Model Output Discussion - Into Autumn 2020.

[Frosty.]

Tonight’s ECM 12z ensemble mean indicates a preety unsettled outlook too me, very similar to the op in many respects, what I would say is longer term there’s something of a north / south split in the zonal flow with the north more unsettled than the south but changeable at best, which is by definition, unsettled...so, quite an autumnal spell and rather cold for a time later next week when there is also perhaps a brief interval of quieter weather and I should mention that across Scotland some wintry ness to higher mountains for a time but then temperatures recovering closer to average as winds come in more from the Atlantic sector.

 

[kumquat]

GFS 18z FI looking like an Indian Summer - almost. Quite toasty, autumn temps West to East getting cooler, but dry and fine.

Eastern Europe down to the Balkans look like going into the fridge.

[carinthian]

Morning all, this latest winter overview chart from GFS produces possibly one of the coldest starts to October ever over the British Isles with sub zero 850mb temps right across the Islands. Great synoptics if you like cold and early snow cover in the mountains with an enhanced deep Euro trough supported by strong Mid -Atlantic ridging to Greenland High and Siberian High.  The Canadian Model and Euros also seem to be heading towards a cold and unsettled start to October , but all still far to way out to be precise in the daily details but looks like thermals will have come out sooner rather than later!

C

[bluearmy]

5 minutes ago, carinthian said:

Morning all, this latest winter overview chart from GFS produces possibly one of the coldest starts to October ever over the British Isles with sub zero 850mb temps right across the Islands. Great synoptics if you like cold and early snow cover in the mountains with an enhanced deep Euro trough supported by strong Mid -Atlantic ridging to Greenland High and Siberian High.  The Canadian Model and Euros also seem to be heading towards a cold and unsettled start to October , but all still far to way out to be precise in the daily details but looks like thermals will have come out sooner rather than later!

C

The strength of the Russian upper ridge seems certain to guarantee a trough somewhere in Europe as we turn the month ....

[Frosty.]

Well I gotta say the ECM 0z ensemble mean seems to have toned down the unsettled outlook somewhat from recent apocalyptic proportions on some output..sure it’s going to become more unsettled and cooler, that’s obvious!..but it probably won’t be as bad as some feared..in other words, fairly typical autumn conditions?

ps..I couldn’t care less about clocks going forward..etc..stick to model output discussion!!!!!!!!!!!!!!!!!!

Edited September 20, 2020 by Jon Snow

[Frosty.]

There’s been some talk about an unseasonably cold early October in good old Blighty!..well, nobody told the GEFS 12z mean..it looks around average to me, even pleasantly warm further s / se, especially in any sunshine!

Edited September 20, 2020 by Jon Snow

[stodge]

Evening all

12Z ECM still rolling out - 12Z GFS OP not much to look at if you are after more settled weather. The strength and persistence of heights over NW Russia leaves NW Europe in a difficult position as it becomes the home of the trough and negative alignment becomes the name of the game as successive LP come down SE from Iceland/Greenland.

12Z GFS Control is a little better as the LP are able to pull away NE and the alignment is positive so heights rise to the south keeping the air flow mainly TM.

12Z GEM isn't too far from GFS OP but the HP is over Scandinavia rather than NW Russia but the net effect is similar.

The problem in microcosm:

The LP cannot ease east as there is a strong ridge in the way, nor can it go north for the same reason so it becomes static over eastern Europe with the British Isles on the cold flank so we get a chill NNE flow. The trough stops the Azores HP coming in so it aligns negatively opening the door for the next Atlantic LP.

[stodge]

12Z ECM at T+240 following the trend:

The block over NW Russia forces the trough SE through NW Europe and down toward the Med.

LP developing over Greenland and Iceland slide SE - unfortunately, the block is too far east for us to get a warmer S'ly flow which is what often happens in the European autumn as the LP digs south to the west of the British Isles. This year, the synoptics at least for late September/early October aren't so promising.

If the block can build slightly more to the west and we advect a S'ly flow it's perfectly possible to see 25C in October but not from this chart.

 

[Cheshire Freeze]

3 minutes ago, stodge said:

12Z ECM at T+240 following the trend:

The block over NW Russia forces the trough SE through NW Europe and down toward the Med.

LP developing over Greenland and Iceland slide SE - unfortunately, the block is too far east for us to get a warmer S'ly flow which is what often happens in the European autumn as the LP digs south to the west of the British Isles. This year, the synoptics at least for late September/early October aren't so promising.

If the block can build slightly more to the west and we advect a S'ly flow it's perfectly possible to see 25C in October but not from this chart.

 

Can see why zonal winds are forecast below average Oct-Dec if that becomes a default pattern. Good, early pressure on vortex formation.

[Mike Poole]

1 minute ago, CreweCold said:

Can see why zonal winds are forecast below average Oct-Dec if that becomes a default pattern. Good, early pressure on vortex formation.

So early days yet, but I see where you are coming from. 

ECM mean, I’m switching to NH charts now, T96, T240:

Unsettled here late next week, and that Russian high does look to be a player going forward. 

[Tim Bland]

11 hours ago, Mike Poole said:

 

Unsettled here late next week, and that Russian high does look to be a player going forward. 

I seem to recall that Russian HP was a dominant feature last winter?

[mb018538]

GFS is a horrible unsettled outlier this morning:



ECM isn't too bad really, once the cooler and unsettled blast clears through Wednesday to Saturday the most of the low pressure systems stay closer to Iceland:

[Frosty.]

Looking a bit further ahead, the ECM 0z ensemble mean indicates a zonal north / south split, tending to be most unsettled further n / nw and somewhat less unsettled further s / se.

 

[mushymanrob]

2 hours ago, mb018538 said:

GFS is a horrible unsettled outlier this morning:



 

GFS a horrible unsettled outlier?.....

looks bang on to me...





 

[mb018538]

42 minutes ago, mushymanrob said:

GFS a horrible unsettled outlier?.....

looks bang on to me...





 

It is compared to the mean and ECM op/mean:



Clearly it's going to be unsettled. Just not quite as bad as that op run made out!
 

[Newberryone]

3 hours ago, mb018538 said:

GFS is a horrible unsettled outlier this morning:



ECM isn't too bad really, once the cooler and unsettled blast clears through Wednesday to Saturday the most of the low pressure systems stay closer to Iceland:

I said in my last post on Saturday night that I didn't consider it a foregone conclusion that post Wed-Fri of this week that these North Atlantic lows would suppress the Azores ridging to any great extent and judging by mb018538 post from earlier today it would appear my prediction may have some credence after all 

[mb018538]

 

A glorious day out for the bulk of the UK....and for once the mighty Arpege hasn’t quite nailed it.

[Iceaxecrampon]

Sat 06z

…..Just a bit too early.

[Frosty.]

Looking at the GEFS 6z further into early October there are hints that high pressure could build in and settle things down..and whisper it but there are also hints of an Indian summer with a long draw southerly and temps well into the 20’s c.

[damianslaw]

Little activity in here today, Atlantic must be back in charge, for now though of the cooler variety, notably so for the time of year in the north.

Models showing a more zonal west east flow as we enter October but variance in terms of position of the trough, could be positive or negative. 

After a lengthy settled spell, Autumn fully kicking in after tomorrow which by coincidence happens to be the equinox. Some northern parts could be recording means around 7 degree mark by end of the week..

[LRD]

The last couple of days the ECM has reminded more experienced model watchers and given warning to cold-loving folk who are new to this model watching lark that modelled Greenland Highs usually fail to materialise

2 or 3 days back the ECM was modelling a proper GH for 2 or 3 runs and a sustained N'ly and even NE'ly for the weekend and early next week. Now we have this:

It would have been a remarkable N'ly given the time of year but good to have a reminder that the models often incorrectly toy with cold scenarios - only to have them revert to something very different with the reality ending up far removed from cold - at this time of year when it doesn't matter

Edited September 21, 2020 by LRD

[I remember Atlantic 252]

Good! hope EC is right and northerly is off! in my location a Sept northerly will feel and look the same as a January SW'ly, 12 or so degrees yuk

[Daniel*]

35 minutes ago, LRD said:

The last couple of days the ECM has reminded more experienced model watchers and given warning to cold-loving folk who are new to this model watching lark that modelled Greenland Highs usually fail to materialise

2 or 3 days back the ECM was modelling a proper GH for 2 or 3 runs and a sustained N'ly and even NE'ly for the weekend and early next week. Now we have this:

It would have been a remarkable N'ly given the time of year but good to have a reminder that the models often incorrectly toy with cold scenarios - only to have them revert to something very different with the reality ending up far removed from cold - at this time of year when it doesn't matter

I haven’t seen any proper Greenland highs well yellows at 500mb in output and it is a cool outlook largely.

London based on ECM 12z barely double figures in north, I’m not sure about you but that’s cold for September.... The model outputs persist with keeping ridging in North Atlantic, fairly unusual, as it looks to ebb away there’s another surge of amplification. I remember in 2008 we had similar in that autumn, and well in that instance the amplified theme did carry into winter. But just speculating. 

[LRD]

30 minutes ago, I remember Atlantic 252 said:

Good! hope EC is right and northerly is off! in my location a Sept northerly will feel and look the same as a January SW'ly, 12 or so degrees yuk

I was neither here nor there on it but as someone who is interested in, er, weather, it would have been fascinating to see what conditions would have transpired if the sustained North wind had have come off

How cold would it have got, what precipitation would there have been, would there have been a very unusual early snowfall on Northern high ground, how low would Sept night time temps have got under any clear skies etc, etc???? Instead we look like we're going to end up with bog standard conditions that we have for about 8 or 9 months of the year!

[LRD]

3 minutes ago, Daniel* said:

I haven’t seen any proper Greenland highs well yellows at 500mb in output and it is a cool outlook largely.

London based on ECM 12z barely double figures in north, I’m not sure about you but that’s cold for September.... The model outputs persist with keeping ridging in North Atlantic, fairly unusual, as it looks to ebb away there’s another surge of amplification. I remember in 2008 we had similar in that autumn, and well in that instance the amplified theme did carry into winter. But just speculating. 

Well, I can't be bothered to look back but I seem to recall that on Friday and Saturday a N'ly or NE'ly was being modelled by the ECM and that a proper GH was being considered at that time. Admittedly it was 168/192 hours away so not to be trusted but that was kind of the point of my original post. Not to trust models promising this, that or the other more than a week out. I see you've posted a chart that is 9 days out.

It's going to be cool later this week, no doubt, but the coming weekend is looking quite different to what was modelled at the start of the weekend just gone