Model Output Discussion 18/11/2012 12Z onwards

[Ian Suffolk]

Excellent output from the 0z GFS, much colder uppers floodng down from the north in the semi reliable. Looks like we could be in for a good run here!

[Dave Kightley]

The GFS run was ok until it hit fl...... I'm happy with whats up to 144h however the p.v just grows again and so pressure stays high around the UK. Looked like a nice split up to that point

[Ian Suffolk]

Look at the last couple of frames of FI thoughI (just for laughs of course.) the cold from the PV just comes flooding down from the NW. I think overall it's a pretty good run, the trends are still heading the right way!

[Dave Kightley]

lol yh! looks like pressure rises in USA and shifts the P.V in the most simple explanation i could think of. What i get out of this run is maybe the growing trend for pressure to be higher closer to the UK at first..

Maybe an expert can explain it better lol

Edited November 20, 2012 by Dave Kightley

[Dave Kightley]

mmm this maybe why???? ... Were on the 18z too

Edited November 20, 2012 by Dave Kightley

[Mucka]

GFS was so so in Hi res but GEM shows the way.

Wind that on a couple of frames and we would be .

[swfc]

The output remains the same within the usual timeframes ete.id advise caution when going beyond even five days at the moment to avoid the usual disappointment always comes during these complicated blocking set ups.A block just to the north of the uk looks the form horse to me with cool light easterlies.the pv is all over the place and altho it does look to split any long term weakening is to close to call regarding an extented cold spell.

[Jupiters Winter]

ECM is very good. A LOT of Blocking. GFS 00Z not far behind But I have begun notice the uppers being upgrading last few runs with the blocking settling in. Looking Promising but as usual long way to go..........>>>>>

Ps: Hands down I love the ECM all the way through---->>

Edited November 20, 2012 by aamiruk

[swfc]

ECM is very good. A LOT of Blocking. GFS 00Z not far behind But I have begun notice the uppers being upgrading last few runs with the blocking settling in. Looking Promising but as usual long way to go..........>>>>>

Ps: Hands down I love the ECM all the way through---->>

The only prob with the ecm is the low does not pull away south east and allow an easterly flow.kind of dilutes the flow but does prop up the block .Not a bad run to be fair longer term

[BLAST FROM THE PAST]

ECM is all about looking NE with the huge block coming out of Siberia. For me signs that this episode will not be a prolonged cold feed through Dec.. Something to watch, GFS collapses the pattern in deep FI, which of course is just that and we haven't got into the pattern yet so not reallly worth worrying about too much.

BFTP

[latitude]

GFS showing less cold options in FI now, it has for a couple of runs. We were all watching FI for the cold appearing, I hope the cold lovers are not ignoring what the GFS is starting to show. Or will everyone ignore it because its FI? As BFTP has aluded to, the pattern collapsing.

[TobyT]

Ecm looking good with heights still building NE by T240 if this comes off a cold pool should soon develop

http://www.theweathe...p500.png?cb=606

So not a bad run from ecm thismorning...great model watching

Must add what others have said this forum make such good reading... especially from the more experienced regulars...I am learning such a lot so thanks guys for all the informative and at time entertaining posts ie Ed`s monkey nuts and hose ;-))

Edited November 20, 2012 by TobyT

[NL]

Matt Hugo has mentioned heights to the NW/N of the UK diminishing around 2nd week of December with a return to zonal conditions.

Matt Hugo Stratospheric Watch thread.

The ECMWF 32 day update overnight as well maintains the signal for northern blocking through the 2nd week of December now with temperatures clearly becoming generally below average by a number of degrees. Without question, this excellent model, has nailed this situation down weeks in advance in terms of the broader change in synoptic pattern. However, what it now shows, is a return to more zonal conditions towards and beyond mid-December which is a concern. The +ve height anoms to the N and NW of the UK disappear by the 4th week of the run and are replaced by lower than average pressure anoms to the W and SW of the UK with temperatures recovering back to nearer average given a more unsettled theme.

[Nick F]

ECM is very good. A LOT of Blocking. GFS 00Z not far behind But I have begun notice the uppers being upgrading last few runs with the blocking settling in. Looking Promising but as usual long way to go..........>>>>>

Ps: Hands down I love the ECM all the way through---->>

It looks good synoptically, but there is still the problem of a lack of deep cold when the E/NE'erly develops as the trough disrupts and sinks a cut-off low over Europe. The initial northerly looks colder, as the amplifying trough moves east of the UK. Nern UK would probably see something wintry - especially over higher ground.

At least GFS and ECM both agree on the trough amplifying and disrupting into the cut-off low over Europe with height rises to the NW towards Iceland and then eventually rises over/to the N of the UK. But nothing to suggest any particularly potent cold spell atm.

But if the Nern blocking holds, it could lead the way to something better as we enter early December, if cold pooling moves in to the NE.

Edited November 20, 2012 by Nick F

[Gibby]

Good morning. Here is my take on the 00zs from GFS, UKMO, GEM and ECM for today Tuesday November 20th 2012.

All models show the next week has an awful lot of rain occurring over the British Isles as Low pressure remains situated either to the NW of the UK when there will be strong winds accompanying the rain at times or later seeing it slip South and East over the UK and down into NW Europe later in the weekend. As troughs continually cross East rainfall amounts will mount up with some flooding problems developing later in the week and over the weekend. It is very mild currently and this is how it will remain through the rest of the week with temperatures in excess of 10 deg C each day. Over the weekend as winds become more cyclonic temperatures will gradually fall over the UK.

GFS then moves us into next week with Low pressure transferring South to Southern England and France with further spells of rain, heavy at times in temperatures continuing to fall with some sleet and wet snow developing over Northern hills by midweek. In FI this morning High pressure is shown to slip slowly SE own over the UK elongating in a SW to NE axis across the heart of Britain later in FI. The weather would become dry and rather cold with frost and fog problems developing at night, slow to clear in the mornings. At the very end of the run High pressure retreats West into the Atlantic opening the door to the North with a front bringing rain South being followed by a cold Northerly with snow showers moving South soon after the runs end.

The GFS Ensembles show a very wet week to come before things become less wet in week 2. Temperatures are shown to be mild at first before a steady but slow fall off to levels just below the norm in the South and near to normal in the North look likely in week 2. There is no sign of any deep cold this morning in the time frame of the run though conditions at the surface could become rather cold in the High pressure type weather some members show.

The Jet Stream shows the flow pumping NE over the UK in the coming 4-5 days before a strong ridging through the Atlantic all the way to Greenland and Iceland develops over the weekend and the start of next week. The returning flow moves South to the West of the UK and down into Spain keeping the UK under a trough to start next week.

UKMO for midnight on Monday shows Low pressure in the Norwegian Sea with a secondary centre moving SE down the North Sea. A ridge of High pressure is building North in the Eastern Atlantic. A NW flow covers the UK with further showers likely in temperatures drifting back towards the seasonal normal or a little below.

GEM this morning shows Low pressure a little further West than UKMO on Monday with the UK covered in a complex Low pressure area early next week. As it drifts SE the weather would remain wet at times with temperatures falling to levels smewhat below normal as winds turn towards the NE in response to high pressure out to the NW building. The end of the run shows a strong NE then East flow developing with High pressure maintained to the North and Low to the South. It would become rather cold and while Northern areas could see a lot of dry weather Southern areas could see some occasional rain in cloudy and raw feeling conditions.

ECM shows a complex Low structure too over Britain to start next week with some rather cold air embedded in the circuation. High pressure builds to the North with Low pressure maintained over the Southern half of Britain with further rain at times here with some snow possible on the highest hills at times. In the North a cold and blustery NE flow could bring some wintry showers, especially near NE coasts but with a better chance of staying dry than areas further South.

In Summary it looks decidedly wet over the next 7-10 days before signs of something a little drier sets up in response to High pressure moving down from the NW later in the period. With winds in the SW the first 5-6 days look reasonably mild but windy with gales in places at times. As we move into next week temperatures fall steadily and it will become rather cold next week. With uppers not particularly cold the continuing rainfall should stay as rain with just the higher hills in the North at risk of some wintry weather as we move through next week. There is no sign of any deep cold arriving during the time frame of the runs this morning, though the pattern is right for something much colder to possibly develop further down the line should Northern latitude blocking be maintained.

[Methuselah]

http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20121120;time=00;ext=384;file=h850t850eu;sess=d1b199406a3a5b79f910c41ce3fa6aad;

But what it also shows, is the possibility of a major cold-outbreak heading down from the NNW...Which, IMO, is more characteristic of snowy winters than is a constant feed of predominantly dry easterly winds, a la February 1986?

[lorenzo]

That cold pool looking quite potent on the ECM 32 update, good signal for temps dropping below average

Lifted this from US Wx, MJO - 300mb flow chart using reconstructed OLR / Rossby Wave analogs. Another pattern predictor to scrutinise.

http://www.atmos.alb...gs/analogs.html

Ensembles coming out with colder and snowier options as each run passes now. First fortnight of December looking promising.

Here at 144 the subtle variances in the ridging.

ECM GFS

NAEFS GEM UKMO

[The Northern Ramper]

Matt Hugo has mentioned heights to the NW/N of the UK diminishing around 2nd week of December with a return to zonal conditions.

Matt Hugo Stratospheric Watch thread.

The ECMWF 32 day update overnight as well maintains the signal for northern blocking through the 2nd week of December now with temperatures clearly becoming generally below average by a number of degrees. Without question, this excellent model, has nailed this situation down weeks in advance in terms of the broader change in synoptic pattern. However, what it now shows, is a return to more zonal conditions towards and beyond mid-December which is a concern. The +ve height anoms to the N and NW of the UK disappear by the 4th week of the run and are replaced by lower than average pressure anoms to the W and SW of the UK with temperatures recovering back to nearer average given a more unsettled theme.

So we are concerned now by the blocking collapse three weeks away when any cold spell is still in FI?

[bradymk]

Some great outputs this morning for start of December.

Also just want to illustrate this morning the huge flip in the CFS for December over the last week or so.

Just over a week ago, and for many previous runs, the CFS was showing a very zonal outlook for December with low heights to our NW/ High to our South West. However the last few days, the model has completely flipped as you can see in the latest run. I don't rate the CFS forecasts highly but just interesting that it flipped so suddenly and has now kept with a cold outlook.

Matthew

Edited November 20, 2012 by bradythemole

[swfc]

So we are concerned now by the blocking collapse three weeks away when any cold spell is still in FI?

If you read matts quote he mentioned concern it may become zonal for a while mid december.To be fair it is possible i guess but i woudnt call it

[itsnowjoke]

Some great outputs this morning for start of December.

Also just want to illustrate this morning the huge flip in the CFS for December over the last week or so.

Just over a week ago, and for many previous runs, the CFS was showing a very zonal outlook for December with low heights to our NW/ High to our South West. However the last few days, the model has completely flipped as you can see in the latest run. I don't rate the CFS forecasts highly but just interesting that it flipped so suddenly and has now kept with a cold outlook.

Matthew

Could the charts flip back though

[liam300]

ECM is all about looking NE with the huge block coming out of Siberia. For me signs that this episode will not be a prolonged cold feed through Dec.. Something to watch, GFS collapses the pattern in deep FI, which of course is just that and we haven't got into the pattern yet so not reallly worth worrying about too much.

BFTP

This is contradicting what everyone else is saying, a lot of people are saying this could be good for the long term.

Can anyone clarify?

[The Eagle]

The ECM synoptically is flawless by 240hrs but as can be seen above the deep cold pool we need to tap is way back over Western Russia, nearly as far back as Siberia. The block would have to hold a few days after this point to tap that.

[snowking]

Could the charts flip back though

Anythings possible my friend. But what I would say is that the ECM 32 has picked up on this signal for around 2-3 weeks now. (Pretty much since the early December time period came into its forecast range), and so it has done a superb job. I do remember last February, however, the model going for cold throughout the month, with the second half in particular looking to be dominated by blocking....this risk then diminished over a period of 2-3 updates a week-two in advance (ie early feb).

So, not flawless, but certainly not ignore-able

SK

[SMU]

morning all-

we are now firming up on the first meaningful cold attack of the winter-

ALL models are now alligned to model a shortwave digging south over the UK, with pressure rising to the NW - heading towards southern Greenland.

This is now at day 5 & 6 so there is around a 85% chance of this happening ( alway have to leave the door open for failure)-

Post that for 7-9 the detail is sketchy - to be expected, but within this timeframe we are unlikely to be able to tap into anything REALLY cold, however with the core +VE pressure centred around Iceland there remains a 'significant' chance of cold developing & moving towards us.

We have X2 chances of getting the cold this way however BOTH rely on some sort of low pressure activity moving south across Scandi acting as a trigger to force the cold west-

Over the next 48/72 hours its important to watch developments both west of greenland- remember we need a low hitting that coast & getting split North / South which will reflect the jet looping over the pole-

OR the rank outsider is we tap the frigid air thats leaking west out of Siberia into Russia out at day 10 on the ECM ( UKMO looks quicker at 144 with the svalbard high)

In my experience we dont ever see the core of this air getting the UK & on the 1/2 occasions it has it takes 2 sometimes 3 trigger lows to hook it all west-

case in point it took 12 days to get the PV from Russia to the UK on 1st Jan 1987-12th jan 1987-

At least out at day 8 9 & 10 Pressure looks nice +VE extending from greenland to Siberia & the PV lobe is trapped slowly circulating west....