Model Output Discussion 01/09/17

[Geordiesnow]

Hopefully the UKMO is right on its slightly sharper ridging in the Atlantic which results in a slightly stronger and sustained Northerly but at least some more chilly and autuminal weather coming up and of course any cold blasts will help to cool the SST's down also.

Longer term as being alluded, the models are favouring strongly of some sort of reverse dipole taking place up in the Arctic which means high pressure on the Russian side and low pressure on the American/Canadian side but whether it has any real affect on our weather in terms of cold weather is far to early to say but I really would not read anything into the GFS post 240 hours charts as it runs at a lower resolution and is called fantasy island for a reason!

I still think its too early to be hoping for too much WAA up in the poles, much rather see a strong PV getting broken up than a weak PV, I mean 30 years ago when the PV was stronger, we still manage to get cold spells and quite potent ones at that so even if the PV is quite organised and strong then that is no bad thing in my eyes. Of course if we have a very strong PV over Greenland then that is certainly more of an issue.

[Yarmy]

7 minutes ago, karlos1983 said:

AO looks pretty much nailed on to go negative.

 

Anyone got access to the Control run? It's literally off the scale.

[Summer Sun]

58 minutes ago, Daniel Smith said:

Am I missing something? The GFS ensembles for London are showing 850hPa temps dropping to -15? Clearly not going to happen but, am I looking at the wrong charts? This new Wetterzentrale design is horrible 

 

 

If it helps you can search your cities/towns here in the select city box http://www.wetterzentrale.de/en/show_diagrams.php?geoid=49069&model=gfs&var=205&run=00&lid=ENS&bw= just select the correct run on the left

[chionomaniac]

13 hours ago, Snowy L said:

I remember Chiono explaining to me about what happened in 2010 as there was nothing in the stratosphere happening that could have indicated the tropospheric vortex being completely destroyed twice in November and December of that year.

 

Basically it was wave breaking in the troposphere, so a troposphere-led split of the tropospheric vortex.

 

BTW I am not suggesting we will get 2010-like conditions, just thought this is a useful example of how we can still get brilliant tropospheric synoptics without the help of the stratosphere.

Just to pick up on this - if the tropospheric conditions are right, then there is a window of opportunity for colder outbreaks to occur, prior to the upper strat vortex strengthening and filtering down to the lower strat and then coupling with the stratosphere.If memory serves me right then any conditions towards La Nina assist this, and even though 'perfect' solar are still a couple of years away, this year conditions are once again ripe for a tropospheric based upper cut wave blow around Greenland. Especially as in early season the 'heart' of the developing strat vortex is positioned more towards the Asian sector. The GFS 06Z seems to be flirting with this idea. 

[summer blizzard]

2 minutes ago, chionomaniac said:

Just to pick up on this - if the tropospheric conditions are right, then there is a window of opportunity for colder outbreaks to occur, prior to the upper strat vortex strengthening and filtering down to the lower strat and then coupling with the stratosphere.If memory serves me right then any conditions towards La Nina assist this, and even though 'perfect' solar are still a couple of years away, this year conditions are once again ripe for a tropospheric based upper cut wave blow around Greenland. Especially as in early season the 'heart' of the developing strat vortex is positioned more towards the Asian sector. The GFS 06Z seems to be flirting with this idea. 

Am i right in thinking that we're essentially playing a game of chase here. We want the trop to stay ahead of the strat long enough to pass the mid-point marker (potential SSW mid-Dec onward) when the strat will lose its legs a little (we hope). 

[chionomaniac]

1 minute ago, summer blizzard said:

Am i right in thinking that we're essentially playing a game of chase here. We want the trop to stay ahead of the strat long enough to pass the mid-point marker (potential SSW mid-Dec onward) when the strat will lose its legs a little (we hope). 

The strat hasn't gained it's legs yet, so is vulnerable trop based waves if they are strong enough - the 'internal wave break' ( my terminology) as opposed to the external wave break following strong EAMT activity that will bring down a well developed strat vortex later in the season through a true SSW

[Tamara]

Seasonal wavelengths will allow an atmospheric circulation pre-disposed to La Nina to induce early cold incursions based on the default Pacific and Atlantic ridges that classically characterise -ve ENSO.

The Atlantic ridge, very early season, will suitably retrogress for cold air advection to UK and NW Europe - especially because as chiono says, the fledgling vortex is pre-disposed to the Siberian side.

Under this regime, the problem often comes as seasonal wavelengths change heading into winter proper. The changing wavelength dictates that northern arm polar jet flow heading downstream c/o the amplified Nina Pacific default pattern increases in tandem with inherent seasonal stratospheric vortex development closer to the pole. It can become a self feeding cycle with the upstream pattern sending a lot of arctic air out of Northern Canada, invigorating the jetstream downstream towards the UK and thus much harder to achieve amplification as the Atlantic ridge is flattened by the polar jet and so orientated much less favourably - with any cold air incursions heading deeper into mainland Europe to the east.

So yes, the "internal wave break" will help transitory cold incursions late autumn into start of winter, but the crunch time (more often than not) comes very soon after.

If Nina is set at the seasonal default, then rossby wave breaking dictated by a strong Pacific ridge increasingly favours the "wrong side" of the pole under low atmospheric angular momentum conditions - with a flat polar jet downstream.

On the other hand, rising atmospheric angular momentum tendency under a more Nino-ish inclined atmospheric circulation will induce repeated positive frictional and mountain torque mechanisms which play the longer seasonal game of externally pressuring the vortex through a stratospheric pathway of wave breaking this side of the pole.

Under an -QBO, which tends to imply a more efficient Brewer Dobson circulation, ozone transport is more greatly assisted from the tropical to polar stratosphere (and hence a more unstable polar vortex ). So, taking into account the more favourable stratospheric pathway mentioned above, better to be seeing GLAAM inclining weakly +ve, instead of weakly -ve for winter cold prospects. That is of course unless one is ok with the early season window "quick fix" and then, quite possibly, finding cold air advection risking being another couple of months of chasing the tail of the donkey.

The default position under a higher GLAMM regime will be low pressure over the Aleutians, replacing the Nina Pacific ridge, and teleconnecting to favour the bolstering of the Siberian anticyclone and increasing the chances of a classic mid winter major warming.

Anyway, enough from me. Whatever happens, I trust you will all enjoy and engage in the seasonal activity on this thread and leave you to it.

 

Edited November 7, 2017 by Tamara

[bluearmy]

It’s clear that something is afoot by the notable increase in IP/HR  (informed posts per hour) 

[bluearmy]

1 hour ago, Yarmy said:

Anyone got access to the Control run? It's literally off the scale.

Yesterday’s 12z ex control was astonishing over the arctic 

Don’t suppose it will upset anyone to post day 15 - just for fun as someone says on TWO

[NorthYorksWeather]

Fairly good agreement on 6Z GEFS that we are not going to see much in the way of mild weather as we head deep into November.

Not sure we can get as cold as last November, which saw some good snow accumulations down to low elevations in the North.

Above ens are for North Yorkshire*

Edited November 7, 2017 by vizzy2004

[chionomaniac]

22 minutes ago, Tamara said:

Seasonal wavelengths will allow an atmospheric circulation pre-disposed to La Nina to induce early cold incursions based on the default Pacific and Atlantic ridges that classically characterise -ve ENSO.

The Atlantic ridge, very early season, will suitably retrogress for cold air advection to UK and NW Europe - especially because as chiono says, the fledgling vortex is pre-disposed to the Siberian side.

Under this regime, the problem often comes as seasonal wavelengths change heading into winter proper. The changing wavelength dictates that northern arm polar jet flow heading downstream c/o the amplified Nina Pacific default pattern increases in tandem with inherent seasonal stratospheric vortex development closer to the pole. It can become a self feeding cycle with the upstream pattern sending a lot of arctic air out of Northern Canada, invigorating the jetstream downstream towards the UK and thus much harder to achieve amplification as the Atlantic ridge is flattened by the polar jet and so orientated much less favourably - with any cold air incursions heading deeper into mainland Europe to the east.

So yes, the "internal wave break" will help transitory cold incursions late autumn into start of winter, but the crunch time (more often than not) comes very soon after.

If Nina is set at the seasonal default, then rossby wave breaking dictated by a strong Pacific ridge increasingly favours the "wrong side" of the pole under low atmospheric angular momentum conditions - with a flat polar jet downstream.

On the other hand, rising atmospheric angular momentum tendency under a more Nino-ish inclined atmospheric circulation will induce repeated positive frictional and mountain torque mechanisms which play the longer seasonal game of externally pressuring the vortex through a stratospheric pathway of wave breaking this side of the pole.

Under an -QBO, which tends to imply a more efficient Brewer Dobson circulation, ozone transport is more greatly assisted from the tropical to polar stratosphere (and hence a more unstable polar vortex ). So, taking into account the more favourable stratospheric pathway mentioned above, better to be seeing GLAAM inclining weakly +ve, instead of weakly -ve for winter cold prospects. That is of course unless one is ok with the early season window "quick fix" and then, quite possibly, finding cold air advection risking being another couple of months of chasing the tail of the donkey.

The default position under a higher GLAMM regime will be low pressure over the Aleutians, replacing the Nina Pacific ridge, and teleconnecting to favour the bolstering of the Siberian anticyclone and increasing the chances of a classic mid winter major warming.

Anyway, enough from me. Whatever happens, I trust you will all enjoy and engage in the seasonal activity on this thread and leave you to it.

 

Hi Tamara, I agree somewhat with this, other than the transitory cold incursions part. The 'internal Greenland based wave break' led to the coldest December in 100 years - we can hardly call that transitory, and furthermore doesn't a Nina-ish atmosphere lead to a more blocked Greenland type regime early doors in winter? That was always my understanding.

[smich]

18 minutes ago, bluearmy said:

It’s clear that something is afoot by the notable increase in IP/HR  (informed posts per hour) 

Indeed! Possibly the most reliable forecasting tool we have at our disposal.

[jvenge]

11 minutes ago, chionomaniac said:

Hi Tamara, I agree somewhat with this, other than the transitory cold incursions part. The 'internal Greenland based wave break' led to the coldest December in 100 years - we can hardly call that transitory, and furthermore doesn't a Nina-ish atmosphere lead to a more blocked Greenland type regime early doors in winter? That was always my understanding.

I'm not Tamara and I'll also try to keep this model related somewhere along the lines ;-)

The 2010 start to winter saw a disconnect between the enso state and atmospheric circulation. This was caused by the amplitude of the MJO in October that year. This cleared itself out and the regular La Nina like conditions resumed. I've read Tamara's explanation of this quite recently and she puts it much more eloquently than me.

There isn't a sign of that this year (yet).

As the winter progresses, the UK is likely to come under the influence of warmer atlantic air and this is most noticeable come February. In December, the influence is less, but as the month progresses it will likely manifest itself as well. All things being equal, which they rarely are, the UK should be looking for the first half of winter to get what they crave in terms of cold.

I do note that some US forecasters are thinking that an amplified MJO is possible based on various analogues they use. That's way beyond my level of knowledge though, but it does seem that forecasts for a cold Western Europe are actually assuming this is going to happen. Who knows.

In cold winter La Nina years (for the UK), there has been something to dampen the La Nina effect.

And now, to try and keep it model related (sorry mods), there isn't any sign that the enso state is being suppressed based on the output. Some of the later November and early December charts are very La Nina like and although I personally don't care too much for longer range models, they are pretty much reading the enso state.

 

[johnholmes]

1 hour ago, bluearmy said:

Yesterday’s 12z ex control was astonishing over the arctic 

Don’t suppose it will upset anyone to post day 15 - just for fun as someone says on TWO

To my poor eyesight that 500 mb flow appears to show a strong westerly into UK and Europe?

[tight isobar]

10 minutes ago, johnholmes said:

To my poor eyesight that 500 mb flow appears to show a strong westerly into UK and Europe?

Due to the placement/alignment of west- north west canadian warming..

Or the 1070 west based modeled greeny high'  its looking that way.

Allowing the atlantic flow-to migrate westwards with exaction of mobility to our shores.

'However'-reiteration- its minor tweaks that need deciphering-via coming prognosis.synoptics..#knife #edge..

Very intresting modeling indeed atm!

Edited November 7, 2017 by tight isobar

[feb1991blizzard]

9 minutes ago, johnholmes said:

To my poor eyesight that 500 mb flow appears to show a strong westerly into UK and Europe?

It is - but he was referring to the pressure pattern over the Arctic.

[dragon falls]

Was there talk a while back about cold earlier then mild Jan Feb but things do and will change.

[bluearmy]

8 hours ago, CreweCold said:

Exactly. I can't see any support at all for any sustained high latitude blocking going forward.

Crewe - given the posts from ed and Tamara plus Jason furtado’s tweet, are you any less concerned re potential as we run late November into December ??

[Methuselah]

Are the 'building blocks' in place yet?

[Coopsy]

2 hours ago, Tamara said:

On the other hand, rising atmospheric angular momentum tendency under a more Nino-ish inclined atmospheric circulation will induce repeated positive frictional and mountain torque mechanisms which play the longer seasonal game of externally pressuring the vortex through a stratospheric pathway of wave breaking this side of the pole.

Under an -QBO, which tends to imply a more efficient Brewer Dobson circulation, ozone transport is more greatly assisted from the tropical to polar stratosphere (and hence a more unstable polar vortex ). So, taking into account the more favourable stratospheric pathway mentioned above, better to be seeing GLAAM inclining weakly +ve, instead of weakly -ve for winter cold prospects. That is of course unless one is ok with the early season window "quick fix" and then, quite possibly, finding cold air advection risking being another couple of months of chasing the tail of the donkey.

 

 

Just when you think you're getting a grip on this meteorology malarkey and this pops up lol. Always something new to learn on this thread. Love it

[Polar Maritime]

33 minutes ago, johnholmes said:

To my poor eyesight that 500 mb flow appears to show a strong westerly into UK and Europe?

Maybe for the far South John, But more North of West mainly as a whole?

[karlos1983]

Whether we actually get the cold in county wide or not is irrelevant at this stage, at the moment it’s looking likely northern blocking will come into play later this month and into December, which is a big part of the puzzle of its cold whether that tickles your pickle at this time of the year. 

Nothing to be nagative about at all with the models showing 1060/1070mb high bang over Greenland. Will it happen....well that’s why we are all here isn’t it? 

[Man With Beard]

Don't think anyone posted an image of yesterday's EC46 (D14-21), so thought I'd throw this in to whip up the frenzy a bit more

one of the strongest Greenland height anomalies I've seen. Even more significantly, EC ensembles have been pretty much rock solid in this direction for nearly a week now.

FWIW - I think it's now pretty inevitable there will be some strong northern heights in the second half of November. But far less certain that it will bring cold to the UK - could be shifted east or west. It's worth taking a step back to remember just how far out this is in meterological terms - we're talking D10-D20, when the reliable is, of course D7 at best.

[booferking]

3 minutes ago, Man With Beard said:

Don't think anyone posted an image of yesterday's EC46 (D14-21), so thought I'd throw this in to whip up the frenzy a bit more

one of the strongest Greenland height anomalies I've seen. Even more significantly, EC ensembles have been pretty much rock solid in this direction for nearly a week now.

FWIW - I think it's now pretty inevitable there will be some strong northern heights in the second half of November. But far less certain that it will bring cold to the UK - could be shifted east or west. It's worth taking a step back to remember just how far out this is in meterological terms - we're talking D10-D20, when the reliable is, of course D7 at best.

Early December anomaly from ECM weekly.

[knocker]

12 minutes ago, Man With Beard said:

Don't think anyone posted an image of yesterday's EC46 (D14-21), so thought I'd throw this in to whip up the frenzy a bit more

one of the strongest Greenland height anomalies I've seen. Even more significantly, EC ensembles have been pretty much rock solid in this direction for nearly a week now.

FWIW - I think it's now pretty inevitable there will be some strong northern heights in the second half of November. But far less certain that it will bring cold to the UK - could be shifted east or west. It's worth taking a step back to remember just how far out this is in meterological terms - we're talking D10-D20, when the reliable is, of course D7 at best.

True enough but it it is pretty short lived as the 25-32 is just about westerly zonal with a nasty upper trough down the eastern seaboard. Just saying.