Model output discussion - Jan 3rd onwards

[Notty]

ECM 12z T_240

Vortex in shreds

Nothing like the GFS(P) at the same time

Edited January 6, 2021 by Notty
Amended

[MKN]

2 minutes ago, Notty said:

ECM 12z T_240

Vortex in shreds

Nothing like the GFS(P) at the same time

Not a good chart for the UK, South Westerlies with two more low pressures ready to wind up and bring more of the same.

[mountain shadow]

1 minute ago, MKN said:

Not a good chart for the UK, South Westerlies with two more low pressures ready to wind up and bring more of the same.

I'm personally happy the way things are going.

At some point the Atlantic will amplify and we'll be in.

[TSNWK]

4 minutes ago, Notty said:

ECM 12z T_240

Vortex in shreds

Nothing like the GFS(P) at the same time

Which I think we should take as a positive..  uncertainty could be our way out from the current situation of the vortex fragmentation post SSW not landing for uk coldies.. can the models truly predict such events with accuracy..

[Griff]

GEM 12Z Leading the way!  

[Anthony Burden]

ECM continues with the high pressure especially in the south,in line with GFS possible 

to ridge north in my opinion.Frost and fog could be on the agenda for the south next week 

Matt Hugo saying watch out for the  15 th to 20th of this month for possible change.

 

[SLEETY]

Noting the Arctic High developing in the gem and ecm runs, let's hope that continues in the coming days, when the colder runs should start appearing 

[ICE COLD]

Let’s add the JMA 12z into the mix . 
 

T192 

[Froze were the Days]

One of the poorest ECM D10's I've seen in some time...and really puts a bit of energy into the Atlantic down to the south west which would shunt the cold air away to the east, not sure how reliable it's been at that range?

[danm]

Seems like a growing trend to build amplification north of the U.K. next week and for a PV chunk to drop into W Russia/Scandi. Good trends, as yet not falling into place for the UK on the ops with the Iberian high still being the main spoiler and a little too much energy to our NW. Plenty to keep us interested though, even if we are almost nailed on to endure a less cold/milder spell next week. 

[Kasim Awan]

1 minute ago, danm said:

Seems like a growing trend to build amplification north of the U.K. next week and for a PV chunk to drop into W Russia/Scandi. Good trends, as yet not falling into place for the UK on the ops with the Iberian high still being the main spoiler and a little too much energy to our NW. Plenty to keep us interested though, even if we are almost nailed on to endure a less cold/milder spell next week. 

Without a trend for heights to fall to our south, the build in amplification will most likely be flattened out. This as the Azores prevents a southerly splitting jet. Really need very strong blocking imo to oppose this strong Azores signal.

[Matt H]

At least the CFS manages to deliver the goods.

 

Edited January 6, 2021 by Frosty Winter

[Windysun1]

6 minutes ago, danm said:

Seems like a growing trend to build amplification north of the U.K. next week and for a PV chunk to drop into W Russia/Scandi. Good trends, as yet not falling into place for the UK on the ops with the Iberian high still being the main spoiler and a little too much energy to our NW. Plenty to keep us interested though, even if we are almost nailed on to endure a less cold/milder spell next week. 

How accurate are the forecasts for predicting where the PV chucks drop?

[Vikos]

15 minutes ago, Froze were the Days said:

One of the poorest ECM D10's I've seen in some time...and really puts a bit of energy into the Atlantic down to the south west which would shunt the cold air away to the east, not sure how reliable it's been at that range?

Don't just stare on those main runs, evalute the ENS and EPS and also the Clusters. This will give a lot more information where the path leads. Synoptics is a very complex thing....

[Purga]

Notice the mean getting drawn down after mid month by more and more colder runs.

The trend is our friend..

Edited January 6, 2021 by Purga

[syed2878]

3 hours ago, Tamara said:

A seasonal absentee by-stander in all this - but a one-off offering from me.

Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some interesting discussion if the snow goggle biases were put away for a moment.

This winter has seen a much greater disconnect of the atmosphere to the La Nina base state than anticipated. Intense seasonal bias confirmation processes customarily disguise this, but if one is prepared to stay detached from that, it has been something of a surprise to the neutral diagnostic elements enthusiast. 

What is meant by this disconnect? In simplest terms, much greater poleward rossby wave propagation has taken place than under a more 'connected' and stable w/QBO La Nina  low angular momentum regime in early winter would usually provide. The autumn itself, heading into the first few weeks of winter, saw (overall)  a much more typical EL Nino type presentation, with a downstream configuration that until the festive period did not, mostly apart from a brief period, feature the expected sub tropical Atlantic ridging and instead a configuration of warm air advection processes c/o an amplified Atlantic trough and downstream European ridging. This alignment ultimately provided the feedback catalyst to assist  the wave breaking that has instigated instability of the polar field, albeit reversal of zonal winds are restricted closer to 10mb level.

Interestingly, global relative angular momentum has been slowly falling since the festive period and continuing into the first days of January.

 

 

The Global Wind Oscillation, a phase plot depiction of wind-flow inertia between the tropics and extra tropics has slowly slipped towards the La Nina attractor phases - reflecting greater harmony with the ocean base state.  

 

The effects of falling momentum are to switch greater inertia into the polar jet from upstream. The initial manifestation of this c/o the weakness across the polar field has been for the usual feed of this inertia to proceed eastwards closer between 50 and 60N to be somewhat roadblocked, and instead looped around the pole and create the blocking structures close by to the NNE and linked to the amplification of the more Nina-esque Atlantic ridge.

However, the difficulty comes with how these blocking structures respond to continued displacement/split processes within the polar field at the same time as angular momentum continues to fall ( *in the shorter term absence of any westerly inertia supplied by tropical forcing)  and much more closely match the underlying base state. This is where the post under reply holds the interest I was mentioning at the beginning and should be treated with better respect

It is perfectly conceivable, at least for a time, for polar jet energy to make greater inroads eastwards at mid latitudes, as the polar field continues to re-organise and as the period of time approaches where zonal winds, at least temporarily, are increased within the lower stratosphere and troposphere boundary. Not to any great levels  by any means, as the overall structures continue to look weak and unstable-but enough to allow a more westerly induced pattern to prevail, at least for a time, with a more traditional Nina-esque Atlantic ridge centred close to the west or south west and ebbing and flowing within the bandwidth of displaced vortexing to the NE.

*The further wildcard is intraseasonal MJO forcing. In keeping with w/BQO Nina-esque regimes, and linked to known periodicity timelines for high frequency activity - it is worth watching out for signs of an eastward convective parcel progression attempting to negotiate the Pacific later in January or possibly into February.    A further variable that could see a sudden and quite dramatic surge in atmospheric angular momentum, tipping the resultant synoptic patterns even more their head.     Impossible obviously to know where and when these may set up hemispherically at this stage - but high impact synoptics are conceivable with very large temperature boundaries across the mid latitudes.

That is all for another time. Perhaps.  Closer to home, putting preference biases completely aside, whatever they maybe - from a neutral meteorological point of view its a very tricky time for numerical modelling ahead which encompasses the ensemble suites and representative upper air anomaly charts . The overriding diagnostic (GWO tropical>extra tropical momentum relationship vs a very disjointed polar field)  susceptible to highly erratic global wind-flow patterns at the tropopause boundaries and creating precipitous jumps in synoptic patterns, at mid latitude,... in either direction.

Falling momentum and weak high frequency MJO activity for the foreseeable future (* above caveat aside ) does weight probabilities towards a more typical sub tropical regime and polar jet flow arcing around this. At the same time and as can be seen, there are very hard to keep tabs of pockets of weak inertia popping op at relatively short notice closer to 60N which quite easily could stall westerly inertia and create subtle eddies within the jet which build very weak 'cold' ridges and derail the movement of troughs from west to east and restrict warm air advection

At present, no outcome is to be discounted or dismissed out of hand, and any discussion should be unclouded by bias preferences and be open minded to the even greater than usual uncertainties. That is not sitting on the fence - its honest objectivity in the face of highly sensitive factors that require a watching brief ,rather than any impetuous call for the sake of wanting to appear confident in appealing to a specific popular outcomes.

 Fantastic and excellent post again tomorrow thank you it is refreshing to get a unbiased view

Edited January 6, 2021 by Blessed Weather
Comment removed

[Battleground Snow]

Improved mean at 240.

Hopefully someone will share the extended

Edited January 6, 2021 by Battleground Snow

[Frigid]

Instead of seeing cold snaps this month, we're seeing a "warm snap". Looks like this milder interlude will probably last for 2-3 days according to the GFS ensemble mean and with every GFS run today, it looks like the mean is going below the 30yr average line. Probably a sign to something interesting to come.

[syed2878]

1 hour ago, Scott Ingham said:

Temporarily with a caveat that this season has seen short term rises in aam from pockets of inertia around 60n which get modelled at short range. I believe Matt Hugo has a tweet about this. Also the ssw has the effect of disrupting westerly energy and creating home grown amplification. The interesting element is the low base state aam interacting with high pressures carved by ssw. This is extremely hard enough to model to as she says not give any confidence to any side of the camp. Warm or cold.

The thing that may tip things in our favour is the expected movement of an mjo cycle into the western hemisphere back end of january which could bring us out of -aam into +aam. 

So in summary

Short term westerly momentum potentially hitting a brick wall against the ssw, pockets of easterly winds from autumn at 60n and an active mjo wave.

Basocally end of january is 50/50. Both camps in the game as her last paragraph suggests.

So the post of "normal winter conditions favroured" wasnt the over riding message no

 And yet scott the update from Exeter if you look or read it today doesn’t really be any good news to be honest more south-westerly in the extended forecast the colder for the north that tell me to an extent that this SSW would not be favourable for us here I hope I am wrong and we get to see the effects of the SSW in the model output soon. 

[PolarWarsaw]

9 minutes ago, syed2878 said:

 And yet scott the update from Exeter if you look or read it today doesn’t really be any good news to be honest more south-westerly in the extended forecast the colder for the north that tell me to an extent that this SSW would not be favourable for us here I hope I am wrong and we get to see the effects of the SSW in the model output soon. 

I'm sure we have done this enough now.

This is the model thread - not the discuss the daily Met Office update thread.

Secondly, again - these updates change every single day and other than the odd generic theme are about as much use as a chocolate fireguard on the surface of the sun. It works both ways, for cold and mild. They reflect the nature of the days model output and normal climatological bias. They are also extra 'useless' in periods where the weather is volatile. 

Edited January 6, 2021 by PolarWarsaw

[PolarWarsaw]

19 minutes ago, syed2878 said:

 Fantastic and excellent post again tomorrow thank you it is refreshing to get a unbiased view for once in this forum I think there’s too many hopecasting 

I don't think many people are hope casting, perhaps you are and that's why you are posting with such a down beat tone to your posts?

At no single time this entire winter has anybody in a position strong enough to give you a certified, guaranteed forecast said there is an ice age inbound. Each and every person has discussed what is 'possible'. Thus, using terms like 'could', 'can', 'might'. 

Therefore, all posts regarding this issue are an opinion and everyone is allowed one. 

Edited January 6, 2021 by PolarWarsaw

[Osbourne One-Nil]

Thank you everyone - I understand that for some they fear they might have to wait a bit longer until they can start looking for the end of the next cold spell, but the more this thread stays on topic the more use it is to everyone!

[Guest]

One thing I do know from years of  looking at these charts is when it starts showing deep cold for the yanks it very rarely is wrong and the trouble is when they're in the freezer we're in the cooker!

[WINTRY WALES]

4 minutes ago, Snowmut said:

One thing I do know from years of  looking at these charts is when it starts showing deep cold for the yanks it very rarely is wrong and the trouble is when they're in the freezer we're in the cooker!

Has there ever been periods where the US and us in the UK are in a cold (very cold) , snowy weather for lengthy periods of time??

Edited January 6, 2021 by WINTRY WALES

[NeilN]

Just now, WINTRY WALES said:

Has there ever been periods where the US and us in the UK are in a cold (very cold) , snowy period for lengthy periods??

I think early 2010 had us both in the freezer? Possibly some of the 1980s ones? I know Feb 1991, the UK was in the freezer and they had an unusually mild winter.