Model Output Discussion 18/11/2012 12Z onwards

[ITSY]

18Z GFS copies the 12 runs of BOM, JMA and GEM...that is a positive sign. If ECM/GFS start producing more easterly based runs in next few days, then we could get some real prospects. and all kudos to the BBC if that happens!

[Weather Boy]

Because innumerable public bodies and populace rely on their steer and that's exactly why they are meeting tomorrow to review things in light of latest seasonal output etc. Lest us forget that they don't have the luxury of discussing a raft of outcomes on a forum, with no media backlash or loss of public and commercial confidence if it all goes pear-shaped! I think their steady and measured approach thus far to some very conflicting NWP output has been exactly as one would hope for from scientists who cannot express any cold or mild preference or bias in their analyses.... they have huge responsibility.

Absolutely. At the risk of going off topic, that was no doubt the reaosning behind their decision to desist from LR forecast after the 'BBQ summer' problem.

But back on topic, it sounds to me from this post that you agree with me!.........in which case, nice to have a professional on board with my very amateur thoughts! (?)

[EML Network]

I can't help but feel that were going to get all the right pieces of the puzzle falling into place for a cold and snowy spell of weather. but that there's going to be no pot of gold at the end of the rainbow.

To me it seems that each time the models are giving us an Easterly or North Easterly were getting the dregs of the deep seated cold way out in Russia.

It's like hitting the jackpot on a fruit machine , only for the damn thing to be empty of money and you get a few 50 pence pieces.

Still who knows what might come afterwards, perhaps this is just the beginning of a lengthy cold spell ??...dare I start to believe ???

[london-snow]

A great 18z which highlights the potential and direction we could head in if things go our way and can also lead to better things down the line. Regarding people stating ' Its the 18z its been for a few to many down the local ' We can only discuss what is put in front of us. Same also applies in the way of trends we can only view the latest run and compare with the next. Very good 18z and let's hope come tomorrow morning things become a lot more clear.

[weather eater]

Firstly spot on post by Ian Fergusson

JP1972

I would say that in fact the GFS handled the lead up to 2010 really rather well

The 18z certainly has some big changes and I can’t say I’m surprised and I wouldn’t be surprised to see more yet.

I must say The 18z is known for throwing up the odd curveball mid and late range run and tonight’s is no exception, if form is anything to go by, tomorrows runs will look nothing like it. Arguably one of the most extraordinary runs I think I’ve seen.

Edited November 18, 2012 by weather eater

[JP1972]

18Z GFS copies the 12 runs of BOM, JMA and GEM...that is a positive sign. If ECM/GFS start producing more easterly based runs in next few days, then we could get some real prospects. and all kudos to the BBC if that happens!

I was only thinking the very same a little earlier.

I've been pretty critical of the BBC long term forecasts previously but they have stuck to their guns (pretty much) and lo n behold they look like they will be on the money as things stand.

I really am glued to the output now and expect to see a cold evolution develop....

[Liam J]

Yet to see some consistency from the GFS lately, how many more gigantic swings can this model pull out of the bag? I'd like to see the 00z also entertain this so we can at least have some firm ground to stand on, until then this run shouldn't be given any more credence than previous runs, also it is the 18z.

It'd be very frustrating if we got the heights in the right place but then had no real depth of cold to tap into.

Edited November 18, 2012 by Liam J

[TEITS]

Have to be honest i've lost some confidence in a cold spell developing towards the end of the month. Whilst I can see a cool E,ly flow developing, I cannot see a cold, wintry spell developing either from the E or pressure building to our NW. My concern is that HP will be centred just to the N of Scotland rather than over Greenland/Iceland.

So my punt is a cool E,ly for the end of the month and we shall have to wait and see what Dec brings.

[Weather Boy]

I must say The 18z is known for throwing up the odd curveball mid and late range run and tonight’s is no exception, if form is anything to go by, tomorrows runs will look nothing like it. Arguably one of the most extraordinary runs I think I’ve seen.

Quite. I think that it is important for us not to overreact to an incredible run like this. Whilst apparently (I'm not sure where they are viewed) some of the more minor models are supporting it, in terms of GFS op runs it is pretty well out on its own as far as I am aware. It would be surprising, to say the least if a snowfest run like that was repeated in the next 24 hours.

It might be on to something, but much more likely, it isn't.

[nick sussex]

I think if we look at all the output this evening the importance of events off the eastern USA becomes apparent:

As the cross polar flow develops in the USA this will force more amplification ahead, you can see that here:

The low near the Great Lakes moves east and this will engage another low off the eastern USA coast:

This phases into this large trough, the key is that we must see these phase and amplify sufficiently, as this amplifies it will help carve the ridge ahead.

We actually do have broad agreement across the big 3 models at 144hrs. The ECM 12hrs, UKMO and now GFS 18hrs all have the same key features and phase those lows.

The differences are really to do with the shape and depth of the troughing near the UK not the overall pattern.

I think at this point its fair to assume that we at least have found some convergence between the models.

After this its where the differences are likely to continue for a while as the models decide on how much that trough amplifies and whether we'll see pressure rises to the ne to help put some forcing on that limpet trough.

So I think we've made a small step forward this evening but still a long way to go.

I'll add these comments from NOAA this evening, they seem pretty happy with the consensus here:

THE GENERAL FLOW PATTERN IS EXPECTED TO RE-AMPLIFY THIS PERIOD,

WITH TROUGHING BECOMING REESTABLISHED OFFSHORE THE WEST COAST,

RIDGING DEVELOPING ACROSS THE ROCKIES, WITH DOWNSTREAM TROUGHING

ACROSS THE MIDWEST/GREAT LAKES/APPALACHIANS LURING A SLOW-MOVING

DEEP CYCLONE FROM THE NEIGHBORHOOD OF BERMUDA TO ATLANTIC CANADA.

ENOUGH SEPARATION EXISTS BETWEEN WEAKENING TROUGHING ACROSS

NUNAVUT AND A SYSTEM CROSSING NEAR THE CENTRAL US/CANADIAN BORDER

TO HELP ALLOW THE BORDER SYSTEM TO CLOSE OFF ALOFT. THE GUIDANCE

GENERALLY AGREES ON THIS SCENARIO

Edited November 18, 2012 by nick sussex

[pyrotech]

Now i might get slaughtered here for saying this, but if you watch run to run 18z GFS the pattern is still there.

Yes at different run times huge differences, but not so 18z to 18z

From thurday 18z to tonights 18z lets look at what it actually has changed

High Nw UK moves Northwest towards Greenland.

Low central West Europe fills quicker. Diminishes

This allows Low to Southwest to move in quicker, also high in North East Europe to ridge South.

This all means an awful lot to actual weather we get, but remember also this was 16 days ahead on thursday.

To me it shows a trend that lots on here have discussed. A blocking trend.

Likely of cold? its what we need to see, but now orientation and exact positions will be required.

Meto have it right, nothing is guaranteed for the UK right now, blocking looks likely but as for actual forecast for uk its a lottery until the blocking is in place.

Now go look at ECM 12z friday for Sunday 25th and todays 12z ECM for that day

Massive changes and in much less timeframe 10days

The GFS does have same theme if you compare run to run and changes deep in fi are believable, The basics are there, but actual weather for us changes dramatically with the same basics in place with slight different depth and orientation. What is evident is some form of blocking, which seasoned members will know, can bring cold to our shores if puzzle fits, however it can also bring a near miss. GFS 18Z was first to hint at this and to some extent again has seen the change of trend thats likely. Yes it has less data but i often find the less data somehow allows the processors to pick up trends in fi better. Why i do not know, but it often drops them in medium term and then picks up again late on.

Biggest lesson here is look at same run time daily for comparrison

Edited November 19, 2012 by pyrotech

[Robbie Garrett]

The Atlantic is blocked!!! from pretty much as soon as we head into the end of the week. That low I talked about on yesterday's 18z is back and it's even better. We are now in a most reliable time-frame for the pattern changer, which in my eyes is what causes this pattern change. 24th November 2012 is where Fantasy Island currently starts, so anything just before then has a good chance of verifying - thereafter is up for grabs...

Just look at the ensembles..

Watch as the low South of Greenland and Iceland heads South East Towards the UK as Northern Heights build around it...

GFS at 140ishHrs

ECM at 140ishHrs

As we head towards the weekend, that low fills in rather quickly creating another low just south of it. Quickly this low gets stuck, and heights assisted by a trough over NE Canada build towards Greenland, this is the crucial time for me and a precursor to a major pattern change...

Especially as those warmer temperatures head towards Greenland, and the Azores links up with the Greenland Surface High. Once this comes within a reliable timeframe for the models, they probably will likely start to firm up on something bigger and better.

Edited November 19, 2012 by Robbie Garrett

[Jonan92]

You will have a nice wake up if you have a look into the 0z run of the GFS, it has taken it where it left at 18z and improve it. Almost a very good split at 228h

[shotski]

You will have a nice wake up if you have a look into the 0z run of the GFS, it has taken it where it left at 18z and improve it. Almost a very good split at 228h

Just had a look at that, Amazing run if it were to come off. very similar setup to 2010 .

Oh Baby

Edited November 19, 2012 by shotski

[scottishandy]

All the ingredients are there on the 00z.

Scandi heights at T120

Vortex going/gone and cross polar heights at T144

Great amplification.

WAA up Greenland W.

Cut off Greenie/Iceland high at T264.

To my eye the only thing missing is a good cold source to come down from the polar regions but that is the only possible downside of the fragmentation of the vortex. As has been said many times, lets get the pattern in place and the cold will come!

Permission to post T384 chart, no-one up so I'll just go for it.

[Polar Maritime]

Morning all, GFS looking very good this morning for blocking over Greenland, starting at t174

Then ending up like this at the end of the run...

Edited November 19, 2012 by Polar Maritime

[snow drift]

The latest offerings from the ECM. So the theme continues and the detail varies. I have a similar concern to TEITS, in that the high pressure shown to our NW ends up being over Scotland. The thought process is not that rational though. I have seen on many occassions that things move slightly East the near we get to T24. Time will tell.I guess thats what you call a split PV. I think we should have a thread that picks a moment in time, say plus ten days and we get to pick an output to what we think it will look like."Spot the Ball but different". Then review at that time. Would be some red faces I think.

Edited November 19, 2012 by snow drift

[BlueHedgehog074]

Quite a reasonable 00Z ECMWF update (for cold) with a cool/cold Polar Maritime flow at 168 hours eventually leading to heights building to the North and West as the Low slowly treks Eastwards. But one aspect I keep noticing about the ECMWF is it seems to keep holding the potential further and further back with the cold potential not looking as though it is getting closer and closer. Tis still great to see the charts keep dishing out blocked outlooks - just hope we can see the possible cold crawl closer to the even more reliable time frame of around 72/96 hours.

[IDO]

This GFS 0z OP run was bound to show up as the model continues to dial through all possible cool/cold permutations. The details are mute at the moment, but the pattern of the Atlantic “closed sign†continues.

The ensembles: http://cdn.nwstatic.co.uk/ensimages/ens.20121119/00/t850London.png suggest the OP is in the cold (850s) 20% of runs, so is not a no hope outlier. Later this week once the cold route is accepted by the milder minority (assumptions aside) in the ensembles then the mean 850s should settle at around -5c. Nothing to ring your mum about, but hopefully the stepping stone to a colder feed.

The GEFS individual runs still show a wide scatter of possibilities: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384. The Control run showing what could go wrong, with a flatter pattern and further reloads needed.

The ECMW is also seeing the amplification, later than GFS, but by T240 beginning to get a whiff of that coffee: http://www.meteociel.fr/modeles/ecmwf/runs/2012111900/ECH1-240.GIF?19-12.

The pressure builds are coming close to the hi-res output so the next few days will quantify how progressive the first strike will be.

In the meantime an Autumnal few days with bands of rain, high winds for most and average temps. By the end of the week, with the westerly flow slowed to a crawl, a trough develops over the UK and stays with us through the run in one form or other.

[snow drift]

Quite a reasonable 00Z ECMWF update (for cold) with a cool/cold Polar Maritime flow at 168 hours eventually leading to heights building to the North and West as the Low slowly treks Eastwards. But one aspect I keep noticing about the ECMWF is it seems to keep holding the potential further and further back with the cold potential not looking as though it is getting closer and closer. Tis still great to see the charts keep dishing out blocked outlooks - just hope we can see the possible cold crawl closer to the even more reliable time frame of around 72/96 hours.

This is an improved output. There is more potential and it gets to the later stages in a less messy way. Nick will be pleased I think. I am not sure that the cold does keep getting pushed back T240 from now is still not the end of the month. This week will be interesting as we now could see the potential move forward on the different runs. Really looking forward to the ECM tonight.

[BlueHedgehog074]

I suppose. Probably should have re-looked at the previous ECMWF runs before having made a judgement about the potential getting put back. At least we do seem to be heading in the right direction for cold/chilly prospects for the future.

[EML Network]

Did someone say there was going to be a pole shift in 2012 ??

[MR EXTREMES]

get a nice 1050mb greeny high in place bingo.

i think im going to eat humble pie and gp and others really have been showing better progs than the models them selfs.

[lorenzo]

GFS 00z is eye candy. Lobe of PV twisting SSE also.

Some total devastation of Mr Vortex in the ensembles.

Day 10 00z and P5

P5 continued...

Interesting to see, however the Greenland pressure ensembles tell the story and scatter begins at just 96-108 hours out.

Good thing is that makes the next 96 hours fantastic model watching..

[Gibby]

Good morning. Here is the Monday morning look at the 00zs from GFS, UKMO, GEM and ECM for today Monday November 19th 2012.

All models continue to show a very unsettled but relatively mild week to come with a broad South or SW airflow over all of Britain with troughs of Low pressure crossing NE or East across the UK periodically. In general the most and heaviest rainfall will be reserved for the West while Eastern areas see rather less in the lee of high ground to the SW or South. There will be some drier and brighter interludes too, more especially in the East.

GFS then takes us through next weekend with very little change before Low pressure slips South to the South of the UK with a wet and rather chillier spell likely for all Southern areas early next week. The North would then turn drier and rather colder. This general pattern of High to the North and Low to the South and East continues through much of the remainder of the run with further rain at times and it will gradually become cold enough for some sleet on the hills with a general deeper cold arriving at the end of the run with a wintry and unsettled synopses in a cyclonic and North flow delivering the risk of sleet and snow for all.

The GFS Ensembles show the gentle trend of cooling just about continuing though overall things are never shown to become noteworthy cold. Instead a period of uppers close to or just below the seasonal normal develop with a tendency this morning for more rainfall shown in week 2 than was previously shown. There is a lot of spread in uppers though between the members after Week 1.

The Jet Stream shows a SW to NE flow over the UK in the coming days before it moves temporarily South of Britain by the end of the week. It then ridges North through the Atlantic towards Greenland before turning South down to the West of the UK by the start of next week.

UKMO for midnight on Sunday shows Low pressure out to the NW with a SW flow over the NW half of the UK. In the SE a weak ridge from Northern Europe covers the area with drier conditions here away from the unsettled NW. Temperatures near to average.

GEM shows unsettled conditions continuing next weekend under a Westerly flow before things turn colder as Low pressure sinks SE down the North Sea and on into Europe, turning winds into the NW, North, then NE changing the weather to rather cold with further rain in the South and East turning to sleet and snow in places later.

ECM shows a similar pattern to GEM with a deep Low crossing the UK late next weekend and away to the East early next week with progressively colder weather developing in a North wind at the end of the run with rain and possible sleet continuing towards the East. With High pressure close to NW Britain by the end of the run it looks like the North and West will become drier as well as cold with frost likely by night.

In Summary the weather is still split into two halves through the course of the models. The overall trend is for a mild and windy week to come with Low pressure centres out to the NW continuing to bring spells of rain and showers to all areas through the coming 5-6 days, always heaviest in the west. Over the weekend as Low pressure moves gently East over the UK the models want to feed it SE into Europe with a pressure rise to the NW bringing rather colder and still unsettled conditions in Week 2. If it verifies the question is whether it will be cold enough to produce anything other than cold rain as uppers are not shown to be particularly low. GFS does move on to show more mouthwatering and favourable charts in the far reaches of FI. In my opinion though although it is increasingly likely to get colder next week I still think that there is a 50% chance tthat High pressure will come down over the UK and give us something rather chilly and frosty rather than see any snowfall, other than in any wintry showers which may run onshore to coastal areas of the North and East. More runs still needed I'm afraid.