SMU

So to repeat what I just added over on TWO bin all the GFS & ECM suites go with a total pattern change in the next 12-24 hours to a very cold easterly at 144-168 quote - Appologies for any spelling- tapping on phone Just to add to me comment from earlier as I have half hour - I can assure everyone I wouldnt just post & comment If I didnt believe it would have a strong probability of happening- I have been saying the same for days on NW but maybe not as clear & as loud - As it stands there is no ensemble support ( less than 10%) for what im saying but im drawing on what ive seen over the last 14 years - watching every run ( winter ) of the AVN > GFS UKMO & ECM right back to the old snowatch days - I guess in those 14 years the amount of runs modelling scandi / Russian highs delivering deep cold to say debilt at 120-144 have been averaged about 2/3 a year ( obviously thats all the runs for 1 outcome grouped together each time ) & of those 40 odd scenarios the deep cold has penetated to the UK probably a third of those occasions - my memory highlights Feb 2005 , Feb 2009 , dec 10, jan 13- Mar 13 ( rem the undercutter ) but of course some more - also the pain of many failures- I would also add that across those 40 scenarios as a rule of thumb the AVN / GFS is as useless as they come - & to top that the GFS ensembles are the cherry on the useless cake - The ECM has performed well - however its lost some of its kudos in recent years - The UKMO has been pretty consistent but of course has occasionally got it wrong- I would like to think I know where to look when seeing these models & what their weaknesses are - GFS never seems to model the scandi blocking well but also its secondary weakness is not having the resolution to seperate parcels of energy ( PVA ) So when you have a scandi block & are reliant on the models deciphering how much energy is seperated & heads SE so the GFS is at its weakest - it will always move the jet through the block at a NE angle until it gets to grip with the real solution - this often arrives rapidly in the 96-120 arena on operationals & usually a day later on the ensembles - so the integrity of the GFS suite today at 144-168 is pretty flakey. The NE angle of attack is then replaced with a SE angle of attack - The euros will be much more realistic & should be prone to less swings ( again ECM has been showing occasional inter run volality since the upgrade - ) Its also become more apparent to me that theres ALWAYS a trend in the days modelling - sometimes its blindingly obvious - sometimes more subtle- I look for these trends in the places that will impact the Uk in the following days - so thats not overhead -& in this scenario its the development & angle of the dreaded shortwaves coming around the high over russia - to the angle of the waves exiting the coast of the US- These nuances & changes at say 72-96 are the ones that have the 'big' impacts on the pattern at 144-168 I find this far more interesting than chasing future possible teleconnection changes as they are far more specific to the UK- which in my view is of course more important - Anyway- We are at the exact point today where a CRITICAL element of the resolution of the energy distribution will have large scale impacts on the pattern feeding Europe ( NW ) including the UK at 144-168 The models for probably 4-5 days have had the MAIN low arriving at 120 stalling out somewhere close to the NW of the UK allowing energy underneath to be sufficient to keep the deep cold east past Debilt- They havent allowed any lows to 'turn over' & advect the cold back west... ECM & GFS 00z both support this scenario by developing a wave off the gulf at around 84-90 which aubsequently gets swept up in the eastward jet ( flat no amplification ) this wave then comes under the parent low at 144 & slides across southern england giving a very brief continental flow on its Northern flank - (ECM 00z + GFS 00z) However as the flow behind it sees additional phasing of low pressures in the atlantic & the subsequent development of the deep circular low - it all sweeps east with ease- Goodbye block-:( Also to the NE towards Norway the models have placed another shortwave with low heights there traversing WNW- this again stops the block forcing ESE towards the UK. So in isolation - theres just 2 shortwave features both conspiring against the UK for cold... But what if the trend of the day was to change the modelling of these in terms of positions? Well then the longwave pattern will follow- Its my proposal that as we reach 72-96 the models will resolve the heights over Norway & across to iceland & as a result will display heigher heights that originally predicted - Vis a vee the Cold air advection heading westward out of the continent will have more directional forcing WSW not WNW Now to address the atlantic profile - The initial deterministic resolution shows a flat jet with one wave exiting the US on a trajectory with the south of the UK under the parent low, but what if the models are going to react to the downstream changes of heigher heights over Norway with upstream teleconnective changes of more accute amplification - IE creating a ridge with perhaps 2 areas of energy exiting the states - If this happens & you throw a ridge in there then you get an inflection point - the sharper the ridge the sharper the inflection point- All of sudden the wave heading for the UK becomes very very shallow & recurves south towards spain & portugal .... Whilst the other area of energy - again becoming more defined & deeper as it traverses a steeper thermal gradient into the lobe of the vortex goes NORTH west of the big low over the Uk- The net of the this is all of a sudden theres energy heading south to portugal as well as a ridge building over the top of our UK low - forcing it south ( not back NW as the GFS keeps doing ) Bonus wise here is the fact that there no immediate energy against the block over southern england - We then allow the CAA to burst west into the UK ( as long as the low exits southern england & doesnt stall ) If it stalls in the south then its just te North that benefits from the Easterly flow. So these 2 key events - if they are the trends of the day & what ive seen the atlantic ridge has shown on the * UKMO 00z * GFS 06z ( not acute enough ) * JMA 06z t84 has the ridge * APERGE 06z t72 has a ridge forming.. I would expect a significantly different suite tonight in favour of cold. Its happened before - I have called that before ( but of course I have also not been right ) Take it or leave it S

Updated NAVGEM 06z 120 no change the updated 06z JMA 84 v the 12z 96 yesterday ( slight time gap ) has now taken away the wave & replaced it with a ridge also the 06z ENS suite is the very 1st GFS suite of this whole 'projection' to find 1 ( maybe 2) runs with the -10c line into england by T144 people can carry on ignoring the changes if they want.... look at the GFS consistency V the NAVGEM over the last 24 hours s

Surely thats obvious for the fact that its run is pretty much an extension of the UKMO 00z- the second best model.. If it was in isolation fair enough....

Last one then rewind to 96 area compare 00z v 06z 00z t90 v 06z 96 You will see that 00z has a shallow 1000mb wave moving ESE across the atlantic which is the system that goes under the main low & allows there to be a westerly flow over the SW of the UK hence easy for the jet to push through where as the 06z is not sure this is correct now & seperates the energy into x2 waves - the first one more southerly track & not developing - but behind that a ridge pushing the second wave NE - As said that not enough this time around to make a difference - but make the same correction again for the 12 & it will - look at the wave on the UKMO & NAVGEM - North east on both & the first wave ends up towards portugal - cheers s

So the feature that the UKMET added back in has now been removed from the 06z as well - at T96 the atlantic starts to throw a ridge NNE but because the low over the UK is not quite sliding south ( yet ) then the ridge gets swamped & low pressure passes under our main low however thats a significant swing to the UKMO ( also a massive infill of pressure over Norway at 120 v the 00z so whilst the outcome is the same on the 06z - 1 / maybe 2 more swings of the pendulum like the GFS does & instead of the energy driving east under the low it will recurve up towards iceland like the NAVGEM all eyes on the 12s S

Anyone following the 06z is seeing a big swing to UKMO & NAVGEM .... Pics for comparisons soon

Thanks Ian Modified to the consensus at the moment by the UKmet ... However the senior forecaster omitted the NAVGEM from his favourites - ive emailed him to include that into the probability weighting Happy NY it would help if yiu could add how many EPS members at 144 are in the UKMO camp... S

Let me just correct you IDO The 3 main models dont show that as the UKMO indicates a different scenario evolving from 144 ( same as NAVGEM 00z ) & seeing as the UKMO has better varification than the GEM & GFS we cannot assume this will be the case even though its a possibility- If the atlantic ridge gets thrown like the UKMO & NAVGEM propose then there will be no deep low- its happened many times before.... as for using the day 16 ENS mean - about as pointless as it was when you posted them last year & the year before that The day 10 ECM & GFS means 10 days ago didnt have a whiff of a high pressure block - so the 16 day is as pointless as a chocolate firegard- S

Overnight UKMO 120 :o could this be a coup for the NAVGEM who remembers jan 13 when the UKMO suddenly flipped to the undercut with a lobe of high pressure over scandi then ECM + GFS followed.... S

If somone can post the link to the navgem 12z that is the best case scenario from having more trough disruption than forecast....

Evening all - just one post from me - as this cold projection ( for want of a better phrase ) has developed apart from the odd rogue run - getting to the third stage where the cold hops the north sea into the UK has thus far always been out of reach- & as a result of that the discussion has been somewhat muted - However as we close in on the reality of the first system ahead of the alleged slider at 132-144 so the models have slowly identified that the block would be more robust than expected, so what was modelled at 156 say x2 days ago in terms of progression of the atlantic eastwards has been taking little bitesize chunks back west over the last 8 runs of the GFS - so the 156 18z from 2 days ago is now the 108 chart tonight- orignally the snowline was WAY back, however now at just 108 the snowline is from eastern scotland down to Holland heres the GFS changes over the last 3 days 156 2 days ago 132 yesterday 108 tonight with enough time & scope for further westward corrections - maybe enough to pull the snowline into the NE & EA also as we reach t96 the trough disruption is significantly more than projected with the low getting sheared at the top & bottom- Also a possible shallow shortwave cutting under the trough base at 120 should again hopefully support some further westward corrections of the cold if we use this rationale of less progressive westward adjustments - then it doesnt take must of a retrogressive adjustment to the 168 & 192 ECM tonight to perhaps bring some snow into the UK along the frontal boundary.... lots of water 'literally' to flow under that bridge over the next 72 hours .... s

After a difficult 24 hours the ECM & GEM 00z give a VERY good continental feed into the approaching atlantic low VERY NICE Snow !!!

Morning - lots of people looking down the line st days 7/8 for cold & snow when some could be on our doorstep day 3 & 4 with the ECM continuing to upgrade to cold as we approach real time T72 sees a cold westerly flow introducing pretty cold uppers for thr north - circa -5c with a pool of -7c air over scotland - This cold pool is important because just a day later we have an atlantic low sliding into that - with the miler air not penetrating that far North - That gives me confidence that a band of snow for Scotland & the North could give accumulations as early as Saturday early hours....... EDIT : day 5 ECM continues to hold any atlantic mixed air away from the borders - so for this uocoming cold spell scotland & the far NE could stay very cold throughout..... s

Certainly still an option & well within the realms of possibility - The slider low at 144 would ideally need more trough disruption & to seperate into 2 systems moving apart - this always allows the CAA over the top an easier pathway west... is it out there yet? look & PTB 6 & 10!!!!!! look at PTB 10 @138 then UKMO 144 s

^^^^ no model is ever any good with such a modality switch - we could go from an AO that peaked around + 4 to values to around -4 in a matter of 2 weeks which is rare as hens teeth - just browsing the late runs - the 18z JMA which runs to 84 is a carbon copy of the UKMO & the GFS ensembles are swinging ( as usual ) around to the euros .... I suspect we have another 3-5 GFS operationals before its on board - I was a little surprised by the muted excitement from the 12Z DET - it shows 3 big snow events for the UK with the north fairing the best, but the majority seeing snow at some point - its not exactly an everyday event widespread snow so we should take it with open arms- Also with each passing run the amount the atlantic makes inroads into the scandi block is becoming less & less so at day 9 & 10 if we have a low trying to get across into the North sea - dont be surprised to see that correct westwards as well All in all a great day with the euro scores up from 8/10 to 8.5/10 ... UKMO takes the run of the day award .... S

Updated t2ms today & yesterday S

Unanamous support for the slider scenario on the 192 ECM mean watch for significant temp drop off ( finally ) in the ensemble suite.... s

I will let someone else post the 240 feb 1996 redux at 216 snow pushing east for the core central belt of the UK wales & the NE inc Ireland

Snow over a swathe of the uk ( NE main ) at 192 drifting south ... needs a smidge more correction though

Nice 168 cold coming into the North sea low pressure getting sheared left right & centre pressure building over Iceland... HUUUUGEEE COLD POOL IN CENTRAL EUROPE

144 in shes going to slide - look at the heights increasing across to iceland deep cold getting closer... snowline mainline east of the UK at this point although some for scotland....

ECM 96 look at the loop of the jet going up over the UK & back SSE through Norway This is normally a prelude to a trigger low dropping into Benelux....

Significant improvement at 120 on the UKMO much much better allignment of the cold across europe - more westserly component 144 should be the first visibility of the UKMO interpretation of the undercut s

Stella UKMO & ECM this morning - both identical at 96/120/144 undercut city !!! lets keep it simple - - trough disruption at 120 /144 - undercutter 144/168 s

Damienslaw - GP kept reffering to a persistent northwesterly flow - nothing about a continental flow .... Anyway my comments on tonight - overall things remain very positive - the 3 steps to cold from the east in the UK are * eastern europe * Central europe * Western europe ( obviously lol ) with step 3 the hardest to forecast & the most volatile I would score the ECM 8/10 tonight - why? well its not the classic big draw Easterly we hoped for - a la 91 however all that means is the convective snow threat may be off the menu - However , to get widespread snow in the UK it requires an element of the atlantic being present with the polar front straddling the UK The most important element today was for the models NOT to shunt the upper air cold pool NW out of europe into scandi as once its up there its hard to recover any cold - What the ECM has done is build the ridge over the top towards iceland holding that deep cold over central / western europe- its then on tap to filter into slider systems that are alligned NW SE across the UK The ECM 192/216/240 has very high snow potential for the UK from frontal snow events & crucially at 240 its looking like theres plenty of sustainability post that timeframe so often do we see cold hitting the UK at 168 only to already be seeing the end at 240 very exciting charts at the moment however FI still at 120-144 leaves stage 3 open to a lot of volatilty we could still hit the jackpot chart at 192 but also still miss the deep cold altogether.... exciting times in a period of blocking not forecast by anyone as theblock has developed well before NYD.... S