Model Output Discussions 06z 04/11/16

[nick sussex]

No fireworks at T192hrs but okay from the ECM. And given the GFS we should be thankful that it wasn't supported by the Euros, in a sense that chunk of the PV heading south doesn't do us any favours.

Its a timing issue really, we need to delay that PV chunk by 24hrs to allow a better chance of the high getting a bit further north and that cold air westwards.

There is though a huge difference upstream between the UKMO and ECM/GFS. It looks like the UKMO phases two shortwaves one in the southern jet and the other coming in from the Pacific which forms a deepish low. The ECM/GFS don't do this.

Although that Pacific ridge pushing south is something that's good for the longer term we're left in a weird scenario because do you want jam now or in a few weeks.

 

Edited November 29, 2016 by nick sussex

[Frosty.]

One word describes the Ecm 12z..anticyclonic indeed the high intensifies next week so it becomes very anticyclonic!

[Methuselah]

5 minutes ago, snowice said:

GFS over doing the sw Tosh?

Ecm over doing the Easterly! 

The wait goes on!

 

It could go either way, snowice, but I'd plump for the ECM, this time...But, hey, what about the 'third way' - that in ten-days' time, we'll all still be asking ourselves the same question?

[booferking]

Time for the Atlantic to admit defeat and give up for this year is different than your normal year, let the easterly commence you troll.

[marksiwnc]

I think fergieweather has given a little clue on his comments.  I assume the cold will last a bit longer than first thought.  maybe only a few days of mild mush.  Ian never comes online this time of the day unless he wants us to know something 

[Mucka]

No sign of Southwesterlies on JMA.

[Banbury]

14 minutes ago, gottolovethisweather said:

I think you might falling into my trap? It will already be nicely cold at the surface I think.

Nooooo it should be quite cold under that HP, I just want even colder

[Frosty.]

And the Ecm 12z ends....drum roll..very anticyclonic

[Geordiesnow]

6 minutes ago, Ali1977 said:

ECM pushing the block north which may link with heights over pole - no breakdown in the high over us here. I wonder if we can go from a cold dry high,  to a colder snowier setup without really getting slightly milder at all. 

Get used to scraping the cars anyway - they didn't get much use last year at all, in fact I've used it more this year before winter than the whole of last winter!!

I'd still be careful in assuming this high pressure spell is going to be full of sunny days and frosty nights, the high is forecast to become a cloudy one from now until the end of the week, the big question is, how much cloud will remain under that high over the weekend, one would think with winds becoming very slack and then veering more from the continent we may see the cloud melting away but we could of course end up with anticyclonic gloom. I'll take most BBC/UKMO predictions on cloud cover with a word of caution because there forecasts regarding cloud cover last weekend were a little off the mark to say the least although in fairness forecasting cloud cover in high pressure situations is never easy.

Happy with the ECM though, high had a better orientation than the 00Z run and there was hints it wanted to send more in the way of lower heights towards Iberia, not too fussed its not showing the cold snowy charts in FI as it be a little irrlevant if it did but hopefully we will see a trend of getting some low heights over Iberia and we go from there basically.

[Ali1977]

UKMO at 144, could the Easterlies in the South produce some wintry showers I wonder - with no 850 maps it's hard to tell but it maybe long drawn enough to tap into some colder uppers from Eastern Europe. Aware it may well be wrong!!

Edited November 29, 2016 by Ali1977

[karlos1983]

2 minutes ago, Ali1977 said:

UKMO at 144, could the Easterlies in the South produce some wintry showers I wonder - with no 850 maps it's hard to tell but it maybe long drawn enough to tap into some colder uppers from Eastern Europe. Aware it may well be wrong!!

Would like to see the 168 chart

[Frosty.]

The GEFS 12z mean is also dominated by high pressure, especially further south..right through the next two weeks +

Edited November 29, 2016 by Frosty.

[BLAST FROM THE PAST]

So I like the idea to see HP control with frosty nights for say 1st week, probably 1st 10 days of Dec for the South.  For me then don't look NE, I'm think to look NW as HP retrogresses into the Atlantic and segment of displaced PV crosses Scotland bringing stormy NW'ly flow.  

Looking superbly cold tonight under what is not low uppers.  More please

 

BFTP

Edited November 29, 2016 by BLAST FROM THE PAST

[nick sussex]

5 minutes ago, Ali1977 said:

UKMO at 144, could the Easterlies in the South produce some wintry showers I wonder - with no 850 maps it's hard to tell but it maybe long drawn enough to tap into some colder uppers from Eastern Europe. Aware it may well be wrong!!

The really cold air is towards the Germany Poland border, that would take another few days to get to the UK. Given the set up on the UKMO T144hrs you'd need the high to pull further nw allowing those colder uppers along the southern flank of the high.

You can track where the cold air is by the Scandi shortwave, the further west that gets the closer the cold air will be, you really need that tracking sw towards the Low Countries, at the moment it seems to be more s/se.

[SMU]

Evening All.

'Positive bias' 

Thats the phrases of the day - once again it fully represents the GFS OP & ENS suite...

Im sure ( well hope ) without repeating the whole of Saturdays post that most people have now grasped the concept of how difficult it is for models to balance energy distribution between the Northern & Southern Streams, more especially the GFS that certainly under resolves that southern arm.  

Having taken a scooting glance at the 00zeds & now the refreshing 12's we have seen the same reoccuring theme from the models as we did Mon through Late Tues where in the mod term forecasts ( 144-192 ) The GFS ops + GEM drive significantly more energy into the Northern streams before slowly retracting the energy southwards in subsequent runs- I would say thats a 'Positive bias'

The other extreme of the spectrum - but equally taking the background signals into consideration-& probably the higher probabilities of occuring are the UKMO & NAVGEM - these could ( unproven ) have a slight negative bias where in these split jet scenarios they slightly overload the southern arm creating the favourable retrograde pattern & undercut-

ECM 12z - SLAP BANG IN THE MIDDLE.

So as a forecaster you have to go on past experience, & like the perpetual GFS failings of previous years & even identical failings thus far this week you have to conclude that every ensemble thats more positively tilited at 120 that the ECM can for now enter the file marked 'trash' - probability of verification 20/80...

We then head over to the 'cluster' of ECM / JMA with their neutral feel & the NAVGEM/UKMO blend that sees the most favourable positioning of the 4 key features on the map at 120 - so lets examine those & see where the changes will occur over the next 48 hours.

UKMO 120

* High pressure in the atlantic sees a slightly negatively tilted high in the furthest position NW compared with the rest of the suite - drawing a slight continental flow

* Atlantic low because of the negative tilt is being forced NNW up towards Greenland 

* Iberian low - being supported by a high %age of the available energy in the jet which is in the southern arm- The key here is the more you get in the southern arm the further the East/North East propergation 

* Scandi Shortwave - Crucial in its location as its our trigger low- & its being forced south because the northern arm is weaker & its looping like a 'n' shape with a sharp inflection point.

^^^ all the above features are in the right place ( for cold ) all because the energy thats going south is enough to get them into favourable positions- it wont be 100% of the full energy as there be a northern arm otherwise we would have a full retrograde up to greenland...

For reference the GFS -

* No iberian Low

* Scandi shortwave no recurve - its being projected east because the northern arm is flat with fast energy 

POSITIVE BIAS......

So the expectation here 80/20 is the landing zone cone if you like is somewhere between ECM & UKMO -

Based on history ive observed

- UKMO a good performer in undercut scenarios ( rem Mar 13 )

- Scandi Shortwaves are near 100% of the time projected to far east & sharpen up as you traverse the timeline of a model so @168 it may be all the way far east as Germany only by 120 its back in Holland & 72 / 96 it can come back as far as NE france ( Rem 2009 Easterly )

 

Therefor my forecast for the next 24-48 hours is for

0-72 minimal change

72-120 GFS to move to more negative tilted low in the atlantic & to show signs of developing the Iberian Low-Also ensemble suites pick the same signal up - perhaps tomorrow PM ( as this is todays 96-144 charts > tomorrows 72-120 )

144 onwards a high probability of the mild / flame ensembles evaporating ( for the second time this week ) to be replaced by an easterly flow of varying degrees of coldness - ranging from 0c - to maybe -8c

We will have to see whats the best possible cold flow we could tap although UKMO 144 looks almost best case out of a mediocre retrograde...

Moving past that - the hemisheric profile looks to get smashed by that huge pacific ridge - importantly the vortex needs to stay in the European or Eurasion quadrent- we DONT want it dropping west across into canada as that will stop any vortex split & cross polar ridge !

All in all we are creeping to a good solution- that will be cold--- can we make it to 'snow' cold...

December CET sub 4c projected....

 

S

 

 

 

 

 

[Ali1977]

Great post by Steve - looking forward to the Ramps and Booms later in the month with any luck!! 

[phil nw.]

A fascinating period coming up.Yes the blocking UK High looks a bore fest on the face of it but as long as modeling shows a large chunk of the pv aligning over the Siberian side then cold prospects remain good further on.

The Atlantic jet will be the weaker for it which increases the chance of the High maintaining, even building later.This will encourage the Siberian cold to come south and then hopefully west towards Europe around and under the block.The fact that we see signs of -ve Euro heights starting to show in the next few days is encouraging.

The models are not yet showing the re amplifying of the NH pattern until week 2 and beyond where signs of a near split in the troposphere vortex are showing in the later frames but this current setup is quite promising wrt keeping us on the cold side with a prospect of something from the east hinted at in the UKMO this evening.

[weatherguy]

Looking more broadly, and less so at the fine detail of a hundred miles here or there which will largely determine what setup the UK finds itself in in a week's time, this is one impressive looking Arctic High showing on the ECM at +216,

 

[SMU]

UKMO 168 continues the eastward propergation of the Iberian low & sends a tighter squeeze of Easterlies over southern England - Very cold surface air - impossible to tell upper profiles

[Frosty.]

it's about time the ukmo verified @ day 6!

[MR EXTREMES]

2 hours ago, feb1991blizzard said:

Its going to be a clear sinker on the ECM if you look at 240, the UKMO and ECM may take more time but it'll be the same result.

i agree been watching from behind the sofa its beautiful fresh week or two on the way.

but its clearly showing that high pressure will establish over southern england or bit further south but cant see no sign of northern blocking.

but it is only november but even into december the vortex is being battered but lets see how powerful the vortex is by mid dec.

 

[phil nw.]

A recent post has been removed- off topic and not in good taste-i may add.

In this upbeat period a little humour around model discussion may be deemed ok in the right context but please all let's try and keep it sensible and informative -and in good taste.

If possible please keep general banter to the other threads.

Thanks all.

 

[Frosty.]

Meanwhile, the GEM 12z shows swly zephyrs setting in by T+240..more runs needed!

Edited November 29, 2016 by Frosty.

[Banbury]

22 minutes ago, Ali1977 said:

Great post by Steve - looking forward to the Ramps and Booms later in the month with any luck!! 

Just tomorrow then

[Methuselah]

51 minutes ago, Frosty. said:

And the Ecm 12z ends....drum roll..very anticyclonic

I know we usually say this in 'reverse' but, wouldn't that chart be wonderful - in July?