Winter Model Discussion - Cold Hunting -12Z 06/01/13

[johnholmes]

Just replying to this after having been away for a while.

I say that because of the issue that while some relationships between atmospheric variables stay constant regardless, others may potentially change if the global climate changes significantly. Due to the latter issue, if climate models are good at reproducing past and present climate, it doesn't mean that they'll do similarly well at predicting future climate under enhanced warming of, say, 2 degrees, and this is a significant problem re. verification of the accuracy of predictions of late-21st century climate.

The same sort of issue could potentially affect shorter-range forecast models- though as their accuracy can be verified very quickly by comparing the forecast against the actual outcome, chances are the scientists behind them would soon be able to tweak the parameterisations appropriately to provide a better fit for the "new" climate and so any drop in accuracy would be short-lived (and probably indistinguishable from the short-term drops you get from the likes of stratospheric warming events anyway).

nothing you say Ian alters the basic Laws of Thermodynamics on which all the models at whatever length they go out to have to follow so I have to disagree with you. I will go and do some reading to see if I can find anything that supports your ideas, if they do then I'm wrong and you are right?

[SP1986]

Interestingly if this one does just elude the British Isles (it won't because we'll still get frost and fog I'm sure), then I suspect there is an increased chance of another pretty harsh freeze on the European continent. The GFS 18z shows this to an extent, but at the moment it's all up in the air, so far as the models go anyway.

[nick sussex]

just seems to be so out of line with everything else

The problem is we don't know what the right trend is!

With so many different solutions today you'd need to be very brave to make a forecast for next weekend. I think the UK is owed big time for the dismal excuse for a winter so far.

So we can only hope that after all the chopping and changing it has a happy snowy ending!

[gaia rules]

This is what we need to be looking at on the FAX charts and UKMO (highlighted) over the next few days.

If this low is centered even just 200 - 300 miles further North, it delays the possibility of an Easterly forming and everything thereafter is very different.

Same applies if it is further East / West / South...this in my opinion is why we are getting so much variance on the models.

This run places it in a good position allowing is to sink South East and the Cold runs over the top of it and into the UK...the 12z had it further North and it also later showed it to split in 2 pieces

The ECM has it further South still, but so far that it doesn't link up into Iceland as the above charts do, what happens is that instead there is a space for the High Pressure to move into which then sinks over the UK

Of course this is all way out at + 144 the UKMO looks nothing like this at + 144 so that Low Pressure system may never even get here, but if it does start to get modeled as per ECM and GFS , then i'll be hoping it can sink SE into the Belgium area so that the cold can ride over it's top and pour into the Uk

EML network you have said it far more eloquently than me. The great thing about today is that when the models have taken into account SSW, solar activity, the massive systems over the arctic, pacific and god knows where else it comes down to a little runt of a low pressure that cant make up its mind whether to go south or visit the UK.

[Timmytour]

Ok....things a bit calmer...time to ask this.

Is it possible that, without the SSW, we would have been on course to have the sort of runs we've been having?

And is it possible that, with the SSW a shot at a spell of winter we had could either be amplified and prolonged as a result or actually disrupted?

In other words is the SSW responsible for our potential shot of winter or is it acting to change the degree to which we get it...good or bad.?

[bobbydog]

The UKMO have updated their fax charts:

http://www.meteociel.../fax/fax96s.gif

http://www.meteociel...fax/fax120s.gif

Sadly they follow that underwhelming raw output.

I don't like either of those but given all the changes lets hope that raw output disappears tomorrow!

aye... but will the weather follow the UKMO........?

[Crepuscular Ray]

aye... but will the weather follow the UKMO........?

No more likely than it following any of the other models! It doesn't follow any of 'em.

Edited January 6, 2013 by Crepuscular Ray

[NorthernRab]

Ok....things a bit calmer...time to ask this.

Is it possible that, without the SSW, we would have been on course to have the sort of runs we've been having?

And is it possible that, with the SSW a shot at a spell of winter we had could either be amplified and prolonged as a result or actually disrupted?

In other words is the SSW responsible for our potential shot of winter or is it acting to change the degree to which we get it...good or bad.?

This is more a question for the stratosphere thread.

Given that the SSW needs time to downwell into the troposphere (takes between 10-30 days), the upcoming colder synoptics are not necessarily linked, but as we approach the middle of January, I'd expect to see some cold synoptics influenced by the SSW. Bear in mind that approximately half of all big cold snaps have no SSW and that half of all SSWs do not lead to cold snaps. (I think that rough statistic is generally correct, some one might be able to give more light on that though).

[nick sussex]

Ok....things a bit calmer...time to ask this.

Is it possible that, without the SSW, we would have been on course to have the sort of runs we've been having?

And is it possible that, with the SSW a shot at a spell of winter we had could either be amplified and prolonged as a result or actually disrupted?

In other words is the SSW responsible for our potential shot of winter or is it acting to change the degree to which we get it...good or bad.?

I'm of the firm belief that without this SSW it would be incredibly difficult to have a chance at sustained cold within the next month.

The NH pattern was stuck in a rut and really as I said a few days back all our eggs are in the SSW basket! we still need some smaller reinforcing warmings to keep the PV from trying to set up again over Greenland and these are still forecast to take place.

Of course as you head towards the end of winter you often have a better chance of blocking but in terms of where we were in January it really was down to that SSW to save us!

[AWD]

London ens;

The EC Op a milder & wetter than average member in FI.

Edited January 6, 2013 by AWD

[Duane S.]

Another day, no wiser.

Quite a few days ago now I posted charts showing what to me was the the strongest agreement of ridging in the NH charts, the NE Pacific ridging. This looks still very much on the cards. From that we would see better heights over the pole and it would work in helping eject the vortex westwards away from Greenland, whether or not it lead to a pure cross polar flow.

But anyway the cold coming or not has always looked to be mid month. Beforehand (i.e. going into next weekend) there has always been the opportunity of a cold spell but it has never seriously looked to be much more than a very tasty starters to the main course. Some posters are putting too much emphasis on it and the implied implications if we don't get a cold spell in the next 7 days. Complete nonsense.

Nothing has been decided tonight and nor will it tomorrow.

[Eskimo]

London ens;

The EC Op a milder & wetter member in FI.

Above average rainfall and below average termperatures, wonder what that means?

[snowmadchrisuk]

Not a bad mean chart from the 18Z ...

[-uksnow-]

Just viewed the ens out to 180, there is a lot of members going for Mid atlantic ridge, easterly, retrogresson of ridge all by next Monday and even a few runs having a deepening low dropping down the North Sea. going to bed now so wont be viewing the full set but i think there is alot of support for the cold tonight on the GFS, part of me wonders if this weekend was its "Wobble" and it may get back on track, but calm down Ed you're nearly ramping now.

[StormyLincs]

Iv'e been lurking in the background of this great site since it first began and to be honest iv'e never seen such confusion in the models before. Am i not alone in being quite pleased with the outputs of the last few days, if only that it has gone from an endless mild SW'erly and rain to where we are now in just a few days.

As one of the possibly more senior members on here, i remember very well the absolute model mayhem that preceded the infamous spell in jan 87. The BBC forecasts changed every day, sometimes the threat of cold and then vice versa the next day. All of a sudden the models came to agreement and the record cold set in within a few days.(I assume this could have been caused by a large SSW also) now i'm not saying we are going to be dumped in the deep freeze just like then but what i am trying to say is that whilst the models are in such a state of flux, there is no point speculating and the best thing to do is watch and learn as i've got a feeling something pretty goods going to turn up soon!..maybe not from the first shot but maybe more likely from a greenie high.

just sit tight and enjoy the ride!

[Panayiotis]

To me this as an ensemble for 144hrs, is looking really good, with the low to the south giving us a snowy easterly.

The same can be said about the 204hrs ensemble (however it is Fi)

It seems that some people on here, are just negative, yes its not an ice age with meters of snowfall but its still descent, compared to what we have had this week!

Edited January 6, 2013 by Panayiotis

[Cumulonimbus Tower]

London ens;

The EC Op a milder & wetter than average member in FI.

There looks to be an awful lot of colder solutions deep in the reaches of FI

[Duane S.]

Just skipped through all the GEFS ens of the 15th (now just inside hi res) and they are stunning.

Huge agreement (relatively speaking) of some sort of well placed HLB and of lower heights beneath us.

The poor ones continue to decrease daily.

[Weathizard]

Very pleased with all the runs this evening, ECM main output is poor BUT, crucially for me, more ensembles seem to go for colder solutions after T168. GFS is very good, I mean considering really we aren't even seeing the true effects of the SSW yet to be seeing charts like that is truly a sight to behold, lots can go wrong but based on the ENS I'd give us at least a 70% chance of at least a transient cold spell effecting parts on the country next week. Onwards and upwards, we may have been scarred in December but we have another shot here, and it looks like there will be many more opportunities for cold in the coming month/weeks.

Can I just say as well, I feel sorry for the mods today, when the toys and dummies and everything possible come out the pram on here its a ruddy nightmare! I always find it ironic how certain posters react when the cold disappears by saying its game over and then comment next how its real knife edge stuff. Lets be honest the UK is practically always on the periphery of the cold, its the nature of the pest that is the Atlantic and all the things that come with it, plenty can go wrong and often does, but we'll get our lucky break eventually in the current sypnotics, I personally love the ride the Model discussion brings, whether it be toys being thrown ect or ramping, its great entertainment and I certainly wouldn't want it any other way!

Evening guys and on to tomorrows long running soap opera! (And I'm not just talking about the models!!)

[Cheshire Freeze]

Means little on its own but...erm....WOW (one perturbation in FI). Just thought I'd post a bit of weather porn.

[Panayiotis]

So from the 13th, all members are below the 0C line, where as earlier there were some still going for above this.Overall this is a very encouraging sign, and hoping to see more of the members trend down as we get near to the time.

Edited January 6, 2013 by Panayiotis

[TEITS]

Great to finish tonight on a high as the GEFS ensembles are the best yet. For the first time the mean drops below -5C around the 13th.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=309&ext=1&y=76&run=18&runpara=0

SLP mean in FI isn't bad either!!

Night all.

[Bonjangle]

Mods delte if this not allowed on here , just read this on WeatherOnline ... bit dizmal but i reckon it's a load of Oblox .

If you can call this remotely anything like 'winter'..... then during the short term period high pressure may be something more akin to it? Higher pressures across the UK will be in control of the pattern through to the middle period of January, the majority of the UK therefore seeing a noticeable alteration in the recent conditions, wet and cloudy weather, replaced with brighter but colder weather.

*... 21/1/13*

Frost and fog will become widespread and where this persists through daylight hours it'll remain cloudy and distinctly chilly, where it clears, rather pleasant, cold but bright mid-winter conditions will establish. There is the possibility of wintry showers developing almost anywhere especially coastal areas exposed to onshore winds, but primarily there'll be a good deal of dry if rather chilly weather on offer, this pattern expected to hold through to the mid- January period. There is evidence albeit tentative that high pressure may hold fast and the wintry weather continues into early February, however this is not substantial at this time and on that basis only the pattern has to be weighted towards a change taking place later this month.

*21/1/13 to 31/1/13*

Into the third week there are indications that the Atlantic westerly may attempt to kick in once more and bring a milder regime back into all areas, with rain and stronger winds establishing, high pressure retreating and allowing low pressure to take control of the pattern. This transition may be 'messy' and erratic but any wintry weather should be replaced by less cold but cloudier conditions.

An unsettled regime looks likely to persist into the latter stages of the month, the most disturbed conditions look set to affecting north-western and western Britain, a build of high pressure to the south should see southern and south-eastern areas of England drier and sunnier for the most part, temperatures here generally holding up.

*1/2/13 to 6/2/13*

Into the beginning of February the Atlantic and low pressure are looking as if they'll be continuing to remain in control, so the generally unsettled and mild-side regime the order of the day.

[Lampostwatcher]

GEFS ENS looking cold

[ITSY]

fantastic set of ECM and GFS ens to sleep on, with huge amounts of cold runs. Impressive for where we are in this developing situation.