Model Output Discussion 26/10 2012 >

[Gibby]

Good morning. Here is my take on the latest 00z output from GFS, UKMO and ECM.

All models show a deep area of Low pressure developing to the North of the UK with an attendant trough sinking slowly SE over the North and West currently which continues on to clear the UK by midday tomorrow. Following on behind eill be an unstable rather slacker showery flow for all. So after a band of heavy rain transfers SE today and tonight colder and clearer weather follows with showers, turning cold enough for them to fall as sleet or snow on Northern hills. This pattern persists through the end of the week and the weekend with some longer spells of rain thrown in for good measure too.

GFS shows the Low pressure moving slowly away East early next week though it's influence is still being felt in the East and SE as late as Wednesday as a ridge of High pressure edges slowly in from the West damping sown the showers and increasing the risk of overnight frost. By the end of the week a weak ridge of high pressure has meandered very slowly East over Britain with some dry and bright if rather cold daytime weather with frosty nights likely. Later in FI High pressure takes control of the UK weather with centres East and West abridged over the UK. This means quiet, Autumnal weather looks likely then with frost and fog becoming major issues night and morning with cold conditions maintained at the surface through the days too. This lasts through to the end of the run with just the NW seeing more wind and perhaps a little rain at times.

The GFS Ensembles show a period of fairly standard Autumn weather with spels of rain and shower mixed in with some drier spells as uppers remain marginally below the long term mean through the period. Withe 850 uppers spread between -5C to + 10C throughout the members there is no sign of any particulary cold weather on offer though if the GFS operational came about then ground level temperatures could become quite cold at the surface later in the run. However, the most support is for rain at times across the UK for much of the period.

The Jet Stream is shown to blow strongly West to East just to the South of the UK over the coming days. as we approach the week mark it ridges North over the Atlantic and weakens somewhat before moving East once more at somewhat higher latitudes.

UKMO for midnight on Tuesday shows Low pressure centred over the Southern North Sea wth a cold and showery Northerly flow over Britain. The showers will fall as snow over Northern hills as temperatures remain on the lower side of normal.

ECM takes the Low away East rather quicker with a ridge of high pressure moving through on Tuesday taking the showers away East and bringing a drier interlude. Winds from the West or NW continue to blow freshly over Britain though with occasional rain on a warm front passing through on Wednesday. Later in the week it's back to square one as Low pressure sinks down from the NW with renewed rather cold and unsettled conditions arriving for all.

In Summary we have a split camp between the operationals this morning. GFS and UKMO hold on to Low pressure longer early next week with rain still likely as late as next Wednesday from our current Low pressure. ECM rushes it away East by Tuesday with a windy spell following leading us back into a case of deja-vu by late next week. GFS on the other hand leads us into a quieter High pressure type spell where fog and frost may become the biggest ingredients to the UK weather. Either model has a reasonable chance of verifying imo though if I had to put my eggs in one basket I would probably favour the continuing cool and changeable conditions offered by ECM as the most likely outcome.

[lorenzo]

Looking foward to seeing this trio of LPs unfold on Satellite. First real autumnal low up close and ugly, with some energy about it.

GFS drags a pocket of 528dam air over the centre of the UK, whereas fax above directs the main flow into mid-atlantic.

Some hatched areas within.... more of the same for Ski resorts.

[johnholmes]

the 3 500mb anomaly charts all point to a continuing unsettled rather cold, or at least below normal temperatures spell, in the 6-15 day time period. Just a hint as the +ve areas edge closer that some parts may see less disturbed weather late on but a bit early for that.

There is also the potential (note the word !) for a cold shot in that period, but unlikely to be more than about 3 days IF it did occur.

Ian F ??

did you get my 2 pm's to you please?

[MR EXTREMES]

I think the models across the board tell the story of autumn.

Vortex this year was a little late in ramping up but this looks the case now.

So I think a few more weeks and were see whether early or late winter.

I'm going for similar winter to 08/09 .

But until further notice the alantic is very very active with some extremely excited weather to be had.

But possibly dangerous.

[Radiating Dendrite]

I think the models across the board tell the story of autumn.

Vortex this year was a little late in ramping up but this looks the case now.

So I think a few more weeks and were see whether early or late winter.

I'm going for similar winter to 08/09 .

But until further notice the alantic is very very active with some extremely excited weather to be had.

But possibly dangerous.

I disagree when you say the Atlantic is very very active.

It is not, yes there is cyclogenesis, but in equal measure there are also high pressure areas to be found across all of the models in terms of the Atlantic.

The weather looks like staying unsettled in the near future, with the possibility of things settling down a little as we move towards mid-month.

[EML Network]

Tonight does look very disturbed over the South and there does seem to be potential for some wild days this week and right through until Sunday.

The overall signal up until about the 7th of November are for HLB to be in effect.

Thereafter the models differ somewhat the GFS wants to give us a Euro High, at least for a while, where as the ECM wants to keep High pressure to our West .

If one was to try and second guess what might develop after the GFS and ECM one could argue that a Northerly incursion looks likely , but with different ways of getting there.

I'd say on the balance of evidence and with the Met Office 15-30 day outlook also gunning for lower temperatures , we could be looking at the possibility of a decent cold spell some time around the 20th November ??

The ECM long range NAO forecast isn't very supportive of this idea though, so there's just as much chance of a Euro High setting up shop , keeping the cold well to the North of the UK, but never that far away so as to when the Euro High pushes off the potential to plug into the cold is increased.

So There's no real signal beyond the 8th November and I would expect a half way house, therefor I expect that as we head towards Mid Month we may very well find that were in no mans land with a more cold zonal pattern and a North South split, I.E North Westerly's.

That's my VERY uneducated guess anyway

[Tim Bland]

I think the silence says it all! 12z no better for us coldies. A solid PV to our north / north east, Strong Azores high. After a promising start it's not looking good. Hopefully the pattern will shift as we head towards Dec. Anyone know when Stuart's winter forecast is released? Happy Halloween all.

[Severe Siberian icy blast]

I think the silence says it all! 12z no better for us coldies. A solid PV to our north / north east, Strong Azores high. After a promising start it's not looking good. Hopefully the pattern will shift as we head towards Dec. Anyone know when Stuart's winter forecast is released? Happy Halloween all.

Hopefully the pattern will change in dec? How about nov it's not even nov yet? I fail to see why ppl get like this , the weather will not have northerly blocking for months on end, even if the next 20 days is horrible maritime zonal with winds south of west, we still have another 10 days left of the month after that, and then we can think about dec, ones really need to take note of the pro's in hear and read there posts, how many times will it take for ppl to listen at last.

[Methuselah]

I think the silence says it all! 12z no better for us coldies. A solid PV to our north / north east, Strong Azores high. After a promising start it's not looking good. Hopefully the pattern will shift as we head towards Dec. Anyone know when Stuart's winter forecast is released? Happy Halloween all.

Just prior to the start of winter, I'd think...Which is, as I've said before, still four weeks' away!

[Continental Climate]

Maybe im just rubbish at reading the charts but i don't think the 12zs are to bad so far

http://www.wetterzentrale.de/pics/Rtavn961.png :- this chart shows that we are certainly not in bartlett or euro high territory like this time last year.

http://www.wetterzentrale.de/pics/Rtavn1201.png:- This chart could certainly be worse, and yes there is a developing polar vortex but that was always going to come anyway.

http://www.wetterzentrale.de/pics/Rtavn1441.png:- This chart again aint wonderful but possibly shows the high in the atlantic trying to move north again and the migration of the vortex to siberia/scandi

http://www.wetterzentrale.de/pics/Rtavn1681.png:- definite movement of the high north and migration of the vortex to siberia.

All in all not a bad run it could definitely be better without a doubt but i don't understand the gloom in here, and its still only october!!!

damn links aren't working go to wetter and check the run out for yourselves guys

[Cheshire Freeze]

I think the silence says it all! 12z no better for us coldies. A solid PV to our north / north east, Strong Azores high. After a promising start it's not looking good. Hopefully the pattern will shift as we head towards Dec. Anyone know when Stuart's winter forecast is released? Happy Halloween all.

Hate it when people say 'I told you so' but I did voice my fears about a tightening vortex and a much more zonal flow as we enter November...this was in the winter thread 10-14 days ago and something the CFS had been trending towards. Whether this is a long term trend or something of a blip I don't know, though I would suggest that there is some importance now on a stratospheric warming event during the next 4 weeks, otherwise I think a prolonged cold outbreak before Christmas may be hard to come by. The usual caveats apply however, sudden disturbances of the PV are by no means precluded IMO but I think if we are to see cold it will be snaps rather than spells. Also, as has been intimated by several recent GFS runs, I wouldn't back against a mid latitude high taking up residence across the UK within the next couple of weeks.

This isn't based on one run or a knee jerk reaction; it's something I've been keeping tabs on for the last few weeks.

[bluearmy]

Just looked at fi on the gfs 12z expecting a horror show. Although not worth too much analysis as its gfs low res, how many times do we have to advise to look at the NH charts before making comments? Continues to look ok to me as far as a lack of central strong p/v becoming established on that run. Of course, it may completely out of kilter with the ens which are probably of more value in week 2.

And mid lat highs in November are fine in my book. Frost and lingering freezing fog. Just like a seventies autumn which, no surprise, preceded a seventies winter.

Edited October 31, 2012 by bluearmy

[SMU]

Hate it when people say 'I told you so' but I did voice my fears about a tightening vortex and a much more zonal flow as we enter November...this was in the winter thread 10-14 days ago and something the CFS had been trending towards. Whether this is a long term trend or something of a blip I don't know, though I would suggest that there is some importance now on a stratospheric warming event during the next 4 weeks, otherwise I think a prolonged cold outbreak before Christmas may be hard to come by. The usual caveats apply however, sudden disturbances of the PV are by no means precluded IMO but I think if we are to see cold it will be snaps rather than spells. Also, as has been intimated by several recent GFS runs, I wouldn't back against a mid latitude high taking up residence across the UK within the next couple of weeks.

This isn't based on one run or a knee jerk reaction; it's something I've been keeping tabs on for the last few weeks.

http://www.meteociel...44-21.GIF?31-18

I wouldnt count your chickens before they hatch.........

Still no sign of the vortex in qaudrent 3 or 4.... all still in quadrant 2- ( just a smidge of low heights into the top side of the pole..)

S

Edited October 31, 2012 by Steve Murr

[Cheshire Freeze]

http://www.meteociel...44-21.GIF?31-18

I wouldnt count your chickens before they hatch.........

Still no sign of the vortex in qaudrent 3 or 4.... all still in quadrant 2-

S

Steve, would love to see a very disrupted and under developed NH vortex persist but I feel it's looking a lot less likely than it was at one point? I suppose things can and probably will change in a short space of time so you may well be right! Must be the pessimist in me!

[UV-RAY]

Hate it when people say 'I told you so' but I did voice my fears about a tightening vortex and a much more zonal flow as we enter November...this was in the winter thread 10-14 days ago and something the CFS had been trending towards. Whether this is a long term trend or something of a blip I don't know, though I would suggest that there is some importance now on a stratospheric warming event during the next 4 weeks, otherwise I think a prolonged cold outbreak before Christmas may be hard to come by. The usual caveats apply however, sudden disturbances of the PV are by no means precluded IMO but I think if we are to see cold it will be snaps rather than spells. Also, as has been intimated by several recent GFS runs, I wouldn't back against a mid latitude high taking up residence across the UK within the next couple of weeks.

This isn't based on one run or a knee jerk reaction; it's something I've been keeping tabs on for the last few weeks.

Indeed CC, it was you highlighting these nearly two weeks ago that brought it to my attention, although we are in a better position to this time last year a lengthy cold spell doesn't seem on the cards this year, as it stands!

[SMU]

No of course Winter is 'ov er'

Its at times like this the models suddenly wake up to pressure over Northern Europe changing to +VE

S

[UV-RAY]

No of course Winter is 'ov er'

Its at times like this the models suddenly wake up to pressure over Northern Europe changing to +VE

S

Indeed, hence why I added "as it stands".

[phil nw.]

Notable that although the vortex is deepening as we go into November there`s enough disruption to it`s shape to indicate that we are not as yet looking at a mild south westerly type of pattern developing.

Those height`s in the N.Atlantic continually buckling the jet through the next week or so.

The GFST120hrs show the flow forced NW-SE with the UK to the north of the JS so with cooler polar air very much in the mix.

Day8 continues to show jet disruption across the Atlantic

a sign that although polar heights are lower the mean zonal flow for the UK is predominantly from north of west.

[Cheshire Freeze]

No of course Winter is 'ov er'

Its at times like this the models suddenly wake up to pressure over Northern Europe changing to +VE

S

Haha Steve, I can't condone those that are suggesting winter is over and I would think these individuals are solely looking for a reaction and to stir things a bit. Even though I think any meaningful cold spells may be short lived over the next 8 weeks, Jan & Feb could be a different story! Who knows. Plenty of model watching over the coming weeks to keep us all enthralled.

[SMU]

Yes Phil & that shows the blocking in Quadrent 3 & 4 nicely...

Im not sure why but im mildly excited waiting for tonights ECM

S

Edited October 31, 2012 by Steve Murr

[I remember Atlantic 252]

I hope this horrid washout low for Sunday shown on GFS is wrong, UKMO dosent have it, bbc and meto tv/websites dont have it, hope ECMWF dosent have it, its the usual sunday washout shortwave setup

[chionomaniac]

Notable that although the vortex is deepening as we go into November there`s enough disruption to it`s shape to indicate that we are not as yet looking at a mild south westerly type of pattern developing.

Those height`s in the N.Atlantic continually buckling the jet through the next week or so.

The GFST120hrs show the flow forced NW-SE with the UK to the north of the JS so with cooler polar air very much in the mix.

Day8 continues to show jet disruption across the Atlantic

a sign that although polar heights are lower the mean zonal flow for the UK is predominantly from north of west.

Exactly Phil.

The PV is increasing but the meridional pattern still remains.

[Bristawl Si]

Hate it when people say 'I told you so' but I did voice my fears about a tightening vortex and a much more zonal flow as we enter November...this was in the winter thread 10-14 days ago and something the CFS had been trending towards. Whether this is a long term trend or something of a blip I don't know, though I would suggest that there is some importance now on a stratospheric warming event during the next 4 weeks, otherwise I think a prolonged cold outbreak before Christmas may be hard to come by. The usual caveats apply however, sudden disturbances of the PV are by no means precluded IMO but I think if we are to see cold it will be snaps rather than spells. Also, as has been intimated by several recent GFS runs, I wouldn't back against a mid latitude high taking up residence across the UK within the next couple of weeks.

This isn't based on one run or a knee jerk reaction; it's something I've been keeping tabs on for the last few weeks.

Hardly a long shot call though CC - it is the 'norm' for this time of the year.

Having said that the PV doesnt look particularly 'solid' right now.

Edited October 31, 2012 by Bristle boy

[snowstorm445]

No of course Winter is 'ov er'

Its at times like this the models suddenly wake up to pressure over Northern Europe changing to +VE

S

It really is incredible. A day of relatively poor runs from the GFS (after weeks of predominantly cold and polar airflows) seems to convince people that the entire month of November, even as far ahead as Christmas, will turn out to be mild. Its amazing. Its as if somehow a predominantly mild (ish) chart will always turn out to be solid, undeniable fact, despite the fact that we are all WELL aware that they change on a daily if not an hourly basis.

There are two with basing your opinion on charts, particularly it seems the GFS:

1. For a start the furthest they go is about the middle of November, so anything after that is just your gut feeling, which from what I see on here changes with nearly every run.

2. They fluctuate daily, as we saw between yesterday's charts and today. I can guarantee we have seen plenty of weather events that appeared on the charts for days but never came to fruition. On numerous occasions the threat of an Indian Summer/Bartlett High appeared on the models only to vanish again within a few days.

I really don't mind if we see a mild November, we have been spoilt with a fairly below average Autumn up until this point. And correct me if I am wrong, but is it not a fairly common occurance to see a polar vortex gather strength during the winter months (hence the powerful storms)? Even if it does arrive it won't always remain a permanent feature.

Anyway, before people decide to write off a month before it has even commenced based on a day of poor(er) runs than previously seen, coupled with pessimistic gut feelings, please bear in mind how unpredictable weather in this part of the world is, and above all, how zonal patterns are by far the most common weather pattern to see at this time of year.

[Gael_Force]

Lol, a bit of orange over the UK and a purple blob in the central Arctic ...we have howls about PVs and first mention of Bartletts!

Look which way the Arctic wheels (PVs) are turning - the flow is much more likely to be northerly than anything from the west going by modelled placement.