Model output discussion - 5th December 2016 - Into Winter we go

[bobbydog]

While everyone is worrying about 10 days plus, at 120hrs, 18 out of 20 members of the GEFS are showing snow for some part of the UK and not just northern Scotland...

For example- 

Interestingly, quite a few have snow for the southern coastal counties, even Cornwall. @knocker Sidney will be most displeased...

 

[Ben Sainsbury]

Not to get any hopes here but I think we're forgetting about the "marginal" snow event that could take place on the evening of New Years Day. As a matter of fact this event has been consistently modelled over the last few days so definitely something we should keep on eye on. However marginal events like these are extremely difficult to predict even 3 days away.

This event really depends on the timing, the sooner we can -5 850hpa temps the better, but then the closer we move towards night the colder the temps. Something to keep an eye on anyway.

The first set show the 850hpa temps and precipitation type on GFS 6z:

This next set shows the 850hpa temps and precipitation type on GFS (P) 6z:

3 minutes ago, bobbydog said:

While everyone is worrying about 10 days plus, at 120hrs, 18 out of 20 members of the GEFS are showing snow for some part of the UK and not just northern Scotland...

 

Interestingly, quite a few have snow for the southern coastal counties, even Cornwall. @knocker Sidney will be most displeased...

 

 

And as bobbydog has just indicated the GFS has support from GEFS members too.
What timing to post at the same time! aha

Edited December 28, 2016 by Ben Sainsbury

[Scandinavian High.]

Is Ian Fergie about he posted a wintery update yesterday for January is it all change now going by some posts on here this morning we are entering a mobile pattern from the south west very confusing some times on here..

[jvenge]

GFS 6z is bringing slightly above average temperatures to the UK after the brief cold short incoming. Different from the 0z, which was keeping things at or below average. I didn't manage to look at the ensembles yet to see how representative it is.

 

Edited December 28, 2016 by jvenge

[shotski]

Just a quick question. 

Why don't they run the GFS parallel at the same time as the op ? Thanks. 

[IDO]

6 minutes ago, abbie123 said:

Is Ian Fergie about he posted a wintery update yesterday for January is it all change now going by some posts on here this morning we are entering a mobile pattern from the south west very confusing some times on here..

Hi

Anyone who claims to know post D7 is just guessing IMHO. Look at the Control at D11:

The mean at the same time suggests the op is probably out of sync with the rest of the suite:

All to play for, and answers are probably a day or so away viz D10 plus.

[carinthian]

If we sit back and look at this wider picture at day 10, the chart remains the same. Two features you rarely see together is the Pacific Maritime Canadian / Alaskan block and Mid Atlantic block persisting for such along time. This formation basically breaks up the normal zonal Rossby Wave flow across North America and North Atlantic. The energy bottles up in the Arctic regions and then is released southwards in waves. Nearer to home we are now starting to see the first release into Europe of Arctic sourced cold with a upper trough now likely over Western Europe by early NY. At day 10 its almost impossible to be precise with forecast charts that far out, but I am sure most of Europe will be on the cold side. As ever the British Isles is going to be nearer the Atlantic High, no Omega Block for prolonged cold just yet, but cold incursions for sure. Its much better than last year.

 C

Edited December 28, 2016 by carinthian

[bluearmy]

Just now, shotski said:

Just a quick question. 

Why don't they run the GFS parallel at the same time as the op ? Thanks. 

Maybe it takes longer ??

ecm para always came out later 

perhaps they run the para suites on slower machines - they aren't using them in anger as yet so no point in rushing them out

Impressive mean at days 8/9 on the gefs

[78/79]

This time last year people would have bitten your arm off for what's on offer at the moment.

[Day 10]

Just commenting on the 6z alone, if we keep getting bouts of winds from a Northerly quadrant then that will do me, surely a few nice surprises could crop up anywhere.

 

 

Edited December 28, 2016 by Day 10
remove image

[marksiwnc]

Just a quick question.  With waters quite warm around the UK and the burst of frigid cold coming down would this not promote some polar lows?  If polar lows do develop then surely the outlook could be anything.  I remember a low dropping from Iceland was a possibility yesterday could this low be a polar low development and the models are not able to pick it up until last few hours??? 

[karyo]

22 minutes ago, marksiwnc said:

Just a quick question.  With waters quite warm around the UK and the burst of frigid cold coming down would this not promote some polar lows?  If polar lows do develop then surely the outlook could be anything.  I remember a low dropping from Iceland was a possibility yesterday could this low be a polar low development and the models are not able to pick it up until last few hours??? 

I am not the best person to answer this question but I don't think a polar low would significantly change the broad pattern. It would of course have short term benefits (snowfall). 

Besides, I think colder uppers for a longer period would increase the chance of a polar low but as this stand this is just a cold shot rather than anything long lasting.

[Weathizard]

23 minutes ago, marksiwnc said:

Just a quick question.  With waters quite warm around the UK and the burst of frigid cold coming down would this not promote some polar lows?  If polar lows do develop then surely the outlook could be anything.  I remember a low dropping from Iceland was a possibility yesterday could this low be a polar low development and the models are not able to pick it up until last few hours??? 

The low pressure that slides down from Iceland isn't a 'polar low'! The term gets used incorrectly quite often on here unfortunately!

 

Under the right thickness and conditions it is possible to get a true 'polar low' here but very rare.

[johnholmes]

32 minutes ago, marksiwnc said:

Just a quick question.  With waters quite warm around the UK and the burst of frigid cold coming down would this not promote some polar lows?  If polar lows do develop then surely the outlook could be anything.  I remember a low dropping from Iceland was a possibility yesterday could this low be a polar low development and the models are not able to pick it up until last few hours??? 

I don't pretend this is the definitive post about Polar Lows but it may help your understanding of them

cripes I wrote it in 2005, there must be more up to date posts that would help?

Edited December 28, 2016 by johnholmes

[Paul_1978]

48 minutes ago, jvenge said:

GFS 6z is bringing slightly above average temperatures to the UK after the brief cold short incoming. Different from the 0z, which was keeping things at or below average. I didn't manage to look at the ensembles yet to see how representative it is.

 

I had a look at the 00z GFS postage stamps at T+192. 

The majority (over half) show a NW'ly. A quarter show W'ly. None show anything from the S/SW. 

By T+240, W and NW'lys are evenly spread, along with the rest of the members showing anything from SW'lys to N'lys. One or two members showing NE/E'ly but they are in the minority. 

[Scandinavian High.]

I could be wrong but at 180 gfs p could this bring snow showers to east coast and south east England I'm still learning so does anyone have any info  on this thanks. 

[phil nw.]

Yes quite a cold set from the 06z GEFs.

A look at the T180hrs mean chart shows the vortex split mores towards Siberia thus weakening the Canadian vortex

this helps to keep the jet tilted more nw-se and with less forcing upstream more chances of developing favourable heights in the Atlantic for the UK.

The 850s and 2m temp for C.England looking quite cold on this run

The clusterings around the same time pretty much all show a flow from the north west in varying degrees with another pulse of Atlantic ridging underway further west coming off the NA seaboard.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cslp&HH=180&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

The split in the temperature ens are certainly swinging around beyond day 7 run to run but the general theme of Atlantic blocking remains.It's just a case of how far north the waves of Atlantic ridging manifest themselves.

It is certainly a mile away from a strong zonal setup so options remain for some more seasonal weather as we go into January. 

 

 

[Gael_Force]

24 minutes ago, Weathizard said:

The low pressure that slides down from Iceland isn't a 'polar low'! The term gets used incorrectly quite often on here unfortunately!

 

Under the right thickness and conditions it is possible to get a true 'polar low' here but very rare.

I thought the upper air had to be very cold (purples on Meteociel 500 temps) to initiate convection for polar low formation. I don't see anything cold enough to the north on the latest run, in reliable timeframe.

[AdrianHull]

Well it's  definitely feeling more seasonal on New Years Day with cold incursions after that with a promise of something on the colder side in the second week of January. 

Remember people! The last 3 Winters were woeful in respects to cold and snow and I'm enjoying today with still having a ground frost up till now with lovely blue sky and sunshine.  So let the trend be your friend and not take 200± charts too much as gospel. 

Hope everyone has had a great Christmas and fingers crossed for January. 

[pdiddy]

1 hour ago, jvenge said:

GFS 6z is bringing slightly above average temperatures to the UK after the brief cold short incoming. Different from the 0z, which was keeping things at or below average. I didn't manage to look at the ensembles yet to see how representative it is.

 

ensemble average stays lower

Edited December 28, 2016 by pdiddy

[karlos1983]

Well if the GFS (p) comes off I might just get PARAplegic 

Edited December 28, 2016 by karlos1983

[shotski]

Isn't that the 0z though, when does the 6z come out ?

[jvenge]

6 minutes ago, shotski said:

Isn't that the 0z though, when does the 6z come out ?

They are always a run behind, so the 0z para comes out at the same time as the 6z. 

I'm not sure I see much point in looking at it after day 7 though, as you can see how much the GEFS are chopping and changing each run, so to me looking at the day 10 para is no different than to cherry picking something from the GEFS.

[Cheshire Freeze]

Cold again...Certainly backs up what Fergie was saying the other day about the signal for a marked cold signature S UK into Jan. HP just to N and a cold easterly S of this.

 

A point on the EPS discussion...haven't they been all over the place for the last 6 weeks or so? One moment looking promising in the extended range, the next flipping to something different?

Edited December 28, 2016 by CreweCold

[bluearmy]

19 minutes ago, CreweCold said:

Cold again...Certainly backs up what Fergie was saying the other day about the signal for a marked cold signature S UK into Jan. HP just to N and a cold easterly S of this.

 

A point on the EPS discussion...haven't they been all over the place for the last 6 weeks or so? One moment looking promising in the extended range, the next flipping to something different?

Those CFS runs are in the same page as the back end of yesterday's eps

the extended eps haven't really been flipping.  the mid Atlantic ridge evident in most runs on the mslp anomoly and also higher than average on the z500 anoms. what I would say is that the anomolies in the 10/15 day period haven't been particularly deep. Hence the opportunity for the Atlantic ridge to edge east next run or the sceuro trough to edge west thereafter. 

the GEFS have looked a little less consistent but with only 40% of the no of members, it's more liable to change on the mean and anoms. 

that 06z suite was certainly sniffing a sinking trough day 8/9 with the ridge building across thereafter. day 8/9 only just after resolution drops so more interesting than seeing something clustering later in the run. it isn't often that the 06z GEFS sniffs the way ahead against the previous cross model offerings but if has happened in the past.