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

[Gibby]

Good morning. Here is the morning look at the 00z output from GFS, UKMO, GEM and ECM for today Monday January 28th 2013.

All models show a broad West or SW flow over the UK through the working week in association with a series of Low pressures North of the UK and High to the South. Troughs will moves quickly NE or East over the UK from time to time bringing spells of rain and strong winds, heavy at times. Temperatures will be generally well up to normal through the week and above tomorrow in the South as a warm sector passes through. It will be cooler in the showery spells with a little wintriness in the blustery winds associated with the showery spells. By Friday things begin to become a little more interesting.

GFS brings a deepening Low pressure across the South of the UK and on its Northern flank some cold air will be drawn into its circulation with some rain, sleet and snow possible for a time at the start of the weekend. By Sunday a weak ridge collapses down over the UK with a fine and cold day leading into a return to milder Atlantic winds to start next week. FI today shows a continuation of the mixed pattern between milder Atlantic winds blowing from the West or NW with rain in places mixed with further cold incursions from the North when widespread wintry showers would occur with temperatures dropping below normal for several days at a time before the Azores High topples another ridge down over the UK cutting of the cold feed for a time especially for Western and Southern areas.

The GFS Ensembles show an agreed trend into rather colder territory as we move through next week. There will be rain at times this week in generally mildish conditions and a cold dip at the weekend in association with the depression over the South at the weekend. Things then trend more difinitively colder next week as successive cold pushes from the North work their way down over the UK.

The Jet Stream shows the flow still moving East over the Atlantic towards the UK before ridging further North over the Azores High later in the weekend and next week as it inches closer to the UK.

GEM today shows a depression at the weekend exiting Eastern England and leaving a brief cold Northerly over the UK before returning polar maritime air cuts off the flow around a High pressure area to the SW. This general pattern of cloudy damp weather mixed with brighter, colder and more wintry showery type weather then continues to the end of the run.

ECM too shows an even deeper area of Low pressure close to the SE on Friday with a couple of cold and potentially wintry days at the end of the week and start to the weekend. A ridge then topples SE over the UK with a return to somewhat milder weather with occasional rain before the next cold front sweeps SE continuing the theme of colder interludes mixed with milder incursions around the Azores High to take us to the end of the run.

The pattern seems quite well agreed upon today with this week totally Atlantic based with wind and rain at times. A depression on more Southerly latitudes at the very end of the week could spring a few wintry surprises for many Southerners before the general theme of High pressure to the SW and Low pressure over Europe sets up with winds from the NW for much of the time. Due to the proximity of High pressure close to the SW the colder incursions behind cold fronts will be most felt to the North and East of the UK while the South and West see more modified conditions while that High stays so close. In any event each cold incursion remains relatively short lived as pressure takes a long time to build further North through the Atlantic, cutting off the Atlantic train and Jet stream from riding over the Azores high. Patience is going to have to be a virtue for sustained cold from this set up though the trend is there for something more sustained for 'coldies' longer term.

[SMU]

Reason for the pesimism-

We have been here before- in that exact modelling position- The exact curvature of the azores high never gets any real decent amplitude apart from the odd 24 hour event-

So yes you will see the -5c line come across the UK for short periods- however thats not the 'instant' snow line-

Cold takes time to get mixed to the surface & from Northerlies thats longer -

http://www.wetterzentrale.de/pics/MT8_London_ens.png

ensemble mean going towards -5c & a tad lower...-

As said above, with a low amplitude azores high that more or less wipes out a chance of a low swinging back south & south west across the UK- the track is more likely to be NW/ SE across the north sea into france & down south-

So yes- so NE winds on the back side however because pressure isnt wedged over Svalbard or greenland the azores high will allow the atlantic to ride over the top-

so you get oscillating mild to cold air - however the cold not cold enough really of you want anything decent ( away from Scotland)

& the mild not being 'that' mild- just something akin to average-

so pretty medicore today.... exactly the pattern that is suggested from that H5 anomaly - being the azores high lumped in the middle of the atlantic-

If people want to see proper ridging then look at Dec 81 & see how it developed-

Also twaddle, ? If we get to the 5th & there is nothing showing in the means from the ECM or the GFS ( proper cold ) then time will be rapidly be running out for England-- again thats not to say we dont have a chance-

S

[TEITS]

Rather surprised at some of the negative posts because to me I remain positive and if anything the models continue to trend in the way I feel it will pan out.

Prior to this though the nasty Low pressure next Saturday is cause for concern. The worry is flooding, strond winds or even snow. At this stage I don't feel as though it will cause too many problems with snow although we could see some backedge snowfall. Looking at the ensembles for this period and I still wouldn't rule out a blizzard but it depends on how far S the colder air moves down from the N during Friday and of course the track of the LP on Saturday. One to watch closely!

Beyond and no change from my post yesterday morning. A period of cold NW/N,lys until around the 7th followed by something more prolonged and colder thereafter. Im still going for the 10th Feb when winter will return with a vengeance.

Look at the PV at +144 and then +240 on the ECM.

Iceland SLP mean has risen 18mb since I last checked.

http://cdn.nwstatic.co.uk/ensimages/ens.20130128/00/prmslReyjavic.png

Now 18mb might not sound much but trust me that is an excellent trend.

[Isolated Frost]

Writing it off after Feb 1st- gosh some are fickle... Wait for the next 4 weeks and then we'll talk!

Very optimistic still for the conveyor belt of seaboard heights to stall and intensify, w/ amplification, the polar jet- retrogression gets a few attempts it seems and there is a developing cold pool associated with the upper troughing over Central Europe.

Patience.

[Long haul to mild]

Rather surprised at some of the negative posts because to me I remain positive and if anything the models continue to trend in the way I feel it will pan out.

Prior to this though the nasty Low pressure next Saturday is cause for concern. The worry is flooding, strond winds or even snow. At this stage I don't feel as though it will cause too many problems with snow although we could see some backedge snowfall. Looking at the ensembles for this period and I still wouldn't rule out a blizzard but it depends on how far S the colder air moves down from the N during Friday and of course the track of the LP on Saturday. One to watch closely!

Beyond and no change from my post yesterday morning. A period of cold NW/N,lys until around the 7th followed by something more prolonged and colder thereafter. Im still going for the 10th Feb when winter will return with a vengeance.

Look at the PV at +144 and then +240 on the ECM.

Iceland SLP mean has risen 18mb since I last checked.

http://cdn.nwstatic.co.uk/ensimages/ens.20130128/00/prmslReyjavic.png

Now 18mb might not sound much but trust me that is an excellent trend.

Would agree that this seems to be a very likely evolution and the ensembles this morning certainly back this up.

What is rather puzzling though is the disagreement on the models this morning re the LP next weekend; the UKMO doesn't even show it at all!

[BLAST FROM THE PAST]

You can tell when the models are grim for cold when you see post showing cherry picked ensembles, nothings changed in the last few days the pattern is flat and low heights over Greenland. Same old, same old, for most of this winter.

They are only grim if

1. One is expecting bitter cold NE'lies with a 1095 to 1150mb GHP in place

or

2. Folk aren't looking at the improvements developing before them.

There is no 'proper' cold this week at least and no issues with that.

BFTP

Edited January 28, 2013 by BLAST FROM THE PAST

[mulzy]

Reason for the pesimism-

We have been here before- in that exact modelling position- The exact curvature of the azores high never gets any real decent amplitude apart from the odd 24 hour event-

So yes you will see the -5c line come across the UK for short periods- however thats not the 'instant' snow line-

Cold takes time to get mixed to the surface & from Northerlies thats longer -

http://www.wetterzen..._London_ens.png

ensemble mean going towards -5c & a tad lower...-

As said above, with a low amplitude azores high that more or less wipes out a chance of a low swinging back south & south west across the UK- the track is more likely to be NW/ SE across the north sea into france & down south-

So yes- so NE winds on the back side however because pressure isnt wedged over Svalbard or greenland the azores high will allow the atlantic to ride over the top-

so you get oscillating mild to cold air - however the cold not cold enough really of you want anything decent ( away from Scotland)

& the mild not being 'that' mild- just something akin to average-

so pretty medicore today.... exactly the pattern that is suggested from that H5 anomaly - being the azores high lumped in the middle of the atlantic-

If people want to see proper ridging then look at Dec 81 & see how it developed-

Also twaddle, ? If we get to the 5th & there is nothing showing in the means from the ECM or the GFS ( proper cold ) then time will be rapidly be running out for England-- again thats not to say we dont have a chance-

S

Agree Steve - members need to keep their expectations in check. A displaced Azores High scenario with energy riding over the top isn't the holy grail. Yes, it's probably going to be colder than average, but without proper high level blocking, no cold is going to be sustained.

The ECM ensemble day 10 H500 anamoly chart tells that same story:

[SMU]

Just to add - any injection of cold for England will need a good sub -7c air to be brought south,colder if the flow is NE over the north sea-

There are no indications that we can get any flow sustained enough to filter this west- the jet will effectivley work as a sheild across the UK preventing that happening-

Using the Iceland SLP in this instance is no good im afraid....

S

[TEITS]

Agree Steve - members need to keep their expectations in check. A displaced Azores High scenario with energy riding over the top isn't the holy grail. Yes, it's probably going to be colder than average, but without proper high level blocking, no cold is going to be sustained.

The ECM ensemble day 10 H500 anamoly chart tells that same story:

Yes but the ECM only takes us to the 7th Feb. As I have suggested over recent days this is the period when outbreaks of cold NW,lys is going to occur, If my instincts are right its what develops a few days later that interests me hence me mentioning the 10th Feb. Hopefully by Wed/Thurs the ECM will be showing the kind of potential that im expecting.

[BLAST FROM THE PAST]

If people want to see proper ridging then look at Dec 81 & see how it developed-

Also twaddle, ? If we get to the 5th & there is nothing showing in the means from the ECM or the GFS ( proper cold ) then time will be rapidly be running out for England-- again thats not to say we dont have a chance-

S

That is very reasonable I'd say.

Steve, I think Feb 1986 shows how cold [proper prolonged serious cold] can develop and set in without a greenie HP. As long as the retrogression continues one would develop. That's why I think some are too 'hung up' on seeing a GHP, unless those folk thinking on GP's forecast.

Also too much 'faith' being shown in the models yet again IMO by some. Only 2-3 days ago we were looking at zonal city, also look at ECM 00z yesterday compared to today...chalk and cheese.

BFTP

Edited January 28, 2013 by BLAST FROM THE PAST

[Methuselah]

I'd say that there's a tad 'too much faith' being shown towards a lot of things, right now, Fred?

[phil nw.]

The ens are quite cold the further we go into February.No GH showing but a cold upper trough digging well south into Europe and the trend for a ridging Azores High regressing further west in week 2 is still the main features of the 00z modelling.

The 850`s means at T240hrs reflect the colder trend along with the GFS ens graph.

These suggest a North Westerly pattern inducing colder air as the AH moves further away.

Let`a see where this goes later=maybe a cutoff Euro trough with weak Hts over the top or that elusive Greenland build of heights if the Canadian Vortex does weaken further.

There is more than one way to prolonging and perhaps deepening cold from this setup.

[Frosty.]

I can see plenty to be happy about with the models/ens this morning, a cold weekend to look forward to with widespread frosts, even a brief cutting NEly as the high topples southeast with wintry showers, then a very brief near average interval followed by repeated cold shots which build to a climax around 8th feb, it appears the major cold would be a week before mid feb and then spanning mid month, it hasn't fully developed yet on the op runs, it's work in progress but there are cold snaps aplenty in the next few weeks and perhaps a more prolonged severe spell in development. As for this week, very unsettled with wet and very windy spells until thursday, then cold air spreading south during fri/sat with wintry showers for the south and east, becoming very frosty in the north and west, then a brief less cold and changeable day or two before we see attacks of cold from the northwest, the most important aspect for me is that the alignment of the jet looks like shifting to a nw/se angle, which makes cold increasingly likely during the next few weeks.

Edited January 28, 2013 by Frosty039

[BLAST FROM THE PAST]

I'd say that there's a tad 'too much faith' being shown towards a lot of things, right now, Fred?

Don't you believe in Father Christmas?

BFTP

[Summer Sun]

Looking at the position of the azores high this morning and its really close through out ECM and GFS's run so for sustained cold the high needs to be a lot further west

This is how GFS see's things

That does allow a colder snap to move in

But again the high wins out

The from the 8th looks to be cooler as the high gets shifted further west

We've got a long way to go yet before we get any sustained cold, the reliable time frame is milder, wet and windy with high pressure slowly moving into the Altantic to cut off the Atlantic train. Sustained cold is probably 10+ days away at the, anything before that is going to be short lived.

Edited January 28, 2013 by Gavin.

[MR EXTREMES]

from what my eyes can see this is a setup we experienced before in 09/10 winter when we went from mild southwesterlys to a block in the alantic and this block stuck out into the alantic for a fair while slowly edged towards greenland.

and in that winter the omega block was a feature could be signs heading in this direction.

what is amazing is the speed this is trying to set this pattern only a few days ago it was doom and gloom not saying people should take things at face value but all the models although slightly different in there outputs are very close so there is a possiblity that a return of cold is on the cards from the current setup the sw west and nw and most of scotland cold well see the best of this from a nw source swinging northerly with renewed cold filtering into europe so if anything does come from a ne easterly easterly cold will be there setup.

i think the strat has done its job throwing the alantic into a short frenzy before heights build the alantic is like to be the area it will settle but the uk is also a possibilty although this would seem ok as it would be fine by day cold at night which today here in the south is the theme its lovely outside looking forward to the next few days of model watching its becoming intresting again.

[bluearmy]

the spreads on ecm/naefs show the shortwaves favoured to run nw/se across the uk - think the first monday of the recently ended spell for general picture. whether we have sufficient surface cold in place is questionable but but we wont be far away. could be knife edge stuff - again !

[phil nw.]

the spreads on ecm/naefs show the shortwaves favoured to run nw/se across the uk - think the first monday of the recently ended spell for general picture. whether we have sufficient surface cold in place is questionable but but we wont be far away. could be knife edge stuff - again !

It` does look marginal Nick with -4C uppers at best-could do with a more direct feed from up north.This looks like a cyclonic NE at day 10 onwards-at least for a while.

http://176.31.229.228/modeles/gens/naefs/run/naefsnh-0-0-240.png?12

Hopefully we get something better down the line.

[TEITS]

Here comes the next N/NW,ly.

+216/+240 should be good!

[Gibby]

There are two main points that I see with my analysis of the charts this morning.

1. The Azores High is misplaced too close to the UK at present steering the injections of cold down over Europe with more modified and shortlived cold incursions for us.

2. The Jet is steered over the top of the Azores High suppressing it's chances of ridging North and maintaining the flow of Atlantic mildness across the Atlantic and towards the UK after each brief cold incursion.

There are also two things that could rectify this.

1. The Jet flow needs to weaken so that ridging North can take place and this is suggested in some output in la la land but not in the near furtue plus..

2. Some form of Northern blocking needs to occur to draw the Azores High North still further and allow the Jet flow to undercut to more Southerly latitudes so that the Low pressure can move deeper into the UK so that we come on their Northern and Eastern flank.

This is the only way I can see cold weather being sustained in the near future as there doesn't look much chance of a Scandinavian High anytime soon. As I highlighted a few days ago in my reports the Azores High is very strong at the moment and doesn't look like going anywhere fast so imo the best we can expect is brief colder incursions with yes some snow for some but I don't think there will be sufficient excitement drawn from a two day toppler type scenario that looks the most likely outcome.

Edited January 28, 2013 by Gibby

[Cecil Hogmanay Melchett]

Here comes the next N/NW,ly.

http://modeles.meteo...gfs-0-186.png?6

+216/+240 should be good!

not really teits still far to much oomph in the northern arm.

[UV-RAY]

It's all well and good saying the charts show promise but we've been hearing those words most of the winter. The last cold spell wasn't nothing spectacular in terms of deep cold, for many places it was simply too marginal for snow either falling or lying for any period of time. The outlook at best suggests transitional cool/cold snaps for the foreseeable, this may change in the coming days but until then I prefer to comment on what the models are showing, rather than hoping.

[TEITS]

not really teits still far to much oomph in the northern arm.

Look at the low heights across S Europe though with the trough.

The outlook is so simple to figure out im struggling to understand why some can't see it. Rather than using just the models we should have more members using their instinct. The 06Z is another clear example of what i've been saying since yesterday morning and that is NW,ly outbreaks followed by a prolonged cold spell beginning around the 10th as we see the PV weaken.

[Nick F]

the spreads on ecm/naefs show the shortwaves favoured to run nw/se across the uk - think the first monday of the recently ended spell for general picture. whether we have sufficient surface cold in place is questionable but but we wont be far away. could be knife edge stuff - again !

Some noticeable differences between 00/06z GFS v 00z ECM with the track of a deepening secondary low (or shortwave as many like to call it) tracking SE late Friday/early Sat. GFS prefers to track the low SE to the SW of the UK across Biscay into Wern France. 00z had a back edge snow event for S Wales and S England as the low tracked into NW France. 06z has the low track towards the Pyrenees! So the precip largely escaping Sern Britain and instead we have a dry cold flow.

ECM, however, has a low to the SW of Ireland deepen and track E up the channel, colder air kept further north as a result, so no back edge snow event would seem likely, rather v. wet and windy for the south:

http://en.vedur.is/w...ntic/#type=prec

Alot of support for the EC deterministic from the EPS:

http://www.ecmwf.int...t!2013012800!!/

So going to be interesting to see what the 12z output does with this low.

Edited January 28, 2013 by Nick F

[Gibby]

The GFS 6z echoes my post earlier to the point of illustrating what I mean when what's needed is some sort of Northern blocking drawing the Azores High with it and allowing the chance of an undercut situation as the Jet is forced South. This 384hrs chart illustrates this perfectly. It's just a shame it's 384hrs.

http://www.wetterzentrale.de/pics/Rtavn3841.png