Model output discussion - 1st December onwards

[SMU]

Evening all -

just one post from me - 

as this cold projection ( for want of a better phrase ) has developed apart from the odd rogue run - getting to the third stage where the cold hops the north sea into the UK has thus far always been out of reach- & as a result of that the discussion has been somewhat muted -

However as we close in on the reality of the first system ahead of the alleged slider at 132-144 so the models have slowly identified that the block would be more robust than expected, so what was modelled at 156 say x2 days ago in terms of progression of the atlantic eastwards has been taking little bitesize chunks back west over the last 8 runs of the GFS - so the 156 18z from 2 days ago is now the 108 chart tonight-

orignally the snowline was WAY back, however now at just 108 the snowline is from eastern scotland down to Holland

heres the GFS changes over the last 3 days

156 2 days ago

132 yesterday

108 tonight

with enough time & scope for further westward corrections - maybe enough to pull the snowline into the NE & EA

also as we reach t96 the trough disruption is significantly more than projected with the low getting sheared at the top & bottom-

Also a possible shallow shortwave cutting under the trough base at 120 should again hopefully support some further westward corrections of the cold

if we use this rationale of less progressive westward adjustments - then it doesnt take must of a retrogressive adjustment to the 168 & 192 ECM tonight to perhaps bring some snow into the UK along the frontal boundary....

 

lots of water 'literally' to flow under that bridge over the next 72 hours ....

s

[Day 10]

gfs a lot closer to the ecm now by 7th re: cold. As Steve has alluded to above the block is putting up more of a fight as things move closer (but hasn't this happened many times in the past?). This isn't over by a long stretch...

[geordiekev]

2 minutes ago, Polar Climate said:

gfs a lot closer to the ecm now by 7th re: cold. As Steve has alluded to above the block is putting up more of a fight as things move closer (but hasn't this happened many times in the past?). This isn't over by a long stretch...

As long as the Azores high remains on it's holidays and replaced by decent low heights, the potential to flip always remains imo from previous winter experiences.

 

[nick sussex]

1 minute ago, Polar Climate said:

gfs a lot closer to the ecm now by 7th re: cold. As Steve has alluded to above the block is putting up more of a fight as things move closer (but hasn't this happened many times in the past?). This isn't over by a long stretch...

Yes a bit of a nightmare forecast for the UKMO. Its noticeable that theres a trend in the models which are are now moving towards a bit more upstream amplitude which could pull things further west. The response if that continues will be to pull the Azores high further west amplify this a bit more and with it shortwave energy and the snow/rain boundary. I wonder whether we're seeing a last gasp response to the MJO.

[SMU]

If somone can post the link to the navgem 12z

that is the best case scenario from having more trough disruption than forecast....

[Nick F]

36 minutes ago, bluearmy said:

the strong Atlantic low for next week which blows away the blocking has been forecast very consistently by the ECM ens since it appeared at day 14 last week. there was hope that it might disrupt se against the block by the time we got within high ens ens but alas, this seems a forlorn hope. there is plenty to be optimistic about for coldies in the mid to long term but I think the short term is no longer much of an option now.  The scots may think differently next week. Their raffle ticket is the right colour at least.

Yes there is some consistency wrt to modelling of the deepening Atlantic low approaching later next week, but I still think past day 7 is still open to error even in these days of increasingly powerful NWP ... particularly given modelling differences GFS v EC wrt to an increasing + height signal to our north now appearing on EC det and EPS along with possible error with the lobes of the trop vortex digging down from Labrador, which may have ramifications for the jet and thus to future low tracks coming out of NE Canada. 

The models have never really thrown a bitter easterly at us at day 7-10 before backtracking, like they might 10 years ago  ... though GFS teased in FI when it first picked up on the ridge building NE to our east and cold pool moving west beneath. But it does feel like we are in uncharted terroritory with regards to extremes of weather patterns, oscillations, and even SST anomalies, so is NWP completely on the ball and adjusting to these extreme anomalies? Quite extraordinary the extreme WAA thrown north to the North Pole by Storm Frank and the potential for the residual warmth's effects on high latitude height fields over coming days ... 

But alas, even with the strong high latitude +height signal,  it still feels nothing changes with our luck most of the time. The U.K. as small as it is, it's like thread the needle trying to get deep cold and snow, even when the cold to tap into is so close by. The age old problem, that darn Atlantic ...

Edited December 30, 2015 by Nick F

[East_England_Stormchaser91]

As said yesterday evening, this next 72-96 hours will be very interesting. Note what I said about that low approaching from the SW. Some models are already showing this now as a channel low heading ESE. Note how much closer the cold is too. Watch this space.

[BLAST FROM THE PAST]

What Big Steve is on about......and as Darren Bett has just mentioned upcoming rain amounts are going nowhere as wet as recently it might be that this not a pointless period to highlight?

 

NAVGEM

 

nice

 

 

 

 

 

BFTP

 

 

 

Edited December 30, 2015 by BLAST FROM THE PAST

[Eskimo]

2 minutes ago, BLAST FROM THE PAST said:

What Big Steve is on about......and as Darren Bett has just mentioned upcoming rain amounts are going nowhere as wet as recently it might be that this not a pointless period to highlight?

 

BFTP

 

 

 

He also said the rain wasn't going to be as wet, to which me and mum both looked at each other went, "huh?" 

[Day 10]

5 minutes ago, nick sussex said:

Yes a bit of a nightmare forecast for the UKMO. Its noticeable that theres a trend in the models which are are now moving towards a bit more upstream amplitude which could pull things further west. The response if that continues will be to pull the Azores high further west amplify this a bit more and with it shortwave energy and the snow/rain boundary. I wonder whether we're seeing a last gasp response to the MJO.

Last one from me tonight, but it will be interesting to see if this trend continues into the mornings runs, fingers crossed!!

[Carlrg]

Its like sitting on the runway at the the end of a great holiday, willing the plane to take off even though it's packed to the rafters full of people, booze fags and duty free. If we all wish hard enough it will happen.

Navgem 12z

http://www.meteociel.fr/modeles/navgeme_cartes.php

[Dunstable Snow]

As Nick alluded to earlier signs of Azores high dragged west and trying to link north up towards Greenland. Not sure that it will make it but signs at last of the atlantic becoming less active. I remain optimistic that we will eventually see a much colder pattern develop as we move into the second full week of January. Those of us that love cold and snow certainly deserve a break having endured the last two winters and the first month of this one !

[Ben Sainsbury]

So on the GFS 18z run, into the disance at 372hrs we see much of Europe under high pressure, highest just a little north of the UK, we see an advection of warmer air, west of the UK, allowing easterly winds through from Northern Europe/Russia. I could see this setup being quite persistent, anyone have an ideas, I am no expert.

[london and south east kent]

Long way out on gfs nice easterly with  heavy snow pushing in to south east of England could be a trend 

[DAVID SNOW]

25 minutes ago, PerfectStorm said:

He also said the rain wasn't going to be as wet, to which me and mum both looked at each other went, "huh?" 

Dry rain is very hard to predict, it does, at times have the tendency to drift

Edited December 30, 2015 by DAVID SNOW

[mike Meehan]

2 minutes ago, abbie123456 said:

Long way out on gfs nice easterly with  heavy snow pushing in to south east of England could be a trend 

Thames streamer?

[nick sussex]

30 minutes ago, Polar Climate said:

Last one from me tonight, but it will be interesting to see if this trend continues into the mornings runs, fingers crossed!!

You can see this change if you compare the GFS 18hrs run with the 12hrs at T132 and T138hrs:

GFS 12hrs:

GFS 18hrs:

 

This might seem a small change but this helps to pull the pattern a bit further west and angle that shortwave energy more favourably.

The NAVGEM 12hrs run goes a step further by really increasing that amplification and bringing in a ridge extension from the Azores high which helps to separate the UK low from troughing upstream:

Not sure whether it will continue with its view but as an example of how it deals with the low and and upstream pattern we can see the big differences this makes if you can clear the low from the upstream trough.

 

 

 

 

[Nick F]

11 minutes ago, abbie123456 said:

Long way out on gfs nice easterly with  heavy snow pushing in to south east of England could be a trend 

Think the 12z EPS have a rogue member from the 9th bringing something that cold too ... but joking aside, good to see there are plenty of colder options than the 12z deterministic for London, so it is by no means without support.

[Mucka]

GFS 18z ensembles correct things somewhat West out to 144 so the best set for some time though still a way to go to get the snow line further S and W.

If GFS 00z improves again there could be some quite snowy runs Midlands Northward, at least until the Atlantic breaks through.

18z ensembles for NE England from last night compared to tonight (short) shows the sort of corrections in graph form Steve alluded upon earlier (potential for day 5+ cold)

 

check the mean for between 5th and 7th has dropped betweeen 1C and 3c which is quite a lot for a mean over 24h

Edited December 30, 2015 by Mucka

[Singularity]

There we go - a decent example from the GFS 18z det. of the sort of thing that's possible when you've got a lot of amplification being promoted by the MJO coupled with a disorganised polar vortex and some higher heights knocking about in the Arctic.

It's a quicker route to colder conditions than trying to build a Euro Ridge up through the UK as the latest ECM det. seems to be ready to try from +240.

 

Things sure are looking different to what some might have imagined going into Jan this year; it could have been a case of watching a rampant vortex hold steady over Greenland while blocking over Siberia nudges it down into the Atlantic  a bit, leaving us with little sign of being able to break free from a wet and wild regime until the effects of a possible SSW kick in. That's the classic El Nino type scenario involving wave 1 activity on the vortex (i.e. just one source of disruption).

Instead, we have an Alaskan ridge being consistently modelled to join forces with the Siberian one, driving wave 2 activity (yep, two sources of disruption to the vortex) which will split the trop. vortex at least for a time and perhaps for a run of days if things go really well. This is where those higher heights in the Arctic come from, and even if the trop. vortex manages to regroup to some extent, those features are likely to keep it in a disorganised state, which not only brings us those chances for cold spells, but also allows those blocking highs to potentially gain an even greater foothold at the higher latitudes, hitting the vortex increasingly hard as we approach mid-month.

That's long looked to be the critical period during which the heaviest blows are landed, with the effects of any SSW achieved manifesting in the troposphere late in the month (or it could be early Feb I suppose). While it can be hard to sustain snowcover in the south at that time of year, early Feb 2008 saw one of my favourite spells of snowy weather with an abundance of heavy showers that brought graupel in the updrafts and snow in the downdrafts. Here's not the place to discuss that of course - just trying to prevent any cries of 'but that's too late, I prefer heart-of-winter cold and snow' 

 

All this, and we still have that disrupting trough possibility in the shorter term to keep us entertained. This is a lot better than things were at the end of last month...!

[West is Best]

Ooooh that's an interesting run. Game back on. I like the inklings of height rise over Greenland as the upstream signals matter if we're to see that  massive cold pool edge ever further west to our shores.

Game on.

[Allseasons-Si]

From being away for a few days,nowt ever changes in here,pick your toys back up and deal with it,we are all a friendly TEAM on here and after all,most of us are in the uk,yes,we are a small blip on the globe but look at the broader picture( n.hemisphere) to look for trends,and i for one see a trend(not garenteed)to colder weather heading this way

good to be back

now,seems nick is talking about the navgem,i like to post this

18z navgem

that is pretty good from what the 12z was showing

by heck,that break did some good.

 

[bobbydog]

barely had a mention but i suppose we've stopped believing in santa now. last frames of the GFS-

Scandi high

Easterly

Snow!

 

[Allseasons-Si]

3 minutes ago, bobbydog said:

barely had a mention but i suppose we've stopped believing in santa now. last frames of the GFS-

Scandi high

Easterly

Snow!

 

Here we go again,phantom of the opera easterly,oh!,mid Jan,that's got to be right

good to see though bobbydog,will this be the one,the countdown starts here and i am going to save that chart.

 

[nick sussex]

7 minutes ago, Allseasons-si said:

From being away for a few days,nowt ever changes in here,pick your toys back up and deal with it,we are all a friendly TEAM on here and after all,most of us are in the uk,yes,we are a small blip on the globe but look at the broader picture( n.hemisphere) to look for trends,and i for one see a trend(not garenteed)to colder weather heading this way

good to be back

now,seems nick is talking about the navgem,i like to post this

18z navgem

that is pretty good from what the 12z was showing

by heck,that break did some good.

 

I'm shocked I would have thought the NAVGEM would have backtracked by now. Normally it picks out a lone solution gets its moment in the sun then goes back into the shadows quickly! The NAVGEM got quite an airing earlier today as I wheeled it out after some rather underwhelming outputs. I still think its an outlier solution and its reputation isn't the best but its nice to look at while it lasts.

I think we might get a bit more amplification upstream to edge things a bit further west but not sure we'll quite get to the NAVGEM solution.

Probably best to moderate expectations and if things upgrade then great.