Model Output Discussion 01/09/17

[bluearmy]

2 minutes ago, blizzard81 said:

I didn't mean game over for winter. Just in terms of how wintry it gets at the back end of November. 

Not game over for November but the longer and larger the upper arctic ridge survives, the higher the odds that we advect decent cold to be Europe.

[swfc]

Well that was different from the 6z????.Whatever happens over the uk we just cant drop them areas of low pressure way south.The almost legendry shortwave takes things north east

[ICE COLD]

Surprised no ones posted these

[carinthian]

2 hours ago, carinthian said:

Arpage is looking to zip the frontal wave SE wards across the SW of England with the heaviest rainfall in the location followed by a swift return of the Polar Airmass to all regions.

 C

That's the scene now. 30cm of snow cover. More in the forecast later on Sunday. Hope that frontal wave stays on a more southerly track as shown above so limits any warm sector on its southern flank for the Alps. However, latest GFS runs seems to hold a more northerly route. If that's the case snowfall above 800m could be possible in North Wales and Pennines. One for you lot to watch . Meanwhile, getting excited about another dump on Sunday night in our part of the Alps. Great weather watching this is.

[coldwinter]

Not sure if its an error or not but only one cluster on the ECM ensembles this morning past day 11. Matches up fairly well with the 06z FWIW.

 

Interesting times....

[northwestsnow]

7 minutes ago, carinthian said:

That's the scene now. 30cm of snow cover. More in the forecast later on Sunday. Hope that frontal wave stays on a more southerly track as shown above so limits any warm sector on its southern flank for the Alps. However, latest GFS runs seems to hold a more northerly route. If that's the case snowfall above 800m could be possible in North Wales and Pennines. One for you lot to watch . Meanwhile, getting excited about another dump on Sunday night in our part of the Alps. Great weather watching this is.

800m??? Does anyone live at that kind of altitude in the pennines? I mean..the higher parts of oldham are 400m but 800??

[Polar Maritime]

The 6z continues cool/cold from the N/W with some quite stormy conditions into Wk2. Further into the run shows heights pushing up into the poles via Greenland drawing a slack N/E flow over the UK.

[Man With Beard]

ECM ensembles this morning pretty much in the same place as last night - at D10, we see low heights close to the UK, a potential ridge still to the south, and signs of heights building to the north:

From D11-D15, the ensemble members were considered close enough to be combined in one cluster

    

I'm not sure that's a good summary, though. Looking at the individual 51 ensembles, the preferred option is indeed height rises in the Atlantic linking with those in the Arctic, and most runs do have low pressure close to the UK - but personally I see more than one cluster. On the one hand, many runs such as the control run sink the low crossing the UK at D10-D11 and then link heights from Greenland to Siberia between D12 and D15, giving the UK an easterly (this is not too dissimilar to the latest GFS 06Z run). On the other hand, though, there more than a few runs that do not sink the UK low and indeed hold it slightly west throughout D11-D15 to such an extent that the influence of the Arctic High never gets to the UK.

My gut instinct is that the potential (sorry to use that word) is still there for an Arctic blast , but it will only be around for a short time, and every time a new low squeezes through the Atlantic then time is used up. I think the pattern can afford the low modelled at D10 and still get to a cold solution - but if another low gets added to the mix after that then the influence of the Arctic High may never get beyond Greenland.

The reason to remain slightly more optimistic is that the Greenland height rise is being promoted mainly by the Arctic High, rather than relying solely on WAA from an Atlantic source which in recent years has failed 8 times out of 10 when modelled beyond D7.

[Polar Maritime]

14 minutes ago, northwestsnow said:

800m??? Does anyone live at that kind of altitude in the pennines? I mean..the higher parts of oldham are 400m but 800??

Highest part is Cross Fell at around 890m so I dought it very much. With Flash 15mile from me being the highest village at 460m. Although C wasn't necessarily saying these elevations are habitable only that said charts show snow potential.

Edited November 8, 2017 by Polar Maritime

[carinthian]

7 minutes ago, northwestsnow said:

800m??? Does anyone live at that kind of altitude in the pennines? I mean..the higher parts of oldham are 400m but 800??

Hi there, that's the forecast freezing level for Sat morning in your location but in heavier precipitation could easily turn to sleet and snow at lower levels due to cooling.  The freezing level by Sunday afternoon will be 300m in parts of central Northern England.

[bluearmy]

Good analysis of the eps from MWB 

imo, current trends are to potentially take the neg NAO a bit west based which will keep nw Europe on the warm side of the trough or at the best under the less cold part of it. Agree strongly re the n Atlantic ridge under arctic influence being more sustained. 

tbh, as long as we get a strong amplified hemispheric pattern delivering wave breaks up into the strat then, given the time of year and the lack of cold enough uppers I suspect a second bite at the cherry will not be far away. 

[northwestsnow]

Well subtle changes to the meto update nowtalking of the uk being under high pressure and temps just below ..

Sounds better than blues musings above inc every coldies worst nightmare...the west based -NAO..the most frustrating setup ever for coldies.

Ecm looks okto me..hoping to see any high in the uk locale ridging into scandy...imo thats where i think we will go late November..:)

 

[Man With Beard]

5 minutes ago, ITSY said:

At the risk of cross posting in wrong threads, this I don't see this update as anything other than an improvement with explicit mention of the S word now appearing...

"UK Outlook for Thursday 23 Nov 2017 to Thursday 7 Dec 2017:

There is an increasing signal that blocked patterns will become more dominant throughout this period. This will bring a greater chance of colder and drier conditions under the influence of high pressure. There will still be spells of rain and showers as frontal systems move across the UK, but these will be interspersed with drier, colder and brighter days. There is also an increasing risk of snow at times, more especially in the north. Temperatures will initially be near or slightly below normal but with an increased chance of below normal temperatures later in the period, with an increased likelihood of overnight frosts."

Well I'm guessing the Glossea is on the same page as the ECM then, as well as the GEFS 06Z which had a very clear sign for high pressure to the north:

[johnholmes]

How about Met O forecasts are put in the correct thread folks and we all stick to our interpretation of what the title says MODEL thread, eh?

[knocker]

Not much point in looking at this in isolation but as I was just passing through, so to speak.

The 06 10-15 GEFS anomaly merely illustrates be wary or jumping the gun once again  It has the previously discussed amplification in the Atlantic but the overall NH pattern is such (ridging across the pole being an integral part of it)  not only facilitates the creation of the strong meridional pattern that stops any west-east improvement but also the distinct possibility of a cut off low in the vicinity of the UK with no pathway for CAA from the north As mentioned last evening this sort of evolution requires precise alignments. Anyway just a passing thought

 

[johnholmes]

This is a brief look at the GFS output for 00 and 06Z out to T+168h and a look ahead to 14 days with the anomaly charts

=xLooking at the GFS output today 8 nov 2017.doc

Edited November 8, 2017 by johnholmes
Sio long since have done this, old brain finally worked out what to do!

[Daniel*]

Makes me think if it were the heart of winter we may have been getting buried in the white stuff, that’s if we get to there, but increasing confidence of Greenland blocking a big rarity in recent years due to the ‘purple monster’. So very interesting times.

 

[mpkio2]

Afternoon all.

It really is "As you were" with the models as they try desperately to pin down the finer details or the potential Greenland/Arctic High scenario....

Saga continues!

In the shorter term, from my untrained eye, it seems the GFS 12z is introducing some colder air than its predesesor06z with the Northelyblast on the upcoming weekend...

06z GFS 08/11 t102:

12z GFS 08/11 t96:

Probably enough for snow on high ground with those uppers, surely?

~mpkio2~

[Daniel*]

12 minutes ago, mpkio2 said:

In the shorter term, from my untrained eye, it seems the GFS 12z is introducing some colder air than its predesesor06z with the Northelyblast on the upcoming weekend...

06z GFS 08/11 t102:

12z GFS 08/11 t96:

Probably enough for snow on high ground with those uppers, surely?

~mpkio2~

It's a pretty common fault for the models to understate or exaggerate the depth of cold air relatively far out. Yes, undoubtedly not necessarily high ground either to pretty low/modest levels for northern Scotland. 

Edited November 8, 2017 by Daniel*

[Ross Andrew Hemphill]

2 hours ago, knocker said:

Not much point in looking at this in isolation but as I was just passing through, so to speak.

The 06 10-15 GEFS anomaly merely illustrates be wary or jumping the gun once again  It has the previously discussed amplification in the Atlantic but the overall NH pattern is such (ridging across the pole being an integral part of it)  not only facilitates the creation of the strong meridional pattern that stops any west-east improvement but also the distinct possibility of a cut off low in the vicinity of the UK with no pathway for CAA from the north As mentioned last evening this sort of evolution requires precise alignments. Anyway just a passing thought

 

Is a cut-off low over us a bad thing? Surely it could drag cold air in? 

[knocker]

10 minutes ago, Ross Andrew Hemphill said:

Is a cut-off low over us a bad thing? Surely it could drag cold air in? 

Not really you tend to get a stagnant surface low pressure area slowly filling with not much happening and little advection.How cold, or not, it gets rather depends on the characteristics of the airmass In these circumstances one would have thought not very. But not to get too wrapped up with this as I'm sure there will be a few twists and turns on the way.

Edited November 8, 2017 by knocker

[ICE COLD]

Check out these charts amazing northern hemisphere view

[knocker]

The gfs does seem to like it's 'bombs' recently

[Polar Maritime]

Yes Knocker noticed it on the 6z also. Aided by a very strong jet streak, Blizzard conditions for the Highlands I would think.. Not much change from the 12z with a cool/cold N/W flow and brief Northerlies. 

[Mucka]

We can only speak in general terms at the moment and with that in mind the big picture seems to be the models strengthening the Arctic blocking in the 8-10 day range compared to previous output if anything.

Also for the same period the Scandi ridge seems to be getting some support again for the same period.

Add to that the strong signal for Atlantic blocking and positive height anomalies moving into Greenland after mid month and some form of cold outbreak in last 3rd of November looks fairly likely though we could still get unlucky with regard to positioning and orientation of blocking.

P14 provides a sort of composite of all those things mentioned above.

Edited November 8, 2017 by Mucka