Model Output Discussions 06z 04/11/16

[bluearmy]

Something of note on the gefs 06z is the development of a mean vortex centre nw of Greenland. Recent output plus eps show no vortex centre away from Siberia with a weak Alaskan daughter. 

Too early to say how this might impact on the pattern if it were to become a trend. Whilst the eps don't show it then probably best to ignore it 

[Coopsy]

2 hours ago, karlos1983 said:

Yup, I can't really see how we won't get a decent cold spell at some point in the next few weeks. NH has not been this well primed for donkeys yonks! It would take some seriously bad luck, almost everything is in our favor. 

And living in the UK we never have bad luck when it comes to cold not coming off ;-) Fingers crossed though

[beng]

18 minutes ago, Glacier Point said:

That allows for the controlling influence of the Canadian ridge to be negated downstream. With the pattern of tropical convective rainfall beginning to creep back towards the Maritime Continent (non-MJO component), this suggest mid Atlantic / possibly Barents Sea / Scandinavia area modest ridge development. These won't be too obvious on week 2 means or even spreads, but small scale mid to high latitude ridges developing within a flow which is well displaced of its norm would be interesting.

Within this context, stratospheric warming impacts will be around the week 3 / week 4 periods. The tell tale signature for vortex splits is very cold 850 values pouring into NW Russia and Northern Scandinavia. Helsinki, Moscow and Murmansk the locations to keep an eye on for extended range ensembles. Some twitching of ensembles for these locations staring to occur but nothing stark just yet.

Intriguing times.

So sounds like there's some support (maybe not the right word at this range) at the moment for a potential easterly mid Dec that might be quite potent given the cold pooling that could be in place should it occur. I might have to look away from the models in the run up given the inevitable dramas around Easterlies! :-)

Edited November 17, 2016 by beng

[bluearmy]

14 minutes ago, Glacier Point said:

Within this context, stratospheric warming impacts will be around the week 3 / week 4 periods. The tell tale signature for vortex splits is very cold 850 values pouring into NW Russia and Northern Scandinavia. Helsinki, Moscow and Murmansk the locations to keep an eye on for extended range ensembles. Some twitching of ensembles for these locations staring to occur but nothing stark just yet.

Intriguing times.

Will be interesting to see if the ec 46 para shows any marked T2 negs for these places on today's run weeks 3 onwards 

 

[Frosty.]

For the last few days the GEFS mean has been showing below average / rather cold and blocked conditions during late Nov / early Dec and the 6z is no different with a weak mid atlantic ridge  and an expanding scandi trough. There would be potential for a noteworthy cold outbreak during this period with no sign of mild atlantic zonality..it looks chilly later this month, cold cyclonic.

Edited November 17, 2016 by Frosty.

[marksiwnc]

19 minutes ago, Glacier Point said:

Another run, another ensemble mean suggesting quite an aggressive +ve height anomaly developing over Hudson Bay in the week 2 period with a switch in the flow to the southern arm of the jet over the US. Western Europe left under a weakish upper trough signal (temps marginally below average).

Two things to ponder here. 

What's to stop the westward movement of the upper ridge over the Canadian Arctic ? There may be some stratospheric-tropospheric coupling going on, but over time we would normally expect such features to shift their position westwards. That allows for the controlling influence of the Canadian ridge to be negated downstream. With the pattern of tropical convective rainfall beginning to creep back towards the Maritime Continent (non-MJO component), this suggest mid Atlantic / possibly Barents Sea / Scandinavia area modest ridge development. These won't be too obvious on week 2 means or even spreads, but small scale mid to high latitude ridges developing within a flow which is well displaced of its norm would be interesting.

Within this context, stratospheric warming impacts will be around the week 3 / week 4 periods. The tell tale signature for vortex splits is very cold 850 values pouring into NW Russia and Northern Scandinavia. Helsinki, Moscow and Murmansk the locations to keep an eye on for extended range ensembles. Some twitching of ensembles for these locations staring to occur but nothing stark just yet.

Intriguing times.

Gp I know you used to provide an in depth summary of the weather for winter especially.  but if you were to place a bet. where would your money be on the likelihood of a very cold snowy outbreak around mid December (or give some kind of percentage wise)  

[Glacier Point]

Just outside my 'embargo' period I'm afraid.

[Nouska]

20 minutes ago, Glacier Point said:

What's to stop the westward movement of the upper ridge over the Canadian Arctic ?

Oh... SNAP....

I've just spent ages making a gif and wittering about this on the strat thread and here it is in coherent and technical detail.

[BlueHedgehog074]

1 hour ago, karlos1983 said:

I give you ladies and gentlemen the only Mid latitude country in the entire Northern hemisphere to be in positive 850 temp values, the United Kingdom 

Thankfully that is the last frame of the gfs 06z

 

I wouldn't be too surprised if that verified (lol).

Must admit, a full zonal Atlantic setup with long drawn Westerly winds does seem improbable at the moment. Despite being only November I think, currently, the Greenland Vortex would rather just chill out watching TV, rather than take on that spot to our North-West. It worked too hard last Winter and it must be very worn out.

 

[Catacol]

14 minutes ago, Glacier Point said:

Just outside my 'embargo' period I'm afraid.

Hehe - but the frequency of your posts at the moment Stewart tells a story. In a week's time, when you ARE able to make a punt for mid December, it will be a fascinating read.

Wish we could pick your brains on January. Sigh....

[marksiwnc]

18 minutes ago, Glacier Point said:

Just outside my 'embargo' period I'm afraid.

Hahahhaha I was expecting that tbh.  one things for sure.. weather forecasting will be very hard over the next few weeks or even months with probably a quite rare setup in the northern hemisphere at the moment 

[nick sussex]

The models are beginning to converge with the GFS back tracking somewhat however its 06hrs solution still manages to develop better high pressure to the nw. Overall it looks like  high pressure taking over for a few days after a wet spell of weather over the weekend and early next week but not clear as yet exactly where that high will be located.

In terms of the ECM judging by its ensembles especially wind directions the operational run seems to have the high too far west and south, the main cluster for De Bilt shows an east/ne flow there from the 24th to the 28th, this would correlate with the high centred further to the ne. After that the main clustering is more between west and north, allied with the increase in precip spikes we can conclude that low pressure will likely edge se on the eastern flank of the high.

The main spread in the ECM ensembles is to the nw over Iceland, its clear that there are some solutions more supportive of the GFS 06hrs run and so theres still quite a lot of uncertainty next week.

Although the models have converged more upto T144hrs the ECM still makes more of shortwave energy to the nw, the GFS less so and the UKMO would still develop better ridging to the nw than the ECM.

Putting aside these earlier issues the outputs seem to be moving to one of some lower heights towards the Med, high pressure near the UK and then the big question whether the high retrogresses allowing troughing to develop over Scandi and whether we get a strong enough pressure rise over Greenland to drive colder conditions se.

Overall not a bad set of outputs and possibilities going forward but we're not as yet seeing a strong cohesive signal towards something  much more wintry. Its possible but not something you'd bank on at this stage, but enough there to keep the forum busy!

[phil nw.]

In spite of the more modest looking Atlantic ridging there's little sign of any trend to our more usual zonal Atlantic pattern.

Just scanning through the GFS 06z mean/anomaly charts further on and there are signs that the Siberian cold pool eases west towards Europe in week 2 with a developing Scandinavian trough.

Still a blocked looking Atlantic with the main ht anomalies across Canada into Greenland,a more west based -NAO with the UK under the cold upper trough.Temperatures a degree or two below average.

Nothing bitterly cold at that point but with a quiet Atlantic we would be well placed if further Amplification to our north west showed up with continental/Scandinavian cold nearby to draw on.

[Frosty.]

Reading between the lines, there is no change to the medium / longer range outlook with height rises expected to the north which would make northern uk drier and cold with night frosts and fog but with southerly tracking atlantic lows heading for central and especially southern uk with wind and rain but also a wintry mix with elevation bringing a risk of sleet and wet snow but also some dry and colder phases with frost and fog which eventually becomes the main weather type across the uk so it's a big change from this time last year in the run up to winter when we had a powerful northern arm of the jet with a monster pv but now looks much weaker and instead more energy pumped into the southern arm making for some wintry interest at times with the PFJ pushed further south. 

Edited November 17, 2016 by Frosty.

[Geordiesnow]

I don't think there is many surprises regarding the GFS dropping its Greenland high set up, its always the case once models pick up shortwaves, they very rarely(if ever) head back the other way.

The main trends will be the UK staying under the cooler airmass with low pressure running up the eastern side of the UK although positioning and strength of these lows are still very uncertain. Mid Atlantic high eventually toppling in does seem to be the most likely outcome as we head into the medium range so all in all, fairly average weather, maybe a tad below average especially at night whereever there are light winds and clear skies.

The warm southerlies running up Scandi is a depressing sight but the models still hinting eventually this will break down and with the forecasts the Arctic PV is actually going to gain some strength then perhaps IF the PV does drop into Western Russia/Scandi, it will actually have some strength to it.

[jvenge]

23 hours ago, Gray-Wolf said:

Obviously you guys are far more genned up on the structures that impact our weather but is there an precedent for what we are seeing across the far north so far this year? Surely the AO falling back negative talks of further WAA from depressions entering the basin and keep any vortex well out of its normal position ( if it can form at all?) so how do the models , out beyond T72, deal with a situation outside normal modelling parameters? Nullschool had the pole at 0.1 c at 15:30 yesterday??? With 15c to 20c anoms widely across the basin surely that has to impact the rest of the hemisphere?

I think it is fairly normal in cold winters not influenced strongly by El Nino/La Nina for the cold to end up where it has been so far. I'm sure someone here has analogue years, but not really what this thread is for. 

[Mucka]

4 hours ago, Man With Beard said:

Still looking at that D10-D15 period ... regardless of uppers, fairly cold at the surface on both ECM (De Bilt) and GEFS (central England) - that ECM control run looks frigid.

  

 

Got a gut feeling though that, slightly along the lines of the ECM, we may see another trough slip through the Atlantic block between T192 and T264, and a fresh build of pressure towards Greenland behind? In other words, a repeat of the D1-D5 scenario?

 

I think we may be slowly seeing a new signal develop along those lines.

The HLB that was being modeled has all but disappeared along with any faint hope of a Greenland high (In November) and even in its very weekend state the PV will not relinquish its grip of Greenland, I wonder if the anonymously cold Atlantic has anything to do with that but whatever the teleconnection we can hope it fades through December.

I could be wrong and we see a reversal in the output back toward some HLB but regardless it still looks good for another bite at the cherry toward end of month with another Atlantic ridge building, in this regard ECM might be ahead of the game with quickly bringing a deeper trough down and displacing high pressure West. I don't have access to ECM so maybe someone else can elaborate but I suspect the cold runs appearing within its ensembles for start of Dec are a result of this trough and associated Northerly flow down the East flank of a renewed Atlantic ridge rather than a block to our North bringing in a NE/E flow. That also makes sense as the milder members therein may well show a West based -NAO with the trough too far West.

If that is correct then ECM Op may be onto something if a little progressive though admittedly the evidence is pretty flimsy as yet.

That would be no bad thing because GFS ensembles have pretty much lost any FI cold signal they had  with the mean for London 2C or 3C higher than the cold cluster within ECM ensembles.

In simple terms there is a signal within ECM rather than within GFS which has lost its previous signal for HLB so makes sense that ECM may be currently leading the way here.

 

As far as ECM V GFS over this first ridge fiasco, we are pretty much seeing a blended solution though GFS was always the only model to go for a ridge building into the heart of Greenland and HLB so much toned down while ECM has found the middle ground between its own operational output and always wanted any high developing from the ridge at lower latitude as a consequence. It is irrelevant though as often the shoe is on the other foot and next time around the roles may well be reversed. No way to be sure which is right when they deviate which is what matters.

 

 

Edited November 17, 2016 by Mucka

[Ali1977]

Having just read the latest METO weather I don't think people should discount some cold weather late Nov or early Dec. There is still a very good chance the blocking ends up in the right place to direct some proper cold weather into the UK - this may not be 2010 type weather with snow and ice days, but it still likely we'll get below normal temps and a chance of some wintry precip for many.

Don't be surprised over the next few days if we get some stella charts cropping up as well as some not so, just be careful what you believe.  The MLB is pretty much nailed, beyond this is all to play for..

[northwestsnow]

Bit strange that the beeb/meto have plenty of rain/sleet/snow around these parts tonight but Gfs 12z even at this late stage has pretty much nothing in the way of precip all night...

Edited November 17, 2016 by northwestsnow

[jvenge]

10 minutes ago, northwestsnow said:

Bit strange that the beeb/meto have plenty of rain/sleet/snow around these parts tonight but Gfs 12z even at this late stage has pretty much nothing in the way of precip all night...

At times I've had every GFS ensemble tell me I should be seeing snow outside, but nothing :-) Not saying it is just the GFS, but snow seems tricky even at short term.

[bluearmy]

The para ecm again more enthused than the op re snow possibilities from both systems T80 and T120 ish

Welsh hills and the sw moors could well be picture postcard opportunities on both occasions

 

Edited November 17, 2016 by bluearmy

[Cheese Rice]

The track of Sundays low is perfect for Southern Wales/Peak District and North/West Yorkshire if we want any snowfall, snow confined to the northern edge of the band mind but if you happen to sit on the northern edge and be on high ground you could be in luck as it travels north east. I'm back in Leeds at 200m on that day so definitely something to keep an eye on. 

Edited November 17, 2016 by Cheese Rice

[bradymk]

Models still struggling with the position of the lows for the next few days. Mondays low much further south on 12z. A dry chilly day for many on this run. 

[Cheese Rice]

38 minutes ago, northwestsnow said:

Bit strange that the beeb/meto have plenty of rain/sleet/snow around these parts tonight but Gfs 12z even at this late stage has pretty much nothing in the way of precip all night...

Its going of the EURO4 model which is why there is a meto warning out for snow above 100m.

Also worth remembering the short range models have significantly higher resolution. 

 

Edited November 17, 2016 by Cheese Rice

[Nouska]

34 minutes ago, northwestsnow said:

Bit strange that the beeb/meto have plenty of rain/sleet/snow around these parts tonight but Gfs 12z even at this late stage has pretty much nothing in the way of precip all night...

They will be using very hi-res short range modelling - closest we'll get to seeing similar is the AROME 1.3km data.

http://www.meteociel.fr/modeles/arome.php?ech=3&mode=142&map=30

Zoom facility.

http://www.meteociel.fr/modeles/aromezoom.php