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Paul

Model output discussion - 16th Nov onwards

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a very fickle model run as has been the case for sometime interesting that the idea of a pattern change in december,

there is very little evidence of this and as ive suggested for a fair few weeks that very much like last winter powerful vortex set up and running the show this winter to.

interesting that the gem this morning showing a very 97/98 winter type set up with very mild start to december a ssw event looks to be our only saviour but up against the vortex thats dominated the last few years.

 

with euro heights consistently forecasted i threw the towel in weeks ago although the start of autumn started with a little excitement.

 

gem-0-216.png?12

nightmare gem 

 

ukmo shows to the ugly euro heights UW144-21.GIF?30-17

 

gfs is also showing the euro high 

gfs-0-192.png?12

although possibly more settled futher into december but nothing wintry for all but the north.

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GFS gets to roughly the same outcome despite taking a bit of a different route to get there

 

GFS 6Z

 

gfsnh-0-384.png?6

 

GFS 12Z

 

gfsnh-0-384.png?12

 

Usual caveats apply, it's a long, long way out and we had several runs from the GFS showing high pressure all over the North Atlantic the other day which have now gone AWOL.

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Here comes another interesting FI I think, lets see if the ensembles start picking up on the trend....

 

Not quite as good as earlier, but similar theme.  It looks like around day 12 the PV starts being obliterated, not quite in ECM range but getting there. 

 

Well we can hope, but given this all happens in the low resolution part of the run, is it a possibility that this is a bias inherent to the model itself? The old GFS was often maligned for being overly progressive and zonal in its latter frames. Perhaps the new one is guilty of the opposite.  

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Well we can hope, but given this all happens in the low resolution part of the run, is it a possibility that this is a bias inherent to the model itself? The old GFS was often maligned for being overly progressive and zonal in its latter frames. Perhaps the new one is guilty of the opposite.

So in a goldilocks sort of way the next update will be just right.

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Well we can hope, but given this all happens in the low resolution part of the run, is it a possibility that this is a bias inherent to the model itself? The old GFS was often maligned for being overly progressive and zonal in its latter frames. Perhaps the new one is guilty of the opposite.  

I think the best description is that the GFS would over-express any solution be it mild, blocked, cold, anticyclonic etc. But that is to be expected when you lower the resolution. The same applies to other models, it is just more obvious in the GFS as it goes out much further than the other operationals.

 

Back to the models, they looks pretty mild and unsettled until the beginning of next week. The chance of the Euro high ridging further north at times though it looms transient at best, the GEM again going very bold with these height rises. Perhaps something more interesting developing by mid-month but that is a long way away at the moment.

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The late autumn and early winter period synoptic pattern is very much featuring an El Nino that at face value resembles the 90's rather than the 60's to the 80's, or, much more recently, that of 09/10.

 

Westerly winds continue to be added to the atmosphere across the tropical Pacific which create Rossby wave eddies that propagate northwards and attempt to plump up amplified ridges as a result of this feedback process. However, the stratosphere is not primed in such a way to start the winter so that poleward propagation of wave activity can transport to higher latitudes and effectively create the type of blocking signal such as seen in 09/10.

 

Also, the basin wide Nino forcing Pacific signal is obviously much stronger than the weaker centrally controlled one in 09/10 and is creating such a powerful sub tropical jet stream that it tracks flat and fast downstream, engaging the Atlantic 'cold blob' and tightening  temperature gradients as it aligns itself to the considerably assisted westerly gyre of this seasons stratospheric vortex.

 

Under this most mendacious of regimes, downstream ridges will remain flat and transitory, and secondary engagement of cyclogenesis will repeatedly keep occuring along the corridor of the gradient tipped jet flow

 

If the winter pattern is going to shake itself from a 90's style Nino signature combined with uncoperative QBO polar westerly vortex and solar forcing signalling, then it is going to require some seismic wave breaking and wave length changing catalyst in order to overwhelm the former factors which are firmly dictating the pattern - both upstream in the Pacific, and, downstream in our Atlantic sector.

 

Without any reliable signal emerging (yet) for such a major event, monitoring the stratosphere in isolation of all else would be in vain.  I don't think we can rely on just traditional Nino feedbacks alone, and Aleutian Low and Siberian High wave breaking features, to be sufficient to (eventually) deal with this seasons vortex. A bit like having a sufficiently solid and fast enough car that needs a key to start it, to enable it to drive fast enough ...through a brick wall.

 

There is a hypothesis that January can often repeat the signature of the high summer polar pressure profile. We come into this winter with echoes of a kind of event in our minds from the summer as something akin to what needs to be repeated by January to switch and then couple the Northern Annular mode from +AO/NAO to -ve..

 

Atmosphere/ocean co-operation of this Nino was fully engaged early in the summer, through, at face value, massively organised eastward moving MJO convection. It wasn't any organised convection however, but rather 'noise related' pocketed convection that flared coincidentally with an intense Kelvin Wave westerly wind burst (WWB) in the Pacific, engaging heat tanking SST anomalies. 

 

Eastward propagating, or erupting, tropical convective activity is a catalyst to add extra forcing to the natural amplification feedback processes that El Nino has on the atmosphere. The further east the MJO related activity moves, the greater the upward relative tendency in AAM, and the greater potential there is for warm air advection related amplification our side of the pole. With sufficiently strong and eastward forcing, there can be consequential switches in the AO/NAO mode, from +ve to -ve

 

This summer, consequent impact on the NH synoptic pattern was dramatic and shook up the existing wave length pattern. As the tropical signal engaged the powder keg Pacific, a  sudden surge in +AAM occured and triggered an equally powerful surge of pole ward warm air advection downstream. Following on from this, a reverse sweep buckling of the jet moved downstream from the Pacific, as global torques snapped back like an elastic band, before Nino forcing pushed them forward again. These wholesale amplifications, swamped the hemisphere wave lengths and induced high impact weather events (including record breaking heat and drought) and sent a lot of warm air into the pole and a consequent -AO signal for July verified.

 

Summer of course features 'out of season' 'polar easterlies and a 'warmed out' stratospheric profile. Its a tad different in winter with a fast spinning deeply cold vortex that has equally cold and stable stratospheric zonal winds to be destabilised and weakened first. However, notwithstanding that, with a suitably potent tropospheric mechanism, we get an idea of what might be spectacularly achieved to a fast spinning wheel if enough tropospheric forcing is available to shoot sudden strong blasts of warm air into it.

 

This Nino features basin wide warmth across the Pacific, but it also very unusually features anomalous warmth across the Indian Ocean. In recent weeks, pocketed convection has occured there and stirred up the MJO amplitude through Phases 1 to 3. This has resulted in 'destructive interference' with the base state strong Nino by taking some of the energy out of the westerly winds across the Pacific due to easterly trade winds being added through the atmosphere and propagating into the sub tropics.   I think this is a process that will repeat and steadily increase in the New Year - with subsequent MJO wave activity stirring up stronger easterly trades, increasing downward pressure on AAM, and nibbling away at the region 1.2 perimeters of the Nino zone and subsequent cooling of the SST's from east to west.

 

However, this is a long term process and will not affect the Nino hold on the global atmosphere any time soon. What it may do though is re-distribute the NH pattern through a more central Pacific forcing which better aids feedbacks for a colder synoptic pattern our side of the pole. We still need that powerful troposphere > stratosphere extra catalyst to make all this possible however - and I think we look beyond natural Nino feedback (based against a back-drop of high intensity vortex) to make those colder patterns possible.

 

With such a rapid spinning ribbon of energy coiled around the stratospheric vortex, it requires pinching in more than one place at a time to properly stand a chance of destabilising it. Sudden lunges and 'elasticity' of AAM (such as seen in the summer) in tandem with eastward moving tropical forcing (noise and pocketed erupting convection in the Pacific), are going to be more effective to induce potent Moutain torque events to affect (approx 14 days lag) the stability and temperature of the stratosphere than a smoothed out lower amplitude homogenous +AAM atmospheric cycle that will continue to favour mid latitude transitional ridging/blocking, whilst a flat subtropical jet and strong PV exist -  not sufficiently 'harming' the vortex to allow higher latitude blocking (taking into account the unfavourable and very hostile stratospheric profile).

 

In this respect, until such a strong amplification forcing signal makes it into the reliable period, it is worth being cautious of taking interesting tropical and extra tropical composites for the medium term at face value, at least this side of the New Year - in the context of the hostile polar profile.

 

To attain any worthwhile blocking requires a very large wave activity response from the Nino and a huge amount of extra tropical (GWO) and tropical signal (MJO) co-operation with each other. Even with significant wave 1 and 2 activity, time is against this happening too soon, and I'm not sure that current programmed ongoing wave feedback will be sufficient - irrespective of FI modelling which can often make signals seem deceptively impressive at distance.

 

Tropical convection emerging in the western Pacific late this month or early New Year is a signal to keep watching with all the peaked latent heat in the Nino 3.4 zone. The forcing from this allied to base state amplification forcing, and Eurasian albedo feedbacks coming to fruition, could be the mechamisms towards the sort of January SSW to do the damage needed. Its far too soon to be able to say anything further on this obviously

 

Without something greater than single whammies though, it will be hard to achieve a -NAO/AO coupling, or certainly sustain one. The AO and NAO are already strongly coupled +ve anyway to begin winter, but we should remember that the Northern Annular mode becomes much more inextricably coupled towards mid winter as the dominant seasonal feedback patterns are strongly effective by this time on the long wave patterns.

 

Additionally, as the winter progresses, the atmospheric wave lengths become less co-operative towards Nino-esque Pacific westerly winds being added to the atmosphere that supply the useful poleward WAA mechanism. This is at the same time as increased resistance to fading WWB's likely will be occuring as easterly trades become more enhanced - especially with anomalous heat already in the Indian Ocean at this peak time, and set to start fading the Nino event increasingly soon, if it isn't doing so already

 

 

The flip side of all this, is potential for a more favourable central Pacific forcing for a while as the focal point erodes to a more centrally condensed size - just over and to the west of the dateline- if factors as outlined in this post can enhance successful utilisation of such a pattern

 

Any long range signals that may be floating in or out within GloSea5, ECM and GEFS numerical models that show more blocked and much colder potential from late this month/but more especially into the New Year will be dependant on the various evolutions and tropical and extra tropical co-operation outlined in this post to verify them - in my humble opinion anyway. Taking into account the negative external stratospheric factors, weighting standard Aleutian Low and Siberian High feedbacks may not be enough on their own - despite the promising outlines by Cohen in respect of these, and associated promising Barents/Kara sea ice feedbacks to assist an SSW

 

Attempted perspicacity by (trying to!) decipher complex meterological tools with the aim of providing objective and un-biased analysis is one thing, especially when taking into account the temptations of ones own seasonal weather preferences to want to spice the posting up a bit

.

The passage of time is another and, as ever, will tell the whole story :)

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Only around 3 or 4 GEFS Ens charts go with the Op, similar to the 06z...I'd be surprised if this trend keeps showing up much longer...

When is the next EC32 run?

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a very fickle model run as has been the case for sometime interesting that the idea of a pattern change in december,

there is very little evidence of this and as ive suggested for a fair few weeks that very much like last winter powerful vortex set up and running the show this winter to.

interesting that the gem this morning showing a very 97/98 winter type set up with very mild start to december a ssw event looks to be our only saviour but up against the vortex thats dominated the last few years.

 

with euro heights consistently forecasted i threw the towel in weeks ago although the start of autumn started with a little excitement.

 

gem-0-216.png?12

nightmare gem 

 

ukmo shows to the ugly euro heights UW144-21.GIF?30-17

 

gfs is also showing the euro high 

gfs-0-192.png?12

although possibly more settled futher into december but nothing wintry for all but the north.

Living up to your profile name again. Not sure why you threw the towel in mid autumn. Normal autumn fare being shown in the output, winter starts tomorrow. The GFS will soon ditch the idea in FI and join the mobile club again.

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The jet stream is looking pretty powerful again over the weekend

 

Rtavn11415.gifRtavn13215.gif

 

Another stormy weekend coming up potentially

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Well at least coldies in Europe aren't being subjected to snowy scenes from the USA and Canada as was the case for much of last winter! The pattern over there is bottling up any cold well north into Arctic Canada.

 

Its hard to see any sustained cold for the timebeing with the PV energized and located where it is, the best perhaps is high pressure further north which I'm sure would be welcome given the amount of rain that's fallen over recent weeks in the UK.

 

The ECM has toyed with more dig south of troughing in the west Atlantic which has helped drive some ridging further north ahead of it, we'll see soon whether this continues.

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Only around 3 or 4 GEFS Ens charts go with the Op, similar to the 06z...I'd be surprised if this trend keeps showing up much longer...

When is the next EC32 run?

 

Tonight. Place your bets

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That was some post Tamara, thanks.

 

It does look as though any attempt at blocking in December will always be swimming against the tide so to speak.

Still, it is nice to see those attempts being graphically illustrated within the MO, even though they remain elusively in FI for now.

 

We do at least have a strong signal that the jet will want to push South from around day 6 though - which should help amplify the pattern, hence the attempts at ridging from this period with varying degrees of success and consequence on our mobile pattern.

 

As always, it is case of highlighting the possibilities from cold lovers perspective from me, but hopefully not with any strong bias. (hopefully :acute: )

 

The start of any increased amplification comes around day 6/7 which hopefully (lots of hope :)) is enough to slow down the Westerly progression and cause a knock on effect upstream that results in some worthwhile blocking while the teleconnections generally point to any attempt being overrun until later in the Winter.

 

I am happy to be patient for now and just enjoy the waxing and waning of signals in the hope something will eventually turn the tide our way and we get to swim all the way to Fantasy Island. (UK Winter wonderland)

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The late autumn and early winter period synoptic pattern is very much featuring an El Nino that at face value resembles the 90's rather than the 60's to the 80's, or, much more recently, that of 09/10.

 

Cheers Tamara.

 

In short, then, a bit more of the same!

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Well winter official starts tomorrow! I'd say we have until mid-march for some real biting cold weather.....so around 14 weeks. 

Pity that the charts show nothing of the sort for the first two weeks of December, so let's put a big red X through 2/14 weeks and hope that the tentative signs of a pattern change mid month bare some fruit. All eyes on ECM!

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Impressive ECM FI this evening.

note not just the WAA and ridge but the build of heights to our NE from 192h

 

ECH1-192.GIF?30-0ECH1-216.GIF?30-0

 

The best we can hope for for now are building blocks such as these to be consistently modeled and built upon.

 

ECH1-240.GIF?30-0

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The ECM does continue with its digging west Atlantic troughing which does help force high pressure further north near the UK, we do also see some weak pressure rises developing to the north and ne.

 

If Santa was reading our letters he'd dig that troughing even further south and cut the jet back further towards the UK!

 

Look west for salvation if its going to happen, that trough would be the trigger. I think the odds are a close but no cigar outcome , we'll see the ECM ensembles later but for the timebeing perhaps high pressure closeby with at least some drier weather more likely.

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GFS back with some reasonable eye candy in FI, I remain unconvinced as such charts remain elusive and are not coming anywhere near the reliable time frame and have little ensemble support. 

 

A few charts from GFS output roughly 7 & 10 days ago with what it was showing for the first weekend of December. 

 

post-9615-0-69760800-1448906024_thumb.pn post-9615-0-38577200-1448909068_thumb.pn

 

Down to less than a week away now and the unsettled westerly regime continues.

 

post-9615-0-86132400-1448909277_thumb.pn post-9615-0-68338400-1448906300_thumb.pn

 

Similar chart from today's output to what it was showing 10 days ago, only now it's been pushed back again to 2 weeks away. 

 

post-9615-0-56979000-1448906380_thumb.pn

 

The GFS does like to lead us up the garden path at times! 

 

 

 

 

 

 

 

 

 

 

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In terms of the ECM if theres to be any chance at all of developing a colder ne/e flow for the UK then the low pressure circled red has to verify and dig further south, you also want to see this more elongated. This effects any ridging ahead of it, you can correlate what the high will do with what this low does. Its still a longshot because trying to get the jet cutting back in towards the UK  at T216 and T240hrs from  ne to sw rather than nw to se is always like pulling teeth in these set ups.

 

Given that the rest of the outputs are a recipe for insomnia then its really only tonights ECM that's of any interest to those looking for something colder. I should stress its a longshot , we'll see in the morning whether the pre Christmas miracle is a possibility.

 

post-1206-0-65712700-1448911670_thumb.gi

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In terms of the ECM if theres to be any chance at all of developing a colder ne/e flow for the UK then the low pressure circled red has to verify and dig further south, you also want to see this more elongated. This effects any ridging ahead of it, you can correlate what the high will do with what this low does. Its still a longshot because trying to get the jet cutting back in towards the UK  at T216 and T240hrs from  ne to sw rather than nw to se is always like pulling teeth in these set ups.

 

Given that the rest of the outputs are a recipe for insomnia then its really only tonights ECM that's of any interest to those looking for something colder. I should stress its a longshot , we'll see in the morning whether the pre Christmas miracle is a possibility.

 

attachicon.gifECH1-192.gif

I was thinking the high to the north east might act so a to deflect the low pressure towards the UK and allow some Atlantic retrogression nick :)

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Interesting system on the ecm this evening. The low way out to west at T120 moves so fast 24 hrs later it's in Sweden. En passant Saturday night it brings some very wet weather and strong winds, gusting 65kts, into the southern half of Britain. Need keep a beady on that.

.

post-12275-0-54922800-1448912262_thumb.p

post-12275-0-06532000-1448912268_thumb.p

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I was thinking the high to the north east might act so a to deflect the low pressure towards the UK and allow some Atlantic retrogression nick :)

Unfortunately the upstream pattern is too flat, we'd need to see that troughing to the west at T240hrs sharpen up. By that I mean lose its rounded shape, you'd want the elongated stretched troughing orientated nw/se which would suggest it might disrupt some energy under the high to the ne. We'll see tomorrow whether we can squeeze out more amplitude and dig south of that troughing to the west around T192hrs, that's really the foundation for cold chances.

 

I'd just like to add something re SM's post. I very much agree with his sentiments. The weather does not behave according to analogues or always whats expected of certain teleconnections. That's why we often see apparent cold equalling background signals not delivering and vice versa. There can be too much emphasis placed on these when really the weather is much more fluid and doesn't always follow whats expected.

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This evenings ECM is one of those where you hope the model has picked upon some weak polar heights in a decent strategic position for which the other models will start to pick it up or even increase the strength of this high.

It won't be picked up on the ensembles or anomalies just yet, probably a good thing considering this

EDH101-240.GIF?30-0

Low heights over Iceland, Euro high, pretty gruesome set of ensembles from the ECM suggesting no let in in the generally mild and unsettled conditions, perhaps the Euro high influencing the UK more strongly at times. The GFS and GEM suites as usual being more bullish about the Euro heights influencing the UK at times.

 

GFS (P)

gensnh-21-5-240.png?12

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We have to tread carefully really, as I have known first hand what it's like to get your hopes up based on a spell of wild model output only to have them dashed on multiple occasions - even having been hardened after many seasons it can still become very frustrating. Yet being realistically restrained all the time gets very dull after not long at all, except in those special winters when we have a lot of signals pointing in the right direction and little to argue the other way.

 

So it is that it becomes a game of chasing the exciting weather but avoiding taking it too seriously.

 

However, I do feel it's valuable to have some reminder from time to time that we shouldn't get carried away when the odds are against what we want.

 

 

The analysis of tonight's ECM det. has seen a lot of 'the game' with a dose of realism from Nick Sussex and I reckon that's about the right formula. 

 

Speaking of that run, it's one of those where even small adjustments upstream will make a big difference in our neck of the woods, so I'd be surprised to see the same thing tomorrow - for better or worse  :)

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CS

Interestingly that ECM ens mean looks like the GFS op as it builds heights into NE Canada & beyond-

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