Model discussion highlights

[bluearmy]

18 minutes ago, northwestsnow said:

Well the SPV is pretty much done by the end but is GFS right ?

It’s currently 2808 dam. By the end its sits s svallabard toward E greeny at 2880 dam. Unless we have further waves etc upwelling then I doubt it’s done.  The ec op has it at 2840 day 10 and the eps mean at day 15 is 2880dam so gfs op looks reasonable re the depth of the spv in two weeks. 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795927

[Mike Poole]

47 minutes ago, KTtom said:

..to add to my negative mood this Sunday evening...the farthest reaches of the gfs backs up what Blue (i think) said this morning of the dangers not having a split...that SPV looks ready to regain control once the series of warmings die out??

Yep, looks like it.  

Since Friday morning, when about half of GEFS were showing a technical SSW (I called it at the time, teach me to count my chickens!) - that has reduced on every run, to zero now!

Look at the pressure chart for the same time T384:

Not a good position, to put it mildly.  

You just couldn’t make this winter up!  The trop vortex has never let the strat vortex rule the roost, and has been as weak as you’d like, but most of the time conspired to leave us in the mild, and even when it hasn’t there’s no snow, so what’s the point?  Now, the trop blocking has weakened the strat vortex, but not enough, the result being forcing down a renewed burst of westerly winds, you can see it here:

The warming is at the top (yellow), will increase the zonal winds lower down (red arrows), which will probably lead to a reversion to +NAO - as shown in most GFS runs.  And then, get this!, then the warming runs out of steam, leaving the remains of the vortex in a bad place.  Leaves us coldies relying yet again on the MJO when the westerly burst has gone through.  

Sorry about the negative post, in future winters that are like 2019/20 we’ll look back at this one, and ask ‘how could we lose from here?’.  And I offer no explanation other than bad luck…

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796072

[Allseasons-Si]

+20c on the jma this evening atop

Edit: infact i think that +20c is off the scale(black hole),meteociel need to extend there color pallette

and still the gefs ens mean geo pot heights showing +ve heights to our NE,so i am still not worried about writing anything off yet

sorry for the quick post,just been busy of late.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796103

[Cambrian]

By means of playing an intricate game of pass the parcel (of successive low pressure systems), the much maligned Canadian PV, along with its newfound mate - the Scandinavian trough, is doing quite the number on the Atlantic ridge, between day 6 and day 10 on the 12z ECM operational run.

At day 6, the ridge is in the box seat, but a little low spins out of southern Greenland, deepening over Iceland by day 7, consolidating and extending the Scandinavian trough at day 8. Meanwhile, another little low has been ejected from south of Greenland, which deepens sharply and moves to the south of Iceland at day 9, to be just to the north of Scotland by day 10, just as yet another low is beginning to curl around the south of Greenland. 

 

In the meantime, the Atlantic high has weakened markedly, from 1045mb to 1030mb, it’s been squeezed south, flattened, forced to ridge west, with lower heights appearing to the west of Iberia. With all the energy it’s spinning out in those little lows, the Canadian PV lobe is itself diminished by day 10, with its influence moving west away from Greenland. 

And looking at that upper trough hanging south to the west of Iberia, shunting the heights to the east of it into the Mediterranean, it’s not too far-fetched to suggest that day 11 would well have featured a low over southern Scandinavia, a consolidated Scandinavian trough and a northerly flow over the UK and Ireland, part of a cross-polar flow from the Bering Sea. Little reason either to suspect that the next low in the sequence, on a more southerly track, will not also jump the Canadian ship, merge with the Scandinavian trough and drag it even further south. 

A really interesting operational run - with an iterative, attritional approach to ultimately getting some Arctic air back into northwest Europe. 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796163

[nick sussex]

The ECM is much improved in its later output from last night.

The day ten shows the latest upstream low facing a struggle to move east as it begins to sharpen up.

Earlier it almost tries to develop a slider between day 8 and 9.

Essentially this is turning into a battle between the main PV located over ne Canada and forcing from the ne .

So the PV feeds energy into low pressure which deepens wants to move more ne against that forcing .

The PV is struggling more by day ten as it’s becoming stretched , much depends on whether we can see more amplification develop across Canada .

This can engage the PV and latch onto it and can help develop more amplitude over eastern Canada .

The effect is to direct more energy se as you can see in its day ten .

 

Let’s hope this isn’t another false dawn ! 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796243

[jethro]

15 minutes ago, billy said:

Yes -7 hear again last night. Although we've had no snow this winter, I can't remember the last time we had a winter with so many hard air frosts with temps below -3 ....Yet strangely enough I saw some daffs in flower in the village yesterday

 

I wouldn't pay any attention to the daffs, so many varieties have been bred, it's now possible to have them flowering from December all the way through to April. Nothing to do with weather, depends upon the variety.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796265

[Eagle Eye]

It's looking less and less likely that a major SSW will occur but we're going to get a fairly weak Strat Vortex for a time I suspect so that's a small plus. It's still possible but very unlikely at the moment in my opinion. Things trending in the wrong direction but not unsalvageable so it's still one to keep an eye on. Anyway, a little animation via Dr Simon Lee from a few days ago, cannot stop watching it...

 

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796221

[Paul_1978]

This may have already been mentioned, apologies if it has. Marco from the Met Office tweeted that if a warming does occur then it is expected to have no impact on our weather as the strat and trop are not coupled. 

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796251

[Mike Poole]

10 minutes ago, Drifter said:

Does one cluster indicate rock solid certainty? Or the opposite?

On occasions one cluster can mean near certainty, especially if in the early timeframes.  More usually, in my experience, though, it means the exact opposite.

4 minutes ago, RainAllNight said:

I will defer to @Mike Poole if he knows any better, but I think it's the opposite:

"When the ensemble distribution is sufficiently homogeneous the cluster algorithm cannot partition the ensemble in a meaningful way, for these cases the ensemble member that better represents the ensemble mean is shown." - says the blurb beneath the cluster charts on the ECM website

Actually wait, "homogenous" means similar doesn't it... so maybe it does show a strong consensus?

Here, homogeneous is more likely to mean ‘not lumpy’!  So it is not saying there is little uncertainty, just that the algorithm cannot discern a small number of distinct, different evolutions within the ensemble set.  And this can happen when there is very large uncertainty, as well as when there is good confidence in a single evolution.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796288

[Eagle Eye]

Despite the warming best attempts, the Vortex still keeps a lot of its baratropic stability with an especially inertial Vortex on its southern most extent as the Wave-1 dominant mode displaces the initial Northern baratropic stability. So that does create an unstable inertial pattern over Eurasia-North America but I don't think it's a strong enough baroclinic Wave to be able to cause a split. This is probable the big reason why displacements can be recovered from. The thermal dampening of Wave-1 with a baratropic pressure gradient of the main Vortex though displaced will allow the zonal-mean to ramp up as the Vortex rapidly balances itself back up towards the initial inertial pattern. Things like to be stable and without a sudden reversal through a split, it's unlikely that the recovery process won't happen quite quickly. Of course we have the warming Wave displacing the thermal-pressure stability so some attempt at a baroclinic instability induced split is attempted via the outer riding Wave but without Wave-2 its simply a fairly weak attempt without much of a steep angled gradient of attack and therefore nothing to really split the thermal-pressure gradient. This meaning that a split is looking very unlikely and a recovery likely once the vertical Eddy's stop being driven so unless we can get a secondary Wave somehow push in like near Scandinavia very quickly which none of the models are really showing, then the Vortex is likely to recover.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796305

[Cold Winter Night]

1 hour ago, Allseasons-si said:

the NWP have been towting at this(control mainly),and i just want to ask a question as it's totally over my head,...do NWP'S(the models) take into account the strat warmings?

i am sure they lag or lack on the subject and i have seen a quick turn in the models when they catch up.

Well, yes. After all, the stratospheric charts and profiles shared by many on here come from the same models as the tropospheric output.
Without the models we would not have known about the possibility of a strat. warming in the next few weeks until it appeared in observations just days ago.

So if the warming happens early enough on the run, you can see the modelled influence of it descending (or not) afterwards.

Caveats are that there is less observational data than from the troposhere to begin with, and, depending on the model design, often less resolution and less vertical layers.

The thing about models having to catch up with strat warmings is more that the sudden time, location and height sensitive changes (from a stratosphere that is usually very stable compared to the troposhere) can make model solutions go all over the place.

Think of a ball rolling down a field. It's not too difficult to predict where the ball will be 5 seconds from now. But then add a player (downwelling wave) that will kick it along its way, but you don't know exactly when, from what direction and with how much force yet, nor do you know if another player (like a blocking high) will be in the right time and place to also hit the ball. Now forecasting the location of the ball 5 seconds from now becomes a more difficult task...

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796226

[nick sussex]

It’s best to be cautious when the models show any northerly whilst you still have a strong PV located in ne Canada .

What often happens is the models often underestimate this and as you tick down things get shunted eastwards .

On the reverse side here we’re seeing the Arctic high trying to keep troughing over Europe .

Its a case of eastwards energy v southwards energy and currently this meets near the UK .

If the Canadian PV can weaken , first signs is an elongation of that and some amplification upstream can aid in pulling this further nw .

If you can separate that from feeding Atlantic low pressure you have a better chance of some trough disruption sending energy se to the west of the UK .

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796369

[bluearmy]

24 minutes ago, northwestsnow said:

GEM looks to follow UKMO 

 

Did someone diss the gem ?

the weakening upper vortex should now be in the starting data on the model runs. Tomorrow we see reversal at the top of the strat around the pole. So I’m now looking for less expected developments in model runs in the 7 to 10 day period. Yes i know this is too far out to be more than watchable at the moment but if we are to see the nwp change it’s current evolution in response to any changes high up then if we don’t see them within a couple days on the modelling then they aren’t going to happen. 
 

I put forward the gem day 10 as the first ‘unexpected chart’ 

(and you have to be looking hemispherically for these developments) 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796455

[Mike Poole]

ECM very similar to GEM at T240, with that feature into the arctic from the pacific side.  Interesting - maybe sniffing something, and difficult for the whole trop vortex to reform as one from there.

GFS altogether different.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796511

[Northernlights]

13 minutes ago, BLAST FROM THE PAST said:

What’s of interest to me is how cold we are, have been with fairly benign set ups…especially to recent years.  It has got really cold, coldest Jan night for donkeys down here from a fairly nothing set up.  And projected, there’s some punchy cold to come from the ‘useless’ northerly topplers.  Not what ‘some’ profess

 

 BFTP

Read somewhere that Australia having a cool summer. Aurora Storm and I speculated at Christmas whether the huge amount of water vapour sent into the Southern  Hemisphere atmosphere from  the South Pacific volcano a year ago might have some small effect on world weather patterns. I believe some water vapour was shot 93 miles up escaping into space.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796653

[bluearmy]

9 hours ago, Vikos said:

Are there any charts for the coupling of tpv and spv available?

this is the gfs op 

Vertical cross u-mean + EPflux

WWW.WEATHERISCOOL.COM

the coupling thing is also complex 

we had a decoupled strat / trop through to the end of December. The upper strat was average to above average and yet the lower strat and trop were decidedly slack 

then we saw the upper strat go into overdrive and it was impossible for the lower strat to avoid the downward pressure from that increase - where else can it go ??

inevitably, once the lower strat goes stronger, the trop can’t avoid an uptick in zonal flow. 

now we see a huge weakening high up and as per the strengthening from higher up, a consequence is the stronger westerlies which were high up are being forced down into the lower strat. There is a notable reversal above 75N but it’s fairly short lived below 10hpa and therefore very unlikely to force any type of reaction further down into the trop regarding any downwelling ‘reversal waves’. tomorrow sees the flow actually go negative in the starting data so we have another day to be 100% certain that there isn’t a late surprise on this into week 2 trop output. 

the 00z runs cut off the n pacific ridge which isn’t great. The eps look to be honing onto a notable nw euro trough end week 2 - how far south that can get not clear.  This trend away from the Azores/Atlantic ridge has been fairly well signalled across the extended fi modelling.  I guess the usual question will be re the euro heights 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796730

[Cold Winter Night]

1 hour ago, mushymanrob said:

I think the summary @Quicksilver1989 and @nick sussex gave in their outlooks is pretty much what the EPS and NOAA charts are suggesting for early February..

It's also a very close match to the Niña January MJO 3 composite, especially in the Western Hemisphere (N-America/Atlantic/Europe).

The Pacific-Alaskan-Arctic heights are a standout feature of the February MJO 2/3 composites, by the way.

It's not unthinkable therefore that we may see more heights to our North appear in the extended output, especially if the MJO lingers a bit in the MJO 3 phase.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796764

[Singularity]

Frictional torques have just started responding to the highly active MJO crawling through phase 3 on route to 4.

So begins the lengthy process that will lead to the next *chance* (can't be stressed enough) of a high latitude blocking episode, roughly around mid-Feb.

Odds of that will be increased if the stratospheric polar vortex is near or below normal strength as per current extended model means. Otherwise blocking highs may be held more toward mid-latitudes, resulting in another spell similar to what we have now.

In the meantime, a more zonal trend is indeed likely in early Feb but I'm not convinced it will be all that unsettled. A high amplitude MJO phase 3-4 on top of a La Niña background should inflate the Azores High to an impressive extent, feasibly enough to maintain an at least transitory influence over much of N. Europe including S UK.

There is however a risk that the displaced polar vortex influences the troposphere enough to fire up some very deep Atlantic lows & throw them up against the strong ridging, resulting in extremely steep pressure gradients i.e. a threat of really strong wind events.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796808

[Catacol]

Have just posted in the strat thread some thoughts - this extended EPS image says it all really.

Time to go find some other distractions for a while. Strat and Trop drivers all wrong for high lat blocking for the next 2-3 weeks. Live by the sword, die by the sword....so when the teleconnections point +NAO and no cold blocking then no sense ignoring the same tools that are used to raise hope at other times. We needed a strat event of significant proportions and helpful shape to overcome the 'wrong' phases of the MJO but the worst case scenario of a minor displacement over towards Europe with no split and little deformation is now becoming the form horse. Watch as blocking returns to the north pacific, cold air returns to the Canadian sector and the atlantic express gets the boost it really doesn't need when the MJO is high amplitude in the Indian Ocean. In hindsight the QBO was wrong, solar activity has been high, Nina statistically makes an SSW more difficult...but we did have some precursor patterns earlier in winter and it was not a false perspective to see a split SSW event as a possibility. However, it is not coming to pass.

We have had frost, and some have seen snow. We have had worse winters. Perhaps the second half of February and into March can produce late interest as per 2013 and 2018. In the last 10 years March is really the only month that has delivered a genuinely widespread snowy spell for the UK with some longevity. Says much about our modern climate.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796949

[Nick F]

35 minutes ago, prolongedSnowLover said:

The GFS 0z run Op looks to be in its own into February.

Not just temperature wise but also with the lack of precipitation shown for both London and Oslo whereas other members showing spikes especially for Norway.

Morning. I think 00z GFS op is probably too high with pressure across southern UK, with its Bartlett-esque high over mainland Europe, a look at the ensembles and the ens mean (below) suggests the jet may push further south with heights / pressure lowering from the northwest with time:

It looks like coldies may have to grin and bare a few weeks of unsettled Atlantic low / westerly domination as head through the first half of February. But we have to expect these bouts of a few weeks of Atlantic zonal weather even in the better winters for coldies.

Good agreement for an extensive TPV spanning Greenland and northern Canada but with the coldest core over Hudson Bay which will push deep cold across Canada into northern US. This serves to fire up a strong zonal jet stream over the N Atlantic towards the UK an all that entails. This could set in for a few weeks with little interruption from MJO, which is over Indian Ocean and looks to either fade into COD or trundle weakly over the Maritime Continent. Correspondingly AAM forecast to remain negative through early February, but hints it may pick up into +AAM territory from mid-Feb, perhaps in response to MJO coming out into COD and perhaps moving over western Pacific - which could lend to more amplification from mid-Feb.

It's becoming increasingly apparent that the minor SSW will have little impact on the trop going forward, so we are now at the mercy of falling back on typical default La Nina winter imprint and MJO amplified in milder phases leading to a milder February ... for now.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4797024

[bluearmy]

Well hemispherically we are now seeing a response in the trop from events in the strat. It should be noted for next time that the size of the n pacific ridge into the pole was not seen on the nwp until we got close to the reversal - however, with the Canadian vortex and overall pattern we will not see any beneficial coldie consequences for nw Europe away from the possibility that we get another cool/cold zonal set up in week 2 which could dig into Europe somewhat.   If the reversal was sizeable around 60N then we could have seen some blocking establishing around 60/65N which might have been of note 
 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4797093

[Nick F]

Trouble is the GFS, and other models too, won't really pick up well if at all shortwaves and resultant secondary lows that develop to the south or southwest of the main parent low in the cold Pm flow at range, which often hold back the deep cold it shows trying to reach us from the northwest past day 10. These secondary lows forming over the NW Atlantic usually, where there is a steep thermal gradient / sharp baroclinic zone. The straight isobars with uninterrupted flow all the way from Labrador Bay to NW Europe rarely come off like it depicts on the 06z for a time.

Looking at the 00z EPS days 11-15 - can clearly see where our flow is likely to come (below) from in early Feb, first 9-10 days anyway, coldest in the west closer to the cold Pm source:

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4797117

[bluearmy]

Annoying that the eps clusters remain broken so we have to wait for the meteociel stamps. The mean charts aren’t  particularly encouraging but the spread at day 10 reveals there is a cluster which takes heights further north 

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4797467

[IDO]

I would not hang my hat on a D10 ECM chart, especially when showing height rises, they are rarely correct. The ens show a complete outlier for pressure:

The mean shows a fall in pressure in London along with most ens, whilst the op has a pressure rise. The D10 mean shows little respite from the expected pattern:

The main tPV chunk to our NW and not a pretty sight.

The ECM gets the rise in pressure due to it modelling a cut-off upper low in the Med, that stops the UK high sinking:

Possible, but at D10 too far out to have any confidence.

So IMBY we will see around 8-days of dry weather before it becomes more unsettled:

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4797471

[Allseasons-Si]

The ICON starting to show heights building to the west of the UK now

12z 174 vs 00z 180

and the 12z at 180...

the gfs and to an extent the control was the first at sniffing this amplified pattern out the other day and now the ECM this morning also latching onto this,yes it's reletively in fl so nothing to get exited about just yet so let's see how this pans out over the next few days

meanwhile,...the jma strat charts are starting to show an uptick in temps at 10/30 hpa,this is to no surprise though as it has been well documented from a couple of weeks or so ago

the jma also splts the spv here at 168 with Daughter lobe over the Alantic and parent lobe over N Scandi,again i am no strat expert and i could be talking rubbish but could this be more favourable for UK cold?

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4797583