Model output discussion 24/01/21

[feb1991blizzard]

4 minutes ago, Allseasons-si said:

 

thanks for these^

The ext EPS clusters plaster heights all over the NW/N and NE...

and there is only two +NAO'S (blue boxes) in there,...i will take that

 

Must admit the 360 look a stonker.

[bluearmy]

30 minutes ago, mulzy said:

Ext EPS mean shows higher heights over Scandinavia spreading to cover all regions to our northwest, north and northeast. Low heights over UK diluting out.

A decent if not desperately cold mean. 

Just pleased to see an improvement on the 00z suite ....

[phil nw.]

Just a general observation.

Currently there is no strong signal for persistent blocking to our north but more a continuing sign of wedges of heights against a jet running along the 50N or thereabouts.

This has all the signs of the ongoing battle between cold v mild around the UK.It's certainly a pattern that's keeping everyone on their toes,there's even a difference at t144hrs on the mean ens charts.

Not surprising given the changes on the updated fax at t72hrs i posted earlier.

Not a classic setup such as a beast or a bitter northerly but this means more chances of snowfall at the boundary as the Atlantic comes in.

We will likely see the mild win at times but then be pushed back by the resurgence of cold. Uncertainty reigns for sure but for model output geeks it does make for some fascinating viewing and indeed should bring some interesting weather.

Edited January 24, 2021 by phil nw.

[feb1991blizzard]

1 minute ago, bluearmy said:

Just pleased to see an improvement on the 00z suite ....

Yes, 0z on the London graph had mild trending written all over it, another 2 runs like that and any corresponding downgrade on the GEFS and i would have been preparing to throw in the towel.

[Mike Poole]

12 minutes ago, feb1991blizzard said:

Must admit the 360 look a stonker.

hey, @feb1991blizzard, how is this looking overall into Feb to you now? Because from where I’m standing it is looking good, the effects of the SSW are now showing impact and the MJO seems to be playing ball (although the MJO is an unreliable witness!). 

From the strat NAM chart here:

I think now as important as the blues at our level at the bottom are, the reds at the top are also important as they will impart force on the downwelling if my understanding is correct.  Make sure we get what has been promised!!

Edited January 24, 2021 by Mike Poole

[Uncertainty]

5 minutes ago, bluearmy said:

Just pleased to see an improvement on the 00z suite ....

Yes BA they were horrific. Didn’t want to moan in here as many people were looking forward to their first snow of the winter and I didn’t want to spoil their day, which at least 30 of the EPS members would have, unless you worship long fetched southwesterlies!

[feb1991blizzard]

8 minutes ago, Mike Poole said:

hey, @feb1991blizzard, how is this looking overall into Feb to you now? Because from where I’m standing it is looking good, the effects of the SSW are now showing effect and the MJO seems to be playing ball (although the MJO is an unreliable witness!). 

From the strat NAM chart here:

I think now as important as the blues at our level at the bottom, the reds at the top are also important as they will impart force on the downwelling if my understanding is correct.  Make sure we get what has been promised!!

Well, looking at the last 2 days worth of ens suites since that bonkers suite on the 18z, i would say odds against any real cold uppers reaching us because as soon as the predicted cold gets sub day 10, they just trend milder, can't rule out the whole of Feb definitively as the FI GFS isn't terrible in the strat, i had previously worried that if we keep having failures we are going to run out of breathing space, but also BA's post saying ECM op showing signs of a split late in the run so would hang firm, but if everything carries on getting pushed back on the graphs for the next couple of days then the writing would be on the wall until pretty much mid feb.

Edited January 24, 2021 by feb1991blizzard

[Mike Poole]

5 minutes ago, Uncertainy said:

Yes BA they were horrific. Didn’t want to moan in here as many people were looking forward to their first snow of the winter and I didn’t want to spoil their day, which at least 30 of the EPS members would have, unless you worship long fetched southwesterlies!

Didn’t even look at the 0z runs (apart from HARMONIE for the regional thread) too busy enjoying the snow, glad I missed a stinker! 

[stodge]

Evening all

Snow finally reached lowland East London this morning and early afternoon. Only a transient covering which quickly melted in the afternoon chill but still it snapped the three-winter snowless streak and it was out first snow fall of any sort since March 2018.

A one-off or a taste of things to come? There's a lot of winter left (and including March we still have two months of opportunities for snow) and last night's output (with the notable exception of Parallel) was suggesting after a brief milder spell the pattern would be shifting again to something colder once more soon after the start of next month.

12Z GEM: T+120 takes us to Friday January 29th. Heights pushing south to the east of Iceland and residual heights over Iberia have compressed the trough channel south but it still covers the British isles and extends east to northern and north-eastern Europe while upstream a shallow trough sits to the south west ahead of a more significant LP moving out of the United States. A light E'ly over Scotland while slack conditions cover most parts and a W'ly air flow runs along the Channel coast. As might be expected, mild air remains to the south but colder air has returned to northern areas with uppers below -4. From there, quite a complex evolution with another LP running east across the Channel and Northern France pilling down a brief but cold NE'ly. By T+180, that has  eased to a col across the British Isles with a new vigorous Atlantic trough winding up to the south and south west of Iceland. Heights over Scandinavia are trying to extend south-west at the same time.  Cold air with uppers below -8 remains over eastern parts and the whole of the British Isles has 850s below -4. Moving on, pressure rises strongly over Scandinavia and by T+240 hp is over northern Norway but the Atlantic is still trying to push in creating a real battleground scenario over the British Isles. At T+240 the main LP is south of Iceland with a secondary feature in the south western approaches and a SE'ly airflow covers all parts. As might be expected, milder air remains to the south and west with colder air to the north and east.

GEM ends with a real battleground which it didn't last night while the other models did.

12Z GFS OP - as with GEM, the trough has begun to disrupt south-east through the British Isles by T+120 with shallow areas of LP within the trough's circulation. Heights to both north and south with a light W'ly to the south and a SE'ly for northern areas. Milder air persists over much of the British Isles with only the far north east and Norther Isles still in -4 850s. From there, the Atlantic trough gets some re-invigoration from the LP from lower latitudes but it elongates east across the British Isles by T+180 as heights begin to rise over Scandinavia.  Secondary LP are forming in the circulation to the south of the trough where the colder and warmer airmasses are meeting. After a brief push of colder air milder air has returned to most southern and western areas by T+180 but it remains cold further north and east. From there, the trough to the north west sends secondary LP across southern Britain and eventually starts to ease south as heights build to the north east over Scandinavia and extend west. A W'ly air flow continues across the south at T+240 but 850s have just gone negative leaving the coldest air still to the north and east.

GFS OP not quite as exciting as GEM for cold fans but still moving in a decent direction looking at the upstream ridging/

12Z Parallel: by T+120 one area of LP is to the east over Denmark leaving a NE'ly covering much of the British isles. A brief ridge is approaching the west but a vigorous LP is approaching from the south west. Milder air remains over southern parts but colder air with uppers below -4 is moving south from Scotland into northern England. From there, the deep Atlantic LP moves east along the Channel into northern France and disrupts south into Biscay as a ridge builds down from the north but this is transient and the pattern "resets" by T+180 with a new positively aligned trough extending south west from the south of Iceland and a new push of milder SW'ly winds approaching the British Isles bringing positive uppers toward western parts. Moving on, the mild regime sets up but heights build strongly to the north resulting in the Atlantic trough re-aligning negatively. By T+240, the main LP centre is over Ireland with the trough extending north west to Greenland and heights sit over the Azores. Mild air covers the British Isles by T+240.

Not much battleground there to be honest despite the northern blocking - Parallel again sits in the milder camp.

12Z ECM - by T+120, as with GEM, a build of heights from Iceland south has pushed the LP systems further south with one shallow trough extending across northern Europe to southern and eastern Britain and a new LP approaching from the south west. A NE'ly covers northern parts with a cyclonic flow elsewhere. 850s are positive in the south but negative uppers elsewhere with 850s below -4 iin north eastern areas. The LP moves east quickly followed by a transient ridge but by T+192 we have a new Atlantic LP to the south of Iceland and a broad run of SW'ly air across the British Isles pushing positive uppers back across most parts after a brief colder incursion. From there, the LP over Iceland edges back west but a hint of upstream amplification and the air flow is more PM in characteristic from the west. 850s just negative over all parts of the British Isles so nothing dramatic.

ECM ends with a bog standard modified PM westerly so showers for most you'd think.

Moving on, a look at GFS OP and Parallel at T+312 and T+384 (February 9th) respectively.

OP ends as a real battleground while Parallel gets to a cold evolution eventually but it's a real struggle with a lot of rain (and perhaps snow) to go before that. Control ends a bit battleground too but with a stronger anticyclonic influence from the south as well as from the east so the full on E'ly goes to the south.

Conclusion: It now seems what was going to be a single milder interlude may be split by a brief colder incursion next weekend. From there, GFS and ECM want to bring back an Atlantic-sourced flow fairly quickly while GEM brings the Scandinavian HP into the mix and leaves the British Isles in a battleground scenario by T+240. GFS OP, Parallel and ECM pick up the battleground idea further into FI and it's an emerging theme for the first week of February and beyond though that will doubtless be dependent on other factors such as the MJO and developments in the stratosphere. I'll leave others to consider next weekend's colder snap and where any snowfall may occur.

[sheikhy]

Whats with the arpege for thursday!!!!ecm looks identical but dont think it has any snow at all?!!

[nobble]

4 hours ago, carinthian said:

Arpege chart going for a snowy Thursday with quite a depth in some favoured places. Will be interesting to see the updated fax for the same day.

C

Wowsers

[winterof79]

12 minutes ago, sheikhy said:

Whats with the arpege for thursday!!!!ecm looks identical but dont think it has any snow at all?!!

ECM

Arpege

[Singularity]

Generally, whenever you see a model run past 5 days range develop a huge trough without breaking lows away, it's time to put the sceptical hat on.

ECM 12z fitting that bill today.

Noticed something about the Scandinavian high potential - a lot of the outcomes have very cold air and not particularly high SLP, which means there isn't much of an impression on the geopotential heights to show up in the clusters. Something to consider.

Probably makes trough interaction with said highs harder to resolve, too.

Will the Atlantic submit? How I wish I had a good idea...!

[Griff]

GFS to give much better heights and full on scandi by day 9

[Tim Bland]

30 minutes ago, sheikhy said:

Whats with the arpege for thursday!!!!ecm looks identical but dont think it has any snow at all?!!

Aperge has found the right page now unfortunately...

[Griff]

1 minute ago, Griff said:

GFS to give much better heights and full on scandi by day 9

See much better already.. 

Ignore the Atlantic... Too progressive. 

(I might have snow fever) 

[weirpig]

2 minutes ago, Tim Bland said:

Aperge has found the right page now unfortunately...

Thats the gfs tim   

[Griff]

GFS trending more towards gem... Honest

[Tim Bland]

8 minutes ago, weirpig said:

Thats the gfs tim   

Oh yes Don’t how I managed that!...Dream is still just about alive ...for another hour

[Mike Poole]

You know, I kind of look at this and think, no this isn’t going to happen...GFS T174:

Where is the system in the Atlantic getting its drivers from?  Numerical modelling errors compounding is my take...this one is for the bin...

[Mike Poole]

GFS 18z // already got all sorts of options on the table at T120:

[Troubleatmill]

10 minutes ago, Mike Poole said:

You know, I kind of look at this and think, no this isn’t going to happen...GFS T174:

Where is the system in the Atlantic getting its drivers from?  Numerical modelling errors compounding is my take...this one is for the bin...

Low heights off the eastern seaboard is the the drivers, can't bin it, as much as it can be wrong

Edited January 24, 2021 by Beano

[nick sussex]

Another frustrating run .

The upstream low refuses to disrupt enough energy se wards , not helped by the bloated shortwave nw of Norway . It’s that area where we need a wedge of heights to extend sw .

That needs to do one ! 

Looking at the overall trends the evolution looks to be one of a wedge of heights to the north . Upstream low moves east phases with the limpet shortwave west of Iceland , that gets pulled further nw . The wedge at the moment gets squashed unable to develop further because of the bloated shortwave nw of Norway .

If there’s more trough disruption then more drama like recent days with an emotional rollercoaster for coldies , possibly some decent snow for favoured areas .

Overall at the moment it’s currently looking a hard slog to develop a Scandi high to bring some deeper cold west  in the day ten timeframe unless one puts a lot of faith in the GEM trend ( good luck with that !)  , ironically now there is deeper cold to the east! 

Given the recent poor model performances all round the hope is they’re ballsing this up aswell and are being too progressive .

Onto tomorrow ! 

Edited January 24, 2021 by nick sussex

[blizzard81]

19 minutes ago, Mike Poole said:

GFS 18z // already got all sorts of options on the table at T120:

It follows the ecm op so it would take a brave man to discount it. The optimist in me however says..... This is the pub run and the ecm op was an outlier at this timeframe. This gives me some hope for the morning runs. 

[Purga]

24 minutes ago, nick sussex said:

Another frustrating run .

The upstream low refuses to disrupt enough energy se wards , not helped by the bloated shortwave nw of Norway . It’s that area where we need a wedge of heights to extend sw .

That needs to do one ! 

Looking at the overall trends the evolution looks to be one of a wedge of heights to the north . Upstream low moves east phases with the limpet shortwave west of Iceland , that gets pulled further nw . The wedge at the moment gets squashed unable to develop further because of the bloated shortwave nw of Norway .

If there’s more trough disruption then more drama like recent days with an emotional rollercoaster for coldies , possibly some decent snow for favoured areas .

Overall at the moment it’s currently looking a hard slog to develop a Scandi high to bring some deeper cold west  in the day ten timeframe unless one puts a lot of faith in the GEM trend ( good luck with that !)  , ironically now there is deeper cold to the east! 

Given the recent poor model performances all round the hope is they’re ballsing this up aswell and are being too progressive .

Onto tomorrow ! 

It's a wonder you've got any hair left Nick