Winter Model Discussion 12Z 22/1/13 onwards.

[damianslaw]

Oh dear, it feels like late dec in this thread today with numerous posts saying thats it no chance of snow or cold weather nos because the models say so, how some of us will never learn, the current cold spell only showed up medium term in all thé models i.e only consensus occured some 6 days before the exchange, what this emphasises is a news to stick to the 6 day reliable timeframe, never bank on outputs for 240 hrs ahead or more.

[Catacol]

Catacol Highlander heres the extended discussions from NOAA:

http://www.cpc.ncep....day/fxus06.html

The PV located north Hudson Bay initially, a trough in the eastern USA for 8 to 14 day with some movement of the PV but not as the GFS does ejecting it too far east.

I'm confused. That report states that model of the day is ECM mean. That is exactly the chart I posted. Is the system that is steaming out into the atlantic NOT the canadian vortex segment? I see the vortex held to the NW in the longer term but this looks to me to be the vortex reforming and then it sets up shop right over Canada once again. End result - strong atlantic westerlies. Any height rises over greenland in that scenario look transient to me.

Timescale here is 2 weeks. I note above that someone has stated day 10 and up for a pattern change. Maybe we are all actually singing from the same hymn sheet here? I agree anything in the 10 - 14 day + area is possible, though the MetO update today isnt good.

Edited January 24, 2013 by Catacol_Highlander

[Lynxus]

... and while I am burbling the MetO update of long term drier to the north and wetter to the south surely suggests they see an atlantic dominated picture for the south with some height rises to the north to deflect the systems south. That sounds like a weaker version of what we have just had. No big high lat block?

I wish people would stop fixating on what the metoffice say in their LRF's.

One second they say cold, the next they say mild all for the same timeframe. Its pointless taking it as gospel..

The models are your best way of seeing what will happen and at the moment, they point to milder weather for most of us.

Yes there are chances of further cold "If" certain things fall in place, however none of these are given as yet.

We first need to get out of what we have now before we can see if we get more.

[Catacol]

the current cold spell only showed up medium term in all thé models i.e only consensus occured some 6 days before the exchange, what this emphasises is a news to stick to the 6 day reliable timeframe, never bank on outputs for 240 hrs ahead or more.

Thats true, but then we had strat prediction charts that clearly showed the vortex splitting and therefore tropospheric height anomalies gaining ground between the 2 centres. The op runs were obviously at odds with this, and so it was an easier call to be dubious of what they showed. Suddenly they changed the modelling of energy coming our way, heights rose and the sliders began.

This time around no such easy strat chart that points to a swift way out of atlantic weather systems. We have experienced posters saying that height rises should be on the cards, but even Chio tonight has stated that we now have to wait to see if the pacific ridge can work its way over to our side. That sounds a bit like hopecasting if you are looking for cold? If the vortex stays stationed in our neck of the woods height rises look tough. Weakened or not, heights wont rise unless it evacuates the greenland sector.

I told a lie in one respect - I said I could not find any model suggestion of an improvement. Wrong. One small grain of optimisim from the JMA 3 - 4 week anomaly mean charts - these clearly show an easterly flow and high lat block starting from day 16 through to 29. So winter perhaps to restart around Feb 10 with peak cold 7 days or so later? One model, one mean... but a little hope.

[kumquat]

I wonder if null set data has been run. i.e if the SSW effects could have somehow been negated from the model output as soon as they showed their hand. I'd expect to see less of that loose cannon "shannon entropy" and a bit more mild mush? Any way this could have been worked as an offset?

[kumquat]

So why are you not buying into the strat warming as a strong guide of predicting & affecting our weather patterns long term?

You are not a expert teits and nor am i but when the likes of the meto are summiting that strat forecasts are showing the way forward i find your disregard to the strat amusing tbh.

Who else is "buying" into it? There's a hell of a lot more research and testing to come before anything with regards to SSWs are nailed. It's (relatively) brand new science and all opinion (both for and against) is valid until the body of work is far more thoroughly tested.

[Timmytour]

I have conceded that this winter will not turn out to be like 1947. I did have high hopes

My attention for February has now turned towards March 1970. I now think the rest of this winter could run parallel with it but for being a month early. So what i can see the models showing in deep FI i can relate to the start of March back then..

Not a bad month, gave me the only memory I have of being turfed out of primary school early because of snow! And, being a month earlier, we could do pretty well out of it.

[chriszoff]

Destructive criticism is a bit OTT. I am simply saying that I don't feel as though we can use the Stratosphere alone to predict whether HLB will occur. We need to use all the variables and this is where us humans come stuck. We don't fully understand all these variables and more importantly understand how they interact with each other.

Basically in my opinion long range forecasting is a waste of time especially for the UK in winter.

Absolutely spot on, nail on the head and please note especially the last 9 words, this Winter is not over and i am fascinated to see how the Strat plays out the last month of winter but so far it has only pushed this Winter towards what i would call a normal average UK winter, it's only considered WOW becuase the youngsters on here have seen 10 years or more of pretty benign Winter Weather, i 1000000000 percent agree you cannot call Winter weather in this country beyond about 4 days and given the last couple of weeks even that is stretching it.

[Paul T]

NAEFS 'Pressure anomalie' charts currently show Low pressure dominanting over the North sea from 4th Feb onwards.

Forget all of your other shenanigans, model watching and analysis, this particular model sweet illistrated that 'That ECM' wouldn't happen at all in Dec and it recently told us of the end of this cold spell 10/11 days prior to Sat's breakdown.

Will be back on this thread early Feb to pull out this chart again

[kumquat]

The question is whether the SSW did play a part in the current cold spell. I personally think that it did because before the SSW, there was no sign of any high pressure to our north at all since mid December. Then all of a sudden six days after the SSW an area of high pressure drifted north from the south and stayed to our north for about 2 weeks. I know it wasn't a strong area of high pressure but it was still strong enough to keep the Atlantic at bay for about 2 weeks.

But this is the six million dollar question, isn't it, because who's to say this isn't part of a rather average UK synoptic winter pattern?

[chriszoff]

I am sorry but at this point I will bow out gracefully to your better analysis and opinion, as it is now becoming quite clear to me that the stratosphere has not contributed to the tropospheric pattern at all over these last few weeks as you suggest, and it is quite obvious that we will not get any high latitude blocking throughout the rest of winter.

I should know better than to spend a lot of time reading research to the contrary and I will contact the metoffice and BBC immediately to inform them that they have been misleading the public in saying as much that the SSW may have contributed to the cold spell.

Thanks for clearing that up.

You are well respected on here here Chio as is TEITS and i admire both of you for your u/s of the models, however are you saying that the current Strat effect has been responsible for the current weather we are experiencing ? Forgive me if i am wrong but i am led to believe that we are only really going to feel the effects by the end of the month, so jury is still out, i think this is still very much a learning curve for all, if we see cold weather and heavy snow !!!, which is sooooooo very subjective depending on your age, in Feb then i think the whole Strat thing may be vindicated, however if we do not then in my eyes this Winter should be classed as normal, as the Strat effect viewed with caution, as i say it depends on what you are comparing to !

[london-snow]

Who else is "buying" into it? There's a hell of a lot more research and testing to come before anything with regards to SSWs are nailed. It's (relatively) brand new science and all opinion (both for and against) is valid until the body of work is far more thoroughly tested.

No i disagree,

Even though i believe the strat forecasts can give you a rough idea to work with such as a split pv or disorganised pv. It like all forecasts can never give a specified forecast.

However it does affect our weather & can be forecast weeks out for example.

~ forecasts show a strat warming.

~ strat warming happens.

~ strat warming begins to filter.

~ strat warming affects our weather.

It does however not promise cold weather but it is a very useful guide infact the best guide that i have seen.

[Thundery wintry showers]

Just before I pop off to bed, a note that the ECMWF operational run and ensemble mean show a strong polar vortex and mild blustery south-westerlies out to around day 7, but during days 8-10 the polar vortex weakens and becomes fragmented, suggesting potential for a pattern change. This, to my mind, supports the suggestion that a pattern change may be around the corner around days 10-14 and that, at the very least, it is premature to call mild zonal weather for more than a week ahead at this stage. The GFS 18Z tonight also shows a similar thing.

On the other hand, a pattern change doesn't necessarily mean a change to a cold snowy pattern- so I'd also advise snow lovers against getting too excited either.

Edited January 24, 2013 by Thundery wintry showers

[Richie V]

Well, either way im happy. Im missing my severe gales big time. Im quite looking foreward to this week. Just cos its zonal doesnt mean my severe gales will materilize, just like the hunt for cold, models often bugger up much beyond 120 hrs. I feel the coldies pain in that respect.

[kumquat]

No i disagree,

Even though i believe the strat forecasts can give you a rough idea to work with such as a split pv or disorganised pv. It like all forecasts can never give a specified forecast.

However it does affect our weather & can be forecast weeks out for example.

~ forecasts show a strat warming.

~ strat warming happens.

~ strat warming begins to filter.

~ strat warming affects our weather.

It does however not promise cold weather but it is a very useful guide infact the best guide that i have seen.

Split PVs and disorganised PVs are nothing new (as we would expect). And their propensity to throw cold out to lower latitudes are also nothing new. I agree that there is a good science to be researched and discovered behind the phenomenon known as a sudden stratospheric warming. How that influences the tropospheric pattern is still up to debate and how it affects the UK winter weather - even more so.

[Panayiotis]

Just some eye candy from the GFS ensembles.....

Perturbation 19 is my most favourite!

[That ECM]

You really can't take any critical remarks can you?

Like I have said many times I am a firm believer that the Stratosphere affects the weather patterns lower down. However it is only one jigsaw puzzle amongst many others and unfortunately many ignore these other pieces and assume the Stratosphere dictates everything. So the reason im sceptical isn't because I doubt the influence of the Stratosphere but our understanding of this jigsaw puzzle amongst all the others.

The problem with this forum in recent years is the Stratosphere has become the new trend and some of the other factors like SSTs in the Atlantic have been completely ignored. So many members now assume that a SSW equals HLB. This clearly isn't the case because we have yet to see a GH in the model output and yet in Dec 2009, 2010 we were treated to a 1070mb GH without a SSW!!

You change your mind more than my Mrs!!!! He has given, on more than one occasion, detailed analysis on why SSW can give us cold and why it will work against sometimes. The need to look at the output showing mild and then make ref to the SSW is more yours. You have said this is an area you do not understand. A little knowledge is dangerous. Why not learn more about this area and see its effects because clearly you are bright enough to read output, it may become an area of great interest to you.

Reading posts from respected posters arguing, not discussing, is like watching your parents argue when your a child. It is most unpleasant. Not actually needed IMO but if you feel the need, then pm each other and save us the annoyance of having to read it please.

[IDO]

Well I respect the experts on here but the GFS certainly is not having it. The GFS 0z is one of the most zonal charts I have seen for a while right out till 9th Feb:

Even then the PV piece looks like it has a week or so before it dies. That chart has zero potential with regards to HLB.

Average/mild for the 13 days after the breakdown according to the latest GFS with rain again the main headline.

ECM is as bad with a continuos feed of energy from the Canadian PV lobe: T240:

The PV piece to our NW has been our nemesis all winter and till it is destroyed it will be the main driver of our weather this winter. Despite assurances from the more knowledgeable the models are not showing this, in fact they are to the contrary, increasing the PV's substance!

The GEFS: suggest a mild five days followed by a return to seasonal averages till the end of FI.

It looks unlikely the models are going to trend to anything wintry in the medium term so we can only hope they flip. From the current synoptics this is a big ask.

[Catacol]

Lots of backwards and forwards arguments going on, but put simply we want the Vortex to focus its attention to our east if we are to get height rises in the correct place and a feed from the east, but instead it is still forecast to dominated the Canadian sector despite the ongoing warming. For as long as this is the case the atlantic will be powered up.

Perfectly possible for more vortex disruption and movement, but increasingly unlikely for the next 10 - 14 days.

I declare myself the founder of the new "I hate the Canadian Vortex" club.

[m1chaels]

So we are 36 hours from a Nationwide snow event. It is great to see the details of the latest model runs being discussed with such enthusiasm.

Any thoughts on how active Friday nights front will be. Will the fact it is an occlusion help the precipitation remain as snow?

Edited January 24, 2013 by m1chaels

[SMU]

Morning All-

Nothing to get get excited about today- Nowt in the models or anywhere to present a change.

The anomalies posted last night by Cloud 10 are in the locations where we expect to see our big cold weather come from, CH presenting the fact that they are there & effecting the weather, TEITS on the other hand looks more towards the Iceland / greenland SLP.

The bottom line they are probably both correct in their own right, however the biggest issue with those anomalies were they were to weak.- & not sustainable.

I dont think the Likes of CH have in any way tried to intimate that something 'special' would happen, however as the days passed & the strat thread gained more interest from people so the whole 'ramp' level & thread became a mix ( like the model thread ) of analysis & assumption- along with some charts that appeared on the GFS with high level blocking.

Plus a lot of people putting a lot of stock in the NW winter forecast & I have to say stewarts sometimes 'over confident' forecasts leading some lesser seasoned regulars thinking that things WILL happen.

We should never presume anything will happen for the UK, bit like saying the 'pattern will relax but reload very quickly from the NE'

some people now beginning to realise that these forecasts with high levels of confidence should be a little less bullish.

Also I note far to much focus on the anomalies in that presentation & far less comment on the 'norm' however thats for another discussion.-

The reality has been that the proceeding 6/7 weeks of winter have been pretty awful, a mediocre December & a very poor start to jan with the CET running towards 8c. The warming has had a an impact, & at the exact propergation time that I have seen before which is in the 15 day window- However perhaps due to the growing level of excitment in the strat thread as things started to happen, as ever expectation gets above reality.

The reality in this scenario after the warming has now propergated & finished is that the response was good & the blocking was ideally located for the UK, the problem has been though its sustainabilty & for the fact we didnt see more than 1 maybe 2 stationary long waves.- The main one being set back over the pole & another in situ ( weaker ) over svalbard oscillating south.

this is punctuated by the AO index only being mildly Negative at -2.

I also recall the post I made with respect to anomalies for Jan warmings for ( IIRC jan 85 & one other year ) the polar H5 anomalies were much more pronounced after the warming & that signal continued for some while-

We now see things returning to normality, so whilst there is some residual warmth in the stratosphere that should overall support the net lower speed of the zonal wind that in itself doesnt support continued blocking at the moment- & doesnt look like changing for some +8 days at least which brings the curtains down on Jan & starts feb on a probable mild note.

Post that there are 4 weeks of Winter left, time for the optimists to see patterns change & things ramp up once again- but from people that have seen it all before as you get past feb 14th the chances do decline away daily- especially for the south of the country.

Also we need remind ourselves there has been no greenland blocking this winter for 8 weeks.- which is generally the key indicator for sustainability of cold for the UK & with that AWOL it makes life very difficult.

So is this current cold spell great- Probably not... memorable for some- for sure. I think we have extracted the very most out of what has been just a 'limited' 500 MB response at 60N to what promised perhaps a bit more....

S

Edited January 24, 2013 by Steve Murr

[Bristawl Si]

Phew! That was exhausting catching up on the thread from last night.

Experienced or less experienced members should realise model output for a week+ in advance can change at the flick of a switch. What's showing up for 7 days+ in the current output can easily flip a few days later.

In 4 or 5 days time we COULD be discussing the next cold spell that looks imminent (according to the models) BUT then again we MIGHT be even more frustrated that nothing cold & snowy is on the distant horizon. Who knows?

Best to just wait and see for now.

EDIT: And agree with Steve M above, for those in the South, once past mid-Feb, any cold tends to be in the form of short 1/2 day 'snaps'. Yes, there's been exceptions in my lifetime but they are few and far between.

Edited January 24, 2013 by Bristle boy

[MR EXTREMES]

ive seen cold snowy easters in my lifetime although not ideal its happened.

there absolutely a strong connection between strat and colder spells in the uk.

its also noted that heights to our north have been rather poor this winter something which would be a good idear to research because i think although we had a decent cold snowy spell theres a certain something that went against us to block this heights build over greenland.

all the models show nothing but a very mild end to jan and the start of feb looks like going the same way.

im a little skeptical of another cold spell in feb but it was not long before this current cold spell that mild was being forecasted by the models only to pop a lil heights to our northeast which sustained enough to give us our cold spell.

problem is now that the vortex is not in a favoured area and has reorganised and the alantic looks much much more powerful is this being read right by the models or are they over reacting to the power of the alantic until the alantic slows then high latitude blocking will have alot of trouble building so it might be worth giving it a few more days to see were we head.

and if the same outlook continues in a few days then it might be game over but theres no 100% answer and mid feb could be a turning point but im firmly on the fence.

all this just goes to show that the weather and our atmosphere will do what it wants when it wants.

still believe that colder winters are the trend setters and the sun is close to its slumber once again.

[Methuselah]

Any chance of discussing the models??

[Frosty.]

Well I went through the gfs and ecm 00z op runs and could only find 1 very mild day (11-12c) that's next tuesday and overnight into wednesday, apart from that, temps look close to average (either just above or below) and there is an increase in colder incursions on both models beyond T+168 hours, so upstream things are looking better for cold shots, especially the gfs which has frequent Pm incursions later which could evolve into something arctic if we can get even better amplification, there are signs of this as there is a bulge of rising pressure in mid atlantic so signs of hope for colder spells are there. In the meantime, this current freeze is going out with a BANG..a spell of disruptive snow for many tomorrow afternoon, evening and overnight before turning to rain on saturday morning and then less cold, wet and windy weather becoming the main feature, the mild peaks next tues then nearer average and remaining unsettled, perhaps a colder shot later next week into the following weekend, it appears the jet tends to become more southerly tracking beyond the next week.