Model Output Discussion 12z 18/10/2012

[A.J]

The 18z looks quite good up until it goes into lower resolution where it obviously loses plot again like night lol

loses the plot, or spots a new trend?......a 'remarkable' run for sure, the way the HP block from T192-252 gets blasted over 1500 miles within 60 hours south-eastwards into central Europe seems implausible to me!

[OldMetMan]

I've been watching the shifts in the models over the last couple of days and now they seem to be all more or less in line regarding the forecast cold air blast. The interest now will, I think be in how long it will last and just how cold it will get, as well as the exact detail of where the axis of the developing cold trough will be.

First, all credit to the GFS for picking up on it first, as well as the GEM. Even the UKMet 120H FAX has it developing now.

The upper flow now is starting to look decidedly peculiar. Look at the jet first:

A couple of very pronounced "troughs" in the jet flow as is reflected in the 500mb analysis:

Both have the look of a major blocking pattern and more stable wave arrangement, such as hasn't been seen for a while.

In terms of actual weather here, the models suggest at least a brief pool of 528dm air crossing the country which could just about produce wintry showers along the east coast, maybe even as far south as East Anglia. Given the sea temps at this time of year I wouldn't hold your breath but there could certainly be strong convection, wintry or not.

I think this is turning into a very interesting pattern which, as I suggested a few days ago, may well repeat itself into the winter proper.

I am sure many of you out there are wishing the situation were happening in January! Patience!

[Robbie Garrett]

loses the plot, or spots a new trend?......a 'remarkable' run for sure, the way the HP block from T192-252 gets blasted over 1500 miles within 60 hours south-eastwards into central Europe seems implausible to me!

I was thinking that, technically impossible right? Bloody computers, what would we do without them ayyee?

London Ensembles are going for it, that's for sure....

Edited October 19, 2012 by Robbie Garrett

[SnowObsessor90]

loses the plot, or spots a new trend?......a 'remarkable' run for sure, the way the HP block from T192-252 gets blasted over 1500 miles within 60 hours south-eastwards into central Europe seems implausible to me!

We may well have a swift breakdown perhaps with the Northerly not even making any real inroads if some key things shift in the earlier timeframe, doubt it would happen as being depicted by the GFS though. It kind of just completely goes off on one after it enters lower resolution post 192hrs.

Edited October 19, 2012 by Anonymous21

[ZONE 51]

500/1000 hpa Thickness

1200hrs next Wednesday:

1200hrs Friday:

It's going to be quite a shock from mild/warm to colder air!

(GFS 12z)

Next is a closer look

Next ECM 850s+surface pressure

Friday 1200hrs

Certainly cold enough for snow on Northern hills

Better throw in the dew points chart,

GFS 12z

Edited October 20, 2012 by ElectricSnowStorm

[Timmytour]

Is it fair to say that the cold blast is now within the sort of reliable timeframe which a short while ago promised us a burst of unseasonably warm weather....only for it to subsequently disappear from the menu?

[summer blizzard]

The chart below illustrates how great this spell shall be for the time of year, to the east we have cold, to the west we have a 'cold' high.

[summer blizzard]

Shall we play 'spot the polar vortex'.. (some serious cold building in eastern Russia if that were to come off)..

[Neilsouth]

Such cold/cool spells at this time of year gives me a bad taste in my mouth, hopefully we don't have a mild winter . I prefer all that cold being bottled up ready to hit!

[ICETAB]

Such cold/cool spells at this time of year gives me a bad taste in my mouth, hopefully we don't have a mild winter . I prefer all that cold being bottled up ready to hit!

Having the cold filter south is a good thing at this time of year, more cold to tap into further down the line. More snow cover in the NH also increases our chances of it.

[BLAST FROM THE PAST]

00z has a succession of Lps diving south over the UK as the HP sinks, reloads/retrogresses each time. This would be snowmaggeddon setup in winter. This is a strange pattern developing but very interesting indeed.....a signal that as some have alluded to that Northern blocking is setting upshop.

BFTP

[IDO]

The signal for colder weather continues with the 0z run this morning.

As we are now nearing the reliable time frame the models will try to give us details as to where this cold pool of uppers will go, and it seems the Atlantic High will delay it and push it slightly east (per 0z).

This output is less cold, which is no surprise, as the OP run of late, has always been on the cold side of the ensembles.

The thickness never gets to 1280, even in Scotland, so snow on high ground best on this run. However 2m temps rarely rise above 8c throughout the run so on the cool side.

HP from Monday till FI (T144) and then we are in another trough (extending to N.Africa) with LP synoptics, but temps lower than recent similar scenarios. This takes us out to T384.

So cool in the long run from this output, so plenty of potential for November...

Edited October 20, 2012 by i'm dreaming of...

[snow drift]

Latest run from ECM starts encouragingly with everything slightly further East.

Edited October 20, 2012 by snow drift

[AWD]

GEM collapses the GHP rather quickly on this run, giving us a short cold shot before pushing it all east. Some decent early snowfall for Scandinavia & Russia though, cooling the landmass here.

The JMA has a much better aligned GHP to the west of Greenland bringing some very cold air over the UK for October, and wintriness possible in elevated northern & eastern areas of the UK. For a cold point of view, this has to be one of the better outputs this morning.

The GFS Operational isnt has cold as previous runs this morning, but it still ended up on the cold side of the Ensembles:

The ensemble memebers above seem to have trended slightly milder than previous ensemble members now.

The ECM splits the GHP off, and sends the jet inbetween Greenland and the UK, bringing a short cold snap before milder air comes up from the SW.

How long the cold phase will last is definetly open to question this morning, with a few of the models keen to collapse it after a day or two, but as ever, things aren't straight forward in this sort of pattern, and further changes are likely.

A shock to the system next week, with both above average temps and below average temps likely.

Edited October 20, 2012 by AWD

[Gibby]

Good morning. Here's a view of the 00zs from GFS, UKMO and ECM for this morning 20th October 2012.

All models show a very slack airflow pattern over the UK from now until about Wednesday. High pressure will lie to the East of the UK with Low pressure to the SW with the trough close to the SE weakening and moving NW over the coming days. The mist and fog problems at night will lessen over the early days of the week as cloudy and misty conditions with light rain move NW over Monday and Tuesday to reach all but Northern Scotland by Wednesday.Temperatures by day will be above normal where any sun breaks through in the afternoons with temperatures generally above normal.

GFS then shows a freshening ESE wind later in the week with steadily cooler conditions developing from the East. the weather would likely stay dry though some rain may affect the SW of England and Wales later. Over the weekend the weather remains mostly dry and temperatures will continue their decline. Rain in the far South will clear away and winds decrease so that frost and fog problems develop widely by Sunday especially in the North. In FI this morning some increasingly cold and unsettled weather develops as Low pressure is pulled down on the Eastern flank of High pressure which recedes back towards the West with a cold Northerly flow and wintry showers or longer spells of rain, sleet or snow affecting all areas later, the snow chiefly on high ground in the North and East.

The GFS Ensembles illustrate a rather cold spell coming up as most members agree now on a fall off in uppers to levels somewhat below the long term average. The operational was one of the coldest options in view though but isn't without support. Small amounts of precipitation are shown overall for the South with rather more in the North with time.

The Jet Stream is shown to break up around the British Isles over the coming days with a new Northern arm taking command blowing well North of the UK before driving SE over Europe in a week or so.

UKMO for midnight on Friday shows High pressure centred between Scotland and Iceland with a ridge SE over the UK. Winds will be quite strong from a NE quarter in the North and an ESE quarter in the South. Fine and rather cloudy conditions would be likely with temperatures sliding downwards to below normal values by the weekend.

ECM shows a temporary cold flow from the North cut off by a ridge moving down over the UK from the NW. The weather would be increasingly cold and frosty with fog too behind a cold front at the start of next weekend. As the ridge moves away SE the winds start to freshen from the SW with the return of rather milder air with rain and drizzle moving up across the UK falling as snow on high ground in Scotland.

In Summary it looks like this morning the first wave of Arctic air is going to be shunted East of Britain to affect more Scandinavian Countries with high pressure more likely to slide down over the UK bringing a drop in temperatures with frost and fog issues night and morning. In the longer term GFS shows a second more successful attempt at an early wintry blast while ECM pushes Atlantic Low pressure troughs NE as the ridge slips away SE allowing a milder South or SW flow back in across Southern areas at least. However, despite all this The Northern blocking remains in place and there will be many twists and turns in outcomes over the coming days before the pattern long term becomes clearer.

.

[liam300]

Good morning. Here's a view of the 00zs from GFS, UKMO and ECM for this morning 20th October 2012.

All models show a very slack airflow pattern over the UK from now until about Wednesday. High pressure will lie to the East of the UK with Low pressure to the SW with the trough close to the SE weakening and moving NW over the coming days. The mist and fog problems at night will lessen over the early days of the week as cloudy and misty conditions with light rain move NW over Monday and Tuesday to reach all but Northern Scotland by Wednesday.Temperatures by day will be above normal where any sun breaks through in the afternoons with temperatures generally above normal.

GFS then shows a freshening ESE wind later in the week with steadily cooler conditions developing from the East. the weather would likely stay dry though some rain may affect the SW of England and Wales later. Over the weekend the weather remains mostly dry and temperatures will continue their decline. Rain in the far South will clear away and winds decrease so that frost and fog problems develop widely by Sunday especially in the North. In FI this morning some increasingly cold and unsettled weather develops as Low pressure is pulled down on the Eastern flank of High pressure which recedes back towards the West with a cold Northerly flow and wintry showers or longer spells of rain, sleet or snow affecting all areas later, the snow chiefly on high ground in the North and East.

The GFS Ensembles illustrate a rather cold spell coming up as most members agree now on a fall off in uppers to levels somewhat below the long term average. The operational was one of the coldest options in view though but isn't without support. Small amounts of precipitation are shown overall for the South with rather more in the North with time.

The Jet Stream is shown to break up around the British Isles over the coming days with a new Northern arm taking command blowing well North of the UK before driving SE over Europe in a week or so.

UKMO for midnight on Friday shows High pressure centred between Scotland and Iceland with a ridge SE over the UK. Winds will be quite strong from a NE quarter in the North and an ESE quarter in the South. Fine and rather cloudy conditions would be likely with temperatures sliding downwards to below normal values by the weekend.

ECM shows a temporary cold flow from the North cut off by a ridge moving down over the UK from the NW. The weather would be increasingly cold and frosty with fog too behind a cold front at the start of next weekend. As the ridge moves away SE the winds start to freshen from the SW with the return of rather milder air with rain and drizzle moving up across the UK falling as snow on high ground in Scotland.

In Summary it looks like this morning the first wave of Arctic air is going to be shunted East of Britain to affect more Scandinavian Countries with high pressure more likely to slide down over the UK bringing a drop in temperatures with frost and fog issues night and morning. In the longer term GFS shows a second more successful attempt at an early wintry blast while ECM pushes Atlantic Low pressure troughs NE as the ridge slips away SE allowing a milder South or SW flow back in across Southern areas at least. However, despite all this The Northern blocking remains in place and there will be many twists and turns in outcomes over the coming days before the pattern long term becomes clearer.

.

Typical poor south east

Models always illustrate the worst for the south of the UK

[bluearmy]

given the drift of the modelling towards the mogreps solution mentioned by Ian yesterday, I have to say this is a great illustration of why no one should get excited by output a week or so away from verification. A month hence and this might be a very frustrated and possibly unpleasant place this morning. Lessons to be learned for the real thing methinks. No reason why the output shouldn't swing back to a colder solution later today but given what surface conditions are likely from such a set up, unless you live on a northern hill, why get bothered over it anyway. Checked my calendar and it is oct 20th. If you are keen to see the cold solution for the uk verify as you believe in repeating patterns, don't worry - the overall solution remains the same and over a season it will progress/retrogress somewhat. pleased to see the NH looking a less than welcoming place for the p/v to develop as far as we can see with any kind of confidence.

[SMU]

^^ Did you actually read Ians post-

MO-GREPS Anticyclonic Southeasterly throughout- & there is a large spread in the ECM ENS-

That has no real correlation with any of the models this morning-& certainly no drift towards that solution-

at day 10 ECM has mild SW flow with an easterly still pushing across Scotland & the GFS has a northerly flow...

The models are still firming up on the first wave of cold & the exact track- UKMO west, ECM slightly further East, the longwave pattern hasnt changed- however as we edge closer to the reality another small shortwave has been forecast to develop which will alter how sustained the flow is & where we go after that...-

the only people that make it unpleasent is when they come on here moaning that something isnt happening that was forecast to-

In terms of Cold & 'extreme' patterns they have been toned down overnight- especially across the US at day 10- thats life move on & see what the 12's bring- all 3 models arent alligned again at 144/168 so phase 2 of where we go is very much unclear this morning...

[bluearmy]

We can agree to disagree Steve but the further east the trough ends up, the more likely the ridge will fill the gap and at the furthest end of the spectrum, that's a soueaster. (I said 'drift towards' which doesn't mean you'll find one to post although the gefs mean isn't far away).

As far as unpleasant is concerned, you've been on here long enough to know how disappointment translates for quite a few. The older heads (members of the 'norwegian shortwave club' have seen it all before and cope)

[weather is fun]

Well looks like the cold spell next week has been downgraded this morning with the cold further east with the uk missing out. Not a bad thing though in my opnion as we dont want the cold peaking too soon. Guess we have to see if things change. But to my untrained eye it doesnt look as cold as it could of done for us later next week.

[Summer Sun]

Freezing winds and widespread snow may arrive as soon as next weekend according to the daily express

Edited October 20, 2012 by Summer Sun

[Liam J]

given the drift of the modelling towards the mogreps solution mentioned by Ian yesterday, I have to say this is a great illustration of why no one should get excited by output a week or so away from verification. A month hence and this might be a very frustrated and possibly unpleasant place this morning. Lessons to be learned for the real thing methinks. No reason why the output shouldn't swing back to a colder solution later today but given what surface conditions are likely from such a set up, unless you live on a northern hill, why get bothered over it anyway. Checked my calendar and it is oct 20th. If you are keen to see the cold solution for the uk verify as you believe in repeating patterns, don't worry - the overall solution remains the same and over a season it will progress/retrogress somewhat. pleased to see the NH looking a less than welcoming place for the p/v to develop as far as we can see with any kind of confidence.

Top post bluearmy, although I'd like to see the GFS 6z and of course the 12z suites from all of the models later before making any firm assumptions on the evolution. Each run now takes us further towards verification & the much more reliable time frame - so the window for any large swings either way will imo be getting smaller, but not impossible - no where near cut and dried by any means, roll on todays outputs......

[Gibby]

lol temperatures may fall to -18c according to the daily express today talk about over hyping things

I think they must have read my last night summary and acted upon it. LOL.

[Cloud 10]

Sorry,off topic.

Edited October 20, 2012 by Cloud 10

[MKN]

Anyway in regards to the model ouput I wouldn't be to worried if we get any snow from this initial attempt. Providing the polar vortex doesn't set up shop going into November we should get many more chances of high pressure being in a favourable position again.

Edited October 20, 2012 by chionomaniac
removed off topic reply