Snowaddict

With regard to a breakdown of the current anomalously cold spell & the medium term... There seems to be a strong to significant propensity for further Warm Air Advection to Northern Latitudes, perhaps north of the British Isles, which was the precursor to this very cold spell. This has been indicated several times on various GFS runs over the past 48 hours & is now being hinted at on the UKMO @ T+144 this afternoon: http://www.meteociel.fr/modeles/ukmo2.php?nh=&ech=144&carte=1021 Now, it may well be that the Jet entails as being just slightly too strong, but I think that there is an outside chance, probably around 10% at the moment, of a displacement of a ridge from the south towards and perhaps into Scandinavia... The UKMO T+144 chart is particularly interesting with low pressure oscillating south of Iceland and lower pressure due east at T+144, with a rapid northward/northeastward progression of the ridge from the south... This is potentially one way of getting into another reload that could begin around the very end of the year and into early January... Pressure remains anomalously high to the variable north and any link up between a displaced ridge from the south should be far easier than usual because of this. Further out and there are indications of a fairly strong ridge off the Eastern US & Canadian maritimes towards T+180, as shown on today's GFS evolution @ around T+192 on last night's ECMWF.. Again, it is possible that a link up to higher than normal pressure to the variable north may occur at this juncture.. The 30mb temperature is certainly a concern at this point as we know that it's present phase could well result in enhanced zonal activity across the North Atlantic some 15 - 20 days from now. We can only hope that we will see a warming over the next week or two.. I would be very surprised to see any snow falling on Christmas day across the south, with a slightly bigger chance of snowfall across the north.. Snow will still be on the ground though at several locations... Overall, it may be a case of a 5 day ''warm up'', relatively speaking before the onset of another potential cold spell & I think the T+144 & T+180 timeframes are the main one's to watch at the moment for the possibilities mentioned above. SA

Also, Ireland would be on the ''colder'' side of that low JS by T+168.. VERY interesting patterns to say the least!

What can I say? Lost for words really, the entire run from start to finish is amazing.. This cold spell has the potential for epic low temperatures and snowfalls on various occasions.. In addition, I would note the evolution in the Atlantic... Just take a look at the Parallel Run: Blizzards, crippling snowfall on Christmas Day, as the lows become elongated and take a southerly track, held back by entrenched colder air.. The British Isles would be shut down if these outputs verified, plus there would be a White Christmas for everyone.. These are classic outputs, treasure them for it's not often you see these types of runs..

With Regard To The Easterly: 12Z Ensemble Analysis: AT T+102 & Onwards... Perturbation 2, 3, 4, 5, 7, 8, 10, 11, 13, 14, 15, 16, 20... That's 65% confidence in the Ensembles for a potent (850's of -8 to -13 or -14 showing) easterly across the British Isles @ T+102 and onwards. Even other perturbations have slightly less cold air or less westward advection, but still opportunities for snowfall. That's VERY high confidence in a potent easterly from the 12Z GEFS suite..

UKMO is still a VERY good run in terms of the easterly, albeit only slightly less prolonged & potent than this morning, especially @ T+144.. I thought that this was going to be a balanced thread? There is still plenty of scope for easterly snowfall from the UKMO along with snow spreading south towards T+144.. Honestly, if people are not happy with these outputs then I don't know what to say!

Whatever the outcome, it will be a major test for the ECMWF model... As I've said earlier, 12Z runs in the past few days have tended to be more potent in terms of cold than the 00Z runs. However, I would hope that ECMWF is nearer the mark. I still don't think that this will be sorted until possibly even the 12Zs tomorrow. Tonight it's ECMWF & GME on one extreme V GFS Middle Ground V Meto at the ''uninteresting'' end of the scale.. Sense would suggest that a middle ground will prevail, but for once it would be nice to see ECMWF verify as shown tonight as the precip charts that I posted earlier are very tasty indeed.

Agreed The Eagle, ECMWF is not freely available apart from a few screenshots so to speak, for exactly the reasons you have outlined above.. Now, whilst it may tone down a bit overnight - I would hope & be quite confident that it is nearest the mark.. For example, the Met Eireann forecasts tonight speak of a wintry spell come mid next week - exactly in line with ECMWF guidance.. In addition, they must have good ensemble support for the operational evolution as they certainly don't call wintry weather unless there is at least a fairly good consensus towards it. The evolution will change yet but ECMWF is still verifying the best out of all models & has been relatively consistent over the past two days, on all 4 runs.. Fingers crossed.

Even more encouraging is that ECMWF, in the past two days has retuned to the top! You can just make it out there with the GFS Parallel Run on the most recent section of the chart.. From the ECMWF Precip Charts @ T+120, Eastern Scotland, the majority of Central & Eastern England along with Eastern and Southeastern Ireland would receive fairly significant snow showers...

IF, & it's a big IF tonight's ECMWF run verified, eastern Ireland could do very well next week, very well indeed. I notice that sleet and snow, albeit at elevated levels, was mentioned on the 6PM broadcast by Gerry Murphy!! - Probably indicating usage of the 12Z ECMWF guidance, especially when G Murphy has mentioned the prospects of snowfall. It's really quite difficult at such a close range to know what the outcome will be. It seems all or nothing when you compare UKMO with ECMWF... If the evolution were that of the ECMWF 12Z, eastern, southeastern and northeastern areas would be first affected in Ireland, with the WNW then taking a pounding later on in the week with the potential for embedded troughs to travel down across the country. Quite stunning output - let's just hope it turns out like that.

STUNNING ECMWF tonight - right from T+72.. However, there are clearly HUGE differences between various sources of NWP guidance. ECMWF and GME seem to be well in favour of a very potent wintry incursion. ECMWF guidance has a cold, snowy spell lasting for at least 9 Days.. GFS 12Z had a somewhat less potent and snow condusive easterly but still followed on with the third cold plunge from the north.. UKMO very different to ECMWF tonight.. What I would note is that ECMWF 12Z runs in the past few days have tended to be tastier than the 00Z runs, so that should be borne in mind.. Overall, a forecaster's nightmare with the potential for significant snowfall all across the British Isles if ECMWF 12Z were to verify along with VERY cold and strong easterly winds next week. Interesting, to say the least.

Very potent air making it across the British Isles on the 12Z GFS Parallel Output.. It looks as though from late Wednesday onwards it will be turning sharply colder..

Apart from looking at specifics in terms of snow etc etc.. This run, broadly shows that we COULD be headed for a very prolonged spell of cold, to very cold weather.. The setup is perfect on the 12Z evolution really for renewed cold and severely cold minima.

An excellent GME/DWD 12Z Output this afternoon.. http://www.meteociel.fr/modeles/gmee_cartes.php?&ech=132&mode=1 MUCH improved on the overnight run with -8's to -13's widely across the British Isles in a stiff easterly wind.. Plenty of snowfall opportunities from that also..

Indeed, although the Parallel Run is an absolute stunner from start to finish with blizzards throughout FI.. From T+180 onwards!

Another excellent early FI T+192 - T+240 section of the Parallel Run.. Again, significant snowfall widespread across the British Isles, crippling snowfall in fact with widespread blizzards.. Maybe not likely at the moment but if cold air becomes entrenched enough then any renewed incursion from the NW/W/SW will almost certainly lead to a period of quite possibly significant snowfall... This has the POTENTIAL to be the most widespread and significant cold spell in many years, with great potential for snowfall.. I actually prefer the ECMWF evolution this evening because it is slightly more potent in terms of the easterly - but all model guidance fantastic & within the relaible timeframe! Fingers crossed that the evolution now holds.

Indeed, streamer type developments off the Irish Sea.. If you look at the frames from even T+120 out to at least T+150... With a flow from the E/ENE, bands of showery activity can develop over the Irish Sea, generally from Nth Country Dublin down to Wexford & can penetrate inland up to about 50/60 miles, depending upon the flow. Areas generally affected in this setup range from West Waterford due north as far as Westmeath/East North Midlands and across to the East Coast.. May be marginal at first on the very east coast but overall, the 18Z GFS Parallel would deliver quite a bit of snow to the east and southeast..

Parallel Run... Snowfall @ T+120 across Eastern Ireland & the Eastern UK, intensifying gradually.. By T+132 Significant Snowfall across the majority of E & SE Ireland & the majoritfy of the UK, with VERY heavy snowfall across East Anglia - moving south.. If this output verifies there will be significant disruption & severe cold next week..

Another excellent 18Z run, I can't believe all this in the more reliable 1 - 6 day timeframe.... MUCH better FAX T+120 chart... Excellent in fact with the 528DAM line across majority of British Isles.. Troughts embedded in a stiffening easterly flow.. It's getting close to the timeframe where this can really begin to be ramped up.. STUNNING synoptics!

They were still using 00Z ECMWF guidance John.. Generally update with 12Z ECMWF @ 9.30PM broadcast, but then again maybe they are also playing it safe..

I saw this also JS... John Eagleton was using the 00Z ECMWF Operational Run, I went & compared it to the overnight ECMWF as the trough was far more elongated & the high nearer to the British Isles than on today's 12Z.. Expect the 9.30PM broadcast to include the 12Z ECMWF guidance..

This ECMWF surely, just surely cannot be correct - although I really do hope that it is! It's exceptionally wintry from start to finish... 850's down to -4 to -6 by T+120... Even at T+72 - T+96 the pattern is set.. T+168 850's of -10 across Ireland, -12 across the UK... Followed by a complete reload from the North. The entire British Isles would be cut off by Day 10 if this run were to occur & with the agreement this evening on the ''upgrading'' of next weeks' easterly I'm sure that the pros at Exeter must be a bit concerned to say the least. One word, from start to finish - STUNNING. IF this run were to verify then we would be heading for a Feb 1991, or even better!

Indeed Matty & just look at T+144... Absolute turnaround from ECMWF... But as you say, yet more changes heavily likely given the inconsistencies lately & the difficulty in modelling this setup..

EXCELLENT ECMWF out to T+120... Shortwave slips into the British Isles with cold air being advected west and strong northeasterly winds... Even at T+96 it will feel very cold.. Just goes to show what changes can develop... I would ignore anything past T+144 at the moment there are so many changes.. But it now looks as if the chances of snow next week have been upgraded significantly across the UK & Ireland, all depending upon the depth of the cold air... Synoptics are fantastic

Eastern Ireland could do VERY well from both of the setups modelled by GFS & UKMO @ T+120 & T+144... GFS 12Z is all round a fantastic run. However, we've been here before & anything past T+96 should be taken lightly at the moment.. Right now I would say that both of the above 12Z's have come somewhat into line with the overnight ECMWF evolution. IF & it's a big IF - it plays out as shown on the latest guidance then snow will be on the way, for many. Either way it's starting to and will get rather cold to perhaps very cold as we continue forward. There is also a growing consensus for a third cold incursion from due north as we head towards Day 8 - Day 10...

In spite of an excellent GFS 18Z Operational, Control, Parallel Run & Ensemble Mean... I would say be weary, very weary because it's very, very uncommon for ECMWF to backtrack as such a close timeframe to realtime. The differences are stark this evening, even from T+72.. Again, as what I said earlier, past letdowns have learned us that GFS can backtrack in one run... As many have said, the 00Z's will be absolutely crucial, along with tomorrow's 12Z's.. In light of every available source of model guidance tonight, including FAX charts, I would lower the potential for a snowy outbreak to 30% & no higher.. It will turn cold, increasingly cold, but whether it will be sustained or snowy is really open to question. I fear that the ECMWF 12Z run will be nearer the mark, but I hope & pray that GFS is correct. I think everyone should lower expectations slightly just in case an overnight reversion to ECMWF 12Z does take place.