Model Output Discussion 12z 07/11/2012

[Frosty.]

Yes I would agree with this, it would be surprising to get a cold evolution for the UK beyond the T240 chart, even if that T240 chart proved to be right.

The models are full of surprises tonight, don't rule anything out is the message IMO.

[Adam lufc]

Why do people keep knocking potential good charts!! Saying the 240 is unlikely to bring anything! Well exactly what do you expect and want! Yes that chart will most likely be gone in the morning but at least it's something to cling onto and keep going. The ecm 240 chart is amazing and would most likely lead onto very interesting times! Here's to see the 18z .......

[phil nw.]

I think I'll judge the model-performance after it's happened...As we all know, from bitter experience, whatever the models might show in FI hardly ever translates into reality.

Indeed RP.We need to remind ourselves the pattern is modelled differently quite early on by the op. runs.

[nick sussex]

The GFS 18hrs has pulled troughing further west than the earlier 12hrs. Still not as good as the ECM , this looks more like the UKMO so perhaps this might give us a clue as to how that could develop if it went further than 144hrs.

[bluearmy]

The GFS 18hrs has pulled troughing further west than the earlier 12hrs. Still not as good as the ECM , this looks more like the UKMO so perhaps this might give us a clue as to how that could develop if it went further than 144hrs.

Energy headed south at T132 which may help the ridging to hold to our east.

[TobyT]

The models are full of surprises tonight, don't rule anything out is the message IMO.

I have to agree, there seems a real possibility of a major change from the mild..ish phase we are currently in...I am very happy with regard to where we are at this point in November...very interesting model watching in the coming days especially as we head towards end of the month with current wave breaking forecast to disrupt the PV and major blocking to or NW and NE.. exciting times ahead

[Frosty.]

The GFS 18hrs has pulled troughing further west than the earlier 12hrs. Still not as good as the ECM , this looks more like the UKMO so perhaps this might give us a clue as to how that could develop if it went further than 144hrs.

At least the 18z is heading in the same direction, baby steps but a good sign

[ukpaul]

The low from the 12z GFS now wound up even more by next weekend on the 18z, very different to the ECM which has it at barely 995 mb as opposed to GFS's 970.

Edited November 11, 2012 by ukpaul

[nick sussex]

Energy headed south at T132 which may help the ridging to hold to our east.

Unfortunately it all goes downhill after that with that low powering up!

At the moment the ECM seems out on its own with its stronger ridge within 144hrs. Still I'd rather have the ECM on its own than the GFS given its track record with high pressure in Europe.

We'll see tomorrow morning whether theres any mileage in the ECM.

[weather_it_will]

The low from the 12z GFS now wound up even more by next weekend on the 18z, very different to the ECM which has it at barely 995 mb as opposed to GFS's 970.

GFS tends to over cook deep lows, so I would not worry unless it is still there at T12

[Zenarcher]

The low from the 12z GFS now wound up even more by next weekend on the 18z, very different to the ECM which has it at barely 995 mb as opposed to GFS's 970.

The low on the 18z exits the jet stream and gains a lot of power. ECM makes it ride the jet stream down SE and never exits or gains power this is why the ECM looks better.

[SMU]

The 18z gets close to the ECm but at the crucial time cannot get the energy under the high-

Once it misses thats it everything goes over the top-

Theres a critical tipping point on the models over the next 48 hours- its around 120-144- so resolution should be quite swift..

S

[ukpaul]

Blimey, this is a run of nasty, nasty weather, lashing rain and hill snow abounding. The PV seems to want to veer right over to Scandi.

[liam79]

GFS tends to over cook deep lows, so I would not worry unless it is still there at T12

if the GFS is over cooking the low is it then also overestimating the effect it has on the ridge to the East?

[nick sussex]

As Steve M mentioned the good thing about this cold tease is that its not a case of hoping that something well into FI survives intact.

Here its all down to events within 144hrs, theres no chance of getting close to the ECM if we don't see that ridge holding in the east.

Generally the models are poor at handling undercutting scenarios but you still need certain things in place to begin with.Theres no grey here, its black or white you either get the undercut or the energy piles over the top sinking the high

[Ice BIast]

if the GFS is over cooking the low is it then also overestimating the effect it has on the ridge to the East?

Yes, its quite a deep low, so it just ploughs straight into the ridge, stopping it from building north.

[legritter]

Just watched the GFS run ,possible clash of the titons coming up after next weekend . i know the modell looks a long way into the crystal ball but certainly great potential and it will im sure keep us all thinking . ECM in the morning will be critical but still along way to go for coldies ,but things are looking up a bit .and of course we have monthly update and data tomorrow .it will be interesting to see which way that low to our west /s/west eventually finishes up , this could be the clue to the eventuall outcome .

[SMU]

GFS ensembles more amplified- quite a long way, but most collapse the pattern after some small signals of undercutting.

remember once the undercutting signal grows then a VERY quick change in the GFS ensembles would appear-

18 & 20 are the ENS to watch.

So lets start with one undercutter at 162-

I bet its up to 3-5 on the 00z-

S

Edited November 11, 2012 by Steve Murr

[Duane S.]

All in all, I'd say the models have served up just about the best they could this weekend from where we were a few days back.

A lot will depend on how much energy can be sent down on the southern arm of the jet, if the northern arm remains powered up we may have to wait a little longer for another shot. Exciting (and no doubt, fraught) times ahead model watching in the next 10 days! We have to hope (and we've good reason to) that the vortex will come under pressure before it can form properly. GP has hinted that the cavalry is coming and it will be quite a sustained charge!

It's a bit risk and reward but I'm quite liking this set up with vortex as it is, because if it can be split and favourably the results could be as extreme as Dec '10. Outside chance of course!

[skifreak]

Blimey, this is a run of nasty, nasty weather, lashing rain and hill snow abounding. The PV seems to want to veer right over to Scandi.

I quite like the potential for the Ski Areas in this run, spells of heavy hill snow with snow still falling (if rather wet) on storm through hurricane force winds from a Southerly quadrant - a very good direction for wet snow to be driven into the key areas of CairnGorm, Nevis and Glencoe esp. Just don't want a repeat of Hurricane Bawbag and it's hangers on that blew entire buildings away at Glencoe!

[snow drift]

As is normal, the different models give different detail but they all show a variation on a theme. That theme to my way of thinking is for blocking as the month progresses. What the actual effect will this have for our little part of the world is not clear at this time and as more runs come we should get a better idea. I would say that I am enthused by the trend for blocking as this will give us a better opportunity for cold, than the weather just rolling in from the west.

I would also add that should it not fall “right†first time, then more chances will follow if the theme of blocking continues.

[BlueHedgehog074]

Although the energy is not quite as successful undercutting the Scandinavia/Euro high on the 00Z ECMWF run (bit too much of it I feel wants to pile over the high towards Northern Scandinavia at 192 hours), some of the later time-frames could still hold some promise. That small deep Low out to the West at 240 hours looks as though it would have more success at going under that large wall of high to the East. The fact the high to the East is also slightly negatively titled would help with this fact I feel, too.

I think considering the ECMWF did start showing an undercutting solution yesterday with those South-Easterly tracking Lows/troughing, it's perhaps no surprise it's having a slight wobble about the evolution at the moment in FI. It's by no means a complete disaster and it looks like some undercutting would still happen. Nevertheless, I do agree with some of the posts yesterday that the more energy that gets diverted to the South of the high, the better chance we should hopefully have at seeing a possible developing Easterly with a lower risk of the high getting sunk to the South like a ship. Will be quite amusing to see what the ECM model unravels for us on future runs and whether we can get other models joining forces with it.

Edited November 12, 2012 by DiagonalRedLine

[cold snap]

the continuation of the theme, not as good as last night.but signs of a block, this has to be what ecm 32 dayer is hinting at.still at the first hurdle ,but potential is still intack from the overnight runs

[Gibby]

Good morning. Here is the morning report of the morning outputs from GFS, UKMO, GEM and ECM for today Monday November 12th 2012.

All models support a wwarm front crossing East over the UK today with a band of rain followed by a mild and moist SW flow for tomorrow. A trailing cold front will affect the NW tomorrow and Wednesday with some persistent rain for NW areas. Further South and East the SW flow will slacken meaning light winds and some breaks in the cloud will allow mist and fog to form overnight and be slow to clear through the morning's It will stay mild though in the South and East for the remainder of the working week. By Friday a front will edge in form the West bringing a freshening breeze and rain slowly East through the day, clearing away the mist and merk from England and Wales.

GFS then takes us into the weekend with the front continuing to cross from the West with clearer, chillier and fresher conditions reaching most areas by darkfall on Saturday. Sunday looks a reasonable day as a transient ridge brings a dry and bright day, especially in the South after mist, fog and a touch of frost lift. A new depression spits it's way NE towards Scotland by Monday with rain and strong winds affecting all areas as we enter FI. In the lower resolution part of the run this morning there is a lot of rather chilly and unsettled weather shown with some rather cold polar maritime air behind fronts giving rise to plenty of showers between more persistent rain which could turn wintry over the hills as Low pressure ares are blocked by High pressure over Europe. The trend shown is for this High to manoeuvre towards Scandinavia, maintaining the block but allowing the continent to cool down markedly. This keeps Low pressure at bay to the West of the UK by the end of the run with a ridge from the Scandinavian High bringing dry and cold conditions for all by the term of the run.

The GFS Ensembles show the Control and Operational runs as cold outliers at the end of the run but not without some support. There are though many milder options shown making the mean for the run near to or just above the long term mean even through the colder phases of the Control and operational. After the rain today the South stays dry until the 17th while thereafter rain at times is likely. The North sees rain at times throughout.

The Jet Stream flow although somewhat erratic maintains a general Eastwards track over the UK and into Northern Europe over the coming week with some ebbing and flowing in strength from time to time.

UKMO for midnight on Sunday shows a trough down the North Sea with a weak ridge affecting the UK through the day. The rainfall from the previous day will of moved away East with drier, cooler and fresher weather eover the UK with some mist and fog patches and perhaps a touch of frost in the overnight period.

GEM shows a ridge too at 144hrs followed by a vigorous depression winding up to the NW with strong winds and rain sweeping NE to be followed by further windy and unsettled conditions as Low pressure's slip slowly East over Britain and introduces a chilly NW flow with showers to end the run.

ECM also has a weak ridge over the UK on Sunday with a weakening cold front crossing slowly East on Monday with a band of rain followed by drier conditions once more for the start of next week. Thereafter the European High strengthen's it's blocking powers while relocating to Scandinavia with a strong and chilly SE flow developing with Low pressure down to the SW in the final day. The weather at the surface would be mostly cloudy with a keen breeze with some rain likely in the far West.

In Summary today the weather this week will be relatively mild with fog problems later in the week as winds fall light and some rain persisting for the NW. Over the weekend somewhat colder conditions arrive from the West with a tricky synopses of troughs and ridges lasting several days for the UK. Thereafter there is a growing trend for High pressure over Europe to reposition further North to allow some colder air to feed West over Europe. The Low pressure's to the West willl likely become blocked with troughs just to the West of the mainland as per ECM. If the High strengthens further a cold ridge from Scandinavia could bring dry and cold conditions as per GFS. It's going to be a bumpy road though with many milder options remaining on the table from the GFS Ensembles but if it's trends we are looking for then there has been an increase in members supporting something of a colder feed from Europe and we need that trend to grow and spread over the coming days and runs.

[BLAST FROM THE PAST]

the continuation of the theme, not as good as last night.but signs of a block, this has to be what ecm 32 dayer is hinting at.still at the first hurdle ,but potential is still intack from the overnight runs

If we isolate the ECM at the moment, timeframe t162 to 240 00z is better than the 12z for cold prospects to reach the UK? The positioning and development of the Scandi Block is further west and better angled. I think coldie fans should be happy with the ECM and is defo following Steve Murrs ideas. Now to look at the others.

GFS slower evolution but heads the same way. If this comes off as progged then that is a very good pick up from ECM 32 as shown by Helen Willetts they suggested winds to come from the east and probably from a Scandi HP for end of the month. Its still a long way off though and is weighted with danger but seems the plausible development for cold with a massive block to our east. In situations like that mild can quickly turn to cold with any retrogression of the block and any undercut. In the stratos thread it was mentioned by C that the vortex is elongated and that more energy could go to the southern arm of the jet.......leading to undercut? Coldies need that retrogression as any retreat would lead to continued mild. However, that block isn't showing any sign of waning.

BFTP

Edited November 12, 2012 by BLAST FROM THE PAST