SMU

Morning All Cracking output for the morning especially the GFS that is really going guns a blazin for undercutting sliding lows & a loaded AO pattern- Just a word on the UKMO 168 as many are struggling to decipher- The UKMO is trying to bend & slide low ( like the GEM ) however we have to make an assumption that the residual heights to the NE are not sufficient enough to disrupt the low to keep steer it south enough, also the energy looks more spread across the UK creating more of a wave going east which would result in less snow- Anyway Its a case of not knowing where to look on the models at the moment as the amazing charts are coming from everywhere ! I wonder how long before the london Mean gets down to -10!!! S

I think perhaps you need to review the 00z runs in terms of day 8-10 that couldnt be further from the truth. The overnights continue where they left off all weekend GFS most amplified, UKMO on the proverbial fence, ECM slightly flatter & the GEM finally being hauled into line. Based on the most recent form you would predict that the ECM will sharpen up a tad on the PM run.. very exciting times- Day 8 & beyond massive -AO.. S

Cheers proof on the chart below that a small system can get through the block & slide SE

Yes snow for the south, snow for the extreme North & deep deep surface cold wedged in the middle !

What date was the Ian Brown infamous WTF - that was a similar slider event..

GFS control @168 Standard toppler ...

I think you need to be careful with just assuming a lobe of the vortex over Canada is going to have the same impacts as the entire vortex setting up in the same locale, especially when there is so much opposing force coming back at it out of Russia ...

Its not a standard toppler im afraid - A standard one has the jet roaring over the top & over the UK- This scenario has one system sliding through the high as an undercut then the jet reinvigorates alligned towards Spain pulling everything that way- we may end up for a short period of time slightly less cold but it wont last long-

Goodnight vortex- totally shredded both sides of the pole

Perfect allignment of the cold so far brings a second bout of -10c over the UK how close will the slider get....

T114 the best yet - all kinky kink over the SE & snow piling into Scotland on this run Also the -10c getting closer to London!

Quite possibly expecting to see some mad charts as we progress through December A proper white xmas would be nice-

Dont normally count the polar one but hey ho !! PS a cobra run in the ECM suite

Thats a nice anomaly chart- although thats a 4 wave pattern ! Also if you look close you see the slight weakness in the blocking over southern Greenland which allows the atlantic in now & again.. On a positive note the ECM 850 ensemble mean V op posted on the page below indicates that when the atlantic slider is looking like arriving the mean is about 2-3 degrees colder than the op ! eyes down for the 18z- S

Sunday monday yes- especially if the High drifts over a little... even here in the SE -5c is easily achievable in -8c air & a slack NNW flow...

Afternoon All - A frantic few days on here with pages & pages of posts flying through in a matter of hours- I think we have 2 main discussion points at the moment- 1) The short to medium term prospects for the UK covering the next 10 days 2) The medium to long term thoughts on December & Winter as a whole... Short term then whats the bad news- well is there much to be frustrated with? only the fact I guess that the megasnow charts that appeared for a day or so have been moderated - Thats because even though the overall pattern is near as damn it identical - the timing & phasing of the jet + low pressures has been modified just slightly to reflect a slightly slower progression south of the cold air- The initial prognosis for the cold was always Thurs PM into the Eve- well now potentially the GFS just holds this off another 12 hours due to a track of that low not being as efficient for cold air advection alligned to the UK- This aside though the potency of the Northerly looks pretty substantial- at this early phase of Winter if you can get the -8c line to the South Coast then your doing very well- We deliver that with other areas of -9 & possibly the magical -10c The flow looks very unstable to me - bringing a rash showers across the usual places exposed in a NNW flow - NI included- perhaps some of the posts & general frustration today has reflected some IMBY desire for snow - well thats life. * In terms of more organised bands of snow I suspect the models havent quite resolved the finer detail yet so I believe we will see some kinks & troughs forming ... It will be all about timing and intensity as that whether areas further south can get any snowcover ! For Scotland & parts of the North /NW sustained snowcover looks a possibility from overnight Thurs onwards for at least 4-5 days... 'The slider lows' - personally I love the name - a potential again for some snow pushing across the UK ( mixed into rain ) for the western portions - The models havent got a grip yet of how these will develop- they are beginning to see the Energy & rough location of development - however angle of the jet is very much up for grabs -indications being the first system will slide past the UK- or possibly into the west, keeping the UK on the very cold side of the jet- although some runs do bring a higher chance of snow across the UK with a shallow system & acute angle... after that it is usually difficult to keep the jet attenuated enough for 2 sliders but we will see... * Post next weekend & more long term the prospects for sustained cold is highly probable- The starting point would be - how many times in the last 2-3 weeks have you seen a return to normal NH zonal conditions past day 10- the answer is probably very low.. From the top down we are seeing the GFS continue to show no coherent downwelling of any meaningful positive westerly winds, with infact a second bout of negativity building in the 10-30 HPA layer at day one 12 -16 The models have been a bit flip flop with this so its not a given- However even with the possible bonus of another reduction of the zonal wind the models persist with the disturbed hemispheric pattern. The H5 anomalies show considerable blocking across the Pacific / pole / Russia & a segmented vortex mostly languishing across the other side of the globe- Whats key here & the reason why we are seeing the models choose the 'non toppler' scenarios is because of how I believe the energy within the zonal wind is being distributed- when we have a high Westerly phase of the zonal wind the Easterly component ( moving west to east ) is very uniform & theres minimal deviation away from that direction- IE minimal poleward vector- In reduced phases & the highly desirable negative phases you have maximised poleward & equatorial vectors & no Easterly Vector- So for December in General we have a zonal wind that kicks on around 30-40 M/S - where currently its heading to around 10 M/S- Thats where all your Easterly progression has gone... Factor in the weak La nina base state which if you use the general analogues you will find a pretty good match for a negative December AO & cold in the mid lattitudes- With that in mind the odds of a below average December are high - with H2 of the month of particular interest as the Russian high starts coming into play potentially backing the pattern up even more... so.. for a change increase your expectation towards cold for the remainder of the month-blocking peak 9th Dec - with maybe a short relaxation before going again towards the 15th ish on the run in to the festive period.... S

Xmas party for me now- just off out crackerack ECM- couldnt ask for more than that... awsome

ECM follows GFS @168 guys...

Look at the energy west of the high pressure it’s split going North East & south / south west- minimal eastward component ... people posting that it’s a ‘toppler’ are the usual crew that want it to happen anyway.

^^ so your just ignoring the UKMET^^

Extreme amplification in the atlantic sees the energy aimed at spain at 168!

Yep agree with Carinth - although UKMO 144 I believe has the low to far North I think based on History somewhere across the Midlands then out towards Benelux- The ECM mean clustering has many more colder solutions that the op & control at day 10/11 for debilt..

Odd flake here & there 1.3c here!

UKMO day 7 pretty chipper Northerly!

Look at the UKMO Blocking EPIC -AO