Model Output Discussion 18th Nov.2013-12z onwards.

[bluearmy]

Moving forward, there is now a consistent trend from the ensembles showing heights rising to our NW and troughing to our NE. The EPS ens highlight this by day 12 on this mornings run.

Heights & temp anomaly / ECM EPS ens 0z

Broadly in line with naefs - maybe a bit more enthusiastic. I guess it depends how fleeting it is. coud be a signal for a decent toppler. What is clear is the noise at that timescale is now too loud to be ignored. we need to see the trend that follows this timescale to establish if its just a colder blip within a generally cool/average period or something more noteworthy. Edited November 23, 2013 by bluearmy

[Frosty.]

I think there is plenty to interest coldies during the coming weeks, I also think the models are struggling with the atlantic high placement and the impact of the forcing caused by the lowering heights to the northwest and north. The Gem appears to be the only model which currently shows sustained high confidence in it's very amplified outlook. There are some wintry looking GEFS 00z perturbations with reload potential and I still believe we will have wintry spells through December, they may be short and sharp but I think there are good signs looking further ahead.

[Captain Shortwave]

I'm not quite sure what to think of the output at the moment, as mentioned yesterday I said the longer range models (CFS/JMA) were going for heights slightly East/North east of the UK to start off December which contradicts what the likes of the GFS/ECM are showing, maybe it's just me but I'm seeing some doubt creeping in to maybe think the models might be reading this wrong here.

ECM/GFS at day 8

Interesting to note both models are creating a similar looking low/cold pooling in the mid-Atlantic which looks to potentially phase with the trough coming out of Canada. I do wonder whether the models will toy with developing a deep Atlantic trough in week 2 which consequently would push the Azores/Atlantic high north east through the UK. Completely contrary to what others are saying with a reasonable trend for another Atlantic ridge from NAEFs/ECM ens. Frankly I haven't got much trust for any of the models recently, but will be watching developments in the Atlantic closely to see where things go. Knowing our luck everything will be wrong and we will continue in weather purgatory (High near the UK).

Edited November 23, 2013 by Captain shortwave

[Weathizard]

This is one of those patterns that seems to have a retchid way of hanging around for a long time, I'd be surprised if we still don't have the high plonked over us in an unfavourable position for at least another 2 to 3 weeks, we need changes upstream and the chunks of PV left over Greenland to be dragged east kicking and screaming by the main part of the vortex which appears to be moving to a pretty good position for future prospects, IF we can get some sort of ridging/cut off high to pull then at least having roughing to our N/NE means it will be cold. Long way out mind and without meaning to sound negative this is one of those disgusting patterns that can cling on for very long periods

[legritter]

The only glimmer of hope as far as i can see on Models is around the 192 mark on ECM  today .as this is just over a week away ,from a coldies perspective there is room for improvement come further runs . but it is looking like a high pressure dominated spell and we need some low pressure moving into mid atlantic or a break up of the vortex ,only crumb of comfort at the moment is its still autumn and 13 weeks of winter to come .And present set up on balance should swing the other way but no guarantees just yet .perhaps tonights runs can give us a shot .

[terrier]

Well ive just run the gfs 6z run and they is nothing to my untrained eye to look forward to from a coldie propective. Think we may see a fleeting glimpse of cold around 7th-9th december. But ive got that feeling we are once again chasing deep fi charts. Which lets be honest have little chance to verify. Think its going to be a very frustrating time for us coldies. And fun for summer sun lol   

[Cold Winter]

A long period of benign, dull weather on the way - quite a bad set up if it's cold or Atlantic storms you're looking for.

 

I'm remaining optimistic however. The lack of Atlantic influence plus the gradual cooling of Europe as we head into winter could set us up for a longer period of sustained colder weather, especially if high pressure moves northeast towards Scandinavia dragging in east/northeasterly winds. The period just before and around Christmas could get quite interesting.

 

Obviously a long way to go until then and anything could happen so don't take my comments to heart!

[Summer Sun]

A lot of the UK is likely to see no rainfall for the next week, the only area prone to some rain is northern Scotland

 

[draztik]

Interesting to note both models are creating a similar looking low/cold pooling in the mid-Atlantic which looks to potentially phase with the trough coming out of Canada. I do wonder whether the models will toy with developing a deep Atlantic trough in week 2 which consequently would push the Azores/Atlantic high north east through the UK. Completely contrary to what others are saying with a reasonable trend for another Atlantic ridge from NAEFs/ECM ens. Frankly I haven't got much trust for any of the models recently, but will be watching developments in the Atlantic closely to see where things go. Knowing our luck everything will be wrong and we will continue in weather purgatory (High near the UK).

interestingly, the Korean Met have a similar evolution to the one you speak of, with heights to our NE and an Atlantic trough thru middle of next month. Tho id hazard a guess and suggest either evolution being highlighted would bring below average conditions to much of the UK.

Edited November 23, 2013 by draztik

[Frosty.]

There are some very wintry GEFS 06z perturbations at various stages of the next few weeks which I have shown here, now to be fair, they are in the minority although there are some, not shown here which have at least got potential to evolve into something colder. Now we all know how fickle these models are and just because the majority are showing a more benign boring outlook doesn't mean to say it will happen, as I have said before, I believe the models are struggling with the exact placement of the atlantic high and that will prove crucial to our chances of having a cold blast at the end of next week and then further on into December, this is a fluid situation and I for one am not writing this off, there is hope for coldies.

[Stu_London]

Even if the high does position in a way to give us a colder shot, the jet profile doesn't really support anything other than any brief transitory events as high latitude blocking looks a long way off at present.

 

Mid latitude blocking looks the form horse with high pressure close to the UK for an extended period. Fog, frost and slightly below average temps look likely, all pretty standard for late November / early December.

 

When the pattern does change, cold weather fans do not want to see the high drift south east into Europe, as that will open door for the zonal train for god knows how long.

[Winter Monsoon]

Problem is with have a jet stream thats pretty much doing this through the whole run:-

 

 

 

Which i think is only helping to keep that high in place with low pressure steering along the jet into norway.  It also remains fairly static - at least thats how i read it.

 

I would have thought we would need that jet to start heading south of us, enabling high pressure to move in a northerly direction, don't really care which way just north will do. With the jet south it would also allow the cold air to flow south. 

 

But thats just a chart produced by a model at 204 hrs - i don't know how reliable the models are at forecasting jet streams at that range so it could be entirely wrong. 

 

[bluearmy]

I always thought the 06z gfs was biased to a strong jet. I know sm thinks that's the 12z but my recollection from years past is tht it's the 06z which tends to ramp up the jet, especially in low res. this has to be anecdotal claptrap but keep it in mind over the next few months and lets revisit in the spring.

[Tom Montalbano]

I think we've learnt in the last few winters to be wary of these 500 hpa forecast anomaly charts.

An anomaly is just that, a deviation from the norm and what we have to keep in mind is, that SW of Iceland you would expect lower pressure, to be observed, at this time of year. What this chart indicates to me is that the current pattern of a mid-Atlantic high, meandering around just to our west and low pressure to our NE, close to Scandinavia, is expected to continue well into the first week of December. Our best chance of any wintry weather reaching our shores, would appear to be on the back of some slight amplification from a mid-Atlantic high but I wouldn't expect it to amount to much at the moment, with still too much energy, travelling through Greenland. We really need the pattern to shift somewhat upstream, over the States and the Pacific, before we start to see more favourable synoptics, in terms of delivering any notable wintry weather on our side of the pond.

Edited November 23, 2013 by Kentish CZ

[Tamara]

I think we've learnt in the last few winters to be wary of these 500 hpa forecast anomaly charts.

An anomaly is just that, a deviation from the norm and what we have to keep in mind is, that SW of Iceland you would expect lower pressure, to be observed, at this time of year. What this chart indicates to me is that the current pattern of a mid-Atlantic high, meandering around just to our west and low pressure to our NE, close to Scandinavia, is expected to continue well into the first week of December. Our best chance of any wintry weather reaching our shores, would appear to be on the back of some slight amplification from a mid-Atlantic high but I wouldn't expect it to amount to much at the moment, with still too much energy, travelling through Greenland. We really need the pattern to shift somewhat upstream, over the States and the Pacific, before we start to see more favourable synoptics, in terms of delivering any notable wintry weather on our side of the pond.

 

Yes I agree - the pattern is stuck with the Aleutian High and likely to remain so for a while to come. With the AO set positive courtesy of the strong vortex then amplification of the atlantic ridge downstream from the pattern over the Pacific is the only route to anything average or maybe slightly below for the foresseable future. I don't think we should expect too much from this amplification however, and treat hints that keep appearing in the further model output with tempered expectation

[Continental Climate]

Yes I agree - the pattern is stuck with the Aleutian High and likely to remain so for a while to come. With the AO set positive courtesy of the strong vortex then amplification of the atlantic ridge downstream from the pattern over the Pacific is the only route to anything average or maybe slightly below for the foresseable future. I don't think we should expect too much from this amplification however, and treat hints that keep appearing in the further model output with tempered expectation

I agree its looking pretty dire from a cold weather point of view http://www.wetterzentrale.de/pics/Recm2401.gif!! That is a damn poor chart and features everything that a cold weather fan must fear ie a northerly running jet and a powerful pressure rise to the south... One thing you can be sure of is when the charts improve they will be there to dampen everyones spirits again.

Edited November 23, 2013 by A Boy Named Sue
Cut the personal remarks!

[shedhead]

No sign whatsoever of anything cold in the latest outputs and very little sign of a potential route unfolding in that direction either.  I suppose if we're looking for a straw or two to clutch then the fact a good deal of dry weather looks likely must be one, with no immediate return to winds sourced around Bermuda being another...but in reality that's about it, at least for now! 

Edited November 23, 2013 by shedhead

[draztik]

No sign whatsoever of anything cold in the latest outputs and very little sign of a potential route unfolding in that direction either.  I suppose if we're looking for a straw or two to clutch then the fact a good deal of dry weather looks likely must be one, with no immediate return to winds sourced around Bermuda being another...but in reality that's about it, at least for now!

hi Shed, i find your analysis a little odd. You seem to be dismissing what the ensembles are showing in their latter stages, without proper reasoning as to why. Of course, usual caveats apply to this output, but you were quick to point to breakdowns in the summer, when the ens pointed in that direction. Now, instead of "tempered" expectations, you completely dismiss. Odd.

[tight isobar]

As regards HLB whether it be alignment nw/ne.or a stagnation of HP upon us..the way the models are at times toying scenarios, nothing as it stands can be either expected,or disregard.but for sure as always change will ....sooner the better!!!???

[johnholmes]

I think we've learnt in the last few winters to be wary of these 500 hpa forecast anomaly charts. 

 

It does of course depend which 500mb anomaly charts one uses and how carefully one uses them. A correct prediction of 70% or more 10-15 days out over a 4 year period whatever the season makes we pretty confident using the 3 that I do use with their outputs. As always IF they show consistency over time and with themselves and are not at 180 degrees to other indicators. Never ever take one run, one model and use to predict what you think may happen. Use everything available and the first class inputs from other folk to help your assessment and analysis is something we can all do on Net Wx. I am constantly amazed at how many folk with no meteorological training have such depths of knowledge.

[Blake]

GEM & NAVGEM similar for next weekend, if I am reading this correct, bring the low further South than UKMO, ECM & GFS anticipate. Strong cold(?) winds from the NW/W.

 

http://modeles.meteociel.fr/modeles/gem/runs/2013112300/gem-0-198.png

 

http://modeles.meteociel.fr/modeles/navgem/runs/2013112300/navgem-0-180.png

 

 

Looking into the start of December, would this be likely to bring in wintry showers, maybe something more substantial across the north and west pushing further south perhaps as far as the M4 corridor? Dam lines ranging from mid 530's near south coast down to 512 at the north of Scotland.

 

http://modeles.meteociel.fr/modeles/gem/runs/2013112300/gem-0-240.png

 

Generally just a browser here, still learning but like many on here, a cold fan in search of snow

 

If I'm wrong, would appreciate some indication as to where I may have gone wrong

 

P.S. html didn't work. Oops.

Edited November 23, 2013 by GUWeather

[MR EXTREMES]

GEM & NAVGEM similar for next weekend, if I am reading this correct, bring the low further South than UKMO, ECM & GFS anticipate. Strong cold(?) winds from the NW/W.

http://modeles.meteociel.fr/modeles/gem/runs/2013112300/gem-0-198.png

http://modeles.meteociel.fr/modeles/navgem/runs/2013112300/navgem-0-180.png

Looking into the start of December, would this be likely to bring in wintry showers, maybe something more substantial across the north and west pushing further south perhaps as far as the M4 corridor? Dam lines ranging from mid 530's near south coast down to 512 at the north of Scotland.

http://modeles.meteociel.fr/modeles/gem/runs/2013112300/gem-0-240.png

Generally just a browser here, still learning but like many on here, a cold fan in search of snow

If I'm wrong, would appreciate some indication as to where I may have gone wrong

P.S. html didn't work. Oops.

It's very much if we get a nw flow it's going to bring a more colder solution than we have now in certain parts of the country as you suggested.

I think I'm now starting to. Think maybe get rid of the mlb and start from scratch maybe Jan will be better I know it's a longtime but if we really want the cold to come then mid December Jan and Feb are real winter months and by then plenty of sustained cold in place to tap into.

The idea of a nw flow showing recently On some model output is certainly something more interesting and the north Atlantic is more cold atm than Europe so atleast there be some wintry cheer for some.

Edited November 23, 2013 by emotional rollercoaster

[Tamara]

John, I think as a seasoned visitor to the threads he won't mind me saying that he has a very good grounding of the main essentials of weather computer model watching and consideration needs to be given as to the context in which he was discussing the use of these anomaly charts Whilst the majority of the anomaly charts will indeed prove very valuable to assessing and discussing the general macro scale pattern in the NH, it is also true that we must be cautious of what they mean for the UK on the micro scale in terms of assessing actual placings and orientation of pressure systems, and not to interpret them too much at face value.

 

We have seen in the last week or so that the 500mb charts have been broadly very accurate in the placings of the anomalies, but crucially they have not been able to tell us the degree of amplification we might have expected from the atlantic height anomalies depicted - that mean the difference between a proper polar incursion and what has turned out to be a relatively low key colder interlude of weather.

Edited November 23, 2013 by Tamara תָּמָר

[TSNWK]

12:00 GFS stalemate rules for the next 10 days. High tending to drift east of south.

[Frank Trough]

hmmmmmmmmmmmmm. No wonder there aren't many comments on the GFS....a progressively Bartlettish borefest.

 

 

 

At least it's only the very start of winter - and i'd rather have that sort of yawnfest early on allowing for my much expected but scientifically unsupported pattern change in time for the festive period....