Winter Model Discussion 18Z 19/2/13 onwards.

[Frosty.]

A nice change from the ECM overnight, the 00z is showing some interesting developments to the north, all that bottled up arctic air may get very close to the uk in early march whereas the 12z last night gave us no chance, the Gfs 00z also shows something similar but always manages to stop the floodgates from opening but it's the trend that's important for now. In the meantime, the blocked anticyclonic spell will go on and on well into next week and maybe beyond next week but at least we should see increasing amounts of sunshine and plenty of frosty nights, the south will have a cold nagging Easterly for several days with more cloud and scattered wintry showers and some local snowfalls before the monster high brings settled weather to the south and southeast too.

[snowking]

We could be at a point where the operationals will start to lead the way. Certainly the 0z ensemble means still keen on the Atlantic winning the race:

(NAEFS, for example, at +360)

(GFS 11-15 day Mean)

However, we saw a similar situation with this current cold spell, where the ECM op lead the way, and then slowly the ECM EPS suite came on board.

I still remain unconvinced as we need a lot to go right for us here (Atlantic over modelled, Greenland high a little more east based, higher heights across Europe to dissipate quickly in situ) but should we see a few consistent run from longer range operationals then some further interest is there for cold fans

I'll be honest, I think i'm ready for some warmth now....but you just cant say no to the sort of plunge modelled by the 18z GFS...

SK

[weather eater]

If a west based -NAO verifies, it will be a rare occasion this winter where gfs op has been in agreement with its extended ens in low res.

When I went with this option for the end of feb/beginning march it was generally the gfs op that was showing this solution +naefs. Since then, things have shifted somewhat such that the block hangs on longer (not unexpected) and we see a split opening up in the nwp between west based neg nao delivering a wsw regime and more centrally based neg nao bringing a threat of more cold to nw europe. Odds still support the former but if the polar profile adjusts a little, the latter would be there in a flash.

As always anything can change but using the last dozen GFS operational runs as an ensemble then a west based NAO looks a pretty clear favourite at the moment. All in all that would give us fairly average early march temps.

[snowking]

At face value, good support from the ensemble mean for the pattern to our north for the ECM op this morning:

How long have we been crying out for that sort of height profile this winter so far!

The issue there remain the higher heights across S Europe, but at this range, theres no guarantees that necessarily would be the final outcome in that region

Just awaiting the mean height anomalies

SK

[bluearmy]

Looking at the nh ecm ens mean plus the spread on uppers days 9 and 10, sprinkle in a tweet from matt re yesterdays 12z suite, check out the split developing on the fi london ens over the past couple of runs and i'm afraid those seat belts need to fastened again!

[Gibby]

Good morning everyone. Here is the daily a.m. report of the 00zs produced from GFS, UKMO, GEM and ECM for this morning Wednesday February 20th 2013.

All models show a cold Easterly flow setting up over Southern Britain behind a weak cold front moving West over the day today and tonight. It will be significantly more cloudy today with perhaps a little light rain or even sleet over the hills as the front passes before brighter weather returns across the South later. Thereafter the next 3-4 days show an increasing and strong Easterly flow backing NE with time over the South while the North sees High pressure sit over the top of them with quiet and brighter conditions with sharp overnight frosts. There will also be a few snow showers or flurries developing across the South and East of the UK perhaps more likely through Saturday as a weak disturbance runs SW across these areas. Amounts and accumulations will be insignificant for most but the extreme SE may see a covering.

GFS then moves into next week with High pressure maintaining it's Scottish position for some considerable time with a continued ENE feed across the South though it will become less bitter with a lot of cloud drifting through though in the breeze. The North would continue fine and settled with probably more in the way of sunshine and eventually nearer to normal temperatures. FI this morning without giving details is basically showing a change to more unsettled conditions as time passes as High pressure receded away SE, However, with a change to more unsettled conditions from the SW and cold air to the North of the UK some engagement between these two air types could occur bringing rain for all and perhaps snow to some northern locations through FI.

The GFS Ensembles show a cold spell for 3-4 days before a shift in uppers towards normal values. Later in the ensemble the range becomes huge with a large spread. The operational was again a mild outlier towards the end in the South while the Control run is at the opposite end of the extreme bringing all of Britain back into very cold air late in the run. With so much spread no conclusive evidence can be drawn from the end of the output today. Precipitation is scant until towards the end of the run.

The Jet Stream shows a split flow developing then being maintained over the North Atlantic and Europe over the coming week with a link between the two to the West of Britain early next week.

UKMO shows High pressure over Northern Scotland and the Northern Isles early next week with much of the UK dry and fairly chilly. It won't feel quite as cold in the South as the NE flow decreases but surface temperatures will still be somewhat suppressed. Sunshine amounts will still be limited and more restrictive to more Northern areas where sharp frosts at night could still occur.

GEM today shows High pressure becoming large and complex over the UK next week with fine conditions for all. The cold NE flow in the South will weaken. Sunny spells will develop for all in gradually less cold conditions before winds settle WNW with some rain reaching the NW at the end of the run.

ECM shows High pressure maintained over the UK throughout next week with it's weakening centre meandering around over the UK. Distribution of cloud cover and any sunny weather will be hard to predict in such a setup. It should become less cold by day but under any clear spells frosts will develop widely. At the final day of the run the pattern is complex with pressure having built strongly over Greenland with a SE moving Jet flow over the Atlantic developing, the UK could come on the cold side of what would be a Greenland Anticyclone in the days that follow.

In Summary today High pressure is in total control of the UK weather for the next 10-14 days. After the very cold conditions of the next 4-5 days a moderation in conditions look likely with quiet and settled weather. Cloud amounts will be very variable to say the least and may often be large restricting large amounts of sunshine. There will be harsh frosts between now and early next week cloud or not, penetrating in the wind over the South. Long term as usual various options are shown but as has been the case all Winter nothing is straightforward and with ECM and to a lesser degree GFS heading for a SE moving Jet from Day 10 some further engagement with cold air from the North is a distinct possibility.

[bluearmy]

Sk, those euro heights are flacid. Won't be an issue if the cold does come south into nw europe

[Frosty.]

As we approach the equinox, it might actually happen: this winter's ever-present 'retrogression signal' might actually lead to something...A 1975-like Spring, perhaps?

There was snow in June that year then a long hot summer.

I'm happy with the model trends, especially if the ecm can keep the 00z evolution going forward, it could turn into a race between the arctic airmass and the atlantic lows pushing up from the southwest, which will win the race, no idea yet.

[shaky]

Nae still looking excellent uppers wise !now has uppers of -11 to -12 coming into england as far north as yorkshire!!before it was up to lincs/humberside so its gone further north!!i thought it would have downgrade everything by now but instead its an upgrade!!

[Cloud 10]

Looking at the nh ecm ens mean plus the spread on uppers days 9 and 10, sprinkle in a tweet from matt re yesterdays 12z suite, check out the split developing on the fi london ens over the past couple of runs and i'm afraid those seat belts need to fastened again!

It wouldn't take much of a shift to get that black hole over central Greenland..

Certainly some teasing from the long range output in the last few days with the

polar vortex shifting east.

[TEITS]

I'm happy with the model trends, especially if the ecm can keep the 00z evolution going forward, it could turn into a race between the arctic airmass and the atlantic lows pushing up from the southwest, which will win the race, no idea yet.

Yep and if the trend continues a clash between the two would result in some very exciting potential. Absolutely no idea where this would occur. Having said this I would still be much more excited at the model output if I lived in N England and even more if I lived in Scotland. Unless we see a shift E then its going to be difficult to get the Arctic blast to push into S England.

[chris55]

An early March freeze/snowfall is still a small possibility this morning and if anything the pattern is leaning more towards cold from the north than yesterday. The positioning and southerly extent of any cold and potential snowfall is far from certain, but that very snowy perturbation number one from yesterdays 06z GEFS has gained a little more support from this mornings 00z GEFS. 7 runs bring the cold south as far as Manchester at some point so that roughly 35%, will certainly be interesting to see how this progresses.

[Frosty.]

Hopefully they will collide over south east England and bury us in 3ft of snow

Yes there's lots of potential beyond the settled spell, like I said, it could turn into a race beween the arctic and the atlantic depending on where the high goes but the ecm in particular looks excellent in FI with a strengthening Greenland High and probably more chance of an arctic outbreak, a big shift in the ecm between 12z-00z.

Edited February 20, 2013 by Frosty039

[chris55]

Yes ECM 240 det is very good and with the sharper trough to the east of the Greenland high (compared to the 00z GFS) heading south east, I'd say a 264 chart would be heading rather cold for the UK..

[Purga]

Yes ECM 240 det is very good and with the sharper trough to the east of the Greenland high (compared to the 00z GFS) heading south east, I'd say a 264 chart would be heading rather cold for the UK..

Yes, it's very touch and go and the HP to the NW could easily slip a bit too much more NW and we could end up with a west based -ve NAO! As always it's very tricky getting cold to the UK and of course the above chart is a long way off. Edited February 20, 2013 by Purga

[CWT2012]

Yes there's lots of potential beyond the settled spell, like I said, it could turn into a race beween the arctic and the atlantic depending on where the high goes but the ecm in particular looks excellent in FI with a strengthening Greenland High and probably more chance of an arctic outbreak, a big shift in the ecm between 12z-00z.

Am concerned about a Greenland High becoming too entrenched as they have been responsible for the succession of washout summers, wish GH would be here in winter and go do one in the spring/summer

But I do think that we have another month of potential snow events, a below average march is my prediction temperature wise

[legritter]

Looking at all current data modells winter is not finished yet .fri/sun i feel some lucky posters will see their bit of magic and if any troughs can stay in tact so will my little patch .will we get our long awaited GEENLAND High come early march ,thats the next bit of betting which should keep us modellers glued to the charts .i know its four days away but there could be some interesting developements coming into s/east on sunday ,i briefly read this somewhere this morning but was still half asleep i will try and remember and post .any new members remember we are in a very quick changing situation regards any snowfall ,as small features wont be picked up untill only a short time from any event ,of course nothing is guaranteed .cheers .

[TEITS]

Good to see some snow showers finally appearing into E Anglia on the NAE.

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2013/02/20/basis06/ukuk/prty/13022206_2006.gif

[bluearmy]

It wouldn't take much of a shift to get that black hole over central Greenland..

thats the op cloud ! the mean is similar but more diluted re the strength of that anomoly.

[No Balls Like Snow Balls]

Is there actually any real evidence that heights will rise over Greenland?, all I see at this minute is speculation and 1 chart showing heights going to Greenland @ 10 days away. Meto still seem confident of a SWerly type after this HP dominated spell, granted Ian F did state yesterday that there were a few ensembles going for a Northerly but I think we will need a lot more evidence to get even a little bit excited.

[TEITS]

Is there actually any real evidence that heights will rise over Greenland?, all I see at this minute is speculation and 1 chart showing heights going to Greenland @ 10 days away. Meto still seem confident of a SWerly type after this HP dominated spell, granted Ian F did state yesterday that there were a few ensembles going for a Northerly but I think we will need a lot more evidence to get even a little bit excited.

Yes I think there will a GH. However the big question is how will this impact the UK and how far S will the Arctic blast from the N push S.

I mentioned yesterday the ensembles were showing a 20C difference. Now at the moment it was only the 18Z GFS showing the potential but this has now been followed by the 0Z GFS and the ECM.

At the moment there probably isn't enough evidence to get excited but again this could depend on your location. With the set up being currently shown its quiet plausible that Scotland is seeing widespread heavy snow and ice days whilst the S is very mild.

Edited February 20, 2013 by THE EYE IN THE SKY

[Methuselah]

Is there actually any real evidence that heights will rise over Greenland?, all I see at this minute is speculation and 1 chart showing heights going to Greenland @ 10 days away. Meto still seem confident of a SWerly type after this HP dominated spell, granted Ian F did state yesterday that there were a few ensembles going for a Northerly but I think we will need a lot more evidence to get even a little bit excited.

Aye, it's been a winter of potential: potential being, that one-or-more perturbations usually show some sort of retrogression, by T+384?

[No Balls Like Snow Balls]

Aye, it's been a winter of potential: potential being, that one-or-more perturbations usually show some sort of retrogression, by T+384?

Yep and every other night I dream that I have won the lottery and get to smack Beyonce's butt every day, but alas it never is reality. In fact I probably have more chance than a GH

[SLEETY]

Good to see some snow showers finally appearing into E Anglia on the NAE.

http://expert-images...022206_2006.gif

look more like sleet showers as the rain and snow symbols are showing on that chart

[frosty ground]

Aye, it's been a winter of potential: potential being, that one-or-more perturbations usually show some sort of retrogression, by T+384?

http://www.wetterzentrale.de/pics/Rtavn001.png

Evidence showing heights over Greenland! Right now.....

The issue being the core of the high is over Canada AKA to far west.

Not sure what you T+384 comment is regarding, clearly it can’t be about the 33% of GFS Ensembles that fall below -10 for large parts of the UK within the 240 hour time frame.