Winter Model Discussion - Cold Hunting -12Z 30/12/12

[Isolated Frost]

A perfect GFS 18z stratospherically, troposphere-wise and finally on the surface (or near enough)- d11 onwards is an example of many solutions that will be touted by the nwp to this mammoth hemispherical change-

Hemispherically, one of the charts of the winter so far (I say hemispherically because snow-wise, we have seen better earlier on in December)- the hint of retrogression, accompanied by the undercut, and the startled PV segment over eastern Scandinavia generally are 'perfection' or thereabouts-

Keeping in mind that we are a long way away, but the GFS suites have been very consistent in allocating blocking heights towards Greenland after d10/d11- this with the vortex dynamics modelled by the ECM and GFS suites is very, very encouraging

^yum

[TEITS]

Another latitude problem

It hasn't even happened yet and your glass is half full already. Okay lets all be worried and try and affect the weather with our emmotions all 1000 odd forum nuts across Britain -as if.

Bt the way what is the wrong side of it. left or right I would have thought it;s nort or southerly position would have been more important....if it happens.

No the wrong side means whether the GH is centred towards the W of Greenland or more towards the E. If the block is to the W of Greenland then you're at risk of LP bringing mild SW,lys and this is known as a W based NAO. Ideally for the UK you want this block either directly over Greenland or even better just to the E. When this occurs you then have an E based NAO which is miles better for the UK.

Unfortunately at this stage nobody knows where any blocking will develop or even if it will. This is why those posting in the Stratosphere thread are urging caution because a SSW does not guarantee a cold spell.

Pretty poor GEFS ensembles.

Very few suggesting any form of N blocking except the control run.

Edited December 30, 2012 by THE EYE IN THE SKY

[AGAL]

No the wrong side means whether the GH is centred towards the W of Greenland or more towards the E. If the block is to the W of Greenland then you're at risk of LP bringing mild SW,lys and this is known as a W based NAO. Ideally for the UK you want this block either directly over Greenland or even better just to the E. When this occurs you then have an E based NAO which is miles better for the UK.

Unfortunately at this stage nobody knows where any blocking will develop or even if it will. This is why those posting in the Stratosphere thread are urging caution because a SSW does not guarantee a cold spell.

I think you missed my point. That being the thing hasn't even happened yet. As for the last several weeks anything that breaks the westerlies and brings drier mild conditions or dry and very cold conditions are both equally welcome. the main issue is that there is a pattern change starting to show.

[Froze were the Days]

No the wrong side means whether the GH is centred towards the W of Greenland or more towards the E. If the block is to the W of Greenland then you're at risk of LP bringing mild SW,lys and this is known as a W based NAO. Ideally for the UK you want this block either directly over Greenland or even better just to the E. When this occurs you then have an E based NAO which is miles better for the UK.

Unfortunately at this stage nobody knows where any blocking will develop or even if it will. This is why those posting in the Stratosphere thread are urging caution because a SSW does not guarantee a cold spell.

Pretty poor GEFS ensembles.

http://modeles.meteo...21-1-384.png?18

Very few suggesting any form of N blocking except the control run.

Doesn't surprise me - that run seems a bit strange to me and as I said the 180z-216z looks like the Atlantic should come alive again with a secondary depression forming and moving north east as per the ECM to a degree. Certainly looking at the medium/long term output with a slight shake of the head.

ECM will have to jump ship to start taking the bait.

[ITSY]

a few ptbs and the control back the op. but given recent changes and the continuing development of the stratosphere (and the downward trending ECM suites) the signal is better now for cold than it has been for the last 3 weeks

[Grimsby Snow Lover]

A step in the right direction if you ask me from the 18z from the GFS. I know the ensembles aren't anything fantastic yet but what I have noticed is that there are more colder runs appearing in FI compared with the 12z. The same could be said about the 00z too.

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

[Panayiotis]

There is a growing signal seen today for some sort of heights to the NW of Britain, the size, strength and position of the heights is too far out to consider but its something seen on 3 of the runs today. (out of the 4).

These are all showing 360hrs for the 00z, 06z, 12z and 18z.

This type of signal was seen yesterday on Perturbation 2 (the NH chart is the 18z but it was also shown on the 12z), yes it is far out in Fi but there is some support for the idea. Lets see how it plays out!

[Panayiotis]

To add to my above post, I did a little test with the meteociel archives, this is what i did:

I looked at the 00z,06z,12z and the 18z from the 14th December and got them all to show +360hrs.

Results:

Notice how they are all different (what you would expect from 360hrs out), this is what the chart looked like for the day (29th December):

Pub run (should we call it this after these results?), got it nearly spot on! (Regarding the strong low to the North, the strong PV and the heights into Europe). Now I hope today's 18z has got it spot on!

Edited December 31, 2012 by Panayiotis

[Timmytour]

GFS 18z is leading the way. So many similarities with 1947 is going to land us with the greatest similarity of all. This time the Easterly is coming with the pool of cold air already there and giving it the strength it lacked in the early part of December.

My my it's going to be cold after feeling so mild next weekend. And my my it's going to get busy in here again!!!! I anticpate we will be upto 25 pages by the end of tomorrow...contrasting with it taking a few days to get that far in the previous thread.

[Slowpoke]

It seems the Atlantic may start losing steam in the New Year (about bloody time). Watch this space!

[Bonjangle]

Bliss, i am glad i seen the winters of the 60s-70s -80s- which were proper . just in here there is so much hype here and there , we dont know whats is going on , like i said along time ago ,PETE TONG ,and it went that way , look and and learn , it will get COLD with some good snow falls .. enjoy Happy New Year !!

[Stu_London]

No the wrong side means whether the GH is centred towards the W of Greenland or more towards the E. If the block is to the W of Greenland then you're at risk of LP bringing mild SW,lys and this is known as a W based NAO. Ideally for the UK you want this block either directly over Greenland or even better just to the E. When this occurs you then have an E based NAO which is miles better for the UK.

Unfortunately at this stage nobody knows where any blocking will develop or even if it will. This is why those posting in the Stratosphere thread are urging caution because a SSW does not guarantee a cold spell.

Pretty poor GEFS ensembles.

http://modeles.meteo...21-1-384.png?18

Very few suggesting any form of N blocking except the control run.

I think given the zonal dross that we have had to put up with over the last 2-3 weeks, the 18z is far from poor.

I've only looked at the operational run but a solid week with little or no rain (Worth being happy about in itself) - followed by a possible evolution leading to easterly followed by northerly.

Almost certain to be incorrect, but expect FI to go wild from here with cross model disagreement and standoff and the whole situation becoming very difficult to predict.

Are we guaranteed cold and snow? No but the prospects are much higher than of late.

Are we guaranteed facinating model watching? Absolutely.

[BlueHedgehog074]

The GFS 00Z is continuing its idea of heights building to the North:

(An example for 240 hours out)

...the High Pressure of which eventually takes its holiday over Greenland.

Although more runs are needed, it is encouraging the signs its showing with both the 18Z and 00Z GFS runs showing similar ideas now, but the evolution to heights building towards Greenland looks like a messy one in my opinion with no obvious Lows trying to undercut the high until near the end of the run. However, I do suspect the fragmented Jetstream to the North of the UK, with a powerful stream of the Jet going well, well to the South of us is allowing the migration of heights to the North/North-West of us:

But we will need runs from other models, such as the ECMWF to start agreeeing with GFS Greenland height building solution to be sure if this is the direction we will head in as well as how the Stratosphere warming will behave in furture charts as this will probably likely to have an affect on the placement of any possible blocking. So, will the 00Z ECMWF take the plunge and follow GFS's blocking solution, or will it turn against it and laugh in the GFS's face?

Edited December 31, 2012 by DiagonalRedLine

[Duane S.]

Huge differences at D10 between the GFS and ECM. GFS has moved the vortex towards the Hudson strait whilst the ECM maintains it in and around Greenland although with signs it's about to follow suit.

It's another nice from the GFS run for us to drool over but I suspect it's a bit progressive, that pressure rise over Greenland starting at about D8 would have to go down as a bonus, I am not convinced it's right. The overall trend I think will be for the dominant high about to sit over us for a good week or so then to pull back a bit into the Atlantic and from there we will see the first serious attempts at ridging northwards, a few days outside ECM's range. Would tie in with MJO 6 as well.

[winterof79]

GFS continues its theme from winters past this morning http://www.meteociel.fr/...2&mode=0&carte=1

http://modeles.meteociel...ivesnh-1947-1-21-0-0.png

An attempt at heights to our n/e too http://www.meteociel.fr/...2&mode=0&carte=1

http://modeles.meteociel...hivesnh-1987-1-7-0-0.png then http://modeles.meteociel...ivesnh-1987-1-11-0-0.png

Not to say any of those will happen but the signals are looking more favourable for us

[That ECM]

GFS continues its theme from winters past this morning http://www.meteociel.fr/...2&mode=0&carte=1

http://modeles.meteociel...ivesnh-1947-1-21-0-0.png

An attempt at heights to our n/e too http://www.meteociel.fr/...2&mode=0&carte=1

http://modeles.meteociel...hivesnh-1987-1-7-0-0.png then http://modeles.meteociel...ivesnh-1987-1-11-0-0.png

Not to say any of those will happen but the signals are looking more favourable for us

http://images.meteociel.fr/im/5846/gensnh-11-1-384_bnx0.png or 20 please!

There are a few more which would make people happy.

Lets hope more and more like these Start showing in future runs.

[IDO]

The GEFS mean showing a gradual return to tomorrow's uppers (-3c) in 15 days time, after a relatively mild 6-7 days.

The OP is a cooler option in FI, but other members also hinting at it's trend:

So a settled period coming up with indications that the current synoptics are weakening, around D8. This I suspect is not due to the SSW and is probably just the ebb and flow of winter. This may of course help, when the strat warming starts to feed in.

The 0z control shows a cleaner Atlantic height's build, and something that looks more possible:

The GEFS mean also, at T300, shows a clear tendency for heights around the UK:

FI starts at around D7-8 and this looks like it will vary on the theme of amplification around the UK, so that is likely to chop and change, placement wise.

The strat signals are remaining strong so things are moving in the right direction for mid Jan onwards.

Edited December 31, 2012 by i'm dreaming of...

[Duane S.]

An attempt at heights to our n/e too http://www.meteociel...&mode=0&carte=1

I'd be interested to see what support there is over the coming days for a NE link and a scandi high rather than heights building over Greenland. It is tempting to look at ECM D10 and wonder if that is the way it's heading.

But I still think any building heights to our NE is a bit of a red herring. Initially at least.

Edited December 31, 2012 by s4lancia

[Frosty.]

The models are continuing to firm up on a more settled spell for the southern half of the uk but for the northern half to continue more unsettled but milder with sswly winds at least until next weekend, the ecm 00z is indicating a very mild spell towards the end of this week, peaking on saturday, the gfs 00z is not as extreme but is still mildish. The gfs goes on to build pressure further north with all of the uk enjoying a fine spell with overnight frost and some fog as winds fall light. Further into FI the gfs 00z is showing the trend that all coldies are waiting for, the evolution to cold and blocked is very nice to see and would be worth waiting for, I much prefer the gfs 00z compared to the ecm this morning.

[bluearmy]

I'd be interested to see what support there is over the coming days for a NE link and a scandi high rather than heights building over Greenland. It is tempting to look at ECM D10 and wonder if that is the way it's heading.

But I still think any building heights to our NE is a bit of a red herring. Initially at least.

I think its something the models will explore over the next couple of days and an fi op run cold easterly is feasible. However, for the time being, i think another drop of troughing to our east will cut it off. Maybe later this is more feasible but the trend to drop the strat vortex into scandi on ecm would tend to make an easterly unlikely. Of course the initial block could drift far enough north to bring a weak one in before the fun and games begin.

[TEITS]

Great 0Z this morning from the GFS and its interesting that those 18Z ensembles I looked at last night didn't really support much in the way of N blocking and yet the GFS 0Z follows the 18Z OP. Shame the ECM isn't as impressive at +240 but even that could develop an E,ly if the run went out further.

Probably worth mentioning that during the Dec 2009, 2010 cold spells I seem to recall the GFS was far more consistent and inactual fact the ECM was pretty poor with its consistency. My observations of following the models over the years is the GFS seems to be quiet good at modelling blocking that develops around the Greenland area. Could that be down to the GFS models the changes in the Stratosphere better than the ECM and how this impacts further down??

I could be talking a load of cobblers though and im clutching at straws due to such a crap winter so far.

[Frosty.]

This would fit with the metoffice 16-30 day recent updates although there is a great deal of uncertainty in that period, this type of chart is probably what they are hinting at, real eye candy compared to the dross coming up.

[Gibby]

Good morning. Here is the New Years Eve Report on the 00z output from GFS, UKMO, GEM and ECM.

All models show a very unsettled day today with a cold front meandering SE over England and Wales through the day with attendant heavy rain and strong winds. As the front clears winds will turn more towards the NW with colder and clearer weather extending SE to all areas by midnight tonight. New Years Day will be a breezy and chilly day with sunshine and showers the most likely course of the day with many Southern and Eastern areas staying dry. The showers may be heavy and wintry in the North and West, especially in the morning. Through Wednesday the NW flow will of backed Westerly with a weak warm front crossing East bringing cloud with rain and drizzle East over the UK followed by rather cloudy but dry weather with temperatures becoming much higher later in the day. Then from Thursday through to Sunday the weather will be dry for most as a large anticyclone develops close to Southern England with a very mild and moist SW flow across most of the UK. In the West and North there would be plenty of low cloud and drizzle over coasts and hills facing West while Southern and Eastern areas see the best of any brightness with any sunshine in the sheltered East push temperatures as high as 13-15C in places.

GFS then shows a steady decline in temperatures as the High declines and moves gently East allowing a Southerly drift to develop with a little rain in the far West towards midweek next week. Thereafter, the trend towards colder conditions continue as High pressure slowly develops to the North with the desire for Easterly winds to take hold and progressively colder conditions with the chance of some wintry showers or snow should the operational verify, chiefly in the North.

The GFS Ensembles show the operational as a cold outlier later in the run, especially for Northern locations with the likely outcome more a case of lowering temperatures towards normal levels as the large High slips slowly SE with gentler conditions continuing with much drier weather than recently in the South with the NW catching most rain.

The Jet Stream shows the endless flow that has been crossing the UK to the British Isles for so long now ridging North strongly over the coming days directed North to the west of the UK later before returning South over Europe as the High pressure block directs the Atlantic traffic far North than recently.

UKMO for midnight on Sunday shows a large High pressure over Southern Britain with fine weather for all. It will be a case of chasing areas of cloud around trapped under the High with some brighter intervals making way for some mist and fog patches overnight while temperatures remain very much on the mild side at that time point.

GEM shows the High relaxing a little further South late in its run with the North seeing a return to occasional rain while the South maintains mostly dry and mild weather though still with large amounts of cloud floating about.

ECM for next Sunday shows a similar scenario with High pressure persisting near Southern Britain in varying shapes and forms. The North will see occasional rain as weak troughs pass over and the cloud from these will become trapped under the High at times giving cloudy and misty conditions further South. For the most part the UK will remain in mild conditions, though temperatures would likely fall back somewhat, especially in the North and East as weak cold fronts cross SE before returning as warm fronts later on.

In Summary this morning there is firm agreement on today and tomorrow being the last of the deeply unsettled spell. Gone will be the gales and heavy rain of recently to leave the UK in quiet and anticyclonic days with a lot of cloud cover and temperatures well above normal for a time. In general the trend thereafter is for the South and East to maintain dry, relatively mild and rather cloudy conditions with the North and West likely to see a return to cloud and some rain but here too, lengthy dry spells seem likely. The GFS operational evolution to a changed synoptic pattern and a colder continental feed late in the run looks a little isolated in the grand sheme of things and will have to be seen as unlikely at the moment given it doesn't have much support from it's own members or other models. It will be interesting to see whether it is replicated in the following runs or just a blip so unless support spreads to the other models and outputs over the coming days I will not make much further comment on it at the moment.

Remember there will be no report again this evening but will be back to the twice daily reports as from tomorrow 2013. I would like to take this opportunity to wish all my readers on my website and forun a VERY HAPPY AND PROSPEROUS NEW YEAR and may all your meteorological wishes come true.

[tinybill]

well looking into fantasy world this morning Jan 11 onwards look-interesting for the breakdown back to some cold weather and some possible white stuff!!

[Bobby]

The ECM and GEFS means at +240 are quite different

ECM

GEFS

With the GFS making much more of high pressure with the ECM showing a flatter more Atlantic influenced pattern.

The NAEFS mean also agrees with ECM, as does the GEM ensembles

NAEFS:

GEM ensembles:

So the GFS and it's ensembles are quite out of touch with the rest of the output and so I'm not buying it's solutions. The ECM and NAEFS are more likely I think so caution with getting excited with the GFS is needed.

Edited December 31, 2012 by Bobby