Model Output Discussions 12z 01/09/2016

[Frosty.]

The GEFS 6z mean shows a change to unsettled trough domination with rather cold or at least below average temperatures, cold enough at times for wintry ppn with snow on higher northern hills and mountains bringing an early taste of winter during the next few weeks with overnight frosts during quieter interludes with winds generally north of west with atlantic ridging but for a while next weekend and early week 2 the winds more from a Nly / NEly point..isn't it nice not to describing swly mush!

[Mark wheeler]

I couldn't help but post this . It looks like the polar vortex first tries to kick out then gives up and then decides well to go to the loo.

[Methuselah]

I'm liking the current model-output...Not because snow is likely, in the short-term, but because the southern North Sea could be a breeding-ground for some interesting T-Storm activity. Especially if there are cold uppers running over, what are currently, warmer than usual SSTs?

[bobbydog]

49 minutes ago, CraigofOldham said:

I wouldn't call it smashed up, I would call it under developed. Low heights start to dominate the arctic region prior to 120 so to me that is signalling the delayed but inevitable strengthening of the Polar Vortex and probably a return to a +AO. If modelling continues in the same vein then any weak ridging into Greenland will get flattened out as we head through Nov.

Model watching has been good the past week or so but I don't think there has ever been modelled a full on Greenland block and the chart posted in the quote from last year, well, we could end up back in that position by mid month imo.

I would expect the PV to strengthen. In fact it will strengthen. The point is, it is going into the season in a weakened state, which bodes well for the winter. As opposed to last year, when it gained strength early and became virtually unbreakable. Time will tell but there's nothing to worry about yet.

[Zakos]

Im not sure, but as it so early on in the season, I believe that if we did get very cold 850 temperatures from an potent easterly, the large temperature difference between the sea and the airmass would create disturbances in the flow and lead to increased snowfall across the UK.

The 12z GFS yesterday showed such a possible scenario, given a slight shift further west

Unfortunately the cold blast has been significantly watered down on recent runs, still time for change in the output. 

Edited October 30, 2016 by Zakos

[terrier]

Well looking at the gfs and ecm output the polar vortex does look to be getting its act together. But as we head into November this isn't anything to be surprised about. It's were we head later into November do we start heading towards a +nao state interesting times ahead I feel. But one thing is clear we do seem better placed heading into winter than the past few years. 

[Frosty.]

Dare I say GloSea5 must still be looking encouraging for coldies during the second half of November..And the first half of Nov looks generally unsettled with below average / cold temps for the most part and cold enough for an increase of night frosts and also for sleet & snow to feature at times through the month ahead, certainly in upland northern uk according to most of the operational runs and the Gefs / Ecm ens mean...Dare I say, November as a whole will be a good month for coldies?. I think I dare!

Edited October 30, 2016 by Frosty.

[bobbydog]

Well the AO is forecast to stay firmly negative for at least the first half of November-

[Mucka]

4 hours ago, bluearmy said:

The 00z eps at their furthest point are splitting the jet streak upstream the other side of the Atlantic but the northern arm is stronger and further north than in the preceding two weeks 

the options remain fairly wide for the time being - will probably be Thursday/Friday this week before we get a handle on which way the 14/24th Nov is likely headed

If I had a gun pointed at me I would plump for mid lat high sat close to the UK - centred just west of Ireland 

bit of a kop out !

You sound like a 15 day mean anomaly chart Blue. 

Me?

No idea. 

I'm just lying low after sticking my neck out backing our first cold snap/spell of the year in a weeks time.

Looks messy, but I will say that the operational runs have continually ebbed and flowed on the strength of Atlantic blocking and generally underestimated it in FI.

For example this was GFS 06z Op for Nov 5th compared to the latest prediction.

 

Of course the atmosphere is in a permanent state of flux so it cannot be assumed background forcings will be largely the same through to mid November but Glosea5 and other long range signals still indicate higher probability of blocking which gives more room for optimism.

As for the nearer timescale and our chances of a cold snap/spell still look good though it may well not be as potent or long lasted as people would like or I fancied.

In relative terms though it will turn cold in the North and chilly in the South for a time at least - thereafter there is a lot of scatter of course.

[bluearmy]

1 hour ago, bobbydog said:

Well the AO is forecast to stay firmly negative for at least the first half of November-

The latest ecm takes it fairly neutral post the 11th

However, the latest gefs doesn't get much above -2 by mid month and the 00z Canadian ens are in the same ball park as the eps

 

 

[SMU]

The mid run GFS through 108 sees better westerly flow of cold air filtering through Scandi with no blocking shortwave -

Should mean better cold air alligned towards the UK at around day 7-9

Slightly better blocking in towards Greenland as well !

s

[Ali1977]

3 minutes ago, bluearmy said:

The latest ecm takes it fairly neutral post the 11th

However, the latest gefs doesn't get much above -2 by mid month and the 00z Canadian ens are in the same ball park as the eps

 

 

METO longer range sounds more condusive to a neg AO, that could change though I guess. Lets see how this GFS models it, the last few GEFS have stepped slightly away from though crazy blocked NHs, lets hope that trend doesn't continue.

[Ali1977]

Different GFS again, I imagine that low could be producing a lot of rain that could be turning to snow on high ground up North as the cold easterlies dig in.

More importantly the PV is once again clearing from Northern Canada again - this could be a very good FI with deep cold already into Scandy....

 

Edited October 30, 2016 by Ali1977

[doctor32]

That low slap bang over uk will produce alot of rain for northern parts of uk bonfire night/day into the 6th, with a very strong gusty easterly... cold raw wind!

 

     

 

 Eastern parts of northeast england would get a real pasting with large amounts of rainfall if this was to verify.

[Mucka]

Great UKMO 144 for Atlantic blocking but poorish GFS for same period with jet riding over the top, take your pick.

Hoping ECM or at least JMA backs UKMO with regards upstream amplification.

What is encouraging is that even the very progressive GFS wants to reamplify in FI.

Edited October 30, 2016 by Mucka

[bobbydog]

8 minutes ago, Mucka said:

Great UKMO 144 for Atlantic blocking but poorish GFS for same period with jet riding over the top, take your pick.

Hoping ECM or at least JMA backs UKMO with regards upstream amplification.

What is encouraging is that even the very progressive GFS wants to reamplify in FI.

There was some concern over the ECM earlier regarding the PV lobe over Greenland. I thought it should hopefully drop into scandi. Let's see what the GFS does with it.

[bobbydog]

Good so far-

[Mucka]

Just now, bobbydog said:

There was some concern over the ECM earlier regarding the PV lobe over Greenland. I thought it should hopefully drop into scandi. Let's see what the GFS does with it.

Yes, it would be normal for the PV to want tos et up there this time of year and people don't like seeing those purple blobs of doom.

It is a concern and we often see the models play around with moving the main lobe of the PV to the Eastern side of the Northern hemisphere but more times than not a residual lobe remain around Greenland and reforms and it is also true that the models have been looking a little flatter and more mobile in FI lately (as with this run as I type) but it is all deep FI and until the longer range models move away from their recent proclivity for a blocking signal through November we may as well remain positive.

[Cheshire Freeze]

1 minute ago, Mucka said:

Yes, it would be normal for the PV to want tos et up there this time of year and people don't like seeing those purple blobs of doom.

It is a concern and we often see the models play around with moving the main lobe of the PV to the Eastern side of the Northern hemisphere but more times than not a residual lobe remain around Greenland and reforms and it is also true that the models have been looking a little flatter and more mobile in FI lately (as with this run as I type) but it is all deep FI and until the longer range models move away from their recent proclivity for a blocking signal through November we may as well remain positive.

We were always going to see a period of more mobile weather at some point this coming month though. We were never going to sail into winter being blocked all the way through. I don't think I've seen one archive run of any year where this was the case. Personally I don't want to see any attempts at deep cold until we're about to enter December. As long as we don't see an entrenched PV setting up to our N and NW then I'm happy. The strat profile is also light years away from last year's offering.

[bobbydog]

4 minutes ago, Mucka said:

Yes, it would be normal for the PV to want tos et up there this time of year and people don't like seeing those purple blobs of doom.

It is a concern and we often see the models play around with moving the main lobe of the PV to the Eastern side of the Northern hemisphere but more times than not a residual lobe remain around Greenland and reforms and it is also true that the models have been looking a little flatter and more mobile in FI lately (as with this run as I type) but it is all deep FI and until the longer range models move away from their recent proclivity for a blocking signal through November we may as well remain positive.

I suppose on the face of it, it could look better in FI 

But look how the strat vortex ends up-

Literally knocked sideways!

[Summer Sun]

GEM is looking chilly for bonfire night tho not as cold as it would be in mid winter

[Cheshire Freeze]

1 minute ago, bobbydog said:

I suppose on the face of it, it could look better in FI 

But look how the strat vortex ends up-

Literally knocked sideways!

Yep, no signal for an early season vortex residing Greenland/Canada (well not currently anyway) which should maintain the risk of N Atlantic/Greenland heights as we head through latter November and into the early winter period. 

We see attempted vortex intensification over the next week or so around the above mentioned areas but with the tendency for quite rapid displacement towards the Siberian side, we are going to see the NWP fiddle about with some Atlantic mobility as a response to this signal. I suspect mid November's weather will not be entirely clear for another week or so.

[johnholmes]

Come on folks it really is going to seem an incredibly long winter no matter if you are a cold or mild supporter if every run is going to micro analyse for deep cold. That  just will not happen, never has never will. Check the old charts for 1946-7 or 1962-63. Neither winter really began before Christmas. Can we have some realistic analysis of pre 240h and how the UK as a whole looks to be with regard to weather please?

Rather blocked for a week or possibly two, beyond that who knows. I certainly do not.And the first week of November is hardly a time to get lying snow for more than a few hours anywhere on low ground south of the Border, or am I totally wrong?

Edited October 30, 2016 by johnholmes

[Cheshire Freeze]

1 minute ago, johnholmes said:

Come on folks it really is going to seem an incredibly long winter no matter if you are a cold or mild supporter if every run is going to micro analysed for deep cold. That  just will not happen, never has never will. Check the old charts for 1946-7 or 1962-63. Neither winter really began before Christmas. Can we have some realistic analysis of pre 240h and how the UK as a whole looks to be with regard to weather please?

Rather blocked for a week or possibly two, beyond that who knows. I certainly do not.And the first week of November is hardly a time to get lying snow for more than a few hours anywhere on low ground south of the Border, or am I totally wrong?

Totally correct, John.

[knocker]

Next weekend still looking decidedly grotty with the upper  low sliding SE  on Friday.

Thereafter it phase in with the cut off low to the south west and then the trough to the east  to form a positively tiled trough orientated south of the UK. This allows high pressure to ridge NE over the UK In the process the trough deconstructs forming another cut off upper low over Iberia  and the next system to gird it's loins to the NW ready to track SE over the UK by T252 but that is for the future/