Storm Christoph (or whatever it's going to be called) is over the west of Norway leaving a slack NW'ly air flow over the British Isles ahead of the next Atlantic feature approaching from the west. Uppers of -4 to -8 across the British Isles by this time. From there, the trough to the north-east fills and a new complex trough takes over from the Atlantic with a chain of LP moving to the north-west of Scotland as the jet moves back north with heights over or to the north of the Canary Islands. The upstream profile does differ from other models with a weaker Atlantic - T+240 surprised last night of course but I suspect it won't tonight. Mild air with uppers of +4 over the south and it's generally mild across the whole of the British Isles at this time. Moving on, a slight surprise as a new Atlantic LP develops and moves NE towards Iceland allowing heights to build across western Europe - the HP by T+240 is centred over northern Spain while a residual LP over Norway keeps a NW'ly flow over eastern parts while a slack flow has taken over the west. This has led to a new plunge of colder air over northern and eastern Britain with the ECM 850 profile over the UK at T+240 very close to that of GFS OP at the same time. ECM once again surprises but all the models are looking at breaking the unsettled flow before the end of the month with some form of heights developing close to the British Isles - the devil will be in the detail but the trend is interesting and we'll see if it develops in the coming days. Moving further ahead - just for a bit of amusement, we'll take the usual glance at the T+312 and T+384 charts from OP and Control: Strangely, though the two runs look quite similar in our neck of the woods, the Polar profiles are very different - OP keeps the PV fragmented, Control brings a strong PV back over to the American side. I see we have a Parallel run tonight - stormy would be a fair content with an active Atlantic and virtually no break in the run of LP from west to east. I've just added the cumulative precipitations chart from Parallel to T+240 - again North Wales and North West England catching most of it with 5 inches over Snowdonia and I'd be worried about flooding on the Severn looking at those numbers. Conclusion: water, water, everywhere it would seem tonight - at least initially. Plenty of rain and snow for the fortunate (north, higher ground). A sniff of a break at T+240 but further into FI, the unsettled theme continues but against the very end of FI the smallest hint of upstream amplification in early February. Frustrating for snow-starved southerners but all is far from lost - February and March are always better bets for the white stuff and again this is far from a typical winter synoptic profile so plenty to keep us thinking about in the days ahead.

Evening all A much more pleasant day in lowland East London - dry with some bright or sunny spells. Certainly after the recent chill and wet, a pleasant change but last night's models suggested rain and large amounts of it would be the dominant feature of our weather for the rest of the month. 4-5 inches of rain in the next 10 days for some western and south-western parts so let's see if the wet theme continues with controlling LP to the north and a series of secondary features coming off the Atlantic and moving through southern parts. Mild in the south but colder with opportunities for snow further north. Onwards and sideaways. 12Z GEM: T+120 takes us to Friday by which time the main LP is to the north-east of Shetland with a NW'ly air flow over the British Isles. The next Atlantic LP is well off to the west with heights over the Canaries and Greenland at this time. 850s of -4 to -8 across the British isles by this time. From there, not much changes as secondary LP cross southern Britain with the main LP to the north and north east by T+180. The air flow remains WNW but with heights rising to the far south and the next Atlantic LP going nowhere in mid-ocean I suspect milder air is approaching but at this time it is only flirting with the far south while it remains cold in the north. From there the jet tries to push north but it doesn't quite happen and instead the Atlantic LP moves east across the British isles and basically the complex trough remains very much in charge with the Azores HP suppressed to the south. The initial push of mild air has been reversed by T+240 with cooler 850s of zero to -4 over most parts. I've added the cumulative rainfall chart for T+240 - again note the large totals for southern and western Britain. GEM keeps the wet theme and while the south is never too cold, the north keeps the coldest air for longest so you'd think some snow would be possible and especially to higher ground. 12Z GFS OP - the storm GFS models is quite fierce and is around 955MB at T+96 - 24 hours later it's filled a little and moved NE towards Norway leaving a NNW'ly flow over the British Isles. By that time, 850s of zero to -4 in the south but -4 to -8 elsewhere as colder air digs in from the north. Moving on, the LP fills and heads back west and by T+180 is just to the north of Scotland with a slack NW'ly flow over northern parts. Further south, secondary LP off the Atlantic have moved across southern areas with heights over southern Iberia and North Africa. By T+180 uppers of -4 to -8 remain over most areas but milder air is approaching from the south west. From there, the evolution becomes messy and more interesting. The Atlantic LP tries to move north but is shunted back west as heights build from the Pole while a small LP approaches from the south west and looks to run along the Channel. Milder air with positive uppers to +4 has reached southern and western areas but the cold hangs on especially in the north east. The rainfall totals look horrendous for north wales and north west England with 4-5 inches in the next 10 days so I wonder if we'll be seeing more flooding along the Severn later this month. OP ends as a battleground with heights building down from the north. Intriguing. 12Z Control - with Parallel having ended its 30 day trial, I'll switch over to Control for a second bite at the GFS output. The T+120 isn't too far removed from the OP. Moving on, the secondary LP systems have been running across southern Britain but by T+180 a brief ridge is in charge but again I don't see huge differences from OP at this stage. Uppers of -4 to -8 remain across the British Isles at this time with milder air approaching. More differences with the OP at T+240 with the main Atlantic LP far to the west and a broad but slack trough across the north of the British Isles and Scandinavia. A new LP is approaching southern Britain with heights to the far north. Milder air has moved into the south but colder air remains over Scotland. Control slightly different from OP but the broad theme of an Atlantic trough and a jet further to the south than you might suppose and residual heights to the far north. 12Z ECM - no huge surprises from the European model at T+120. Colder air is feeding down from the north by this time. Moving on and the Scandinavian LP continues to fill as a new Atlantic LP moves towards Ireland with the main system far to the west. Heights to the south and a SW'ly flow over most of the British Isles. Positive uppers are over Ireland and the south west but the north east in particular keeps colder air for now. As we know the road to hell is paved with tantalising T+240 charts from ECM and tonight is no exception. The LP moves east across the British isles and is over Denmark but with upstream amplification we end on a N'ly for the British Isles but the uppers aren't that cold yet. Signs perhaps of renewed uncertainty in the model output as we approach month end - again, with no raging PV or Atlantic the opportunities for amplification are there. A quick glance further ahead at both GFS OP and Control in further FI: Unfortunately, Control hasn't finished the 12Z but OP has and it's more than a little interesting. As I expected a few days ago, the Scandinavian HP finally comes into view and while the 500 chart might look like a near miss, the 850s tell a different story with some cold air for the end of the month and it remains very close by into February as a real east-west battleground develops and the Atlantic looks a lot quieter. Is this symptomatic of the MJO moving through 6-7-1 and offering some opportunity for amplification. Conclusion: the immediate theme is wet but coming into the far edges of FI are more than a few hints of a new cold evolution with GFS OP leading the way and ECM hinting at something different. Let's see if this develops over the next few days as a new trend. For now, I'm much more worried about flooding.

Evening all Well, some saw so/me snow this morning (if they were up early enough, lived high enough or were far enough east). Nothing of course in lowland East London but it was nice to see some sunshine to end the day. Last night's models had a central theme and that was rain - plenty of it especially for southern and western areas. Worryingly high totals given saturated land so I'll be having a look at the precipitation numbers tonight on the GFS OP. All the models went mild by T+240 last night so let's see what tonight's manifestations have to tempt and tantalise: 12Z GEM: it's been singing from the mild hymn sheet for the past few days and has in my view led the way on the evolution. T+120 takes us to Thursday and by then the LP has moved east to Southern Scandinavia but the residual heights are preventing the trough dropping too far to the south. Instead, it has phased west into the Atlantic to create an extended complex trough linking right back to the eastern seaboard. West or North-west winds cover the British Isles by this time. Uppers of -4 to -8 away from the south of England where zero to -4 air holds sway. Moving on, the trough remains dominant with secondary LP moving east across southern Britain with the main LP centred just off the Norwegian coast keeping the secondary features to the south and linking back to a large mid-Atlantic LP. Heights remain over Greenland but with the warmer air starting to move west while heights also persist over Iberia and North Africa. Uppers of -4 to -8 remain by T+180 but with milder air approaching from the south west. From there, little changes - the jet moves back north briefly but by T+240 the next LP is crossing central Britain with strong W'ly winds across southern parts. It's mild everywhere by this time with uppers of +4 across the south. As I've been saying for days, our problem is or are the heights to the south which are fed by the mid-Atlantic trough which has nowhere to go in the absence of a strong zonal jet to kick it east. The main theme is rain and I've added the cumulative rainfall chart to show 4 inches or more or rain for southern and western areas in the next 10 days. 12Z GFS OP - differences with GEM at T+120 with a more vigorous LP closer to the British Isles - indeed, that's quite a storm for the North Sea and real storm winds for Denmark's west coast. Small secondary LPs sit in the trough upstream. 850s of -4 to -8 coming down across the British Isles but zero to -4 further south. From there, the storm moves north then fills and moves back west to be just to the north of Scotland by T+180. The trough extends south through the British Isles with secondary LP within its circulation so it's a cyclonic flow over the British Isles with positive uppers close to the south coast but colder air persisting further north. From there, the LP to the north of Scotland gets drawn south and west and merged into the general circulation as heights move into Iberia and push the jet back north but at T+240 one of the LP centres has started moving east to be over northern Scotland with the main LP still in mid-Atlantic. Positive uppers cover not just the British Isles by T+240 but most of north western Europe with a wash of TM SW'ly air. Again, I've added the cumulative precipitation chart for T+240 with approaching five inches of rain for parts of south wales in the next 10 days. Wet, wet, wet - sounds like an 1980s pop group, doesn't it? 12Z Parallel - not hugely different to the OP at the same time though the storm perhaps a smidgen less intense. From T+120 Parallel diverges a bit from OP and GEM. The initial LP moves east into Scandinavia and a new LP centre forms to the north of Scotland and by T+180 is over the Faeroes. Meanwhile, a separate Atlantic LP from the eastern seaboard phases into the circulation and rushes eastward deepening to be across southern England by T+180. Cyclonic flows over the British Isles by this time with positive uppers over southern and eastern England but -4 to -8 air still to the north. The LP crosses southern England and continues east into northern and north eastern Europe and is over Belarus and Lithuania by T+240. A ridge is moving in not from the south but from the north and this has cut the flow to the trough leaving the main trough spinning in mid ocean. Cold air continues over the British Isles with -4 to -8 air generally and colder air moving into Scotland. I've added Parallel's precipitation chart showing a slightly different rain profile - note the high rainfall totals for eastern coastal counties. Parallel goes cold at T+240 - the first sign of a new trend. We'll see - to be fair, Parallel was quite early in calling an end to the cold spell so it's not to be ignored for all it's early days. 12Z ECM - I'm expecting bugger all from the Mild Model so I'm not going to be disappointed when it shows a raging blowtorch at T+240. The T+120 looks very close to GFS OP but with perhaps a less active upstream profile. Uppers of zero to -4 generally by T+120. From there, the trough aligns positively to the west and with height rises to the south, a SW'ly covers the British Isles by T+192. However, the cold air hangs on at this time with uppers still -4 to -8 generally but positive uppers are approaching. From there, areas of LP cross the centre of the British Isles as heights continue to rise from the south with the residual Atlantic LP far to the west. Positive uppers have extended through Ireland, Wales and England but colder air hangs on in Scotland. I make that 3-1 to mild overall but not as convincing as last evening by any stretch so overall an upgrade for cold fans. Let's have a look at the extended FI from GFS OP and Parallel respectively: OP brings the PV back over to our side of the globe but Parallel doesn't really and I note the return of the Russian HP on Parallel albeit it's no influence on the weather over the British isles at this stage. Control ends very unsettled with a strong PV back over Greenland/NE Canada. Conclusion: a step forward for cold fans tonight but no more. It still seems unlikely we'll end up on the cold side of the trough given the strength of heights to the south but Parallel shows this as an option so we have to consider it. The main theme remains rain and some serious amounts in the next 7-10 days. Little or no sign of anything settled in the next 14 days to be honest with the Atlantic trough dominant through all charts and all models despite (or perhaps because) of the absence of strong zonal winds.

Much better 18Z Parallel for cold/snow fans: Note the heights to the south are suppressed with the ridge orientated east rather than north east.

Evening again all Two points - first, much more consistency across the models at T+120 and T+240 tonight than there has been for several days. Why? The higher DAM air mass over Greenland exits to the left over Canada and from that point on any UK cold spell is in big trouble. Keeping that keeps the Greenland HP block in the game and the jet to the south. Second - the persistent indicator of heights rising to the south. I think I saw this first on an ECM run a week ago. My only explanation for this is that it's down to the fall off in zonal winds. As LP exit North America, instead of heading east and flattening everything in their path supported by a powerful jet, they move more slowly and as they deepen they throw forward heights. As the Greenland block has kept the jet to the south and the LP are exiting North America at lower latitudes, the slow motion leaves the heights rising through Iberia which in turn kicks the jet back north and aligns the trough positively through the North Atlantic and that's it for cold fans until another amplification. I still think there will be a significant pattern change into February with heights rising over Scandinavia in response to the PV moving back over to Canada.

Evening all Am I going to see some snow tonight and tomorrow morning in lowland East London? A transient covering wouldn't surprise but those to higher ground will, as always, have a better chance for heavier and long-lasting snow. I'll leave that to others and concentrate on my evening look at the medium to longer term options. Some miserable forum members this morning with some of the overnight output putting the UK (and especially the southern half) on the milder side of the street while the battleground might yield some positive outcomes for snow fans further north. Let's see where this evening's out put takes us - last evening we had some common themes of Greenland heights and a complex trough over Scandinavia but persistent heights to the south threatened to push the jet back north and keep the south of the British Isles in a milder airflow. 12Z GEM: - the mildest of the options yesterday evening making little or nothing of the wedge of heights south from Greenland and not breaking the Atlantic trough. T+120 takes us to next Wednesday and the LP has drifted down to cover much of the British Isles but milder air hangs on in the south east under a cyclonic SW'ly. Heights persist over the far south east of Europe and a new Atlantic trough is heading towards north-west Europe. Southern and Eastern Britain has positive 850s (up to +4) but negative uppers have moved into Scotland and Northern Ireland behind the cold front which is moving south east. From there, the trough remains very much in charge with a series of secondary LP moving across the south while the main centre remains to the north and east over south-west Scandinavia. By T+180 colder air has finally filtered through to the Channel coast with -8 850s over northern parts. A new and deeper LP is approaching the English Channel from the south-west. Moving on and by T+240 clear signs of the jet heading back north as heights rise over south-west Iberia with a transient HP ridge about to cross the British isles ahead of the next Atlantic trough. 850s of -4 to -8 over the British Isles at this time but milder air is approaching from the south-west. The plume of warner air vacates Greenland at T+168 and from there it's only a matter of time before the jet kicks back north. A decent run for northern Britain but for the south very unsettled with a lot of rain and at the end of FI a clear sign of a return to milder conditions for all. 12Z GFS OP - a strong run for cold fans last evening. At T+120, a good example of how minor changes can have huge impacts. GFS has a slightly deeper LP and a smidgen further south so by T+120 the colder air has made more headway. The upstream profile differs in that, unlike GEM, there is a narrow but distinct gap between the Atlantic troughs - this may or may not be significant later. The push of milder air in the early part of the week has been largely replaced by colder PM air (except in the far south east). The break in the Atlantic trough doesn't last but it allows a small LP to head into the Mediterranean suppressing the heights and allowing a colder NNW'ly airflow down across the British Isles by T+180. Shortwave LPs have closed the ridge upstream. -4 to -8 850s across the British isles by this time with some colder air nearing northern Scotland. From here, however, the trough over Scandinavia remains in control until heights start to build from the south and by T+240 there's a SW'ly flow across the British Isles with an active Atlantic LP moving NE toward Iceland and the jet moving back north. Milder air is moving across Ireland and the far south-west but colder air hangs on further north and east for now. GFS OP heads to the same place as GEM which suggests a theme and I suspect that's where Parallel will be heading. 12Z Parallel - we're starting to see some consistency in the T+120 output after a number of days of divergence. Parallel looks very close to OP at the same time. The milder air is still over southern and eastern England at T+120 but the colder air is pushing south and east. From there, a fairly familiar path but at T+180 the main LP is to the north so it's a slack airflow across the British isles with heights rising around the Canaries and new shallow LP coming east in the Atlantic trough as the warmer air vacates Greenland to the west. Uppers of -4 to -8 generally with colder air coming into Scotland by T+180. Moving on, the heights to the south play their role in pushing the jet back north and by T+240 Parallel joins the other output in having a SW'ly flow over the British Isles but do I see a hint of heights to the north east again? Milder air is marching north and east across the British Isles by this time. That's 3-0 to the milder evolution by T+240 tonight - I don't expect ECM to do anything different if I'm being honest. 12Z ECM - no surprises at T+120. Cooler air with 850s of zero to -4 is gradually displacing the milder uppers by this time. By T+192 the colder snap has ended for southern parts as the Iberian HP is already building north east and pushing the jet back north. The brief push of colder air is being displaced by milder air from the south and west. It's not quite that simple as the LP to the north of Britain dives SE while a major Atlantic storm is heading north in the middle of the ocean. There's a residual LP to the west of Norway with heights persisting over Iberia and again just that hint of heights to the north east. The milder incursion is delayed but not I think for very long. So, 4-0 to mild by T+240 but not a straightforward evolution perhaps and ECM teases by dropping the LP SE suggesting a hint of new heights to the north east which is also teased by GFS Parallel tonight (as it was yesterday in further FI). Let's see if further FI plays this theme on either GFS OP or Parallel taking us towards month end: One of them brings a raging PV back to Greenland/NE Canada and the other doesn't. Parallel indeed shows the jet heading back south at the end of FI and colder air returning to the far north. Control restores the PV into far FI but more over Canada so I'd be looking for height rises over Scandinavia into February. 10 HPA charts - all look the same - from the shattered PV a new lobe emerges at T+192 from the far east of Siberia and moves back over our side of the globe though much weaker than you would expect a this kind of year. I suspect this is the part of the reason for the end of the cold spell and reversion to something more Atlantic-driven. Conclusion: it looks as though we will be transiting via a brief cold spell to a prolonged spell of Atlantic-driven weather which could be very wet and at times stormy in the last third of the month. I'm still looking to the north east for height rises in February but that's a very long way off at this time and it looks as though cold fans will by the early part of the week after next looking at a minimum 14 days of milder weather. A long long way from any notion of winter being "over" and it's fair to say we've had mild spells in most winters in the last few centuries so nothing unusual in that but it does look wet and that might cause some issues in the next 10-14 days.

Yes, lots of miserable downbeat so-and-sos this morning. GFS 06Z Control is a thing of beauty for fans of cold and while I think southern Britain is looking marginal, plenty of opportunities for snow for those further north on the morning output. @chionomaniacis right about the synoptics - the most interesting for a long time and a lot still to be resolved starting with tomorrow.

Evening all Some have done very well out of today's stalling weather front and for those who've had snow, kudos. In lowland East London, cold rain has, to no one's surprise, been the order of the day. Moving ahead, milder air looks set to return for a while as we await a possible change to colder conditions at the end of next week. I say "possible" because the output has been consistent in its inconsistency in recent times with both milder and colder options to the fore as the battle between the competing airmasses rages close to the British Isles. For cold fans, will tonight's output be the highway to heaven or the road to hell or perhaps the road to nowhere? All are on the table so it's eyes down for a full model house: 12Z GEM: T+120 takes us to Tuesday next week. A mild SW'ly airflow covers most of the British Isles with a trough to the north and west and heights to the south and east. A ridge is pushing down out of Greenland at the same time. Mild air covers most of north-west Europe by this time. From there, the Atlantic trough develops and the push of energy from the lower latitudes causes the main LP to push over Scotland and deepen considerably in the North Sea to be a strong LP off the Norwegian Coast by T+180. In its circulation, a series of small secondary LP run west to east across southern Britain with new LP developing to the west of the Azores and heights over North Africa. A cyclonic SW'ly flow for southern parts with a strong NW'ly on the western flank of the LP for northern Britain. Uppers zero to -4 in the south but colder across the north with -4 to -8 850s in evidence. Not much changes with the trough remaining positively aligned from lower Atlantic latitudes to Scandinavia with heights persisting over North Africa and Iberia. The WSW'ly air flow keeps the air mass mild over Britain with only occasional colder incursions. GEM steps well back from some of the colder evolutions of past days with the heights to the south stopping the trough coming south and keeping us on the warm side. 12Z GFS OP - at T+120 considerable differences between GFS OP and GEM. The former now has a phased trough over the British isles with a secondary LP moving across Ireland but the ridge from Greenland has split the Atlantic trough and has dug a way south. Milder air is in place across southern Britain but it's turning colder again from the north and west. From there, the main LP to the north west of Scotland moves east and develops as a complex trough over Scandinavia with a NNW'ly flow across the British Isles by T+180. Atlantic shortwaves are forming but the main trough is held well to the west as heights persist from Greenland but are also developing around the Canaries. Uppers of -4 to -8 generally across the British Isles with some colder air coming into northern Scotland. After T+180, the trough over Scandinavia remains the controlling feature with the main centre moving back west while a secondary feature develops over south-west Ireland and deepens to be sitting over my house at T+240. Heights remain upstream with a ridge from Greenland to Iberia. Milder air has returned to far southern parts of Britain but colder air remains elsewhere (with all that flows from that). GFS OP is an excellent run for cold and snow fans in the medium term - cutting the Atlantic trough is vital - in this instance the heights to the south link with those from Greenland and hold the troughs in situ. You'd think the T+240 evolution would be quite wintry for the Midlands and part of Eastern England but I'll leave it to others. 12Z Parallel - Unfortunately for cold fans, the T+120 evolution looks similar to GEM with heights over the central Mediterranean and a mild SW'ly over most of the British Isles with +4 850s in charge. A small LP is passing the north west of Scotland at this time. Moving on, the LP moves east and deepens to form a complex trough over Scandinavia. There's a developing upstream ridge and between those features a NNW'ly flow is drawn down over the British Isles with uppers of -4 to -8 generally and colder air coming into north-eastern Scotland. Moving on, the trough extends back west briefly but begins to fill just to the east as a small HP develops in the frigid Scandinavian cold pool. The Greenland ridge pushes strongly south east at the same time forcing the jet further south with just a small corridor to the south west of the British Isles in which secondary LP can run east towards the Channel. Milder air is trying to push in from the south-west but it remains cold to the north-east at T+240. Again, we see how cutting off the Atlantic trough pays dividends with no zonal winds or PV to send the Atlantic LP east - they spin north and heights can build upstream of western Europe maintaining the cold flow from the north. 12Z ECM - no real surprise on the T+120 with the mild air flow in situ and a promising sign of upstream amplification. Positive 850s over most of the British Isles. From there, the LP moves east to Scandinavia and belongs a complex feature in the cold airmass. The amplification upstream remains albeit not solid with a deep LP south of Greenland at T+192. A NW'ly air flow covers the British Isles at this time. Coldest air remains to the north and west with 850s of zero to -4 for southern counties by this time. From there, the amplification window closes and the Atlantic trough takes over - by T+240 a new LP is approaching the south-west of the British Isles but heights remain subdued to the south and the trough alignment is neutral. Milder air has returned to southern Britain and it's less cold further north. ECM is a curiousity - I just don't get its Atlantic profile in the critical T+120-T+192 period. It looks like a west-based NAO except it isn't. GEM brings back hints of the PV but the other models don't by T+240. Moving further into FI, a glance at GFS OP and Parallel at T+312 and T+384. OP catches my eye as it shows what I think will be the next big hope for cold weather fans as we move towards the end of January and into February and that's the Scandinavian HP. On the OP it develops but isn't able to influence the weather over western Europe owing to the strength of the Atlantic but we'll see if that evolution gains any traction in the next week or so. Parallel is less inspiring and less convincing it I'm being honest with heights to the south ruling the roost but it's a long way from zonal. Control is a very good run for cold fans with the cold air in place over the British Isles throughout and again there's a hint of heights to the east developing at the end of the month. 10 HPA charts - Control maintains a strong warming from the Siberian side throughout FI as does OP and Parallel but the fact remains this isn't your normal monster PV with an inner core of -84. Lowest temperatures are -68 and the PV is much smaller and more disorganised. Conclusion: While GEM and to an extent ECM are a sign of caution, GFS gets us to a cold option and Control keeps us there even if OP and Parallel return the Atlantic further into FI. The main themes of heights from Greenland a complex Scandinavian trough are common so a N'ly of some form looks likely. The longevity and severity of any cold spell look to be governed by the upstream amplification which can endure in the absence of a zonal jet and a powerful PV at least for a few days or longer if Control is correct. I'm interested in the first signs of heights to the east in far FI - it may well be there will be a milder interlude (7-10 days) before any heights to the east get involved but with continued weakness in the PV I'm still thinking February could be a "Scandi" month. For now, milder early next week and then a return to something colder next week (possibly). I think I've already said that.....

Evening all A damp old day in lowland East London but I was struck by the lack of wind (no giggling in the cheap seats, please) so whatever was happening was going to keep happening and pretty slowly. I'll leave others to muse on the immediate fun and games - as always, I'm expecting nothing in my part of the world but beyond the immediate, there were strong signals for a colder evolution into the final third of the month. Last night's Parallel was the exception and this was due to maintaining strong heights over the Mediterranean which prevented the trough moving too far south and leaving southern Britain in a very mild SW'ly. Keeping heights low to the south is as important to the evolution of cold as building heights to the north west or north east. Anyhoo, let's see what tonight's soft, strong and highly absorbing pictures tell us. 12Z GEM: T+120 takes us to next Monday at which time the British isles is in a north-west to westerly flow between an area of LP over the Faeroes and an HP centred over Iberia. Upstream, heights extend to Greenland with the nest Atlantic LP further south at this time. 850s below -4 in the north but zero to -4 in the south with milder air close by to the west. From there, the LP to the north sinks south and phases with part of the Atlantic trough forming a new elongated trough from the British Isles east to the Baltic. A slack flow over the British isles at T+180 with heights building south east from Greenland and the next LP far to the west. Any positive uppers are along Channel coasts with colder air moving down from the north with uppers of -4 to -8. By T+240, the trough extends over much of Europe with main centres over the Baltic, Northern Britain and the Northern Adriatic. A cyclonic flow extends over the British Isles back to an elongated Atlantic trough but I note a ridge moving into Iberia trying to push the jet back north closer to the British Isles by this time. Heights persist over Greenland. Colder air has pushed down from the north with uppers of -8 or below but by T+240 these have moderated slightly. 12Z GFS OP -not bad from GEM - I'll give it a 7/10 as I'm worried about heights returning to Iberia but on to the GFS OP. At T+120 some subtle differences from GEM. The Atlantic LP is closer and deeper than on GEM while the HP to the south is weaker. The LP to the north extends to a second centre over northern Scandinavia. Uppers of -4 to -8 over the British Isles by this time with milder air approaching from the west and the coldest air over south-east Europe. The Atlantic LP moves toward the British Isles, phases with the LP to the north and deepens to be over Ireland by T+180. Heights persist to the north-west and over south-eastern Europe. Milder air has pushed through the British Isles but colder air has pushed south to the west of Ireland. From there, the LP moves across the British isles and then SE into Europe and by T+240 is over Italy with a secondary centre over the Low Countries. With heights persisting to the west, a NE'ly flow is drawn south across the British Isles. Colder air has therefore pushed south with uppers of -4 to -8 generally, coldest in the west. 12Z Parallel - well, OP got there though it wasn't pretty but that looks a more solid and longer-lasting evolution (he said hopefully). On then to Parallel - will it be the jewel in the crown or the fly in the ointment (as it was last evening)? Again, subtle differences by T+120. The HP to the south extends from the Azores through Iberia to France. The Atlantic LP to the west seems a smidge further north than on the OP while the LP to the north seems weaker as do the heights around Greenland. Areas of -4 to -8 remain over the British Isles with milder air encroaching from the west. From there, the Atlantic LP and the LP to the north phase and develop a new deep LP to the north-east of the British Isles while heights extend south east from Greenland. A new Atlantic LP sits far to the west but the heights to the north haven't quite split the trough by T+180. A NW'ly air flow covers the British Isles and colder air is moving down leaving the positive uppers combined to the south east and uppers of -4 to -8 moving into northern and western areas. Moving on and the battleground develops with initially cold air over the British Isles but a new Atlantic LP deepens far to the west but as it goes nowhere it throws heights up into Iberia which kick the jet north and looks as though it will cut any cold spell short. Uppers remain -4 to -8 over most of the British Isles by T+240 but milder air isn't far away. 12Z ECM - heights to the south look like they will cut any cold spell short by sending the jet back north and leaving the British isles on the warm side. Finally, the Europeans for the evening. Not too surprising at T+120 with negative uppers remaining over the British Isles though with milder air again threatening from the west. At T+192 ECM resembles GFS Parallel but with a simpler and deeper LP to the east Of Scotland once the phasing of the troughs has occurred. Colder air has swept back south and east by T+192 with uppers of -4 to -8 generally. The controlling trough remains in situ but the interaction between the cold air and the warm air along the pressure gradient leads to the formation of a strong secondary feature which deepens intensely to be over north-west France by T+240. Milder air is close to southern coastal areas in the warm sector of the LP but it remains colder elsewhere. Neither ECM nor Parallel give much optimism to the longevity of any cold spell with the Atlantic threatening to move in and the jet moving back north. Let's see what further FI has to offer from GFS OP and Parallel: The very epitome of chalk and cheese - GFS OP you'd want to take home to meet the parents, Parallel you'd want to avoid at all costs. Control has a cold spell and interestingly at the far end of FI brings in heights to the north-east but turns milder for the British Isles. On then to the 10 HPA charts - OP keeps a strong PV despite almost continuous warming from the Siberian side and Parallel is similar as is Control so the PV re-strengthens despite the continuous warming - okay? Conclusion: a step back for cold fans tonight. The hint picked up by Parallel last evening continues this evening though not to the same extent though it's a concern ECM is tempted by it. GFS OP is a superb run for cold and snow fans but it looks as much an outlier as Parallel. There's an evolution to something cold from the north or north-east but the severity and duration remain far from resolved. To be fair, there's no sign of a raging PV anywhere tonight so the question becomes whether heights over southern Europe can be suppressed long enough to allow the cold to take hold or will the battleground scenario be the answer which may be good for the north but not for the south?

Evening all I'm beginning to enjoy this milder weather but that might put me in the minority here. Clear signs of a return to colder conditions next week irrespective of any brief colder incursion this week. The notion of the "battleground" getting plenty of interest with perhaps the trough aligning west-east through the middle of the British Isles leaving the south mild and the north cold - it's happened before, no reason why it couldn't happen again. Still, let's see what tonight's contrafibularities provide. 12Z GEM: T+120 takes us to Sunday and a shallow LP lies to the north of the British Isles with a trough extending south-west. Heights persist over Iberia with a new HP building NW toward Southern Greenland. A WNW'ly air flow covers the British Isles. 850s are zero to minus four as some colder air moves into the north-west behind a cold front. The trough moves SSE down the North Sea and by T+180 is to the east of the British Isles. Upstream, the trough is clawing its way back north against the Greenland heights and the next Atlantic LP is looking to phase with the trough over the British Isles. Weak heights persist over Iberia. Colder air is pushing south over the British Isles in a NW'ly flow with uppers of -4 to -8. From there, the evolution gets a little "odd" - essentially, the cold air of the trough over the British Isles engages with the warm sub-tropical air to the south-west and explosive cyclogenesis occurs with a deep LP over southern Britain By T+240. Another deep LP spins away to the west of the Azores while strong heights persist over Greenland. Milder air pushes into the far south but it remains cold to the north with a keen ESE'ly wind and I can't imagine someone somewhere wouldn't cop a lot of snow from that evolution. 12Z GFS OP - GEM ends dramatically implausible to this observer but there you go. On then to the GFS OP. At T+120 there are already some differences with the GEM. The Atlantic LP is more vigorous and to the south-west of Iceland. Heights exist to the south and west of this potent little LP but it's calm over the British Isles with a ridge of HP from Iberia keeping it quiet. 850s of zero to minus four so nothing too dramatic at this time. From here, the LP moves slowly east before starting to sink south across the British Isles. The ridge is extending south from Greenland to the Azores while residual heights remain over Iberia. A cyclonic or W'ly flow over the British Isles by T+180 with uppers still zero to minus four with the coldest air still out to the west. The trough meanders east and south east across the British Isles and by T+240 is over northern Germany with an extension back west. A new Atlantic LP is developing and slowing moving toward north-west Europe while heights persist over Greenland. 850s of -4 to -8 across the British Isles at this time. 12Z Parallel - well, the GFS OP gets to the same point as the GEM but 60 hours later so we can call GEM progressive by comparison. Let's see where Parallel sits. Again, a slight variation at T+120 with a ridge extending west from the HP which is positioned further north on Parallel than on some other models. A SW'ly air flow for northern and western parts but a light flow further east. The LP is more complex with centres to the north-east and south-west of Iceland at this time. 850s are broadly negative, mainly zero to -4 but with some colder air in the mix at this time. From here, the divergences become considerable. It looks as though heights to the south and south east over Europe are much stronger and that keeps the trough and the jet further north. The Greenland ridge doesn't extend as far south and east and the Atlantic trough is aligned positively across northern and western Britain and into Scandinavia leaving southern and eastern areas in a mild or very mild SW'ly air flow by T+180. +4 850s for the south, -4 uppers for the north so quite a sharp gradient. Moving on and strong heights to the south over the Mediterranean continue to keep the trough to the north and west and feed very mild air up over the British isles and north western Europe by T+240. An awful 850 chart for coldies with very mild air (uppers to +8) spreading across western and central Europe and any colder air kept well to the north and east. 12Z ECM - Parallel is a right kick in the gonads for cold fans but it shows what can happen if heights get too powerful to the south. On then to ECM and by T+120 most of the puzzle pieces are where they should be. The LP is to the north of the British Isles with the trough back into the Atlantic and heights building toward Greenland. The last of any milder air is clearing out of the south-west with colder air moving down across the British Isles by this time. The LP extends east and south east across or to the east of the British isles and by T+192 has a centre over the Baltic leaving a slack flow over the British Isles. Heights extend south and east from Greenland at this time. Uppers are -4 to -8 with even colder air coming down into northern Scotland. In the following 48 hours, the trough remains over or just to the east of the British Isles with a new LP over southern England by T+240. The Greenland heights are perhaps starting to weaken. Cold air persists over the British isles with uppers below -8 in many areas. I make it 3-1 to cold at T+240 this evening and the synoptic evolution of GFS OP, ECM and GEM isn't too dissimilar. Parallel fails because it blows up heights over the Mediterranean which stops the trough sinking over the British Isles and north-west Europe. Moving further ahead, let's see how the vastly divergent GFS OP and Parallel continue further into FI (T+312 and T+384 respectively). It's all very battleground - oddly enough, Parallel is mostly mild but ends colder while OP is mostly cold but ends milder (at least for southern areas). Neither has a raging PV strangely enough but both wash the warmer uppers out of Greenland by about T+288 after which there's plenty of weather if southerly-tracking LP systems are of interest. As for Control, a thing of beauty for fans of snow with the LP systems a smidgen further south so the colder air remains over most of the British Isles with plenty of Channel-type LP systems. On to the 10 HPA charts, the warmings from the Siberian side continue but the vortex seems more resilient and holds the line. Conclusion: the temptation will be to look to the north or the east but the key place to look is the south. For the cold air to hold over the British Isles, we need to keep heights as low as possible to the far south especially over the Mediterranean. Parallel is a nightmare for coldies because strong heights over the Med and south-east Europe stop the trough dropping far enough south to put the British Isles on the cold side and instead we get a flow of mild or very mild SW'lies with the cold air held to the north and east. The other models all profile this differently but the future evolution of the "battleground" is also dependent on the profile to the south. IF the trough digs deep enough in the Atlantic, heights rise across southern Europe, the trough aligns positively and the milder air prevails. If it doesn't, shallow areas of LP can run east into north-west Europe and the British Isles stays on the colder side. It is, as someone has said, a "high risk high reward" scenario. Parallel shows what can go wrong, Control shows what can go right. It's on a knife edge.

Evening all The mild air finally reached lowland East London overnight and it was actually pleasant to be out and about for my lunchtime exercise walk. I don't need the occasional bit of cold but I'm getting to the time of life when I appreciate the mild a little more - heresy I know. Two distinct evolutions on offer last night and it all depended on whether heights could build in mid Atlantic - if they could and cut off the Atlantic flow, we'd be on the cold side of the trough but if not, we would be on the warmer side. Here goes.. 12Z GEM: T+120 takes us to Saturday. The HP ridge has slipped away to the south as a shallow LP moves in from the Atlantic. Weak heights persist over both Greenland and Scandinavia. After a brief colder interlude milder air has returned to all parts of the British Isles with positive uppers. From there, the LP moves slowly across the British isles but heights build strongly upstream and link to Greenland creating a strong mid-Atlantic ridge. The LP develops into a complex trough over Scandinavia and the North Sea with a NE'ly air flow covering all parts by T+180. Progressively colder air is moving south and east with zero to -4 850s over southern and eastern parts with uppers of -4 to -8 for most other areas and -8 850s coming into northern Scotland. From there, heights sink slowly south but there' still amplification to Iceland while the tough has also moved south into Europe maintaining the NE'ly air flow over the British Isles. It remains cold with -4 to -8 uppers at T+240. 12Z GFS OP - a cold evolution from GEM but let's see what GFS OP offers. At T+120 already different from GEM at the same time. A more robust HP with cells over Denmark and to the west of Ireland with the LP further north over Iceland. Milder air across southern Britain but it remains colder to the north at this time. The divergence continues to T+180 - it's a messy evolution with the LP over Iceland starting to sink SE towards the British isles but extending the trough north east. A shallow LP north of the Azores and a large HP centred over Austria as strong heights build south out of Greenland. After another push of cold air, milder air has readily returned with positive 850s over most of England and Wales by T+180. After that, the LP moves ESE across northern Britain and deepens as it moves over southern Scandinavia with an elongated trough back west to the British Isles. Heights over Greenland are keeping the jet to the south and there's a NNW'ly airflow over the British Isles at T+240. Uppers of -4 to -8 for most parts with colder air lurking to the north. 12Z Parallel - GFS OP gets there in the end but it's a bit of a struggle. I suspect many will see a lot of excitement up to T+120 with a shallow LP moving north to south but by T+120 it's a messier evolution with HP to the south and west but a shallow trough coming into the west of the British Isles. Residual heights over Scandinavia but the upstream Atlantic profile dominated by areas of LP. After some incursions of colder air, by T+120 it's mild for all parts with +4 uppers over many parts. From there, a new HP comes off the eastern seaboard and phases with heights over Greenland to build a strong mid-Atlantic ridge down to Iberia. The LP over Iceland has sunk SE to be over Ireland by T+180 with a shallow trough extending north-east. A SW'ly cyclonic air flow over much of the British Isles with uppers generally zero to -4 by this time. The LP sinks south but phases with a new Atlantic LP to forma an elongated trough to the west and south. Heights persisting over Iberia and Greenland leading to a slack flow over southern and western parts and an E'ly over northern and eastern parts by T+240. As might be expected, colder air to the north and east with milder air to the south and west. 12Z ECM - 2-0 to cold with 1 draw is how I would call it so far but let's see where ECM is - last evening it didn't end too well but the OP was a notable outlier which calmed a few nerves. On then to this evening's offering. The T+120 again quite different form some of the other models. The HP over northern Iberia extends a ridge to Scandinavia with a new HP developing to the north west. The LP sits to the north west of the British Isles with the trough extending south and east. Milder air has pushed across the British isles with positive uppers for southern areas. From there, the LP drops south east through the southern North Sea to Denmark while a new LP and also moves south-east but on a more southerly track and by T+192 is over Germany as a shallow but extensive trough north into Scandinavia. The HP which was to the north west whas phased with heights building over Greenland to produce a strong ridge by T+192 keeping the jet to the south and a NNE'ly air flow over the British Isles. Uppers of -4 to -8 by T+192 with uppers below -8 over northern Scotland at the same time. From there, the trough extends back west as the Greenland ridge relaxes slightly and by T+240 the cold trough covers the British Isles and east through southern Scandinavia to the Baltic. A slack NE'ly persists over the British Isles with -4 to -8 uppers persisting with pockets of colder air over central Britain. Looking further ahead, let's look at some far FI charts for GFS OP and Parallel (T+312 and T+384 respectively). Both outputs are full of interest synoptically and bear witness to the confusion affecting the NWP at the far edge of FI. OP is all about the battleground while Parallel goes colder with some -12 uppers for southern and eastern areas before the battle re-starts anew. Control is running late so I can't comment on that as I like to match the same runs each night. That leaves the 10 HPA charts for OP and Parallel - perhaps the warming on the OP not as strong tonight as previous runs. However, the Parallel splits the vortex apart once again in far FI with three distinct vortex lobes at T+384. Conclusion: - solid progress for fans of cold tonight and clear signs of another colder spell (whatever happens this week) developing during next week and into the last third of the month. Perhaps some indications the stormier evolution of recent GFS FI output is beginning to change with Parallel keeping the PV weak but the battleground scenario remains the form horse but still well into FI. By T+240 three of the four model outputs discussed show cold or very cold evolutions with renewed Greenland heights allowing the trough to develop to the east and a N'ly or NE'ly air flow to develop over the British isles. Getting that wedge of heights to block off the Atlantic flow is crucial but as of tonight and with all the caveats and caution applicable at this stage, there are reasons to be modestly cheerful.

Evening all The end approaching of two weeks of below normal temperatures and while it may have yielded no more than some frosts and a bit of fog for lowland East London, if you've had snow, good luck to you. The model output this time yesterday suggested any reversion to milder conditions "could" be short lived with three of GEM, GFS OP, GFS Parallel and ECM all going for cold solutions at T+240 albeit of differing kinds and by differing routes. There was also more than a hint of more "normal" conditions later in the month with a resurgent vortex and an active Atlantic. Plenty of uncertainty even as early as T+120 - will we see resolution or will we be in the need for salvation after this evening's musings? 12Z GEM: T+120 takes us to Friday by which time an anticyclone covers the British Isles with centres over south west Norway and a larger centre to the south and west of the British Isles. Calm conditions prevail for most with a slack SW'ly flow for northern and western areas. An Atlantic LP is close to Iceland at this time. Uppers of zero to -4 a this time over the British isles, coldest in the east and south. From there. the Atlantic LP meanders east and north east and forms a complex but vigorous LP over northern Scandinavia while heights rise upstream in the Atlantic with a ridge from the Azores to Greenland. This leaves a flow of NNW'ly PM-sourced air over the British Isles by T+180. Colder air is moving down from the north and north west removing the last of the positive uppers from south east England by this time. The trough over northern Scandinavia sinks slowly south and by T+140 covers the British isles and much of north-west Europe as a complex feature. 850s of -8 cover much of the British isles by this time. 12Z GFS OP - a cold evolution from GEM. On then to the American OP and by T+120 it's quite similar to GEM with a long ridge of HP from just west of Iberia through the British isles to southern and western Scandinavia. Colder air has returned with uppers of -4 to -8 with the coldest air on the southern and eastern sides of the ridge. The HP weakens away to the south from there as the LP to the south-west of Iceland at T+120 moves slowly east then south east to be over north-west Britain by T+180 having phased with a residual trough far to the east. Heights have developed over Greenland and extend south and east as a narrow ridge into mid-Atlantic. Uppers of zero to -4 over the British Isles by this time with the warm sector in the LP crossing at that time. As heights develop further over Greenland, the LP over the British isles sinks south but merges with a new LP approaching from the south west. The battleground is the British Isles with -8 850s and a chill NE'ly wind in the north and milder air trying to come in from the south and south west. 12Z Parallel - OP screams a battleground evolution and there would inevitably be snow for someone somewhere were that to verify. Parallel will be intriguing as always - at T+120 the immediate difference is in the upstream profile with a shallower LP further south than on GEM or GFS OP. By T+120 milder air over Ireland and uppers to zero to -4 elsewhere. From there, the divergence really begins. There is no attempt to build pressure through to Greenland. The LP over the Atlantic at T+120 passes to the north of Scotland by T+180 with a new LP approaching from the west. The cold air is kept well to the north with the HP over or to the west of Iberia keeping a WSW'ly flow across the British Isles. Uppers of zero to -4 across the British Isles at this time. From there, the evolution goes in a diametrically opposed direction to the OP. The LP moves across the British isles and pulls down a cold N'ly but by T+240 there's a clear Atlantic-driven profile with heights lowering over Greenland and a familiar SW'ly flow across the British Isles. By this time, the brief cold plunge is already on its way out as positive uppers approach from the west. 12Z ECM - Parallel very different from the OP. Let's see where ECM is at the same time. It was out on its own with its evolution yesterday but at T+120 it's broadly aligned with the other models though I note the Atlantic profile is different again with a more complex trough. Milder air perhaps trying to come in from the west but some residual cold air over eastern parts of the British Isles at this time. The Atlantic LP moves east to Scandinavia and with heights developing in the mid-Atlantic to Iceland a NNW'ly air flow covers the British Isles. Uppers of -4 to -8 by T+192 keeping it cold. However, there's no amplification and instead shallow areas of LP are crossing from south of Iceland to Scandinavia in a WNW'ly flow by T+240. Milder air is back across the British Isles by this time. After last evening's 3-1 win for cold, it ends 2-2 tonight with GEM and GFS OP in the cold camp and Parallel and ECM ending milder. Moving further ahead, a look at far FI from both GFS OP and Parallel and given their huge divergence at T+240 I suspect they will be similar as two dissimilar things in a pod OP is cold and very decent for snow fans - Parallel rather less so. Both want to restore the PV to its usual place and strength by the end of FI. For the second night running, Control stays cold throughout. Looking elsewhere, as for the 10 HPA charts, little change from Control with another strong warming after mid month exerting further pressure on the PV. OP is very similar as is Parallel. None of them force a second split but all keep the PV under pressure. Conclusion: we seem tonight to have a milder path and a colder path and a lot depends on the evolution from T+120 to T+180. If we can get a new push of amplification into Greenland by T+180 and split the Atlantic trough, we're more or less set for a colder evolution. If not, the Atlantic prevails and we stay on the milder aide of the trough and if it's the latter it could be a long journey back to cold. If we can get that amplification, we could have several days on the colder side of the trough with all the possibilities flowing from that but it's finely balanced tonight.

Yes, I noticed that. ECM OP went on a completely different path to GFS and GEM yet the end effect was much the same. The thing with which I'm struggling is the GFS which continues in far FI to fire up the PV and the Atlantic as though the current SSW hadn't happened. My theory is the repeated wave 1 warmings from the Siberian side are sending the PV back over to Greenland/NE Canada where it is somehow able to re-strengthen in situ and, aided by a return of stronger zonal winds, energises the jet later this month. Now, IF the PV has been as weakened as the 10HPA charts suggest, I can't reconcile that and the longer-range model output. Are we using the usual GFS "bias" toward an Atlantic reset (to be fair, Control goes down a different, much colder and less intense PV route) or are we expecting a more "traditional" second half of winter which would suggest the impact of an early SSW is much less than some have suggested?

Evening all Before I do my nightly bletherings, thanks to all who provide similar or slightly different. We all have our different perspectives and it's good to see the debate on here. Most bring evidence-based argument to this forum and long may it continue. Last night's output did nothing to dispel my confusion of recent days - the considerable divergences in synoptic evolutions across and within the models at unusually short ranges suggest a plethora of signals (or perhaps no strong signal). The significant trend towards a milder evolution have been displaced by synoptically more interesting charts. In essence, it's the perennial battle between competing air masses and as is all too often the case the battleground is the atmosphere over the British Isles. Mild or cold, rain or snow, step up and placez votre bets as I'm sure they don't say at Monte Carlo. 12Z GEM: the most bullish initially for a milder solution, GEM backtracked quite a bit last evening toward a (briefly) colder spell before the re-assertion of mild at T+240. T+120 tonight take sus to Thursday and we can see the battleground scenario evidenced. HP to the south and heights building into Scandinavia bringing a frigid air flow out of Russia while the Atlantic trough extends to the north and west of the British Isles and between these systems a W'ly flow covers the British Isles. Despite that, the briefly positive uppers have been chased away by cooler air (zero to -4) returning from the north west and I also note the sharp gradient in the uppers over Central Europe. From there, well, nothing much happens. The Atlantic LP disrupts to the west as heights try to build through the British Isles but a small LP make sit through before filling up to the south-east. By T+180, the flow is slack from a mainly W'ly point. Frigid air is over central Europe by this time but for the British Isles it's mildest to the west and coldest to the east with a broad spread of zero to -4 850s. A cut-off trough remains in the Atlantic and this moves SE across the British Isles by T+240 and with heights building to Iceland a NNE'ly flow is established over the British isles with uppers generally below -4 and if you like that sort of fans, there's a nice area of -24 850s over north-west Russia and east Finland. 12Z GFS OP - GEM offers an oscillating background with little or no push from the Atlantic side. The American models were perhaps the most synoptically interesting yesterday - in FI it was real battleground stuff. Tonight, well, let's see. By T+120, notable differences with respect to GEM. The Scandinavian heights are better defined and the small area of HP has phased with the ridge from Iberia to put the whole of the British Isles (except the Hebrides) in a slack flow. There are milder incursions and by T+120 the 850s are zero to -4 with some very cold air over Germany. From there, it's broadly an anticyclonic tale with heights over or to close to the British Isles but by T+180 there's a slack trough to the north and a shallow feature over Europe but for most of the British Isles it remains calm with uppers broadly negative but varying from zero to -8 with coldest uppers to the north and east in a slack flow. From there, it gets "more interesting". Atlantic heights build north to Greenland and the Scandinavian trough drops over or to the east of the British isles drawing in a potent N'ly by T+240. It's much colder with -8 850s widely and -12 850s approaching from the Faeroes. 12Z Parallel - so that's 2-0 for the cold evolutions out to T+240. Parallel is always one of the more intriguing model sets. The T+120 perhaps closer to GEM than the OP with heights to the south, the north and north east and the Atlantic LP to the south of Iceland pushing in a flow of WSW'ly winds which have brought positive uppers to western regions and it's generally milder across the British Isles. From there, it's a very different evolution as an Atlantic LP deepens and moves NE to the west of the British Isles. New heights extend it from Iberia to Greenland while a weak HP persists over Scandinavia. It remains mild over the British Isles at this time. From there, the LP spins round and eventually eases towards the British Isles. Strong heights over Greenland look to be sending the jet south but the trough has expanded from the original cut-off LP to form an elongated trough across the Atlantic and into Europe. Secondary LP are forming in the flow to the south and a frigid airmass is coming over Scandinavia with -24 uppers. For the British Isles, it remains on the mild side - more so in the south than further north. 12Z ECM - I'll be honest - the parallel evolution from T+120 looks nonsensical and is symptomatic of the model output "struggling" with the data and the signals. ECM should provide some sanity though I wouldn't put my money (or yours) on it. ECM's T+120 illustrates the Battleground situation well, The British Isles is on the warm side of the struggle with an HP to the south-west and LP to the north-west. However, colder air isn't far away with heights over Scandinavia and a residual cold flow over Eastern Europe. Average temperatures over the British isles at this time. By T+192 ECM has gone on its own journey - a million miles from Parallel (see above). The Iberian HP expands into a significant anticyclone to the south west but small troughs extend south down the North Sea from the north leaving a weak N'ly flow over much of the British Isles. Colder air with -4 850s is established by T+192. From there, the HP edges a little further west but ridges north toward Iceland. Heights persist over Scandinavia and that allows a shallow LP to linger close to southern England with a draw of ENE'ly air across the British Isles. It's got colder again with -4 to -8 heights generally. I make that 3-1 to cold by T+240 but all by very different routes so the overriding message remains the number of options on the table but none of them showing a raging Atlantic and long-fetch SW'lies from huge LP systems created by strong cyclogenesis. Looking further on, GFS OP and Parallel at T+312 and T+384 respectively. Those raging Atlantic SW'lies I was mentioning a moment ago - there they are in the furthest recesses of FI on both OP and Parallel. Both bring back a strong PV in the last third of the month to Greenland and NE Canada - is this a response to the next round of wave 1 warmings? 12Z Control is cold for most of the run - it doesn't bring as much of the PV back either. On then to the 10 HPA charts - Control keeps the PV weak and disorganised though it shows some sign of rallying at the end of FI. The OP leaves the PV shredded under a succession of warmings, Parallel maintains a more robust PV despite the warmings. Confusion II - this time it's personal: - there seem to be more routes to cold in the medium term. It will warm up a little in the shorter term but the colder air is close by and the evolution to something more anticyclonic seems one option and with a sluggish Atlantic amplification opening the door to a push of cold from the north or east remains firmly on the table, Developments into further fI looks driven by the PV but I'm finding the GFS OP and Parallel evolutions harder to reconcile with what's happening. There will be a recovery of zonal winds from the current reversal but that's to be confirmed - the theory seems to be more wave 1 warmings from the Siberian side will send the PV back over to the Atlantic and as zonal winds pick up so will the jet as we head into the latter part of January. I'm far from convinced.

Evening all Another cold day in lowland East London and tomorrow will mark two weeks of below average temperatures since Storm Bella - another sharp frost overnight as well. Yes, it's not feet of snow and -20 uppers but in the context of recent times, not too bad. An evolution to something less cold or even mild is assured but some signs last evening of that not lasting while GFS went off not just on one but on a series of ones as the prevailing stratospheric happenings continue to play out in the atmosphere. On then to tonight's plateaux du jour from the models - will it be a sensual delight or a one way trip to the bathroom? Let's see.. 12Z GEM: T+120 takes us to next Wednesday. There are significant changes from the modelling of last evening at this time. The LP currently developing over to the west of Iceland, which on some earlier output was going to come south across the British Isles, then was going to stay to the north or north-east is now moving east before sinking south over western Scandinavia and quickly forming a trough south-east into the Ukraine. The HP to the south remains over Iberia but a nose of LP has split the ridge to new heights to the east of Iceland. Frigid air sits over Scandinavia (-16 850s anyone?). Over the British Isles, the initial push of milder air is replaced with a new plunge of colder air on Monday and Tuesday especially over northern and eastern parts with milder air trying to return from the west by T+120. It's a complex situation with a lot happening. From there, it doesn't get any simpler - basically, heights build to the west of the British Isles aligning north-south while weak heights sit to the north and north-east and the troughs sit over Poland and southern France respectively. A weak N'ly flow covers much of the British Isles with -4 to -8 uppers back in charge with the milder air pushed away to the south. From there, the HP slowly topples across the British isles and into north-western Europe with a weak Atlantic flow coming in although heights persist to the north. Milder air has reached almost all parts of the British Isles by T+240. 12Z GFS OP - that was an interesting run from GEM which was the most bullish for mild a couple of days ago. The American OP was quite bullish about a mild evolution yesterday but let's see what it offers this chill Friday evening - big differences from GEM as early as T+120. A more straightforward Atlantic-based evolution with HP over or just to the north-west of Iberia and a run of WSW'ly winds with a complex upstream Atlantic trough and the residual Scandinavian trough over the Baltic States. Again, a brief push of colder air back south but GFS pushes this away quicker than GEM and by T+120 most of the British Isles is in a milder airflow. From T+120 it's the GFS OP's turn to go complex. The Atlantic LP goes nowhere slowly and heights rise through the British Isles to Scandinavia but a small lobe of the trough develops into a secondary LP and crosses the British Isles being in the southern North Sea by T+180. 850s are zero to -4 over much of the British isles but with milder air again encroaching from the west. Oddly enough, it gets even messier from there with the Atlantic LP cut off by a new wedge of heights extending south-east from Greenland to Iberia with a new Atlantic LP diving SE. The trough over the British Isles extends from eastern Iceland through the British Isles (with a secondary feature over East Anglia) and further south-east to the Balkans. Weak heights are now over Scandinavia. Colder air has extended back through the British Isles by T+240 with uppers of zero to -4 generally. 12Z Parallel - another significant upgrade for cold from GFS OP and the chart a million miles from GEM at the same time. On then to Parallel which was more bullish for cold yesterday. Once again, differences as early as T+120 with Parallel positing a more robust Atlantic with more defined heights to the north and a weaker HP to the south. Milder air is back across the whole British Isles by this time. From there, heights develop over Scandinavia and points further north and west and this deflects the Atlantic LP SE down the North Sea. By T+180 a shallow LP is off the north west coast of Scotland with heights persisting to the south. Milder in the south but colder air persists in the north. From there, the Scandinavian heights dissipate but heights build over Greenland and these start to push the jet and the LP further south so by T+240 the LP are crossing the British Isles but the divide between a mild south and west and a colder north and east persists as do heights over Iberia. 12Z ECM - Parallel is intriguing as well albeit mild for many and especially in the south. Finally, ECM and with the huge uncertainty in the other models, I expect something completely different. By T+120, ECM has a more progressive Atlantic profile but otherwise nothing too dramatic. Milder air covers all parts of the British isles by this time. By T+192, a wedge of heights has tried to build into Scandinavia but a new Atlantic LP over Iceland has thrown a trough over the British Isles even as heights rise upstream. It's still on the mild side at this time. The heights manage to split the trough by T+240 with a new wedge of heights running from west of Iberia north-north-west to Greenland leaving the British Isles on the cold side of the trough with a series of weak LP to the north and east. It's colder too with -4 uppers generally and -8 uppers approaching the east coast. It's a fascinating split - ECM and GFS OP take us back cold, Parallel is heading the same way as T+240 and only GEM has a milder solution. I note 12Z JMA is cold by T+192 while UKMO teases at T+144. Looking further ahead, the usual "far FI" charts (no, not T+144) from GFS OP and Parallel at T+312 and T+384 respectively. After nights of real divergence, some notable similarities in OP and Parallel this evening. Both show strong Greenland heights - neither shows a raging PV in its usual place, both show a jet tracking south and both show real cold cores to the east. Looking further afield, 12Z Control has plenty of cold as well. As for the 10 HPA charts, Control keeps the vortex under pressure with a series of strong warmings through FI. Similar evolution on OP and Parallel. Confusion: - yep, that's still in charge tonight. Apart from GEM, which offers something colder around T+180, there's a general move towards something milder early next week despite a brief final push of colder air from the north. From T+180 GEM makes less of any Greenland heights and brings back a milder evolution. GFS OP and ECM have the ridge SE from Greenland to Iberia which keeps the British isles under the cold trough while Parallel is nearly there but keeps the door open to the Atlantic albeit with the jet being pushed south. Further into FI, the story is one of a southerly jet and LP moving over the British Isles so potentially a lot of weather as we move further into January with milder spells and colder spells aplenty. The south always perhaps on the milder and wetter die but a lot of snow opportunities further north with the PV settling over or close to Scandinavia helping to steer Atlantic systems south and east. All I'll say is there's a lot of weather forecast - what, when and for whom is up for grabs.

Evening all A pleasant but chill day in lowland East London and it seems some may get some snow tonight or tomorrow. I'm not optimistic for my corner of the world but I'd like a really severe frost to last most of the day for a change. It's not much to ask. The model output was awash with uncertainty last evening with all manner of different synoptic evolutions at T+240 and some marked differences as early as T+120. Will tonight bring clarity or confusion? My money (and it remains very nice money) is on the latter but we'll see. 12Z GEM: the most bullish of the output last night towards a mild evolution. T+120 take sus to next Tuesday - a ridge of HP from Iberia to Ireland dominates the weather. A complex LP over Scandinavia has pulled down some frigid air while a new Atlantic LP is to the south of Greenland. SW'ly winds cover much of the British isles but a residual chill NW'ly affects extreme eastern areas. The initial push of milder air in the second half of the weekend is displaced by a colder push of NW'lies early next week with -4 to -8 uppers returning for eastern parts. From there, the evolution becomes more complex - HP remains over Iberia but the ridge disappears as Atlantic LP tries to move in but with no jet to push the systems forward and heights building from the north, the trough is forces south and east over the British Isles by T+180. Mild air has pushed across the British Isles but a frigid block holds sway over Scandinavia. From there, the LP eases to the east and we get a brief blast of very cold NE'ly winds before a lobe of HP moves down from Greenland through the British isles to Iberia. Heights are strong over Greenland with the jet well to the south and a ridge over the British Isles. by T+240 the coldest uppers have moved to the south and milder air is again trying to encroach from the west. 12Z GFS OP - a sharp pull away from the mild evolution of yesterday from GEM. GFS OP was quite mild as well so let's see if it follows the trend. At T+120 marked differences to the GEM. A small LP sits over southern Britain with a more pronounced build of pressure north to Iceland and the next Atlantic LP far to the west. After a brief milder spell, colder air is already coming down from the north with -8 uppers close to northern Scotland. From there, the HP ridge remains in charge through to T+180 with weak Atlantic features moving NE and a long-fetch SW'ly in charge. This pushes milder air into Scandinavia. From there, the evolution gets a little messy but essentially the HP remains to the south and LP to the north-west with Greenland heights developing but not influential. It remains mild over the British Isles by T+240 with the coldest air far to the north. 12Z Parallel - the OP keeps things mild but the Parallel was an intriguing offering yesterday. At T+120 there aren't huge differences with the OP. Colder air is pushing south across northern and eastern areas of the British Isles in the wake of the Scandinavian trough while milder air approaches from the west. By T+180 the weak Atlantic LP systems are close to the west but there's not much happening to the north and east and a strong ridge of HP is developing upstream in the Atlantic. Mild air covers the British Isles during this period. From there, weak areas of LP cross the British Isles and then ease SE and by T+240 one such elongated LP is off the north-east coast with a WNW'ly flow over the British isles and a cut -off Atlantic LP with further upstream ridging from Greenland. Milder air remains over southern and western parts while it's slightly cooler elsewhere. 12Z ECM - not quite sure about Parallel. It's almost as though it wants to go somewhere interesting but doesn't know how. Yes, it's all computer generated modelling and I shouldn't personalise it. Perhaps ECM can restore some sanity. It doesn't help with another different evolution at T+120. The British Isles is in a col with heights to north and south and LP system to the east and west. Milder air has pushed into most areas but it's still cold to the north. From there, the Atlantic LP goes nowhere slowly and heights try to build through the British Isles from the south. A light N@ly to the east of the ridge has drawn -4 uppers back in to the UK while it remains mild to the west. It looks as though the Atlantic will take over but at T+240 the LP is moving across the British Isles while the HP eases WNW to join with heights over Greenland. The possibility of a mid Atlantic block forming and leaving the British isles on the cold side is obvious. Not for the first time, ECM tantalises and teases at day 10. Moving further on, the usual T+312 and T+384 charts from the GFS OP and Parallel runs respectively. Both end mild though one has a powerful PV over Greenland and the other doesn't. Looking elsewhere, 12Z Control ends stormy with a super-charged Atlantic. On the 10 HPA front, Control still has the second warming (which might explain why we are seeing a restored vortex in our part of the planet in far FI) which doesn't split the vortex. OP weakens the vortex more noticeably. and Parallel is much the same. Conclusion: GEM and ECM tantalise with some interest in their evolutions but GFS seems less interested tonight in promoting anything other than a mild Atlantic with HP to the south of the British Isles. I'm wondering if the second warming is being seen as a more traditional wave 1 warming which will shunt the PV back to Greenland/NE Canada where it can re-strengthen and fire up a strong zonal jet. It seems odd that a major SSW now seems to have so little impact later in the month but GFS has been playing this tune for a while. ECM at T+240 is a real tease while GEM at the same time isn't too bad. There are still significant synoptic differences early in the evolution so it's hard to take too many of the later charts too seriously.

Evening all First, thanks to everyone who enjoys my nightly ramblings on the medium to long term model output. I try to keep it light-headed and sometimes light-headed and while I enjoy snow, cold is where I'm at but when you see the writing on the wall for a cold spell, it merely starts the countdown to the next chase. Milder weather looks likely after the weekend and into next week but with interesting developments in the stratosphere could this be a blip before the cold returns? My money (and very nice money it is too) has been on an anticyclonic evolution but we need the HP somewhere interesting to draw in the frigid air rather than the benign and dull westerlies. The route to very cold starts from very mild in my experience. 12Z GEM: T+120 takes us to Monday next week and the milder air is with us with a long ridge of HP from east of the Azores to south-western parts of the British isles. The LP which develops over Iceland is over Scandinavia delivering plenty of winter for them but the cold PM air flow looks like it will miss us and we have a benign drift from the WSW with a shallow but extensive Atlantic trough to the west and south west. A shallow LP crosses the British isles but by T+180 there are signs of amplification with the Atlantic LP deepening and going nowhere allowing heights to rise in front of it meaning the HP over the north-west of Iberia ridging north over the British isles to weak heights forming to the north-east of Iceland. The mild or very mild regime very much in charge at this time. Not much changes from there - the mild anticyclonic regime strengthen its grip with the HP moving slowly north and by T+240 extending a ridge to Iceland. A small LP extends east, then south-east into the northern North Sea and Scandinavia. Mild or very mild air (850s of +12) is briefly displaced from the north-west but any frigid air is well to the east at this time. 12Z GFS OP - a mild or very mild outlook from GEM which was the most bullish of the models last evening regarding the extent of the mild regime. On then to the Americans and the GFS OP - at T+120 some subtle differences from the GEM. The Atlantic is closer with a more progressive profile and the HP ridge weaker with the core further south. Cold air persists over southern England while milder air is spilling in from the west and north west. The divergence intensifies as you might expect as we move on to T+180 - the HP is over or just to the south of the British isles with a slack or calm flow for many and a residual trough over Norway. As we often see in these evolutions, it's colder in the south closest to the residual cold continental air and milder in the north and west. From there, the evolution is fascinating as the HP tries to build north to meet heights coming from the Pole - one lobe of LP gets through before, by T+240, the gap is closed. The air mass over the British Isles cools slightly with positive uppers confined to the far south-west. 12Z GFS Parallel - GFS OP very different to GEM and intriguing to say the least - I'll be fascinated to see where it goes further into FI. As for Parallel, it's also different as early as T+120 with the Atlantic trough phasing with the trough which is still over the Norwegian coast. The HP sends a weak ridge from the Azores over southern Britain. Still some -4 uppers over southern Britain at this time but it's getting a little milder further north. By T+180 it's looking like a complex and messy evolution. The HP is trying to build north through the British Isles while the Atlantic LP systems are going nowhere slowly far to the west and the trough remains over Scandinavia. By this time, colder air is restricted to northern and north-eastern parts of the British isles with milder air further south and west. The complexity continues from T+180 with heights to the far north becoming more evident pushing the trough to the south and aligning it negatively as the HP recedes so a more unsettled evolution by T+240. Cooler air spilling east with frigid air (-20 uppers) over Finland. 12Z ECM - again, another very different evolution with the whole evening screaming confusion and uncertainty even as early as T+120. Once again, T+120 looks different - the Scandinavian LP is further south and close to the south western coast of Norway with a weak ridge extending south from Greenland. Mild W'ly winds over most of the British Isles with the HP centred west of Biscay. Moving on and while t looks briefly as though the Atlantic will take charge, by T+192, the HP is over Iberia and heights remain to the north with a ridge from the HP. It's generally mild over the British Isles at this time with a feed of cooler air into the north-west. By T+240, however, the Atlantic re-asserts with the trough aligned positively and a long-fetch SW'ly air flow. Milder air hasn't quite arrived but is approaching. A disappointing end to the ECM but on a night of confusion in the models should I be surprised it's a case of "safety first"? Looking further ahead and with even more buckets of salt than usual, the T+312 and T+384 charts from the GFS OP and Parallel runs respectively. As alike as two dissimilar things in a pod - one is mild and the other isn't. Looking elsewhere, 12Z Control is completely different, mild for the most part but at the end of FI turning colder and stormy from the north with some very cold air moving in. On to the 10 HPA charts and Control has another strong warming after mid month which further weakens the stratosphere. The FI warming is even more marked on the OP run but is much more muted on the Parallel. Conclusion: There was a popular series on Radio4 called "I'm Sorry I Haven't A Clue" and that's where I am tonight. GEM is bullish about a mild evolution but GFS much less so and ECM somewhere in the middle. FI is probably T+96 onwards but a couple of thoughts. The trend is for heights to try to push north from Iberia to link with heights coming south from the Pole. For now, the Atlantic seems to have too much energy to make it happen but the Atlantic is sluggish and propping up all this is both the weak PV and the frigid air to the east which is acting as a block in its own right. For now, the Scandinavian trough holds sway but it's possible we could see heights develop in time which would be fascinating. Those who argue the PV split/displacement is causing issues with the modelling have a point and it's difficult to be definite about the medium to longer term evolution tonight.

Evening all :) It's that time of day when I look at some of the medium and longer term trends on the output. The key development over the last few days has been the growing consensus for an end to the current cool/cold non-event /spell (delete as appropriate) and an evolution to a more anticyclonic spell with HP initially to the south or south west of the British Isles promoting mild W'ly or SW'ly winds but with the Atlantic sluggish to moribund, the opportunities for amplification at higher latitudes seem to be there but will they work for the British Isles? 12Z GEM: T+120 takes us to Sunday and by then the British isles is under a ridge of HP from the Atlantic with a significant LP in the Norwegian Sea. 850s are around zero but milder air is moving in across Ireland and into western parts of the United Kingdom. Moving forward, the LP over the Norwegian Sea fills as it moves SE into Scandinavia while the HP over the British Isles eases south but with the Atlantic still sluggish, weak heights are trying to form over or just to the north. 850s continue around zero in slack or even calm conditions. From T+180, the HP moves into Iberia and around its western, northern and eastern flanks a succession of LP move to the north of the British Isles and down into eastern Europe. Mild air covers the British Isles in a benign weather environment. 12Z GFS OP - for those of us who like interesting and unusual synoptics, GEM was ditchwater-like in its dullness. I'm not expecting much better tonight if I'm honest but let's see what GFS OP has to offer - at T+120 a ridge from the Canaries through the west of Biscay to south-west England leaves a flow of WSW'ly air over the British Isles while LP remains to the north. 850s are still zero to -4 at this time. By T+180 not too different from the GEM with a weak ridge of HP covering the British Isles. Some colder air has infiltrated the north and east behind a trough over Scandinavia but milder air is encroaching from the west across Ireland once again. From there, a new LP from lower latitudes swings NE well to the west of Ireland throwing a ridge into Iberia and mile or very mild SW'ly winds over the British Isles by T+240. The PV lobe looks to be over eastern Scandinavia with some very cold air. 12Z Parallel: - GFS OP keeps the mild theme but Parallel still has a residual NE'ly for the far south of Britain at T+120 with the trough more influential than on other models. Uppers are generally zero to -4 but some colder air close to the south coast. The evolution to T+180 isn't too surprising with a weak ridge of HP extending north from Iberia through western Britain to Iceland while the trough digs down over Scandinavia. Colder air to the north and east of Scotland once again as milder air returns from the west. From there, it gets more interesting as the LP from lower latitudes swings NE but fills as it does so and keeps further to the west allowing the ridge of HP to persist in tandem with heights building to the north of the British Isles. Milder air has come in but cold air is very close to the east coast with -4 850s over East Anglia. 12Z ECM - an intriguing Parallel but I'm not expecting anything from the mildie's friend, ECM. No real surprises at T+120 - perhaps the LP a smidgen further south than on other models. By T+192 weak heights over Greenland with the main HP over Biscay and the Scandinavian trough away over the Baltic States. Milder air for all by this time as you would expect. From there, a bit of a surprise as heights build to the north at T+216 before the anticyclone re-centres over the British Isles at T+240 with a slack Atlantic and a small LP north of the Canaries helping to prop up the new HP. Colder air is pushing back into the south-east on a light NE'ly breeze. Looking ahead, I will, as usual offer the OP and Parallel output at T+312 and T+384 respectively for direction of travel/casual interest/waste of space (delete as appropriate). Confused? That makes two of us. Looking elsewhere, 12Z Control also ends very messy. The 10 HPA charts all show the PV recovering from the initial split/displacement ongoing but coming under further attack after mid month and being shoved around a prize boxer having a bad night. Conclusion: - signs of more interest in tonight's output with both ECM and Parallel hinting at the anticyclone setting up near or just to the north of the British isles keeping any milder interlude fairly brief. Both GFS OP and GEM keep the mild theme going and the GFS suite into far FI is just all over the place so I suspect those claiming the models are struggling with the impacts of other events may have a point and certainly I have no clue much beyond mid month tonight. In the medium term, a milder 3-5 days looks likely but cold air is never far away and we aren't looking at anything too dramatic - indeed, next week could be quite benign and quiet before it gets more "interesting" again.

Evening all A chilly day here in lowland East London but the models were preparing to call time on the cold spell last evening. GEM and to an extent ECM were bringing in milder air by the end of the week while for GFS the milder conditions were postponed for a couple of days. With events in the stratosphere providing an intriguing contrast, would this be a pattern change for the rest of winter or a brief interlude - probably too early to tell but perhaps this evening will offer some clues (or perhaps not). 12Z GEM: T+120 is Saturday and by then the NE'ly has been pushed south as the Atlantic ridge builds across the British Isles. To the north, a significant storm has developed close to Iceland. The airmass remains cold over the British Isles at this time. From there, the LP heads SE into Scandinavia and by T+180 is centred over Sweden with a secondary centre to the west of Norway. A N'ly air flow covers the British Isles with weak heights over Iceland extending SE while the previous Atlantic HP has continued south. A brief milder interlude is replaced by a new push of colder air from the north. The evolution up to T+240 gets messier - the Azores based HP moves back NE to be centred over or to the west of Iberia with a weak Atlantic feature moving toward Iceland and a hint of heights over Scandinavia. Milder air moves slowly east across the British Isles by T+240 but significant cold air sits just to the east. 12Z GFS OP - GEM is unconvincing but as we've seen recently, there's no jet to power deep Atlantic storm systems from west to east. It's more like a summer chart than a winter one in some ways. On then to the GFS OP. By T+120 the general pattern is in place - a more pronounced trough over the western Mediterranean and a new LP over Iceland with a small ridge of HP across the British Isles at this time. The air mass over the British Isles remains cold - -8 uppers in the south east and a new push of cold air approaching from the north west. The LP pushes SE to the north and north east of the British Isles and is over Denmark by T+180 with a N'ly airflow to its western flank. Heights to the west look insufficient to stop a new push from the Atlantic. Uppers remain chilly at -4 by T+180. I am of course wrong about the heights which develop to form a new anticyclone over or just to the south of the British Isles by T+240. The residual trough remains over Scandinavia and again the Atlantic is doing nothing slowly. As with GEM, milder air is slowly encroaching from the west by T+240. 12Z Parallel - for all its modernity, Parallel has thrown up some interesting solutions in recent days but with GEM and GFS OP unusually close at T+240, let's see if it goes down another path. No real surprises at T+120 but perhaps a more defined ridge into Scandinavia. Indeed, Parallel does go a different route - the Icelandic LP fills more or less in situ and after a final flourish from the European trough, the HP builds in by T+180 settling conditions down as milder SW'ly winds reach the far north and west of the British Isles. However, by T+180 milder air is over or close to all parts. Not much changes through to T+240 with the HP intensifying over or to the west of Biscay and feeding mild SW'ly wins over all parts. Just to note Shetland stays on the colder aide with -8 uppers. 12Z ECM - Parallel breaks down the cold spell more quickly than GEM or GFS OP as the Icelandic LP doesn't get involved. On then to ECM and no surprises at T+120. By T+192 it has also brought back the milder Atlantic air with the HP to the south west and the Icelandic LP having moved east toward northern Scandinavia and a new LP forming to the far west to the south of Greenland. After a final cold push at the weekend, milder air is back over all parts by early next week. The T+240 map is strongly anticyclonic but I don't see a raging northern arm to the jet at this time so do we get a hint of height rises to the north east as well? Maybe but for the moment the milder Atlantic air has won out. Moving further into FI I offer, as usual, the T+312 and T+384 charts from GFS OP and GFS Parallel respectively. As we saw last evening, one builds a huge PV back over Greenland and NE Canada and the other doesn't. I'll leave you to figure out which is which. Looking elsewhere, 12Z Control is also very anticyclonic. Beyond that, the 10 HPA charts show the PV recovering into far FI with core temperatures back to -72 - it's not the size or strength you'd expect in mid January to be fair. Conclusion: can we push the cold through the coming weekend? Possibly and especially if the Icelandic LP is a player but the clear theme is anticyclonic with the initial HP build to the south or south-west which allows milder Atlantic air to push across early next week. From there and in the absence of a raging Atlantic, we have to wait for amplification (Parallel hints at this in far FI) to push the HP further north. GFS OP builds a strong PV in far FI with which I'm struggling and perhaps we need to keep looking for signs of heights over Scandinavia as frigid air isn't too far away. Many areas which have seen huge rainfall totals will welcome drier conditions and of course fog and frost can be issues with clear skies at this time of year but that's detail to be resolved.