Winter Model Discussion 18Z 3/2/13 onwards.

[bluearmy]

Jason isnt completely wrong. But he isnt right either! No worries on that run whatsoever. once the cold is in wirh snowcover, a slack continental flow with uppers of 0c can deliver an ice day in feb.

i wouldnt pay too much attention to the ecm 00z run post the onset of the undercut. Whilst the end of the run resembles the ens mean, what happens inbetween is open to much conjecture.

Excellent cold oulook and the reamplification that the gwo predicted in evidence.

[Jason M]

I have to reply to this,

If you actually read the forum carefully and listen to the more experienced ones it was only John Holmes yesterday that gave a very well explanation on why absolutely know one should be looking at uppers outside the 72hr range because the DO change from run to run.

Looks at the bigger picture , look at the Synoptics .

Also im sorry but it's nonsense the things you say, we have -10 850's over us by the wkend m how on earth anyone can say thats not deep cold is beyond me ? This time of year Europe is very cold, and believe me the uppers will be very cold from the continent .

I stated yesterday that 2005 was a rare event because Europe had an unusually mild spell infact mild winter, which is why the uppers wasn't there. This year is very different .

These Synoptics are perfect this year for a very cold outbreak, why look at charts that's 200 hours away when we have so much cold and snowy weather inside 144 hrs ?

And I need to reply to this. Had you read the title of this thread carefully you would have noted its the model discussion thread. On that basis I'm perfectly entitled to comment on the uppers after 72 hours. All I'm saying is that the cold pool is limited on this occasion based on current output. I stand by that assessment.

Europe at present is actually not very cold for the time of year. Over the next few days the models may well play around with the orientation of the scandi high which will of course alter things for better or worse.

I am fully aware of the difference between between Atlantic and continental sourced cold air thanks. I stand by my view that it will be cold, it may well snow but that it is a fairly ordinary mid / late winter spell.

Try to be less patronising in future.

Jason

[Frosty.]

Ecm 00z is another very wintry run and the gfs continues to backtrack from it's zonal outlook but it still has a lot more improving to do to catch up to the ecm, however, further into FI the gfs is cold and blocked with slider lows and snow events for most of FI but it's this coming weekend that i'm talking about, the gfs still showing that eastward bias but it's getting there slowly. The best thing about the ecm run is seeing the azores high put back in it's place, squished back from whence it came.

[Severe Siberian icy blast]

And I need to reply to this. Had you read the title of this thread carefully you would have noted its the model discussion thread. On that basis I'm perfectly entitled to comment on the uppers after 72 hours. All I'm saying is that the cold pool is limited on this occasion based on current output. I stand by that assessment.

Europe at present is actually not very cold for the time of year. Over the next few days the models may well play around with the orientation of the scandi high which will of course alter things for better or worse.

I am fully aware of the difference between between Atlantic and continental sourced cold air thanks. I stand by my view that it will be cold, it may well snow but that it is a fairly ordinary mid / late winter spell.

Try to be less patronising in future.

Jason

I appologise i came across as patronising .

If your aware of how things can change from run run to run then why say this cold spell will lack the deep cold uppers when as you say you know it will change on the next run? Not to mention the fact it was a false statement . You used the last frame on the ECM to highlight your point , but you overlooked the -10 850's at 144hrs , then you went on to say this cold spell will not be anything noteworthy which is why the lack of posts from other members , but failed to mention the time of morning when 90% of us are in bed.

[weather eater]

NOAA go for a blended solution of the ECM/UKMO upstream in the eastern USA. They didn't think much of either the GFS or GEM which is good news.

Very good news indeed, obviously there is a long way to go and although the ECM is being consistent with the idea of an easterly and how it sets up, it does produce a different version of the further evolution on every run, to a degree that’s to be expected, but I do have a little concern with this at the moment, as every evolution it produces seems to be slightly more wishy-washy than the last, hopefully that will change over the coming days providing it doesn’t fold completely, still plenty of time for that unfortunately. On the plus side, by the end of the run we do appear to be losing the lobe of the PV from Greenland, this should then enables heights to build further to our north and hopefully NW.

[Mair Snaw]

omg 168

Happy birthday to me!!!!! if that comes off i will be one happy man.. went to bed last night thinking it would all go the shape of the pear over night but its just getting better with every run....

[Gibby]

Good morning. Here is my take on the 00z output from GFS, UKMO, GEM and ECM for today Monday February 4th 2013.

All models show good agreement on events that take us through the working week with just small subtle differences on what may happen on Friday. A developing cold and very strong WNW flow occurs over the UK today which is replacing the still relatively mild conditions in the South this morning. Wintry showers already into the NW will extend to all areas by tonight giving snowfall to some and blizzard in severe gales to the NW. Tomorrow will see a very unsettled day with sleet and snow showers early turning less wintry through the day but with a continuing NW gale. By Wednesday winds will of turned Northerly as the parent Low drifts SE down the North Sea and away into Europe. Winds will decrease steadily as the sleet and snow showers become more confined to coastal counties in the East and North as well as around Irish Sea, Welsh and Cornish coasts. By Thursday the Northerly flow will weaken further with showers close to the East Coast but dry, cold and bright conditions elsewhere probably giving way later in the day to cloudier conditions spilling down from the NW with rain, sleet and hill snow for a time which may persist into Friday before drier weather follows later Friday with cold weather hanging on for the majority of places.

GFS then shows the weekend starting with a cold and frosty ridge of High pressure kicking Saturday off before a band of rain from an Atlantic depression moves in from the West with rain and hill snow, the snow principally in the hills of the North and East. Showery weather will follow in a cold and blustery North wind, with the showers becoming wintry again for most through Monday. The specifics of FI as always are unimportant but it does suggest the rather cold weather will continue with showers or longer spells of rain at times with snow on hills under association of SE moving Low pressure areas due to high pressure away to the NE.

The GFS Ensembles show a rather colder look to them today with most members keeping 850's below the long term mean throughout much of the run. The operational was one of the colder members but there does appear less evidence of such a steep recovery of temperatures beyond the Northerly blast of this week. Precipitation amounts do show an increase though most likely indicative of SE moving Low pressure over the UK.

The Jet Stream shows a continuation of the flow pumping over the Atlantic and Southeast over the UK and on down to Southern Europe. The flow breaks up over next weekend before slipping slowly South over the Atlantic, passing to the SW of the UK and again down towards Southern Europe.

GEM today shows a ridge collapsing SE over the UK next Saturday quickly followed by Low pressure also moving SE delivering a pell of rain and hill snow to the hills of the North. This is then shown to move away SE only to be replaced by a larger, deeper Low to the North of the UK bringing rain and strong winds followed by squally showery weather in a cold West wind to end it's run.

UKMO shows a ridge of High pressure across the UK on Saturday with a cold and bright day likely. By Sunday a trough moves slowly East across the UK with rain and hill snow in the North and East moving gently in from the West through the day.

ECM finally shows the ridge too on Saturday but it shows Sunday's depression and trough further West taking the Low pressure SE to the SW of the UK meaning the rain and snow risk is held for more Southern and SW areas while the North and East see drier conditions away from snow showers near Eastern coasts. Then as High pressure builds strongly over NW Russia Low pressure continues to slide decaying troughs SE over or just to the West of the UK with milder air trying to move into the UK on repeated occasions with attendant rain and snowfall in maintained rather cold conditions.

In Summary the models look somewhat on the cold side of normal through most of the output this morning. GFS has now picked up on SE moving depressions and troughs with even GEM coming on board for a time next weekend. UKMO looks OK this morning at 144hrs as the trough looks like it would slide SE allowing pressure to build more from the NE while ECM keeps the wintry theme going that it's been showing of late with the Atlantic hitting the buffers as it comes up against the High pressure zone to the NE. With the UK once more finding itself on the boundary of milder Atlantic conditions to the West and cold potentially wintry conditions a shift in the pattern West or East of 100 miles or more could have profound differences to the weather we will experience at the surface. Much more swings West and East to this developing pattern will be no doubt shown over the coming days.

[Stu_London]

The last word on this. You do need slightly colder uppers in Feb, especially later, to sustain snow cover. The reason Feb is often coldest month is that SSTs are lower so air mass is less modified delivering the colder uppers that are needed. On topic, still not entirely convinced, but does look like a 7-10 day (at least) cold spell starts today.

[TEITS]

I shall begin by addressing some of the comments on upper temps being progged. What you have to remember is upper temps of say -10C will bring much colder surface temps if the flow is from the E compared to say the N, even colder if the flow is from the SSE/SE,.However I do understand where Jason M is coming from. What could happen is at first we pull in upper temps of around -10C but despite the flow coming from the E we actually start to see less cold uppers spread from the E. Based on recent ECM runs this could well occur especially if the E,ly flow continues into +240. Ideally in the medium range we need to see the block back W with an arctic surge moving S down the right flank of the block.

Back to the rest of the output and its pretty clear the models are coming together but its very uncertain how far E or W the slider is going to be. A very real threat of a snow event on Sunday but at the moment this could occur as far W as Ireland/Wales or E Anglia. The GEFS ensembles show alot of uncertainty as early as +120.

http://cdn.nwstatic.co.uk/ensimages/ens.20130204/00/t850Cambridgeshire.png

[Frosty.]

Happy Days !

Yes ian it will be happy days indeed if the ecm 00z verifies.

Severe weather taking hold during today with winds gusting to violent storm force 11 across the far northwest of the uk and increasingly windy elsewhere but that's only half the story, wintry showers becoming heavy and squally across the north and turning to snow, firstly across scotland and then across n.ireland and n.england, there could be as much as 20cm accumulation in exposed higher levels of scotland with severe drifting and 5-10cm in some other areas. Southern england looks sunny and drier for most of today but showers arriving later, tonight looks cold with wintry showers across most of the uk and icy patches as temps fall to around freezing point, sub zero over the snowfields in scotland and the hills of northern england. Tomorrow looks rather cold with more wintry showers and more general rain/sleet associated with the warm depression core will push south from scotland through the day with even colder air then digging in behind from a more direct northerly point, midweek looks cold with Nly winds and snow showers, especially for eastern coasts of scotland and england, trending drier from the west as pressure rises to the west of the uk, frosts becoming widespread, by thursday, another cold day but the Northerly winds easing with showers dying out apart from the far northeast of the uk, a brighter and drier afternoon on thursday but with a widespread frost forming in the evening.

Edited February 4, 2013 by Frosty039

[TEITS]

Jason I'm with you to, the uppers just don't look that cold and that was my worry. I was to afraid to say anything for the same reason.

Hopefully once the week progresses we will see colder uppers modeled.

I think some are misunderstanding the situation or misreading Jason M posts.

At first the upper temps are easily cold enough i.e +144, +168. however around +216/+240 it appears we lose these very cold upper temps. This could easily change though.

Will this be another Feb 91, Jan 87? No chance. However we could see a snow event on Sunday followed by heavy snow showers into E areas on the following Mon/Tues. Beyond this a risk of snow moving into W areas towards the end of the week.

Make no mistake this progged E,ly is nowhere near as promising as the E,ly that was progged in Dec. This is due to the time of year, strength of E,ly, blocking to the NE, less cold upper temps. I still feel this cold spell will deliver but it won't bring record breaking cold as some have suggested.

[IDO]

The cold pool over most of Europe is not as cold as you would expect. Simon Keeling (expert) tweeted:

weatherschool

The level of cold weather is questionable with the GFS, GEM & UKMO models nowehere near as chilly. 'Cool to cold' still better description.

04/02/2013 07:54

"Ice Days" at the moment is well OTT. Even the last cold spell, where I am, there was rarely a frost and daytime temps were 2-3c, enabling a slow thaw, and it is likely not to be as cold as that!

Edited February 4, 2013 by jethro

[jethro]

Morning All, please can you quit the sniping now. Although last night's fishiness was completely off topic, it was at least pleasant to read and showed you can all get along when you want to. I've deleted some posts, no one really wants to start their day on here by reading grumpy, argumentative posts. We may have a lot to look forward to this week, it's really not worth falling out about when it hasn't even happened yet.

[Captain Shortwave]

Jason M, yes I think that you are talking a lot of sense. The cold pool over most of Europe is not as cold as you would expect. Simon Keeling (expert) tweeted:

weatherschool

The level of cold weather is questionable with the GFS, GEM & UKMO models nowehere near as chilly. 'Cool to cold' still better description.

04/02/2013 07:54

"Ice Days" at the moment is well OTT. Even the last cold spell, where I am, there was rarely a frost and daytime temps were 2-3c, enabling a slow thaw, and it is likely not to be as cold as that!

This is very true. This is due to the fact that the high pressure cell is only just about to build into place to our East caused by a rapid surge of warm air over Russia so no Siberian blast (yet), So the cold pool is pretty much over Scandinavia and central Europe. Of course get the block in first and see what happens, chances are we will probably have more cold to tap into than we see now when the day approaches. We will probably to sustain stronger cold need the polar vortex to drop into Russia giving us a cut off high over Scandinavian high with severe cold going down the eastern flank, hopefully as the Canadian vortex seems to be weakening perhaps this process could include some retrogression westwards too which would be perfect.

Edited February 4, 2013 by Captain shortwave

[oldsnowywizard]

Ok let's leave the discussion about uppers and cold .. Jason is fine to post what he wants and anyone can respond . IMO of looking at the charts even if post 240 not so cold uppers come in by then ( based on the current models) the cold air and snow cover is entrenched so it should have a little impact on temps in favorable areas.. After all we all know that 850 temps aren't the only factors to determine 2m temps... Just look at the -5 850s over northern Russia with 2 m temps of -20 and below ...can't post as on the mob.. Jason carry on with the posts and lets see how this goes down ... Lets be honest it will probably end up being a Bartlett high and blow torch in 10 days :-)

Edited February 4, 2013 by oldsnowywizard

[Severe Siberian icy blast]

I think some are misunderstanding the situation or misreading Jason M posts.

At first the upper temps are easily cold enough i.e +144, +168. however around +216/+240 it appears we lose these very cold upper temps. This could easily change though.

Will this be another Feb 91, Jan 87? No chance. However we could see a snow event on Sunday followed by heavy snow showers into E areas on the following Mon/Tues. Beyond this a risk of snow moving into W areas towards the end of the week.

Make no mistake this progged E,ly is nowhere near as promising as the E,ly that was progged in Dec. This is due to the time of year, strength of E,ly, blocking to the NE, less cold upper temps. I still feel this cold spell will deliver but it won't bring record breaking cold as some have suggested.

So can I ask pls TEITS why if the deep cold is there much earlier on (by deep cold I mean 850's of -10 or lower ) why is it even worth looking in detail at anything other than trends at 200hrs plus ? I fail to understand the negativity on something that's 10 days away I really do ? Anything can and proberbly will change/happen in the coming runs, weather it's colder uppers penetrating the high via a low on the eastern flank , or just about anything else to change the upper profile for better or worse .

2 or 3 days ago , yourself and many others on hear was douptfull of an easterly in any way shape or form , but now it's odds on , as I said back then I was always with the thought that the ECM was right , and now it's proving correct , why question the severity of the cold when in truth no one knows . Especially when we have Europe looking very cold be this wkend with very cold uppers , they don't just disappear in the matter of days , surely the trend is northern blocking , with an easterly looking likely of sorts , and a signal for undercutting ? No more no less at the minute as far as I'm concerned .

[Methuselah]

Ok let's leave the discussion about uppers and cold .. Jason is fine to post what he wants and anyone can respond . IMO of looking at the charts even if post 240 not so cold uppers come in by then ( based on the current models) the cold air and snow cover is entrenched so it should have a little impact on temps in favorable areas.. After all we all know that 850 temps aren't the only factors to determine 2m temps... Just look at the -5 850s over northern Russia with 2 m temps of -20 and below ...can't post as on the mob.. Jason carry on with the posts and lets see how this goes down ... Lets be honest it will probably end up being a Bartlett high and blow torch in 10 days :-)

Good idea OSW...Off-topic posts could well end-up here:

[lutfishah]

Lol what was the uppers when it snowed in march or April or even later : )

http://www.standard.co.uk/news/britain-heading-for-snow-and-freezing-temperatures-as-march-rolls-back-to-winter-7244001.html

[johnholmes]

It really is awful how some cannot discuss the weather without being unpleasant. Discuss yes, have different opinions yes, but do you really behave the way you do on here some of you if you are face to face with someone in a discussion?

Anyway back to the models and again for those new to the 'game' do look at the comparison charts I discussed yesterday for the overall pattern.Once the pattern shows changes in that black line I used then there is very little confidence in the upper air being correct let alone the surface. That is the constructive way to look at the weather rather than bickering like spoilt 7 year olds.

link to follow below with my comments

[swilliam]

ECM Ensembles out

As expected quite a bit of divergence after next weekend although the majority stay cold. This is evidence by the ensemble means

<-8 for many eastern and central areas at 168

Still below -6 at 192

[BLAST FROM THE PAST]

I shall begin by addressing some of the comments on upper temps being progged. What you have to remember is upper temps of say -10C will bring much colder surface temps if the flow is from the E compared to say the N, even colder if the flow is from the SSE/SE,.However I do understand where Jason M is coming from. What could happen is at first we pull in upper temps of around -10C but despite the flow coming from the E we actually start to see less cold uppers spread from the E. Based on recent ECM runs this could well occur especially if the E,ly flow continues into +240. Ideally in the medium range we need to see the block back W with an arctic surge moving S down the right flank of the block.

Just want to pick up on and add to this. Dave is right especially the bit in bold. Feb 1986 was a bitter cold month, the freeze started end of Jan and by 3rd Feb it was really cold at the surface BUT look at this.

Not that impressive, but at the surface it was. However, to prolong it we needed what Dave said so look at the following.

Here it comes, the HP from the east has moved towards Greenland

And we see arctic air flood down from the eastern flank to get to this

BFTP

[SMU]

Morning All-

So another day, another output that gradually sees the lesser models swinging to the ECMs, & the ECM maintaining its consistent pattern for yet another run.

Have we got 'very cold air available' to us- ive seen this bounced around by a few today, well if you take the MEAN of the runs then probably at the end of the week we go from cold to rather cold, with a spread of temps ranging from 1-5c. However thats the mean of the runs, take the ECM in isolation & 'assume' the others will move to it then we go from cold to very cold at the surface- maybe 1-3c, but can we get those ice days.

Lets look at the debilt run for 00z

http://www.knmi.nl/e...agse/index.html

as we can see the 00z ECM has got 5 consecutive ice days for holland & at day 10 looking at the OP run it certainly has 1/2 more ice days on the cards as winds swing SE.

The ECM overnight has England favourably placed in terms of uppers & surprisingly has the best uppers of the projections to date-

Taking London this week:

Day 3 -6C

Day 4 -8C

Day 5 -8C

Day 6 -9C pockets of -10C

Day 7 -10C

Day 8 -10C

Day 9 -9C pockets of -10C

Day 10 -7C However wind direction SE http://www.meteociel...1-240.GIF?04-12

So no dicernable change.

Analising the above without snow cover & wind direction I would say the surface temps will pan out something like this. bearing in mind frost will become an increasing problem.

So for somewhere in the middle like Oxford.

Day 3- Cold northerly but dry. top temp 4C.

Day 4- Chilly Northerly- sub zero overnight, max 4 or 5C.

Day 5- Transition day, rain & sleet frontal clearing- Max 3C.

Day 6- Mainly dry overnight frost, Max 2/3C

Day 7- Very cold overnight -5 ~, Max 1/2 C

Day 8- Chance of Snow, Max 1C

Day 9- Very Cold overnight Max 0/1C

Day 10- As above Max 0/1C

As you can see above the leap of faith to the ECM solution puts us towards ice day territory- & with general slack winds overnight temps will fall away.

With the added chance of snow day 6/7 this increases the ice risk chance by loading the very lowest columns of the atmosphere with cold air, however the dewpoint ( which appears to say sub zero past day 7) will support it.

In summary, unless super cold uppers ( Sub -10c) arrive in a spectacular fashion from the east or north then our country usually takes 2/3 days for it to fully mix to the surface- probably 2 days as the cold is already present as the surface anyway.

Ice days are a possibility & in the mix although probably slightly at the low end of the probability scale at the moment- depending on snowfall.

So not having looked at the reading ENS yet I would say you will see 3/4 days of 2C maxes on the last 4 days of the run.-

Cheers- eyes down for the 06z plaice your bets,

S

Edited February 4, 2013 by Steve Murr

[stodge]

Morning all

I have to say a cursory perusal of the main 00Z output has left me none the wiser this morning. I see varying support for a rise in pressure to the NE but with the Atlantic never far away.

http://www.wetterzentrale.de/pics/Rtavn1201.png

An almost classic "Col" chart and potential perhaps for a little fog and frost down south.

http://www.wetterzentrale.de/pics/Rukm1201.gif

Very similar. It's worth noting that the LP in the Baltic was a key factor in undermining the potential December cold spell as it prevented ridging from the Russian HP cell into Scandinavia. A feature like that poses a similar threat this time.

http://www.wetterzentrale.de/pics/Recm1201.gif

The best of the big three for my part of the world. The Baltic LP is less pronounced and the HP is able to develop into Scandinavia. I note the Azores HP is less pronounced here as well.

Last decade, one of the "routes to cold" in an otherwise often-miserable synoptic scenario was to get the Azores HP and Scandinavian HP to "link" - that at least advected some colder air into the SE.These were often undone by the lack of low heights on the Continent but at least we have those this time at present.

http://www.wetterzentrale.de/pics/Rgem1201.gif

This looks uncertain to say the least. Lots of shortwaves and a confused synoptic pattern though the fundamentals are there.

http://www.wetterzentrale.de/pics/Rngp1201.gif

This is the poorest scenario for cold fans overall. The Azores HP is more pronounced, the Scandinavian HP much less so and the LP over the Baltic more extensive. With no ridging from the east, the Atlantic has no block to overcome.

Overall, we can say it's not looking mild. Here in lowland East London, as I've said before, I don't expect snow to stay for long - the fall of two weeks ago was gone in 72 hours - but I certainly don't rule pout snowfall under the right conditions. That said, none of these charts scream snow to me - they do suggest a quiet period of cool/cold weather with frost and fog possible. I think longer-term we may be looking at an anticyclonic spell moving into mid and late February which might well deliver cold but perhaps not snow.

[chris55]

Superb ECM (again) the slider Low is what we should be focusing on as this is the key, how far east /west it is will decide some important factors, the possible snow event and it's location, how far west east the milder air gets in, then how it will pull the cold air west as it moves south and east. GFS has it all to far north and west, UKMO is just about ok but probably wouldn't pull the easterly in afterwards as it looks likely to just fill, the consistent ECM is best again this morning.

Also on the uppers, ECM has by far the coldest 850s right out to 216,

Also with regards to the 850s debate, It is kind of like comparing Champagne, say you were offered a £100 bottle, which is rather delicious, or a £1000 bottle which is obviously better slightly sweeter etc. but still champagne. I guess some may compare the ECMs 850s with the slightly cheaper bottle, IMO it's still delicious and will certainly do the job, but the more expensive bottle may be that bit sweeter. Anyway I'm just going to enjoy my champaign, it's a lot better than a luke warm cup of tea (thats the Atlantic)

[Severe Siberian icy blast]

Just want to pick up on and add to this. Dave is right especially the bit in bold. Feb 1986 was a bitter cold month, the freeze started end of Jan and by 3rd Feb it was really cold at the surface BUT look at this.

Not that impressive, but at the surface it was. However, to prolong it we needed what Dave said so look at the following.

Here it comes, the HP from the east has moved towards Greenland

And we see arctic air flood down from the eastern flank to get to this

BFTP

Yes that looks very good , the thing is anything can happen over the coming days/weeks , and a trough dropping down the eastern flank of the high looks very possible , the vortex is modelled to loosen its grip on the Canadian sector over the next 10 days so that opens an opportunity for the Siberian sector to play a part , and if it can drop into Russia then our friendly high can begin its retrogression toward Greenland .

I think as ever this cold spell is very much a developing situation and I'm sure things will change over the coming days, just good to see the easterly move into the more reliable time frames.

On a separate note I would like to apologise for my part to Jason for my attitude .

Edited February 4, 2013 by Severe Siberian icy blast