Model Output Discussion 29th December - Into mid-Winter.

[nick sussex]

Its safe to come out from behind the sofa! I almost couldn't bear to look at the outputs this morning but I found my model anorak reserves and ventured into the light! Running joke only if you've seen Poltergeist!

After one of the most painfully slow episodes of the GFS playing catch up we're slowly inching towards agreement. However there are still some important differences and the UKMO is a bit further east with the elongated PV which we'd want to see corrected further west, also the jet loop back towards the Low Countries is much better on the ECM and the colder air further north.

The issue for the UK even with the better ECM is generally the slack flow, ideally you'd want a stronger flow to develop some convection off the North Sea.

That may well change in future runs, much depends on the development of low pressure over southern Europe, preferably you'd want also to see a westwards correction even in the ECM. I haven't seen the precip charts yet but the jet cut back does bring a shortwave very close to the se which given the cold uppers should be snow.

Overall I think we need a couple more runs before being completely confident of getting the Scandi block at the right latitude, with the GFS and UKMO still not as good we need them to move towards the ECM solution today.

Edited January 10, 2017 by nick sussex

[joggs]

37 minutes ago, Chris.R said:

I think it's ON! 

 

It'll be interesting if it's start moving nearer the reliable.

Also the mo update later will give us a heads up one would imagine.

[bluearmy]

The eps do spread post day 7 but that's fairly normal on the eps with 51 members - and the spread isn't all bad anyway.

todays suite varies from previous days 8/12 by not consolidating the ridge across s scandi but trending west more our longitude and further west thereafter - anomolies not too bad for latitude but could be a tad higher.

in the extended low hights drop in from the north and scandi trough/low heights establish again as the east Canada high drifts its influence a little east towards w Greenland, drawing the Atlantic high anomolies west.

As mentioned yesterday morning, the euro trough modelling is going to be very uncertain judging by previous episodes. That has a huge effect on any CAA across us. 

Let's hope the ec det continues to lead the way with the eps playing catch up post day 7. Usually the other way around and given the gefs are more suppressed, wouldn't be counting any chickens yet. 

Plenty of potential later this week - as ever, expect the worst and anything white on the ground will seem even more magical!

[Summer Sun]

Of course these snow depth charts can't be taken as a given but....

[snowbob]

Right cmon gfs stop fighting ecm

you know you want to

we won't judge

 

[Tim Bland]

Still a chance for southern and south western areas on Thursday Morning.  Looks like south Downs, SW Moors and Cotsworlds etc could see a light covering with sleet in the towns.

Re ECM / GFS debacle I have seen it many times before in 15 yrs of model watching.  What we are likely to see is a middle ground,  this to me looks like a mid lat block over us stretching to Scandi. This will mean a slack easterly for the south.  I expect the GFS to creep towards ECM over next few runs and the ECM to back track slightly until they meet in the middle.  It is very rare for one model to be totally correct and the other wrong.  Hope I am wrong though and ECM is 100% correct!

 

[loafer]

12 minutes ago, Summer Sun said:

Of course these snow depth charts can't be taken as a given but....

Interesting - that reflects the frontal snow potential I said a few posts ago. What is interesting is that the GFS snow charts are showing that even though their uppers are very marginal for snow. ECM is much cleaner in that regard.

[The Weather Dragon]

From the model output - my analysis is that we will end up with a mid latitude block - the 'form horse' and general signal for this winter. There is no indication for significant high latitude blocking - unfortunately 

[bluearmy]

The 12z gfsp which isn't on meteociel as yet managed to get the ridge to Denmark and allow a cold flow into the s of the uk by day 10 

[Johnp]

6 minutes ago, snowice said:

ALL 51 AT THAT RANGE WOO.

As discussed earlier, that was a tad misleading from Matt. You need to read the follow up tweet.

Edited January 10, 2017 by Johnp
.

[Met4Cast]

6z already slightly more amplified than the 00z, all heading in the right direction thus far. I'm sure we'll see more support from the ensembles too. 

[frosty ground]

Interesting feature running down the north sea coast.

[doctor32]

06Z run looks slightly better, everything just a tad more west and again heading more in the direction of ECM... in my eyes anyway 

[doctor32]

Just now, frosty ground said:

Interesting feature running down the north sea coast.

Yes, although deepending on 850 upper temps and dew points at said time will determine if this will produce more snow for eastern areas or just wintry mix...

[That ECM]

Look at Italy at t84 on O6z v earlier gfs run at t90 

[weirpig]

might even see a chesire gap feature cropping up for those further inland.

[Ravelin]

GFS continues with subtle changes at t108.

0Z   6Z

Higher heights close to Iceland and the low over the Med digging slightly further south into N.Africa.

[Luke Attwood]

1 minute ago, Ravelin said:

GFS continues with subtle changes at t108.

0Z   6Z

Higher heights close to Iceland and the low over the Med digging slightly further south into N.Africa.

 So is this positive for cold?

[Ravelin]

2 minutes ago, Luke Attwood said:

 So is this positive for cold?

It's positive if you want the GFS to follow the ECM solution, the latter of which is the colder of the two going forward.

[Weathizard]

It's still considerably flatter than the ECM

[frosty ground]

A move towards the ECM..... 

[Met4Cast]

I suppose it would have been too much to expect the GFS to build heights towards Scandi cleanly. The 6z is definitely an improvement but it's so incredibly messy, definitely not the clean evolution of the ECM or UKMO. It starts to build heights North-East then just sortof stops before trying again.

 

[Ravelin]

Just now, frosty ground said:

A move towards the ECM..... 

Definitely, and also an interesting little feature off the coast of Kent for those down there?

[Nick F]

The broadscale mid-upper level flow differences between 00z GFS and EC ops start after t+144 (though we do have surface differences before then at the weekend)

As the comparisons show ECM extends troughing / low heights further SW across southern/western  Europe early next week compared to GFS, as the  ridge builds NE - which prevents to much ridging in the Atlantic pushing east - whilst GFS also pushes more energy east out of Greenland. N.B. see that deep low west Azores too on EC - that suggests more energy in STJ pulling Atlantic troughing further south

You can see on the ECM 300 hPa winds - the jet returning SW on southern flank of block building NE is further west - allowing cold air troughing over Euro land further west

GFS has equatorward jet further east + poleward jet to the NW of UK further east - which doesn't allow as good position of block for UK cold advection from east

So we can see the upper pattern differences and it maybe that GFS may not be handling as well the returning equatorward jet over Europe and extention of troughing SW and W to our south.

Also worth mentioning that the polar stratosphere is undergoing changes that may benefit blocking over and to the NE of the UK too, a huge ridge in the stratosphere will weaken winds above northern and western Europe and may help re-inforce ridging building NE

Edited January 10, 2017 by Nick F

[Man With Beard]

Getting there

  compared with  

although it brings in a mild sector, temporarily: