Model Output Discussion 23/11/2012 18Z onwards

[Ice BIast]

Early days, but the 18Z already looks a bit better to me at T60, making less of that shortwave to the north and there's more WAA going north.

[TAFKAP]

All this talk of whether it will snow at low levels/coastal regions is all guess work. Remember the 26th Oct this year we had snow falling right on the coast here in the north east..wish I'd kept the charts from that day to compare them with what's to come.

Just use the netweather archived charts! You can look at the charts for any date in the past you fancy.

[Geordiesnow]

I know its only tiny details and it won't change the overall trends and output but the differences between the GFS and ECM at 72 hours in terms of what weather we may get on Tuesday is a bit remarkable, GFS would be cold and wet on the eastern coasts and quite miserable, whereas the ECM looks like it will probably be a little bit brighter and showery, UKMO was more towards the ECM but its a bit more half way now.

[Cloud 10]

Hmm, tough to call really, depends on so so many different factors. Looking at it from an IMBY perspective the ECM doesn't look marginal at all after about +144, -6C or lower uppers for the most part and winds not directly off the sea is usually good enough for snow, but for central and southern England and coasts exposed to northerlies then it's much tougher to call. On the UKMO I'd imagine at +144 inland bits of northeast England and southeast Scotland would be seeing snow, perhaps more like graupel or sleet or drizzle at the coasts and without any elevation, but probably by about +168 or +180 we'd be looking at a very snowy set up one way or another. If snow cover establishes, and by the end of next weekend fairly widespread snow cover, if not necessarily all that deep, is entirely possible, the cold becomes tougher to dislodge and we create our own localised cold pool which gives us an edge in marginal setups.

Good post there LS

A bit far out to be looking at specifics but if the ECM at 168 hrs did verify as shown,i would expect

any showers/troughs to be mainly of snow and hail even on the coast due to the very low thickness

values shown,as well as pretty good 850 temps.

What a great chart for the first day of winter.

[Panayiotis]

Heights looking stronger in the artic (notice the little yellow dot)!

Edited November 24, 2012 by panayiotis

[ITSY]

t+90 only minor changes, potentially snowy across scotland as -5/6 uppers approach the far NE. Expecting them to recede before returning.

[Cloud 10]

All this talk of whether it will snow at low levels/coastal regions is all guess work. Remember the 26th Oct this year we had snow falling right on the coast here in the north east..wish I'd kept the charts from that day to compare them with what's to come.

That was a pretty fun day!

[ITSY]

arctic high more south, feed is colder, atlantic further away and shortwave seems to be handled 'better'. only at +114. tentative, albeit positive, signs.

[Jonan92]

Much more clear this time

[Geordiesnow]

t+90 only minor changes, potentially snowy across scotland as -5/6 uppers approach the far NE. Expecting them to recede before returning.

Tbh, the uppers are slightly colder than earlier runs now as I assume the flow over Scandinavia has become more "still" instead of the southerly flow that some runs were showing therefore we got slightly colder upper air temps. Shame the snowcover is not more widespread as the models may forecast even slightly colder upper air temps as a result.

Upto 114 hours, its slightly better than the 12Z run but the Norwegian shortwave is still being a nuisance imo. Its not that unusual for shortwaves to form in that area during slack blocking set ups so its one we have to keep an eye on as it could change the output.

[ITSY]

Tbh, the uppers are slightly colder than earlier runs now as I assume the flow over Scandinavia has become more "still" instead of the southerly flow that some runs were showing therefore we got slightly colder upper air temps. Shame the snowcover is not more widespread as the models may forecast even slightly colder upper air temps as a result.

Upto 114 hours, its slightly better than the 12Z run but the Norwegian shortwave is still being a nuisance imo. Its not that unusual for shortwaves to form in that area during slack blocking set ups so its one we have to keep an eye on as it could change the output.

Agreed. The best part of the run for me is the arctic high pushing the real cold over lapland and scandanavia further south. Could see it 'topple' so to speak onto us, a la ECM

EDIT: that shortwave is in danger of turning into a full blown LP if it combines with the other one coming down from the arctic. Like you say, on a knife edge. Can you imagine if it weren't there altogether? It'd be a direct tap into that heft cold poool...

Edited November 24, 2012 by ITSY

[JCP]

At 126hr the chart is ludicrous and appears to be a weak northerly spreading from Lapland to the equator !

[Tim Bland]

Shortwave se of Greenland is gone at 144hrs... Going to be more in line with ECM IMO

[Geordiesnow]

This run also keeps the consistency of having the trough heading into Scandinavia, surely the UKMO will back down tomorrow regarding the trough and therefore the easterly!?

Trends are, we will see a cooler Northerly with the trough heading into Scandi being the cause of this, which in turn will try and get rid of the cold air over Scandinavia into the Norwegian sea and therefore in terms of building a cold pool over the east means we have to start all over again.

That said, a Northerly is not a bad thing if its unstable and cold enough and too me, the latter looks marginal.

I think it looks more or less certain it will turn colder next week, just how cold and how much snowfall there will be is yet to be decided.

[Bristawl Si]

This run also keeps the consistency of having the trough heading into Scandinavia, surely the UKMO will back down tomorrow regarding the trough and therefore the easterly!?

Trends are, we will see a cooler Northerly with the trough heading into Scandi being the cause of this, which in turn will try and get rid of the cold air over Scandinavia into the Norwegian sea and therefore in terms of building a cold pool over the east means we have to start all over again.

That said, a Northerly is not a bad thing if its unstable and cold enough and too me, the latter looks marginal.

I think it looks more or less certain it will turn colder next week, just how cold and how much snowfall there will be is yet to be decided.

You always try to find the negative stuff.

Trend still there - detail to be decided 'on the day(s)'.

[Interitus]

Those in the north don't be surprised to see some snow tomorrow GFS has picked up on it very late

It is not actually true that it has picked up on it very late, if you change the base time on those weatheronline GFS plots you can see that they have been showing coverings of snow for today onwards for a number of days.

Don't think there is any to speak of right now contrary to these charts, and in any case at this time range it should be on the NAE if it was a serious likelihood.

Edited November 24, 2012 by Interitus

[Panayiotis]

Cooler upper air (-6C) coming to our shores earlier on this run at 114hrs compared to 159hrs.

Edited November 24, 2012 by panayiotis

[kate1]

Sorry, could you explain why the UKMO would back down?

[ITSY]

the charts speak for themselves. GFS seems to be opting for ECM solution, the cold does arrive and the shortwave is shortlived.

Anyone who is unhappy with that run must only be those who like mild weather; it is an excellent high res and an upgrade on previous GFS runs.

Edited November 24, 2012 by ITSY

[I remember Atlantic 252]

Seems better than 12Z, cold uppers arriving in my area 7am Sat 01 Dec, from north

[EML Network]

One thing that has remained consistent is that from WED - FRIDAY it looks to be very dry, and considering what's been happening and what is to come over the next couple of days, I'd say that would be a welcome relief to some.

And yet ANOTHER run that has the whole UK under - 5 uppers on the first day of Winter

[Weathizard]

GFS seems to have got its act together, going to ignore all after 192 though. Will be interesting to see the ensembles this evening.

[snowstorm445]

Is it my imagination or is the deep low near Labrador attempting to shove the Greenland High out of the way. Its really squeezing that Atlantic Ridge quite tightly.

[phil nw.]

Hello Winter!

We are getting there.

[Nick F]

Sorry, could you explain why the UKMO would back down?

Perhaps UKMO is like a disobedient child that will be forced to act in an adult way like its parents GFS and ECM.

UKMO is rather different in shape with the low over Europe, with a flatter easterly flow over the northern side, rather than the elongated low punching north into Scandinavia on GFS and ECM. UKMO not necessarily wrong though