Model discussion highlights

[Met4Cast]

The AAM is largely progressing as expected, increasing +ve MT following the recent +FT should begin to drive up global AAM again by next week, this all largely led by the recent MJO phase 7 evolution, that itself looks to re-emerge again into March. All this coming together at a time -ve anomalies will be propagating down from the strat and into the trop and you see why NWP modelling is consistently modelling higher latitude blocking into March.

Fairly good confidence of a Greenland high but UK surface conditions are yet to be determined, broad direction of travel though favours cold conditions vs mild for eg but the prospects of a west based -NAO still need to be considered and remains a possibility on the table.

If we look at previous SSW's with successful downwelling welling we tend to see the "drip drip drip" of negative anomalies with multiple rounds of blocking, albeit weaker with each one. As we go through March it's plausible we'll see another go at amplification following the one we've all been watching however seasonal wavelength changes, i.e the jet stream begins to migrate back northwards  as we progress through March may throw in some added complications. 

Longer term, a recent tropical wave in the Pacific has significantly dented the easterly La Nina trade winds signalling a sign that La Nina is finally, after 3 years beginning to release it's grip.

 

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809467

[TEITS]

I would be wary of taking the predicted max temps as gospel. If we do see the very cold N/NE,lys via the Greenland high then due to the time of year you will see a massive difference in temps when under a heavy shower. More than plausible to witness temps drop from 7C to 0C within mins whilst under a shower.

At the moment snowfall is more than possible looking at the latest models. However deep lying snow lasting for days is unlikely whatever the temps. The amount of cloud cover is going to be very important as is the timing of any snowfall events.

I see Nick F beat me to it.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809318

[bluearmy]

34 minutes ago, Mike Poole said:

When we’re involved with a long range chase like this it is easy to be caught up in the swerves of the op runs, and also the general zeitgeist of the ensembles.

A pattern can seem elusive, and not really able to be backed up with charts, but here’s my personal view on where we are now:

The Greenland high is already prevalent in the modelling and will become set in stone once the models digest the second reversal of winds upstairs.

The cluster of runs that miss to our east will wither - that evolution is old hat now.

There will be a reflirting with the west based option.  This will carry some risk as we count down, but at the same time some injection of moisture from the Atlantic direction could fuel some serious snow if it falls right.

The balance between sustained really cold uppers, mild winning out, convective snow and battleground snow will go down to the wire…

Looking at the rise/drop/rise and then sharp drop in strat zonal flow over the next week, I’d be cautious about any week 2 modelling Mike and interpretations.  The envelope is huge imo 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809436

[mushymanrob]

I dont think its all "up in the air" nor do these GFS runs bother me.

ALL Anomaly suites are consistent, until/unless they change then the GFS 06z will be closer to the solution as that run is closest to what all Anomalies are predicting.

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809566

[Paul]

Latest from @Nick F on the goings on around the SSW, what the models are showing and what may be to come into March:

Latest on the Sudden Stratospheric Warming and whether it will bring a cold and wintry start to March

WWW.NETWEATHER.TV

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A Sudden Stratospheric Warming (SSW) is now underway, with the stratospheric polar vortex already displaced from the pole over northern Russia. A second warming next few days likely to lead to a coupling with the...

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809744

[bluearmy]

8 hours ago, Met4Cast said:

This sinking high scenario has become a bit of a trend throughout todays runs, particularly on the ECM suite. 

Too much energy is being left over Canada which then tries to move eastwards, it erodes the high and prevents proper retrogression.

I don’t think it’s as simple as that - you need a decent upstream trough to drive WAA to raise the ridge and retrogress the e Atlantic high. Those runs that lose the upstream trough allow the Atlantic heights to escape in to n America which leaves our ridge to sink se and the best we’re left with is a wedge which won’t cut it at this time of year. Then you’re waiting for another attempt at WAA. 
 

I don’t want to sound like a stuck record but until the next dive of strat zonal flow comes into closer view of the starting data (probably tomorrow/Saturday), the nwp beyond day 7 is just pretty patterns. It’s interesting that we had a pretty decent cross model extended ens agreement a couple day ago which has begun to lose some clarity with each run. Wonder what percentage of the eps clusters post day 10 will retain the ridge into Greenland and sceuro trough 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809835

[johnholmes]

I cannot remember ever seeing a higher 500 mb anomaly than that from last evening between Iceland and Thorshaven of something a bit in excess of 330 DM

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809879

[knocker]

23 minutes ago, ANYWEATHER said:

In all respect,Mushy, Those Anomaly charts were showing a stormy February, when we actually got one of the most benign Februarys I can remember !

That is simply not true with 'stormy' being particularly misleading. If I remember correctly the upper flow was generally south westerly/westerly  resulting in very much a north south split with Azores high pressure more influential in the south'. Some randomly selected charts

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809915

[mushymanrob]

1 hour ago, EML Network said:

only problem with these charts though is that the UK is right on the borderline so even if they do come off its going to be yet another all NE facing coasts affair and you can see that LP'S ready to strike from newfoundland bringing with it warmer air from the West.

 

 

Hi
I chose the charts that showed when the cold arrives,  subsequent dates increases the low anomaly over us and shunts the "borderline" further West.

As i see it, these charts suggest an initial burst of cold,, then a mixed bag, and yes there probably will be shortwave lows bringing less cold air, even mild at times. But imho the general theme is cold and this includes snow (even if its transitory).

1 hour ago, ANYWEATHER said:

In all respect,Mushy, Those Anomaly charts were showing a stormy February, when we actually got one of the most benign Februarys I can remember !

 I used the NOAA when i said that, they were inconsistent and failed to pick up on the subtropical highs strength - which all models did. As a result the "stormy" conditions were shunted further North...

26 minutes ago, jellybaby1969 said:

The issue many have is that each day we are looking at day 10 .....never day 5 6 7 or 8 for winter to return.  We are now looking probably beyond next weekend and then as we go into the new week we will be looking at mid month for anything resembling a wintery scene. Yes I appreciate posters  can only attach charts for what the output shows . . However it just shows how incorrect they are if everyday there is a reset to day 10...it seems every day is a day 10.

The evolution the EPS has long been forecasting was day 15, it correctly predicted the development of this high, its drift to our North, then up towards Greenland. Its only in the last few days that the cold synoptic pattern has been in place and the arrival of the cold has come down from day 15 to day 12.

It is a long way off, and IF there was any inconsistency in these charts then i wouldnt be so confident.

To be clear... I believe these charts have picked up on the most likely pattern into early March. I suggest that it will turn very cold around the 7th, but could be earlier or later by a couple of days.
Im not predicting a lengthy freeze, after an initial very cold blast itll become messy, think cold unsettled... milder/less cold spells mixed with further colder events. There will be snow in the forecasts, but chances of it lying for long probably arnt great for most lowland areas.

However, we need to wait a day or two to see IF or WHEN the NOAAs support the EPS. They are heading that way and agree at day 11.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4809981

[Kirkcaldy Weather]

On 31/01/2023 at 20:17, Kirkcaldy Weather said:

Extended movement still could be promising for further fun by End of Feb + into March 

23 days ago.

I've ticked the composites that will be most relevant moving forward 

The perfect combination of MJO phases 2 & 3 followed by the current evolution in phases 6,7+8. 

Very interesting a historic blizzard warning issued by NWS Los Angeles and that cut off trough can be seen in the phase 5 pattern (additionally the developing blocking in our vicinity) 

As mentioned above the composites for the MJO through phases 6>8 fit lovely 

 

There will be wintry showers probably graupel + snow on Saturday from an East / Northeasterly flow 

 

Current outlooks keep the MJO between phases 6-8 even within the extended range which would suggest to me that blocking could be the common theme throughout March.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810021

[bluearmy]

32 minutes ago, phil nw. said:

Looking at the Strat again and up to day 10 zonal winds do not reverse below mid-Stratosphere although dropping off to low single figures lower down.If we are to see any real effects from the next warming then we are looking to mid-March and beyond and that's if it filters down to the surface.

Of course we are still learning the effects of these ssws and things may work out for one last shot of cold but that imo is another wait beyond current ens guidance.

I would again remind everyone that the atmosphere exists at latitudes other than 60N. At day 5, the lower strat is heavily reversed down to 70N.  There is no magic bullet at 60N 10hpa. The whole atmosphere is a fluid single entity from top to bottom

 

ref the strat and trop not being coupled - let’s look at 06z gfs from 10 hpa right down to 500hpa. There is no way that the strat and trop are not coupled. there may not be a reverse zonal flow in the lower strat and trop at 60N  but the hemispheric pattern is imprinted throughout the atmosphere, top to bottom. 

    

 

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810049

[Nick F]

Probably not worth reading too much from the model output past day 7/8, GFS op keeps chopping and changing with how quickly the blocking high near UK retrogrades west or northwest and declines, how far west or east the cold plunge moves south towards northern Europe and how much undercutting of the block there is over the N Atlantic by lows. 

But the broad idea of blocking high near northern UK loitering into next week before drifting west or northwest to allow a deep cold plunge towards UK / North Sea tail end of next week has been on the cards for a while from most model ensemble guidance. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810126

[damianslaw]

We are entering closer to the time period when anticipated downwell effects of SSW will begin to emerge just outside the reliable timeframe.. note the word 'closer' and 'just outside', we are not there yet.. next 3 days is the transitional phase, early next week when things will become much clearer. Today alas just another day to tick off... and watch the models do there thing.

In the reliable - high pressure dominating, some colder continental air infiltrating into England and Wales over the weekend, and under cloud we will see quite a cold raw day on Saturday - something we haven't had much of this winter is cold associated with dull overcast grey skies. Frost in clear breaks and temps at or even a little below the seasonal normal, but the dry theme of the last 5 weeks will continue to see the winter out. An exceptionally dry second half to the winter - one of the driest on record I imagine

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810317

[Cambrian]

A week is a long time in polarvortices….

….and perhaps seems even longer 

But that really is a realignment, and a rapid one at that, taking only from day 3 to day 10 to completely vacate North America and arrive at northernmost Europe by day 10. 

The 12z ECM is a very impressive operational run, the best one yet for the potential cold spell in March. The high pressure is not only being pushed south, it’s getting squeezed as flat as one of those things I ate several of on Tuesday night. It has no way back from there. 

It’s actually the low heights of the western Atlantic trough that perform a full arc, up through Arctic Canada, rejoining the core PV over the top of Greenland, that then start pushing down to the west of Scandinavia. 

It’s a straight and strong northerly flowing down through Svalbard behind that cold front running from off the southwest of Iceland through to the low in the Norwegian Sea. This chunk of PV looks like it’s going to drop its trough bang centre down the North Sea and Norway and that northerly is perfectly set to drive the associated front(s) on its western flank down through the UK and Ireland. 

From that day 10 setup, this longwave polar trough is lovely and broad, and beautifully aligned to bring a very cold, and potentially very wintry spell to much of northwest Europe.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810273

[MattH]

Morning.

If your winter patience is wearing thin then the next week or two weeks will put that to the test even further! - While the debate does go on as to how and where the recent signal for blocking patterns to the NW has originated from, what does carry high confidence is that model (NWP) volatility will continue in the coming days and no doubt weeks, it is a logical outcome given the MJO and SSW influences, etc.

Overall, the recent craziness from some of the NWP, in terms of retrogressing the high towards the NW and bringing in a very cold N'ly airflow by the opening weekend of March is, IMO, related to the MJO and not any SSW influences, there is too much evidence to support this. Also, it is worth highlighting that this upcoming secondary and significant warming has not yet even happened and isn't expected to take place until the final few days of February, as highlighted well by the recent ECMWF plot.

 

What we could be seeing within NWP is an initial amplification of the pattern and retrogression, linked to the MJO, but as the upcoming additional strat warmings take place, there may well still yet be a period of 'flushing out of the W'lies' within the system and, in a way, it is not a surprise to perhaps see the huge Greenland blocks being watered down now, with something of a more displaced high to the W and SW by the opening weekend of March - Does this mean that is it for cold synoptics? - Most certainly not, it's just back to the old situation of having to wait yet again.

There are so many variables in place that support blocking patterns and a heightened risk of cold weather patterns looking ahead, I just have a feeling some of the crazy charts in recent days have been a false dawn and come too soon, linked to the MJO and not the SSW, but there is still plenty of time for all the key drivers of the medium and long term to come together to bring some wild and crazy late winter synoptics to the British Isles as the first half of March progresses. Also as a side note, if/when the time comes for cold weather to make an appearance, then at this time of year, for anything noteworthy the British Isles really does need to be looking at getting the -10C 850mb isotherm over it, if not below.

Cheers, Matt.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810396

[Met4Cast]

Quite a cold cluster 8th-10th March so it's possible we're simply seeing cold/blocked patterns being pushed back somewhat vs previous modelling outputs. Very tricky forecasting at the moment with a lot going on for models to try & resolve.

@Singularitypointed out to me on Twitter re: MJO plots, tropical storm Freddie is currently passing through the Indian Ocean which might be interfering with the RMM plots, this throws a further complication to the overall evolution and a further issue for modelling to attempt to resolve. 

The "chase" isn't over.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810517

[bluearmy]

24 minutes ago, nick sussex said:

The irony  continues.

The easterly downgraded over the last few days and because of the re-invigorated jet linked to the strat warmings this puts paid to the MJO induced blocking to the nw.

This happened earlier in the winter where another promising pattern bit the dust because a warming flushed down more westerlies.

So heads you lose tails you lose !

Then all the chips are now on the next major reversal and time ticks along.

I think the moral of the story is UK winters mainly suck big time and you need a perfect alignment of the stars.

The ECM day ten just about sums things up with the troughing too far east and for good measure it leaves a little piece of vorticity left over Greenland so no chance of heights rising there !

The major reversal happens on the 27th . With patience of coldies now almost gone we can struggle onto early next week to see if this wretched excuse of a winter can throw up an early spring surprise.

Apologies for the rather moaning nature of the post !

Yours and Matt’s post sum things up nicely 

that small piece of vortex tha ec op leaves over Greenland is indeed a pain but it’s post day 7 on an op run so we’ll park it for now. Without it, that run would be loaded with potential come day 10! 
 

Matt’s assertion re the ridging that was shown on the nwp for next week being more MJO than ssw probably correct because the second warming imprints the strat into the trop - this has been fairly well accepted on here for some time. But what we didn’t have in the modelling was that the MJO led height rise would be messed about with consequences from the second warming as the vortex begins to evacuate from Canada and heads east in a way which won’t allow those heights to rise. 

I would also say that the weaker strat does allow the MJO to take precedence in driving the trop patterns - that weaker strat is ssw related to the first warming.  As indicated yesterday, the second warming likely interferes with a promising evolution for nw European cold courtesy of the MJO.  Come the end of March we may well look back and shake our heads on just how unlucky we’ve ended up given the background telecons and ssw.  And to make matters worse a cold april more than feasible on the back of the downwelling waves which are likely from the reversals over six weeks or so. 
 

however, the straw to clutch (and it’s a big straw because the overall pattern is already a cold one), is that come the end of the weekend, the second deep dive into reverse flow will have begun and we could well see some additional amplification introduced into the models within the next week or so as the atmosphere slows more than currently modelled. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810420

[Eagle Eye]

Things are looking fairly good as we go into the future in terms of the background signals though cold has to be increasingly long-fetched at this time of year.

With the initial MJO phase 6-7 lag we see blocking to our north with a Greenie-Scandi pattern possibly as a result of AWB which may help with vertical Eddy driving and the pulling down of the reversal that should have reached the lower Strat by this time. Given baroclinic eddy life cycles and wavebreaking we can expect this to allow for further displacement of lower Strat vortex remnants and continued upwards tropics-polewards forcing Trop-Strat based to allow for the tending towards zero potential vorticity lobes to break Strat Vortex +VE zonal mean areas away from directly over the Arctic. Best outcome is a Greenland/Iceland - Scandi dipole that best drives the rotary pattern to best go against the lower Strat Vortex strength as lower Strat recoverys quickest quick speed is neccesary and so vertical dipole driving is probably the best way given initial setup. That may help speed up downwards Trop response and storm track response best seen in the current MJO forecast with a potentially very strong RMM Phase 7-8 return best for later Winter Nino like conditions. Given decent current mountain-Strat AAM wave driving this intraseasonal change to Nino like atmoshperic state would have been better slightly earlier of course but it's the best chance for cold since December if not better. Shame about timing since long-fetch likely requires correct pivot which is more likely to come from cyclonic wavebreaking but let's wait to see the response to the MJO Phase 7-8 around mid March. Essentially, this first northerly (ish) chance may not be the only one if we're lucky.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810650

[northwestsnow]

This is the  snowfall trend since 1973

The evidence is overwhelming, it's defo not my imagination!!

In particular NW Europe becoming a snow desert..

It's a very interesting if depressing analysis.

Big winners in +NAO are the Turks.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4810986

[MattH]

Take a look at the N Hem view of the 00Z ECMWF - https://www.wetterzentrale.de/en/topkarten.php?map=2&model=ecm&var=1&time=216&run=0&lid=OP&h=0&mv=0&tr=24

To me, that is one of the first runs that shows a more obvious and large change in trop pattern linked to the SSW. Note how earlier in the forecast period the low heights and low pressure systems dominate over the Canadian arctic and Alaska. Run through the sequence and get towards the end of the first week of March and - boom - the whole pattern over that region of the N Hem has rapidly changed, along with a clear and obvious displacement of the main tPV to where you would expect it given the strat developments as well.

Time will tell whether it's a one-off run, but that has stood out significantly this morning and needs watching closely but continues to tie in with the broader expectations and risks looking ahead in terms of northern blocking and colder air eventually arriving from the N or NE, etc.

Cheers.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4811028

[MattH]

An interesting shift in the 00Z MOGREPS this morning, which are just getting analysed. A good number of these show the colder flow from the N and NE by the 5th and the 6th, certainly worth taking note if MOGREPS is showing this, but clearly, there is a lack of consistency, but one to keep tabs on.

Lastly, the associated loop from top of the strat to the bottom clearly shows evidence of how this morning's 00Z Det EC imprints from the SSW onto the trop, very easy to match up the key +ve and -ve MSLP and 500mb height anomalies when you look from top down now...

Steady away.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4811058

[Met4Cast]

Micro-analysing every single run at this stage is futile because it'll be entirely different again on the next one. I don't think in all my 15 years of model watching I've seen such a consistently large ensemble spread between runs, usually there's some sort of idea of which way things are trending but currently there's nothing. Run after run. This I think, is when teleconnections can be incredibly useful.

Away from the chaos of NWP modelling, teleconnections are pointing in a semi-clear direction. 

A strong +EAMT (East Asian Mountain Torque) event is unfolding thanks to a strong jet stream crossing the Himalayas, this helps to drive amplification downstream in the eastern Pacific, driving the AAM upwards (likely to be reflected in the next several days) further perturbing the jet stream. 

The MJO re-emerging into phase 7 should help to sustain the on going +FT (frictional torque) thus driving further +MT (mountain torque) events & a repeat of what I've just said above. 

This in theory, should at some point begin to impact the weather patterns in the Atlantic lifting our stubborn high from a mid latitude block into a high latitude block. I'm terrible with timings, originally I said this was likely during the early part of March but I suspect tropical storm Freddie has somewhat delayed things as it's interfered with the MJO temporarily. We're probably still looking at the 2nd week of March but perhaps slightly more towards the middle of the month now, albeit with the caveat of my timings often being out. 

Now, whether that = UK cold or not remains to be seen, we still have the problem of trying to work out where any high pressure systems will develop/retrogress to and until NWP modelling becomes semi-useful again, there's no point in trying to pin that down. A trop response to the SSW is likely in early March with the TPV shifting to Asia, what follows in the Atlantic? We'll have to wait and see. 

Enjoy the weekend, take a break & come back to the models on Monday, I doubt they'll be in a better shape than they currently are but you probably will be!

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4811112

[Eagle Eye]

Looking at the background signals and everything is lining up fairly well for early to mid March for now as the general signal for the best transfer of momentum via mountain torque temperature. Heat over the Himalayas so upwards wave transfer of momentum into the Strat and circulating into the Trop also exciting a Rossby Wave packed which breaks cyclonically and extends the Pacific jet but also the Tropopause to Strat part of the Wave could really help bring down the SSW quicker than expected.

That extension of the Pacific jet when combined with everything else really helps slow down the Atlantic jet which connects everything together for a potentially good start to March.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4811176

[Guest]

6 minutes ago, prolongedSnowLover said:

It looks very Baltic in the Norwegian ski resort of Kvitfjell when we’ll be there  

I don't think you've mentioned you're going skiing in Norway, are you going skiing in Norway by any chance?

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4811428

[Weather-history]

ECM 12z from 10 days ago  for today

 

and reality

 

GFS 12z from 10 days ago for today 

GEM 12z from 10 days ago for today

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4811441