Model Output Discussion - mid Autumn

[Rain All Night]

ChatGPT can now have a go at interpreting weather model output charts...

I've just noticed that its very first statement is wrong about the MSLP around the south coast, lol...

Edited October 12, 2023 by RainAllNight

[CoventryWeather]

Good post again by @Kirkcaldy Weather, thanks for the input. Some uncertainty over the extent of the Scandi high, seems to be a rather brief feature as the vortex moves towards Siberia in a rather weak core. My idea is that the end of the month/start of Nov could provide a couple of strong northerly winds, as retrogression of the high towards Greenland happens. GFS shows this well this morning, and I feel it's a trend that's likely to stay for a while..

[sheikhy]

Gfs 06z much the same again at 168 hours!not letting go of the cold air from the east!!something has to give this evening!!if gfs has this correct it would be a massive victory!!!i think its wrong because ecm is my king model and always has been!but even a king can have his bad moments!

[MattH]

The key differences between the likes of the GFS bringing a chilly E or NE flow and a milder flow from the UKMO and the EC, is how the main development of the ridge takes place. Some of the last few runs of the GFS are absolutely text-book in terms of what you need to look for to get a Scandinavian high. The reason the UKMO and the EC don't really get there is because they make more of the cyclonic pattern to the NW, over Greenland and Iceland, with more than one main low pressure, the one that stops the amplification is east of Greenland at 126hr - https://www.wetterzentrale.de/maps/UKMHDOPEU00_126_1.png

However, the GFS has one large area of low pressure, one low over Scandinavian and then another low over Iberia that is waiting for trough disruption to connect to the trough of Scandinavia, which then essentially 'pulls' the low over Iberia eastwards which props up the main developing high pressure. On the Wetterzentral plots, in particular, you then get the text-book 'finger' of yellow colours at 500mb tha arch northwards and then north-eastwards into Scandinavia as the large dominant low near Greenland pumps warm air up on the western side of the ridge, which, as ever, builds GPH and hence the high develops.

It is quite fascinating to watch these kinds of synoptics whether they come off or not, obviously this kind of pattern would be what many cold fans would die for come the winter months, but forgetting all that, it is more of a learning experience for those wanting to keep tabs on the key features that can help develop a Scandinavia high in the future. I wouldn't rule out the GFS just yet, despite the lack of agreement from other models, as the evolution is very difficult to model, if the GFS has got a better handle of the synoptics near Greenland then it will come off, but equally if it hasn't and there is more than one cyclonic development there then a flatter pattern is more likely.

Regards, Matt.

Edited October 12, 2023 by MattH

[Rain All Night]

The general vibe for a couple of weeks from now is that the high-lat blocking won't have gone away and may even have moved backwards towards Greenland, but there will be a continued risk for us of LP incursions from the southwest. The troughing signal over easternmost North America is very strong:

Yesterday morning's EC46 (the most recent that we have) also hinted at eventual retrogression of the high-lat block:

Edited October 12, 2023 by RainAllNight

[Metwatch]

GFS OP this morning back to how it was on most of its runs yesterday it seems. Looking at the ensembles there is some limited support but doesn't remain the most likely solution for the colder airmass to arrive from the east.

ECM 00z ensembles similar with a few members going colder, but most returning the warmth sourced from the south east, which means a Scandi high is still present, shown on the ensemble average below. So surface temperatures would more likely than not stay around average, which is around 14C by day for the next week locally.

More runs to get closer to that time frame certainly needed but somewhat interesting times ahead higher up in the troposphere rather than at the surface currently!

 

Edited October 12, 2023 by Metwatch

[minus10]

Well ...jff...the gfs 6z really teasing the winter synoptics out...

..

First ...scandi high..

...then cold pool to the south..

..then Greenland high..

...fairly decent trop vortex to the east at the end...now if this was late December..

..obviously op still in the minority of the ens and not the preferred solution as mentioned above..

...but certainly interesting to see how this plays out and the effect on the position and strength of the growing vortex..

[Ali1977]

6 hours ago, Ali1977 said:

Hello everyone, It’s nice to be back - there’s  lots of blocking showing up in a phase that’s usually all about the ramping up of the PV - FI on the latest GFS would be a nice place to be heading into early November for us coldies!!

 

The latest GFS FI even trumps the last one Synoptics wise, unlikely but the main take is the complete lack of PV over Greenland!! If - huge If - this happened, a very cold bonfire night would be on the cards, feels like about 35 years since that’s happened  

[Addicks Fan 1981]

Looks like pretty dry weather for a couple of weeks according to the latest EPS chart, can't believe that these anomoly charts aren't posted enough here.    

 

EPS Model – 500mb Height Anomaly for Northern Hemisphere | Tropical Tidbits

WWW.TROPICALTIDBITS.COM

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EPS model forecast of 500mb Height Anomaly for Northern Hemisphere

Looks like a west based negative NAO situation to be honest, but at least it's not bringing in the worst of anything.    

[Rain All Night]

1 hour ago, Addicks Fan 1981 said:

Looks like pretty dry weather for a couple of weeks according to the latest EPS chart, can't believe that these anomoly charts aren't posted enough here.    

 

EPS Model – 500mb Height Anomaly for Northern Hemisphere | Tropical Tidbits

WWW.TROPICALTIDBITS.COM

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EPS model forecast of 500mb Height Anomaly for Northern Hemisphere

I have been posting the EPS 500mb height anomaly charts (usually the Europe and/or North Atlantic views, rather than the entire Northern Hemisphere) on most days, often overlaid on top of the 500mb + MSLP mean charts, because I think the combination looks rather cool and gives good insight. Example:

 +  = 

[Mike Poole]

Both the GFS and GEM start the afternoon runs with a Scandi high delivering an easterly for the south by T240, supported by low heights over Germany.

With the main vortex over Siberia, a pressure rise over Greenland looks the logical next step.  

[Rain All Night]

I'm not keen on UKMO's T+168h chart, will be interesting to see ECM's as that has up to now consistently shown the most miserable outcome for the second half of next week.

[East_England_Stormchaser91]

Stronger signals in the mid timeframes for a significant cool down towards the latter stages of the month. If we do see those heights develop successfully over Scandinavia, it’s going to feel positively raw compared to the recent 20c temperatures that we’ve seen! 
A cold, crisp and potentially frosty bonfire night perhaps for a change. Wouldn’t it be lovely! 

[Cheshire Freeze]

Lovely synoptics on offer at the moment but I'd temper that by saying that I'm not a fan of Greenland heights in October and November. It's key at this point that we see heights maintain to our E and NE rather than to our NW...this is because we want pressure on the developing vortex leading into winter.  Greenland heights can very easily be swamped.

There does seem to be an inverse correlation between the NAO state in October and that in winter...so a +NAO October would be the best bet. Atlantic trough and heights to our NE is where it's at IMO.

Edited October 12, 2023 by Cheshire Freeze

[Rain All Night]

12 minutes ago, East_England_Stormchaser91 said:

Stronger signals in the mid timeframes for a significant cool down towards the latter stages of the month. If we do see those heights develop successfully over Scandinavia, it’s going to feel positively raw compared to the recent 20c temperatures that we’ve seen! 
A cold, crisp and potentially frosty bonfire night perhaps for a change. Wouldn’t it be lovely! 

7 minutes ago, Cheshire Freeze said:

Lovely synoptics on offer at the moment but I'd temper that by saying that I'm not a fan of Greenland heights in October and November. It's key at this point that we see heights maintain to our E and NE rather than to our NW...this is because we want pressure on the developing vortex leading into winter.  Greenland heights can very easily be swamped.

I guess we will want to be keeping an eye on the daily EC46 charts for the week 30 Oct - 6 Nov, the latest of which suggested that a chilly bonfire night might well be on the cards but that the northern heights might be heading into a Greenland-shaped booby trap around that time too.

Edited October 12, 2023 by RainAllNight

[Cheshire Freeze]

1 minute ago, RainAllNight said:

I guess we will want to be keeping an eye on the daily EC46 charts for the week 30 Oct - 6 Nov, the latest of which suggested that a chilly bonfire night might well be on the cards but that the heights might be heading into a Greenland-shaped booby trap around that time too.

There is truth to the saying 'if ice in November can bear a duck, winter will be nothing but sludge and muck'.

[blizzard81]

8 minutes ago, Cheshire Freeze said:

Lovely synoptics on offer at the moment but I'd temper that by saying that I'm not a fan of Greenland heights in October and November. It's key at this point that we see heights maintain to our E and NE rather than to our NW...this is because we want pressure on the developing vortex leading into winter.  Greenland heights can very easily be swamped.

There does seem to be an inverse correlation between the NAO state in October and that in winter...so a +NAO October would be the best bet. Atlantic trough and heights to our NE is where it's at IMO.

Yes, I've read that inverse October NAO many times over the years. I don't know if it's my imagination but I'm sure there is also a correlation between the October AO and that in the proceeding winter. Not the inverse though. So a negative AO in October gives a much better chance of a negative AO in the following winter. I haven't heard it mentioned much in recent years though?

[jy]

Strong rumours emerging that VAR is being introduced  to weather forecasting.If prime time forecasts have got it badly wrong and a serious and obvious error has taken place then 3 other models can ask the Met Office to reconsider and change the forecast..for example a Channel Low.Blizzard nailed on only for it to scoot off into France a case in point.

[Metwatch]

GEM now showing a much colder than usual airmass right at our doorstep to the east, even bringing some snow accumulations to central and southern Germany, though the elevation is a little higher there.

The heights in Scandinavia does slowly migrate on the GFS to Greenland as some have mentioned with the PV over Siberia, but that is quite far out.

At look at the modelled 300 hPa winds from the GFS 12z, for next weekend showing the jetstream is in quite an anomalous position / direction of flow.

Edited October 12, 2023 by Metwatch

[Cheshire Freeze]

2 minutes ago, blizzard81 said:

Yes, I've read that inverse October NAO many times over the years. I don't know if it's my imagination but I'm sure there is also a correlation between the October AO and that in the proceeding winter. Not the inverse though. So a negative AO in October gives a much better chance of a negative AO in the following winter. I haven't heard it mentioned much in recent years though?

I guess we have to hope that this is the winter of the Scandi HP

[Methuselah]

I'd welcome a chart like this, were we in January, February or early March., but not in October; cloudy, windy, cold and sometimes drizzly weather is not my cup of tea! 

[Rain All Night]

31 minutes ago, Methuselah said:

I'd welcome a chart like this, were we in January, February or early March., but not in October; cloudy, windy, cold and sometimes drizzly weather is not my cup of tea! 

It does seem to be a case of either having a trough to the southwest, or an ineffectual cold pool to the southeast... the main benefit of the Scandi high seems to be the pretty-looking 500mb height charts, rather than the actual weather it brings! (though other posters have pointed out that it might help to weaken the stratospheric polar vortex later on, if it sticks around for long enough)

Edited October 12, 2023 by RainAllNight

[Metwatch]

The UK under a warm airmass on the ECM 12z, but huge contrasts again with the -10C 850hPa isotherm spanning right across western Russia to eastern Europe.

Such a blocked pattern, just imagine it was modelled to be like this 8 weeks from now! However long this may last, some weakening on the SPV if so.

Edited October 12, 2023 by Metwatch

[Cheshire Freeze]

2 minutes ago, Metwatch said:

The UK under a warm airmass on the ECM 12z, but huge contrasts again with the -10C 850hPa isotherm spanning right across western Russia to eastern Europe.

Such a blocked pattern, just imagine it was modelled to be like this 8 weeks from now!

The positive of the ECM run is that it maintains heights to our E at the same time as shearing off the Atlantic trough. We could end up with an early wave 2 attack on the developing vortex in that scenario

[Mike Poole]

3 minutes ago, Cheshire Freeze said:

The positive of the ECM run is that it maintains heights to our E at the same time as shearing off the Atlantic trough. We could end up with an early wave 2 attack on the developing vortex in that scenario

Two things I would like to note here.  First about the point you make about putting pressure on the strat vortex (and your earlier post), and second about why I would like to see the modelled blocking patterns come wholly to fruition - far too early for snow, of course, but that isn’t the point just now.

First, re the strat, there has been some talk in the winter thread of Ural blocking being what we want to see.  I’m not sure it is as simple as that, and if you look at this paper on blocking precursors to SSWs:

On the Relationship between ENSO, Stratospheric Sudden Warmings, and Blocking

JOURNALS.AMETSOC.ORG

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Abstract This paper examines the influence of El Niño–Southern Oscillation (ENSO) on different aspects of major stratospheric sudden warmings (SSWs), focusing on the...

From the abstract:

‘The results reveal an ENSO modulation of the blocking precursors of SSWs. European and Atlantic blocks tend to precede SSWs during El Niño (EN), whereas eastern Pacific and Siberian blocks are the preferred precursors of SSWs during La Niña (LN) winters.’  

‘SSWs occurring during EN are preceded by amplification of wavenumber 1, whereas LN SSWs are predominantly associated to wavenumber-2 amplification.‘

So, even if all other things are equal (they aren’t this year), it being El Niño, blocking in the Atlantic (NW) might actually be preferred.  

But things are not equal this year, weather patterns and SSTs have been unprecedented and, as I have said in the winter thread, I reckon all bets are off with trying to predict from past precedence, and this brings me to my second point about the blocking showing on the models.

I’d actually quite like the GFS to win this battle with the more amplified solution.  It is unusual for the GFS to be promoting the most blocking, ECM less so, anyway - usually it is the other way round.  There has been a preponderance this year for stuck weather patterns with a meridional jet, and the last thing I want to see late autumn into winter is for a relentless zonal onslaught to take the place of that right when it is getting interesting.  (There is reason to fear one, possibly, due to the positive Indian Ocean Dipole.)  Which is why I think seeing high latitude blocking patterns now suggests interesting weather patterns to come - and gets us in the game if they persist into winter if we get on the cold side of them.