chris55

Yes but if you had -5c with a polar maritime airmass (a lot more moisture) you'd have been scraping for a lot longer. Dew points infer the temperature at which moisture condensates out of the air. As soon as the air temp drops below the dew point frost will form. You can have temps of 0/-1C with dew point of +2 and you'll get a lovely 'hoar frost' whereas like at the moment with temps down to -5/-6C and dew points around the same temp or colder a thick frost doesn't form. Obviously on metal and glass these rules alter slightly and very localised variants will effect things but as a rule when dew points are lower than air temps frost doesn't really form

As long as the ppn actually makes it up into the Westcountry (there is a risk it may stay to far west) then I can see places from Bristol to Gloucester getting a memorable snowfall. Many other places in the firing line obviously but from a personal regional point of view that's where I'm focused. lets hope everyone from Newton Abbot to Tewksbury, east and west, gets buried eh 'come on you beauty'

They must still use morgeps and UKMO as Ian specifically quoted 'met office models" on his 650pm forecast. what kind of contracts they have negotiated with meto group and the Met Office is not for us mere mortals to know, but it seems likely they have access the whole suit of models. sorry mods off topic I know.

Sounds like quite a battleground scenario unfolding reading through the updated text, always very hard to nail down north south boundry in this type of sitiuation. i would imagine those fabled winters gone by had many a set up like this, I know it's very late in the season but you wouldn't be arguing with that fact if you end up on the boundary line with all the fronts turning to snow. middle UK could well be buried!

GFS ensembles slowly seeing the fact the warmer uppers may not make it as far north as it previously predicted. definite shift, clustering of the warmer runs subsiding and more members quickly returning cold after the low edges in

UKMO disrupts the low and takes the centre through the channel this is what we want to see if it's an increased risk of snowfall rather than rain you want to see further south. EC and GFS both take the low west under the high and the centre ends up over Ireland. far from decided yet !

UKMO by far the best run yet for a major blizzard effecting a large swathe of England and Wales, as in these kind of situations (the likes we have not seen for a long long time) northward progression is crucial, UKMO is blizzard central for many

The end of this week could well produce the biggest blizzard parts of the country have seen for many many years. Lots of modelling yet to come on track/details but could be memorable UKMO looks to pull the low back west under the high, keeping the cold continental air flow for most :0

I remember 2010 where the models were keen on a quicker breakdown but the MET office were having none of it and they were proved right. Now this low for the end of the working week could be the mother of all snowmakers as it moves into the cold air, but where - when and how far north is open to days of modeling yet.

EC looking amazing this morning, snowstorm potential later in the week and Wednesdays flow is looking quite unstable with plenty of kinks and and embedded troughs you would think,

Growing trends now after the initial blistering cold, the next stage could well introduce fronts/low pressure systems into the mix equaling a hugely increased chance of frontal snowfall and blizzards for some:)

GFS 12z is a little out of kilter regarding the push from the south, however for a memorable snowstorm for the southern half of the UK im hoping we can introduce some moisture laden fronts into the cold air, but not to far north

Thanks for this Matt, I have been following the models for years but have never come across this term 'sublimation' (when has it ever been applicable to uk cold? just highlights the significance of the upcoming spell) The reason it caught my attention was because of the olympics, seeing snow falling on the TV and all the tracks/courses layed out with snow, yet the surrounding countryside is bare, with no snow cover. I did perhaps think this was due to the severe dry cold air they experience but now I know it's down to sublimation. always learning

EC 120 (and the rest!) show a synoptic evolution modelled that we have not seen for some 30 years, with the orientation of the high and the associated cold pool combining to create a "Tsunami" type easterly flow. superlatives have all been used..... so just look and behold. Ps... SSW....'cheers :0

Every single inch of the UK sub -10 (and some) !!!! from Shetland to jersey to the far reaches of northern island!!! i don't think I have ever seen that....ever!!

We will be talking about this spell for many years ! ec 120 -10/12 engulfing most of the uk........trough incoming from east.....insane cold pool following. Just unbelivable stuff and the likes we have been waiting for for many many years. worth the wait.....hell yea :):):)

Note that little trough/kink moving through Wales, some snowfall on that you would think

Just catching up on today and I know I'm in the middle of the EC 12z chat but GFS 120 and beyond is peachy high aligned perfectly. UKMO a little boring, cold yes, but with little action upto 144, though beyond im sure we will hit the sweet spot. hopefully EC is siding with GFS as I type this.

When you think about a locked in Barlette...... this chart is epic Theres levels to the love :0

First impressions since back from work..... those GEFS are stunning. nuff said" (now I can catch up on today's drama)

It's coming, just need some more energy underneath to drag that cold pool west, but in fairness EC has been consistent with ist slower progression of the deep cold.

GFS ensembles are the best we have seen in terms of agreement in getting the very cold pool into the uk! Spread reducing and clustering tightening. EC slower with the very cold pool remaining to the east at 144, should make it eventually you would think, UKMO with a better shape to the high at the same period with the westerly flow under looking stronger thanks to the more developed trough to the south east.

There is a trend to cold/very cold and yes many members go cold very cold, but I was highlighting how until we see solid tight clustering (as we see up to the 23rd) on the pattern then we can not be truly confident of the outcome.

EC op for next Saturday, cold 850s still a way off, though cold at the surface. Ties in with the more tame TV forecast and tweets etc. The early onset of the proper cold looks to be the less likely option, its into Sunday and next week where the very cold air may avect west. And with the solid building blocks in place for a robust Scandinavian high we just need to hope things align favourably

GEFS highlight the facts clearly. Just look at the spread from 23rd!! I know they can be easy to ignore but they are an important tool in deciphering the probability of the operational run, tight clustering = high confidence in outcome large spread = low confidence in outcome in laymans terms, until we see solid clustering on that cold pool smashing into the UK then nothing is guaranteed, and frankly ensemble data is the true forecast tool, taking operational runs in isolation can lead to a skewed view of probabilities and ultimately a misrepresented view of model performance. That being said obviously we are still in with a massive chance of proper cold just that the spread on the ensembles highlight the other routes we could end up with.