Model Output Discussion 13/11/13 >

[ITSY]

For all newbies and learners out there, this is the DREAM run (taken out of the GEFS ensemble suite from this morning's set):  

http://www.meteociel.fr/modeles/gefs_cartes.php?code=7&ech=6&carte=1&mode=0

 

so last one from me-  this is where its at- the November 2010 run- very very plausible....

 

Some of the synoptics on offer are absolutely fantastic, and I hope (though don't necessarily expect) to see the amplification of high pressure to our N/NW/NE become more vertically aligned than it is now. This, as Steve alluded to on the previous page, will essentially negate the lack of cold temps over Europe at the moment by offering a direct short cut through a far more potent N/NEly type setup than on offer on many models at the moment, which deliver us with a much coveted Easterly, but which lets us down as the source (over Eastern Europe) is far warmer than normal, so the wintriness is reserved for high ground only. This is basically, in absolute Lehmann's terms, what happened in 2010 and why we got such a severe dose of winter so early (which is also explained by Steve on the previous page). If we don't get the vertical alignment out around Southern Greenland and the Atlantic, we won't get a severe or unusually snowy cold spell for most (not all), as a Scandi high will only bring cold and seasonal weather given the warmth over Europe.Having said all that, some scenarios on offer go on to produce a mega block over Western Russia (a result of a developing scandi high), like this:http://www.wetterzentrale.de/pics/Rtavn3481.png

If this verified, it is likely that short term frustration would develop into something far along the traditional Easterly route and bring us much colder and snowier weather across from a cooling Europe, albeit further down the line. But a word of caution for the newbies in particular: This is not a win-win scenario just yet, and plenty of things could happen between now and next week to scupper the development of either of these two scenarios - although make no mistake about it, if the first scenario verified, it could be something quite special. Ramp over. 

[MR EXTREMES]

met office recovery in temps is only because of higher upper but hey three days of cold upper cooling uk then a recovery but still slightly below average due to surface heights over the uk so when recovery in temps is talked about it must be put into perspective no mild weather and updates from the met could change as time goes on could turn milder in there updates could turn colder in time.

 

but over all below average and most likely staying below slightly due to surface cold and no real influx of milder southerlies westerlies or south westerlies.

[ronan]

No point really looking at these until Sunday/Monday to be honest. Sometimes nice for eye candy but that's about it!

[Nick B]

http://www.meteociel.fr/modeles/gefs_cartes.php?code=4&ech=6&carte=1&mode=0

 

 

With quite a phenomenal GH at the end, just for interest.  One of many, many possible perturbations showing, of which of course none will be exactly correct, but fun to see.

[TwisterGirl81]

Along with Scotland some southern parts could see temperatures struggling to get above zero next week for a time, though the south west keeps temps around 7 to 9c on Tuesday before taking a tumble on Wednesday

 

 

First snow of the season for some in the south is possible on Wednesday

 

 

What part of Devon are you in? as snow is still on show for parts of Devon

Exeter and on the charts posted there seems to be snow but on the GEFS I saw this morning for 'Pricipitation chart' it seemed to have all but dissapeared and was more up in Wales, fingers crossed

 

We'll need to wait and see but from my experience Devon & Cornwall generally get downgraded but here's hoping to an epic snowfall like we had in 2010, we had aout 9 - 10 inches in Exeter which is really rare 

Edited November 14, 2013 by TwisterGirl81

[Cheshire Freeze]

Well looking at the models as they stand it seems as though just as the GFS decides to play nice, the ECM and UKMO back off somewhat. I don't particularly like the look of the ECM and the UKMO looks as though it would go the same way at 144 hours.

 

 

Seems to be due to that little low S of Greenland. Hoping for better tonight TBH.

[Summer Sun]

Summer Sun check the charts that you are posting! These are from the previous run the 00z. If you check again the snow has gone from the south on the 06z. 

 

Well thats strange as these were posted well after the 06z update and I know for certain I never clicked previous run, so I can't understand why there not the 06z

[BLAST FROM THE PAST]

BFTP=PLEASE read what he posted rather than getting the wrong end of the stick. He is not writing off winter but merely commenting that sleet rather than snow is likely for low lying areas whereas if in January or February similar synoptics would be more likely to give snow, or am I off my trolley? If you are just making a 'funny' then best you do this in the other thread please Fred?

John

I have read it perfectly well thank you, and although it was meant tongue in cheek my post it reads that we could have done with these synoptics in Jan and Feb as he feels they will be wasted now......that suggests that he thinks they might not happen again?  

Anyway lets not take it too seriously, there is enough of that on here. 

Re mentions of 2010, that did seem to be seen coming [not the record cold] but the great synoptic set up.  This proposed one seems to be more 'sudden' don't we think?  Will it get that amplified.  Its interesting one

 

 

BFTP

Edited November 14, 2013 by BLAST FROM THE PAST

[JK1]

I know this is way way out and most defiantly will change & probably won't happen but if it did & went through us would that mean another wind storm? just curious

Edited November 14, 2013 by JK1

[TwisterGirl81]

I know this is way way out and most defiantly will change & probably won't happen but if it did & went through us would that mean another wind storm? just curious

 

 

I'm a novice but that looks like it would be a really bad blizzard if it were to hit the uk.....But those type of lows tend swing north west so I'm sure the whole country would be affected but it would be northwestern area's like northern ireland and Scotland, Northern England that would take the brunt....that's what happens 90% of the time....buggers!

Edited November 14, 2013 by TwisterGirl81

[MR EXTREMES]

indeed twister girl that would be a slider and it would also be mega at this time of the year although saying this we need the deep cold into Europe.

but would certainly help with heights to.

[ronan]

Well thats strange as these were posted well after the 06z update and I know for certain I never clicked previous run, so I can't understand why there not the 06z

 

When you click in to view the run you have to click below it to view current run. Thats why there are 2 screens on the page so that you can compare the previous run with the current run.

[TwisterGirl81]

i'm liking the windy part, but the blizzard part not so much, but it will most probably change so

 

Unfortunately it will take an epic snow storm to hit the uk for the infrastructure to get it's act together, one day we will get hit by a major snow storm (worse than 2010) and it really will shut the country down, it's happened before and it will happen again, it's just a question of when (snowmageddon) .....I don't know why we don't have snow ploughs etc, I'm not sure if they do in northern area's but we certainly don't in the south....I mean I know we are on the gulf stream which keeps as not as cold generally in winter to what we should be given our latitude but we do get affected by northerlies and easterlies from time to time in the south....

 

I love epic weather in all manors so i'd like to see this verified but then not so much because I know some people wouldn't take warnings and get killed.....Especially the elderly that don't have family and their neighbours don't think to check on them and keep them safe!

indeed twister girl that would be a slider and it would also be mega at this time of the year although saying this we need the deep cold into Europe.

but would certainly help with heights to.

 

Thankyou   Quite pleased with myself....Can I please ask what a slider is and why we would need the cold into Europe?

Edited November 14, 2013 by TwisterGirl81

[SMU]

Well looking at the models as they stand it seems as though just as the GFS decides to play nice, the ECM and UKMO back off somewhat. I don't particularly like the look of the ECM and the UKMO looks as though it would go the same way at 144 hours.

 

 

Seems to be due to that little low S of Greenland. Hoping for better tonight TBH.

 

Agreed - 

 

Up until 2009/10 I never saw a high pressure ridge out of the atlantic to then get undercut & remain in situ over Greenland as a cut off high.

Every time the ECM or any model presented this is didn't happen, the end result was an overrunning pattern & a toppler..-

However it has happened a couple of times in the last few years- so it 'can' happen...

 

Worth noting though that its not fully cut & dried just yet.....

 

S

[Team Jo]

Hi folks, Just a polite reminder that there are heaps of other places for one-line snippets, and 'Will it snow in my Garden' type discussions. A good place for localised discussion is probably happening in your Regional

[Man With Beard]

Not often I get time to post something longer, so here goes...some talk this morning about a repeat of November 2010, well, how realistic is this idea? November 2010 was pretty much perfect in terms of bringing cold and snow at such an early stage in the season - I would say, if there are 5 steps to getting to a repeat of Nov 10, charts such as the GFS 06Z get us to step 3. 

 

Step 1: A flat zonal pattern is interrupted with a bit more amplification (i.e. the colours on the chart go up and down, rather than in a straight line left to right) - this is happening right now (and the good news for the rest of winter is that zonality has wasted some of its fuel on October/early November:

 

Step 2: Amplification in the Atlantic increases to such an extent that low pressure is able to drop from the north through the UK

 

Step 3: Now it gets really interesting. Low pressure takes the opportunity to get under the Atlantic High both in the Atlantic and in Europe, forcing the High to settle to the north of us. GEM T186 shows one variation of this - some other models are similar (ECM doesn't quite manage it this morning but not a million miles away)

 

So looking good for steps 1 and 2, step 3 also looks quite possible though not nailed on yet. To be honest, just getting to step 2 alone could lead to some surprise snow events - we're just about in the time of year for that now - but real winter junkies will be hoping for steps 4 and 5 - so let's look at what happened in 2010...

 

Step 4: High pressure pulls back toward Greenland. This is crucial for getting the real cold in, as it allows another plunge from the north to infiltrate deeper cold - you can see the deep purples to the north-east...

 

Step 5: Bingo! With nothing to block its path, the low heights flood through northern Europe, drawing deep cold at the same time.

It's one-way traffic from the north-east now, and so a couple of days later, we see -8C uppers entrenched over the UK, with more to follow

So, could it happen again? For now, the models are kind of heading in the right direction so "possibly", but the truth is we'll need a bit of luck, especially in getting a Greenland High just where it needs to be. And, even if we do get stuck at step 3, that alone may be enough to provide something wintry though very marginal in central/eastern areas and you'd want a stronger flow over the North Sea, a shorter sea-track, cold fronts with no warm zones preferably passing through at night and maybe a degree or two less on the 850s.

 

A real turn around from the zonal motorway of just a few days ago and lots to be looking out for!

Edited November 14, 2013 by rjbw

[Team Jo]

Unfortunately it will take an epic snow storm to hit the uk for the infrastructure to get it's act together, one day we will get hit by a major snow storm (worse than 2010) and it really will shut the country down, it's happened before and it will happen again, it's just a question of when (snowmageddon) .....I don't know why we don't have snow ploughs etc, I'm not sure if they do in northern area's but we certainly don't in the south....I mean I know we are on the gulf stream which keeps as not as cold generally in winter to what we should be given our latitude but we do get affected by northerlies and easterlies from time to time in the south....

 

I love epic weather in all manors so i'd like to see this verified but then not so much because I know some people wouldn't take warnings and get killed.....Especially the elderly that don't have family and their neighbours don't think to check on them and keep them safe!

 

Thankyou   Quite pleased with myself....Can I please ask what a slider is and why we would need the cold into Europe?

 

 

Hi Twistergirl, - Lots of info in the Learning Guides here for you to Browse through

 

http://forum.netweather.tv/forum/5-the-netweather-guides/

[Frosty.]

I think there is now cross model agreement that we will have our first arctic blast during the first half of next week and some areas will have significant accumulations of snow, especially on higher ground, there is a risk of snow showers merging ino longer spells of snow on hills but on some low ground too, and with widespread icy patches and increasingly sharp frosts through to the midweek period. The met office then indicate less cold weather but I think their confidence in the period beyond the middle of next week is rather low and lacks much in the way of detail and considering some of the perturbations so far today, I think a large ? hangs over what happens later next week and beyond. It's nice to know late nov and through dec they expect temps slightly below average which would boost the chances of snow relative to the zero chance of snow we have seen so far in this generally tedious autumn..but things are about to become very interesting and exciting beyond the weekend, let's see how it all unravels.

Edited November 14, 2013 by Frosty.

[Cheshire Freeze]

Agreed - 

 

Up until 2009/10 I never saw a high pressure ridge out of the atlantic to then get undercut & remain in situ over Greenland as a cut off high.

Every time the ECM or any model presented this is didn't happen, the end result was an overrunning pattern & a toppler..-

However it has happened a couple of times in the last few years- so it 'can' happen...

 

Worth noting though that its not fully cut & dried just yet.....

 

S

 

Fingers crossed that the ECM can replicate its pattern of yesterday.....a smoother transition to something interesting longer term- rather than just a 2/3 day wonder. Yes the GFS/GEFS are nice today but I don't trust them as far as I could throw them.

Edited November 14, 2013 by CreweCold

[SnowBallz]

Unfortunately it will take an epic snow storm to hit the uk for the infrastructure to get it's act together, one day we will get hit by a major snow storm (worse than 2010) and it really will shut the country down, it's happened before and it will happen again, it's just a question of when (snowmageddon) .....I don't know why we don't have snow ploughs etc, I'm not sure if they do in northern area's but we certainly don't in the south....I mean I know we are on the gulf stream which keeps as not as cold generally in winter to what we should be given our latitude but we do get affected by northerlies and easterlies from time to time in the south....

 

I love epic weather in all manors so i'd like to see this verified but then not so much because I know some people wouldn't take warnings and get killed.....Especially the elderly that don't have family and their neighbours don't think to check on them and keep them safe!

 

Thankyou   Quite pleased with myself....Can I please ask what a slider is and why we would need the cold into Europe?

 

Hi,

 

The colloquial term "slider" refers to the behaviour of a low pressure system as it interacts with an entrenched area of high pressure.  To contextualise, for our region (NW Europe) if there was a large area of continental high pressure (perhaps a 'Scani High') and a low pressure system was tracking towards it from the Atlantic, a "slider" would be if the low pressure system undercut and tracked south of the the high pressure.  This specific interaction of the two pressure systems - with associated warm/cold gradient) often creates the conditions for extreme winter weather.

 

'Sliders' can be difficult, as - in the main - they are dependent on strong, stable and favourably orientated high pressure systems - characteristics which are often rare in conjunction, it not in isolation.  The opposite to a 'slider' is when the low pressure system tracks north of the high pressure system; less mixing, less gradient, and more likely to result in the breakdown of an entrenched pattern, ie: blocking.  That is not to say that high pressure cannot re-emerge, just that there is a correction of the general pattern of W - E flow (as opposed to a retrogressive E - W, when blocking is present)

 

In respect of 'cold into Europe', that's really about depth of thermal gradient.  If the continent is cold - and this time of the year it is still relatively warm, albeit cooling rapidly - then the high pressure will be sourcing very dry, very cold air from the depths of Russia and Eastern Europe.  As that bitter and dry air smashes into the warm and moist air within a low pressure system, this is where thermodynamical fireworks takes place, or - as Steve might say - 'BOOM!'.  Basically battlegrounds, where cold meets warm.

 

Hope that's helpful?

 

SB

[Gavin Hannah]

Rjbw - there has been quite a number of runs with step 3 shown as the likely outcome so i'm gona say we're more than halfway to step3 being checked off. The LP in the Atlantic is key to wether we get beyond step 3.

I put it at 50-50 atm.

P.s great post. We should name it the 5 steps to 'snovana' lol.

[MPG]

I think the models have agreement on next weeks cold spell. After that a slight warm up in terms of upper air temps and 2m temps due to a easterly flow off the continent. The 'warm up' I describe could give the setup required for a sustained period of below average temperatures. With low pressure in Europe we could be game on.

[PolarWarsaw]

Fingers crossed that the ECM can replicate its pattern of yesterday.....a smoother transition to something interesting longer term- rather than just a 2/3 day wonder. Yes the GFS/GEFS are nice today but I don't trust them as far as I could throw them.

 

I agree. 

 

At this stage I tend to think that the ECM/UKMO are the models we should be following, but glancing a cautionary eye over the GFS updates. I think we can safely say that 'nothing is nailed' and any talk of snow in X place is jumping far ahead of the gun at the moment. From a coldies perspective we need to look at the ECM coming back on board to it's theme last evening 12z. I think one thing we can safely say is - it's going be generally colder countrywide for a period next week. 

 

How cold? Chance of snow? How long will it last? - all questions to be answered in the coming 72 hours or so.

[snowking]

We're obviously limited by the ECMWF's decision to take away the EPS postage stamps just as we move towards something interesting *stomps feet on the ground*

 

But in terms of the temperatures heres a comparison between the ensemble maximum and minimum temperature projections between the GEFS and the ECMWF EPS:

 

Key:

 

ECMWF Max. Temp

ECMWF Min. Temp

GFS Ens Max. Temp

GFS Ens Min. Temp

 

 

Pretty good agreement in terms of the overall temperature trends at least.

 

I'm also quite happy with this as an ensemble mean solution from the GEFS at T+300:

 

 

High pressure to the North, low pressure to the South, and the tropospheric vortex really rather stretched.

 

A few signs of some sort of disturbance up in to the stratosphere at the same timeframe, whilst not necessarily a full split, certainly two visible centres with some potential here:

 

 

We even see something similar up to the 30mb level based upon the 6z GFS:

 

 

Whilst this is of course just one run we did see something similar from the 0z too at the 100mb level at least.

 

Meanwhile whilst we don't see anything too similar from yesterday's ECMWF 12z stratosphere forecasts, we do see the very obvious ridge to the North-West of the UK at the 100mb level, signalling the potential for high pressure to remain around this area out to day 10, along with a troughing structure to our East and South-East:

 

 

Once again this is reflected right up to the 30mb level, though other than the ridging structure the vortex looks otherwise rather stable at this level:

 

 

So the significant cool down and the likelihood of some wintry precipitation next week. Could we be looking at something tropospherically-led more extensive? The signs all appear to be there but I remember a similar situation involving a Siberian high from last year too. Totally different kettle of fish with GIN corridor heights, but still some need for caution beyond the start of next week at this stage.

 

SK

Edited November 14, 2013 by snowking

[Paul]

Michael Fish has just updated his weekly forecast and is talking wintry weather..

 

http://www.netweather.tv/index.cgi?action=michaelfish;sess=