Model Output Discussion 29th December - Into mid-Winter.

[nick sussex]

 The ECM and GFS are broadly similar in pattern but theres a key difference upstream which could tip things in our favour. For newbies take a look at the NH view of the ECM, you can see that as that amplification works across the USA between T168hrs and T240hrs how this attaches to the PV and causes that anti clockwise motion which pulls the PV away from the ne/n, helped also by the high over Siberia. We're not talking of deep FI here, the actual catalyst begins at T168hrs. We still could do with the PV further away especially over eastern Greenland and need those low heights there and Svalbard to be replaced with ridging.

[Mark Neal.]

5 minutes ago, bluearmy said:

Two things - how the hell is this evolution a surprise to anyone ?

and the eps have been notable in their desire to drop uppers days 8-12 to quite low mean values so -8 is not necessarily off the table 

Absoutely, and following your updates on the whole thing i have got that impression too. Just wonder if we can get something sustained after days 8-12, looks like a flow of NW/N looks a good bet, how cold will it be?, can we get troughs in flow to give people the S word etc? Thats to be answered, and much closer to the time. Growing cause for optimism. 

Edited January 5, 2017 by Mark N

[Scandinavian High.]

9 minutes ago, tight isobar said:

Yes as bluarmy alludes' post day 8 particularly ignore. .However with modeled cross polar height and deep set northerly incursion. .its hard to do that.

Cracking northern hemisphere for uk cold!!!!

Could this bring any snow down to the south east of England..

[Frosty.]

The Ecm 12z turns into a thing of beauty which even aces the Gfs run and snow, the missing ingredient so far this winter would certainly arrive if either the gfs or ecm are close!..could be exciting stuff later next week onwards..hopefullycheers gang

[Kentspur]

1 minute ago, abbie123 said:

Could this bring any snow down to the south east of England..

Only if a polar low decides to attach itself- otherwise unlikely.northwest/northerlies mostly give us dry cold air in the south east

[feb1991blizzard]

1 minute ago, bluearmy said:

Two things - how the hell is this evolution a surprise to anyone ?

and the eps have been notable in their desire to drop uppers days 8-12 to quite low mean values so -8 is not necessarily off the table 

Yes, this has been on the table ever since the GEFS new years morning, Its the Easterly that would have took a big leap of faith on my behalf butwhen you get PM airmasses modelled consistently and theres any kind of potential amplification upstream, a N'ly is never out of the question, its more than a topler although probably unlikely that this will mature into a cold spell that we will be talking about for years but a cold spell none the less is looking odds on now.

[Captain Shortwave]

ECM/GFS/GEM at day 8

      

 

Solid agreement on a north west or even northerly flow developing as we become increasingly influenced by a trough just to our east. On the northern hemisphere perspective there is a lot of promise going forward with blocking possibly becoming increasingly extensive towards Siberia. We are heading in the right direction and mid-month is trending cold, possibly cold enough for snow to low levels. Can we work an even better solution down the line?

Edited January 5, 2017 by Captain Shortwave

[tight isobar]

Abbie123..

Way to early for geographical insight to any precipitation values/levels. ..

But with current output and uppers hinted at there's possibilities countrywide! 

[stainesbloke]

5 minutes ago, abbie123 said:

Could this bring any snow down to the south east of England..

If we see a polar low develop then quite possibly. Otherwise this setup would give sunny, cold conditions by day with perhaps the odd wintry shower.

[mother nature rocks]

It's a New Year, a fantastic forum and now even the models are starting to look a whole lot more promising. So let's all in enjoy whatever the models ( and the weather) throw at us as something is definitely afoot.  

Hopefully 3 feet deep!!!!

Proper winter is coming soon!!

MNR

[Luke Attwood]

14 minutes ago, abbie123 said:

Could this bring any snow down to the south east of England..

Well as with any northerly,favoured areas are Scotland and coastal areas. But with that cold over the UK there is every chance of snow.

[nick sussex]

On current form you'd back the ECM over the USA against the GFS. Remember all that drama with shortwave energy in the Atlantic that the GFS had this was effected by its flatter shortwave running east across the USA which downstream led to a messier picture, its still flatter than the ECM but has made corrections during the day.

We're again dealing with flatter versus more amplified. The key timeframe for us is T168hrs onwards if we want to have hopes of a happy ending. I've done one of my now infamous paintjobs to illustrate this.

ECM T168hrs                                                    GFS T168hrs

                

The more amplified the upstream pattern is at this stage the better chance we'll have of pulling the PV chunk further nw and this then has an effect of whether we could get the Russian ridge to extend over the top of the troughing to meet up with the displaced Azores high. 

        

 

[Duane S.]

Another day, no change at all on the general theme. I'm still seeing this as a 3 shot (in terms of amplification waves) evolution.

Shot 1, sets the scene (no great shakes, cold PM airflow), shot 2 (in view D9 / D10) close but no cigar (expect snow in the North, mainly on the hills but also at lower levels), shot3 (around 13-15 days time) our big chance to get some proper cold in and HLB forming somewhere above the UK.

Outside chance shot 2 may prove enough but I think probably not at the moment.

[pyrotech]

Well the GFS, ECM all looking promising

 Here is a tweet from Ian (bottom of this post in bold)

I think basically the met office are also seeing potential of what we are seeing but as Ian says still some uncertainty

 

I read this as maybe not only is there some room for movement away but also maybe initially a fairly dry feed is also possible with costal areas  getting highest potential

We all know on here that shortwaves and troughs are unlikely to really show up until very late on

Anyway Ian's actual reply is below so you can read it as it was said

 

Ian Fergusson

@fergieweather

Jan 05

 

@Floodwarncouk models have been toying for a few runs now with broad idea of a more pronounced NW'ly to N'ly outbreak, but still early days

[Decemberof2010]

Nice to see you back posting the cold charts Frosty

Fingers crossed you'll be posting a lot more cold charts in the coming days!!!

 

[Tamara]

Probably not the best time to post this and *appear* to burst any NWP virtual bubble over latest operational roll-out with some boring analysis, but nevertheless such that is intended to be objective and useful.

The concerns expressed in the posts of late autumn and start of winter related to breakdown of +AAM/weak Nina disconnect and w/QBO stratospheric tightening through December have come to haunt - flying in the face of repeated alluring NWP ensemble suites which continued, periodically, to tempt many cold weather model watchers right up to the turn of the year. So further (apparent) kill-joy, however realistic it may be, is risked here.

The evidence has been gathering through December to keep harbouring and increasing those early doubts, and some of the latest stats confirm exactly why we are struggling to carve out a consistently sustained upper cold pattern in the UK with a lower angular momentum state establishing and a seasonal vortex which has harnessed the assistance it needed.

The Southern Oscillation Index, in contrast to the ENSO disconnect of autumn, is now steadily accumulating positive figure returns - typical of a Nina imprint on the atmosphere. However weak that is set against a neutral ENSO ocean state.

https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/

The atmosphere/ocean disconnect process (declining SOI) reversing since start of winter. The disconnect period was when the initial starter destabilisation process on the early season vortex was created

 

Easterly wind/+ve Outgoing Longwave Radiation (OLR) anomalies are evident close to the Dateline in the Pacific - also consistent with the weak La Nina signature that has been evolving through December on the atmosphere. Note also that currently the most organised tropical convection is indicated in the East Indian Ocean - further evidence to point to current lower atmospheric angular momentum state

 

The Global Wind Oscillation has slumped and stagnated back to a very low amplitude and indeterminate orbit phase, consistent with lack of help from the tropics (MJO) to add westerly component to the atmospheric circulation and help amplify the pattern sufficiently downstream to create more sustained and meaningful cold air advection - than attempted topplers

Never to be taken completely at face value anyway and the actual GWO signal is very weak, but this composite for GWO Phase 1 into 2 of mid latitude high pressure ridging extending from Atlantic to SW UK not a bad reflection of short term (to day 5) NWP in terms of height anomaly, albeit troughing across N Atlantic not so clearly in evidence

              

 The question further out is how much amplification is available to enable troughing to dig through Scandinavia along with greatest coldest air advection. To now the coldest upper air has continued to be taken south east through central/Eastern Europe into the Eastern Med, and the UK struggling to tap into more than transitional Polar Maritime air as the Jetstream flows around the Atlantic/Azores Ridge 

Notwithstanding the evenings NWP which has unravelled as I type and suggests what is probably, imo, the very maximum and temporary bandwidth that could be extracted from this very ordinary typical January La Nina mid latitude high pattern, what can weaken the Azores Ridge and add further amplification and make some of the FI extrapolations that have been/are being seen closer to reality?

Frictional Torque enhancement is indicative of rising angular momentum tendency, southward moving tendency of the jet and greater amplification flux enablement. These factors relaxing the grip of the sub tropical ridging as dictated by the upstream Pacific Nina pattern of anomalous ridges in both the NE Pacific and the Atlantic

Eastward propagation of tropical convection into the Western Pacific will forge such helpful trends closer but such an evolution is not as easy as the late autumn when the extra tropics were more co-operative and receptive to additions of westerly winds and poleward rossby wave propagation (amplification) heading eastward through the Northern Hemisphere. (This process was halted just as it was about to deliver - hence the seeming consensus for amplified cold early on).

For the reason why it might not be totally straightforward, we return to the OLR anomalies map. MJO activity has to negotiate the easterly wind anomalies present in the Pacific which would tend to snuff out the convective wave through the wind shear evident in front of it. On this basis we can look at the W&H plots and extract early caution as to how attempted eastwards propagation might progress as  we head through January.

 

 

 

As much tropospheric forcing as possible will be needed to create amplification and also agitate the wQBO assisted vortex (sounds all to familiar).  Hopes maybe rest on further retrogression of the Pacific ridge allowing the vortex position to shift NW,wards. This allowing some height rises to the NE to arrive via the back door courtesy of greater amplification arriving from upstream. Its in this sense that increased amplitude of any convective activity stemming from the Pacific is most required and welcomed.  Seasonal wavelength changes as we head deeper into the second half of winter mean that such an evolution becomes more and more important to enable eastward propagating convection (and hence the downstream amplification)

Otherwise this could well continue to be a season of mid latitude settled high pressure alternating with less settled westerlies and truncated chilly NW'erlies.

@chris55 I think that it has to be pitched against the macro factors which haven't allowed the degree of amplification required. Close yes, but the weather patterns don't subscribe to being "unlucky" in terms of human wishes and preferences The fact is that the small degree of split energy to the southern arm of the Jetstream c/o the small area of low pressure close to the Azores (which supported the Atlantic ridge above it but ultimately destined to become the short term cut-off feature that indeed verified) was outweighed by the upstream energy c/o slightly supressed low AAM state and w/QBO vortex

@Steve Murr  Its worth reading the post which is detached from any emotional preference. It doesn't exclude any cold possibilities at all, what it does is continue to offer pointers to what can go wrong which this season proves again to be sensible and wise. Maybe also it tries to pitch probability against chasing lost causes. I am sure you will agree that a lot of wasted energy (and participant expectation) can attract attention to oneself, but ultimately be wasted and (in the second instance) over exposed and left unrequited..

Edited January 5, 2017 by Tamara

[weathermadbarnsleylad]

53 minutes ago, Purga said:

Very nice ECM 240h chart

Not particularly cold uppers but the synoptics are packed with potential

 

 

[Stuie]

28 minutes ago, nick sussex said:

On current form you'd back the ECM over the USA against the GFS. Remember all that drama with shortwave energy in the Atlantic that the GFS had this was effected by its flatter shortwave running east across the USA which downstream led to a messier picture, its still flatter than the ECM but has made corrections during the day.

We're again dealing with flatter versus more amplified. The key timeframe for us is T168hrs onwards if we want to have hopes of a happy ending. I've done one of my now infamous paintjobs to illustrate this.

ECM T168hrs                                                    GFS T168hrs

                

The more amplified the upstream pattern is at this stage the better chance we'll have of pulling the PV chunk further nw and this then has an effect of whether we could get the Russian ridge to extend over the top of the troughing to meet up with the displaced Azores high. 

        

 

Nick, from what I have seen States wise your 2nd chart (GFS) appears to be one touted. I`m not going to name names but a "said" name expects a "warm" up over there which would relate to chart 2 more than chart 1.

[Frosty.]

8 minutes ago, Decemberof2010 said:

Nice to see you back posting the cold charts Frosty

Fingers crossed you'll be posting a lot more cold charts in the coming days!!!

 

Thanks..hopefully I will..encouraging signs for snow starved coldies from around this time next week onwards. This week has been / is nice and cold with widespread frosts but hopefully, after the milder nondescript blip this weekend we will see a marked change setting the stage for snow and we will see snow if the 12z runs are on the right track.

Edited January 5, 2017 by Frosty.

[Dancerwithwings]

UKMO 12z 144h

168h

180h

http://www.weathercharts.org/charts.htm

[weathermadbarnsleylad]

I must say both ecm and GFS looking good for late next week onwards I'm gonna have to take with a pinch of salt at min if still shows on the 12z Sunday il be a lot happier been led up that snowless garden path too many times this winter but is looking good. 

[nick sussex]

4 minutes ago, Stuie W said:

Nick, from what I have seen States wise your 2nd chart (GFS) appears to be one touted. I`m not going to name names but a "said" name expects a "warm" up over there which would relate to chart 2 more than chart 1.

The ECM also warms up most of the USA but its before then that theres these differences. The GFS has already had two failures upstream versus the ECM in the last week. I'm not saying the ECM will verify just that if I had to put my last pound on a model to have the correct pattern upstream then upto T168hrs it would be the ECM not the GFS. Even NCEP in their past discussions have commented on the flat bias of both the GFS and the GEFS.

[legritter]

Evening gang ,nice to come on here and read some interesting posts ,and see some wintry looking charts ,probably the best position we have been at this winter .let's hope for some upgrades over the coming days ,cheers gang 

[blizzard81]

21 minutes ago, Tamara said:

Probably not the best time to post this and *appear* to burst any NWP virtual bubble over latest operational roll-out with some boring analysis, but nevertheless such that is intended to be objective and useful.

The concerns expressed in the posts of late autumn and start of winter related to breakdown of +AAM/weak Nina disconnect and w/QBO stratospheric tightening through December have come to haunt - flying in the face of repeated alluring NWP ensemble suites which continued, periodically, to tempt many cold weather model watchers right up to the turn of the year. So further (apparent) kill-joy, however realistic it may be, is risked here.

The evidence has been gathering through December to keep harbouring and increasing those early doubts, and some of the latest stats confirm exactly why we are struggling to carve out a consistently sustained upper cold pattern in the UK with a lower angular momentum state establishing and a seasonal vortex which has harnessed the assistance it needed.

The Southern Oscillation Index, in contrast to the ENSO disconnect of autumn, is now steadily accumulating positive figure returns - typical of a Nina imprint on the atmosphere. However weak that is set against a neutral ENSO ocean state.

https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/

The atmosphere/ocean disconnect process (declining SOI) reversing since start of winter. The disconnect period was when the initial starter destabilisation process on the early season vortex was created

 

Easterly wind/+ve Outgoing Longwave Radiation (OLR) anomalies are evident close to the Dateline in the Pacific - also consistent with the weak La Nina signature that has been evolving through December on the atmosphere. Note also that currently the most organised tropical convection is indicated in the East Indian Ocean - further evidence to point to current lower atmospheric angular momentum state

 

The Global Wind Oscillation has slumped and stagnated back to a very low amplitude and indeterminate orbit phase, consistent with lack of help from the tropics (MJO) to add westerly component to the atmospheric circulation and help amplify the pattern sufficiently downstream to create more sustained and meaningful cold air advection - than attempted topplers

Never to be taken completely at face value anyway and the actual GWO signal is very weak, but this composite for GWO Phase 1 into 2 of mid latitude high pressure ridging extending from Atlantic to SW UK not a bad reflection of short term (to day 5) NWP in terms of height anomaly, albeit troughing across N Atlantic not so clearly in evidence

              

 The question further out is how much amplification is available to enable troughing to dig through Scandinavia along with greatest coldest air advection. To now the coldest upper air has continued to be taken south east through central/Eastern Europe into the Eastern Med, and the UK struggling to tap into more than transitional Polar Maritime air as the Jetstream flows around the Atlantic/Azores Ridge 

Notwithstanding the evenings NWP which has unravelled as I type and suggests what is probably, imo, the very maximum and temporary bandwidth that could be extracted from this very ordinary typical January La Nina mid latitude high pattern, what can weaken the Azores Ridge and add further amplification and make some of the FI extrapolations that have been/are being seen closer to reality?

Frictional Torque enhancement is indicative of rising angular momentum tendency, southward moving tendency of the jet and greater amplification flux enablement. These factors relaxing the grip of the sub tropical ridging as dictated by the upstream Pacific Nina pattern of anomalous ridges in both the NE Pacific and the Atlantic

Eastward propagation of tropical convection into the Western Pacific will forge such helpful trends closer but such an evolution is not as easy as the late autumn when the extra tropics were more co-operative and receptive to additions of westerly winds and poleward rossby wave propagation (amplification) heading eastward through the Northern Hemisphere. (This process was halted just as it was about to deliver - hence the seeming consensus for amplified cold early on).

For the reason why it might not be totally straightforward, we return to the OLR anomalies map. MJO activity has to negotiate the easterly wind anomalies present in the Pacific which would tend to snuff them out through the wind shear evident in front of the convection wave. On this basis we can look at the W&H plots and extract early caution as to how attempted eastwards propagation might progress as  we head through January.

 

 

 

As much tropospheric forcing as possible will be needed to create amplification and also agitate the wQBO assisted vortex (sounds all to familiar).  Hopes maybe rest on further retrogression of the Pacific ridge allowing the vortex position to shift NW,wards. This allowing some height rises to the NE to arrive via the back door courtesy of greater amplification arriving from upstream. Its in this sense that increased amplitude of any convective activity stemming from the Pacific is most required and welcomed.  Seasonal wavelength changes as we head deeper into the second half of winter mean that such an evolution becomes more and more important to enable eastward propagating convection (and hence the downstream amplification)

Otherwise this could well continue to be a season of mid latitude settled high pressure alternating with less settled westerlies and truncated chilly NW'erlies.

 

                             

Oh dear! You are fast becoming the grim reaper of this forum lol. Seriously though, your post may help to keep us coldies grounded. We have all been bitten too many times this season so far.

[Purga]

Some decent cold clusters showing in the EC ENS