Model Output Discussion 01/09/17

[knocker]

By 12 Thursday the ecm has the upper trough situated over Iceland with a pathway down to low pressure around the Azores. Giving a surface analysis of a deep low over Iceland with associated front and rain to the west of Scotland where south westerly gales are getting under way. The front actually trails down Ireland and away to the south west as far as the Azores. In the next 24 hours the front and rain track south east across England and Wales finally  clearing the SE by Friday lunchtime. Meanwhile the main low has slipped to the south east of Iceland and more rain and strong winds are impacting.Scotland, perhaps some snow on the high ground.

[blizzard81]

12 minutes ago, bluearmy said:

But that Atlantic profile won't allow for any reinforcements which means it will just fill in situ. Result is slowly sinking MLB as the jet runs across the top - only positive I take from that ecm op by day 10 is the continued absence of Canadian vortex. 

Too early to be thinking of the main course. I would bank the mid latitude block for now. 

[Man With Beard]

I think there's still room for a better Arctic High/North Atlantic High link up. It's very, very close. The idea of Scandi heights linking with the Arctic is by no means dead either. Small margins at play here. We're in the game at D6 but it isn't game over. Though the key player for early season cold - a strong Arctic High - has trended further away in the past 36 hours.

[bluearmy]

The eps mean  retain plenty of  split flow in the southern arm to keep the euro troughing happy approaching day 10. 

[bobbydog]

nice output all round really, when you look at the bigger picture, blocking in november with good wintry synoptics but not so cold as we would like... not to worry... then, as some of our more learned members have pointed out, maybe a more 'zonal' (ish) december, with a possible return to blocking by the end of december/new year. add in a weak La Nina, a strong easterly QBO and an arguably transitional PDO, it becomes all very.... '1962-esque'.....

(zips up flak jacket....)

[Frosty.]

I just think its great that there is hardly any mild weather showing apart from tues / wed / thurs next week and I feel coldies are in the game for some cold shots from the nw / n / ne from late next week onwards...interesting / exciting times as long as the met office are on-board!

[summer blizzard]

Personally i think that the outlook from the Euro is great. At day 8 we have a northerly and the trough in the Atlantic is negatively tilted to some degree. Where the Euro screws us is that it suddenly deepens a tiny low around Iceland (possible given the thermal gradients around the area) which seems relatively unlikely. As such i don't think we'd see the pattern sink so quickly. 

As for the GFS it has a quicker jet which means we get a less direct northerly as quickly but the lack of a random low near Iceland means the Atlantic undercuts (and then in FI does so again). 

My conclusion tonight would be that both models are perhaps trying to default a little fast towards the end (they both positively tilt that Canadian Trough behind even after the GFS spits out the undercut) however the outlook for the next week is clear with another northerly coming for next weekend and probably some kind of pressure build to our north or east afterward. 

Edited November 11, 2017 by summer blizzard

[Man With Beard]

23 minutes ago, bluearmy said:

The eps mean  retain plenty of  split flow in the southern arm to keep the euro troughing happy approaching day 10. 

Indeed they look more promising for cold at D10 than D7, which is a surprise - guessing quite a few go down the GFS route

  

[mpkio2]

Some very nice output on todays12z suites!

The positive today is that the UKMO has dropped its previous runs pattern and joined GFS/ECM!

However, I'm still not buying into anything post 17th November because past that point is FL territory.

Some nice eye candy charts though!

[chrisbell-nottheweatherman]

1 hour ago, mpkio2 said:

 

However, I'm still not buying into anything post 17th November because past that point is FL territory.

 

This needs repeating in this thread, IMO.  I thought earlier when we saw temperature and ppn. outputs for Central England that the 17th was the point at which uncertainty noticeably increased, and I don't think that this is discussed frequently enough here.  Spread between the perturbations, including the operational and control runs earlier in the period need to be considered as well.

[ICE COLD]

7 minutes ago, chrisbell-nottheweatherman said:

This needs repeating in this thread, IMO.  I thought earlier when we saw temperature and ppn. outputs for Central England that the 17th was the point at which uncertainty noticeably increased, and I don't think that this is discussed frequently enough here.  Spread between the perturbations, including the operational and control runs earlier in the period need to be considered as well.

The operational and control sit together throughout the 16 day period on the 12z GFS.

[chrisbell-nottheweatherman]

1 minute ago, ICE COLD said:

The operational and control sit together throughout the 16 day period on the 12z GFS.

Indeed, but the individual members diverge around the 17th, so making bold pronouncements on the expected situation beyond then is, IMO, pointless; one can speculate or discuss the possibilities, but I've read at least one "nailed-on" comment here today regarding the 18th and 19th which seems premature given the uncertainty from Friday onwards.

[ICE COLD]

3 minutes ago, chrisbell-nottheweatherman said:

Indeed, but the individual members diverge around the 17th, so making bold pronouncements on the expected situation beyond then is, IMO, pointless; one can speculate or discuss the possibilities, but I've read at least one "nailed-on" comment here today regarding the 18th and 19th which seems premature given the uncertainty from Friday onwards.

Oh yer it's definitely not nailed yet . The models keep flip flopping . Even the BBC week ahead is saying there is going to be a block but not sure where it will set up ? 

[Tim Bland]

11 minutes ago, ICE COLD said:

The operational and control sit together throughout the 16 day period on the 12z GFS.

Yes and as per the bottom “snow row” there is no more than a 1 in 20 or 5% chance of snow in the south unfortunately. Hopefully this will increase 

[mpkio2]

7 minutes ago, chrisbell-nottheweatherman said:

Indeed, but the individual members diverge around the 17th, so making bold pronouncements on the expected situation beyond then is, IMO, pointless; one can speculate or discuss the possibilities, but I've read at least one "nailed-on" comment here today regarding the 18th and 19th which seems premature given the uncertainty from Friday onwards.

Yup, agreed.

Good that the Op and Control are in syn, but noting is "nailed on" yet.

I'm keeping positive because many models are singing from the same hymn sheet re cold pattern potentially setting up. 

But I'm still cautious until we get nearer to 17th Novememberand see what the models say then.

Still keeping the faith, chaps!

[Rocheydub]

1 hour ago, mpkio2 said:

FL territory.

 

 

Can you please explain what FL territory is? Thanks

[Had Worse]

1 minute ago, Rocheydub said:

Can you please explain what FL territory is? Thanks

Fantasy land (FL) also known as FI or fantasy island

[blizzard81]

Very happy with the ecm ensembles. Very much marrying up with the meto extended forecast. 

[mpkio2]

Latest from Gav'sWeatherVids on the upcoming (Potential!) cold spell. Taking a look at the ensembles on meteociel!

A Good watch with a pretty balanced summary of where we are.

Enjoy!

[Had Worse]

Its nice that the toys are staying in the pram.  Would be good to have toy throwing ens for a laugh.

Next weekend is looking interesting given the wind direction, might have to get the shovel out.

[Snowy L]

18z not looking pretty. Atlantic low is going to power through between the Atlantic and Greenland high it seems.

Edited November 11, 2017 by Snowy L

[swfc]

Really need that low at 155 hrs to go up the west coast of greenland not mid atlantic!!!

 

 

 

 

Edited November 11, 2017 by swfc

[knocker]

After last night's anomalies worth a quick look at this evening's to see if there any further indications as to where the evolution is going.

The 6-10 (the latter part of which is where the pattern starts a transition) is much the same as previously. Upstream the twin vortex lobes Russia and N. Canada and the strong N. Pacific ridge with the tenuous connection to the high cell in the Franz Joseph Land region. The Canadian lobe has troughs orientated SE & SW and also a pathway to the trough north and east of the UK.

There is a fairly flat westerly upper flow across the US but it splits on leaving the eastern seaboard where much of it swings SW around the ridge south east of Greenland and then north west over the UK to the trough just to the east whilst the other arm more in the direction of Iberia and points further south

Thus the likelihood of it staying unsettled in this period with troughs tracking north of the ridge and dropping SE in the vicinity of the UK possibly introducing some quite wintry weather particularly in the north with temps below average.

The transition continues to be indicated in the 10-15 period.  Upstream the two vortex lobes become more diffuse and the Canadian one drifts into the Arctic as the high cell over Franz Joseph Land loses it's identity. This promotes positive anomalies NE Canada and Greenland and the Atlantic ridge and the trough to the east moving east. This leads a much slacker NW flow as the UK becomes more under the influence of the HP and more settled weather with temps below average. There is a fine line here and there is not complete agreement between the three downstream and the key remains the precise amplification and orientation of the two major players.

Edited November 11, 2017 by knocker

[Rocheydub]

23 minutes ago, Had Worse said:

Fantasy land (FL) also known as FI or fantasy island

Right so. Never heard it referred to as Fantasy Land. Has been Fantasy Island since Moses was a child! Or is this a misnomer created on the internet maybe? A bit like FI in the first place! :-)

Fascinating output at the moment. Nothing set in stone, but a wee bit too much excitement here considering the time frames involved.

[Mucka]

GFS 18z goes with the theme of a flatter pattern too and just a brief waft of cooler uppers which are gone before the weekend is out.

High lat blocking has certainly been watered down through today but maybe just a wobble.