Model output discussion - winter proper underway

[DIS1970]

Latest GFS starts the procession from the 25th, cold, snow, etc, definitely on the back seat now, for a few days (possibly weeks!), certainly hope not though.

[Singularity]

Into a critical period these next few days as we find out whether the tropical forcing will be sufficient to keep the N. American ridge-trough sharp enough that the Canadian-Atlantic vortex lobe remains more Canadian and we get to see it kept independent of the Scandinavian lobe, possibly with small LPs breaking away and moving across to the S of some degree of ridging NW of the UK.

ECM 00z is the closest run I've seen so far from the more credible models, with UKMO looking ripe for similar progression as of day 6. GFS continues to suppress the tropical forcing more via stronger interference from the La Nina oceanic state in the Pacific. Chances are this is the forcing being overblown by bias relating to the GLAAM negative bias, but I'm wary of calling it out at this time... things are so very poised, but a poke from the wrong direction and we'll fall down on an unpleasant side. 

[Dennis]

i say we have the ridge  - 

[nick sussex]

An improved GFS 06 hrs run with the PV held further back to the nw.

The jet track also corrected further south. This is a positive trend and going in the right direction .

Its also noticeable that the low which was originally forecast to blow up over the UK is now being weakened.

On to tonight’s outputs now , let’s hope we can see more amplification upstream .

Edited December 19, 2017 by nick sussex

[northwestsnow]

GEFS 6z seem to be trending the wrong way for coldies

Infact they look very wet even for London after christmas day right through to early 2018 -

Goodness knows how wet they will look further north and west..

Think coldies are hanging our hats on that EC 0z operational(not backed up by ens) ..leading the way here- 

If EC op is wrong i think its safe to say we are going to be scratching around in FI for crumbs of hope..

 

[northwestsnow]

1 minute ago, nick sussex said:

An improved GFS 06 hrs run with the PV held further back to the nw.

The jet track also corrected further south. This is a positive trend and going in the right direction .

Its also noticeable that the low which was originally forecast to blow up over the UK is now being weakened.

On to tonight’s outputs now , let’s hope we can see more amplification upstream .

6z GEFS are wet, wet and wet again Nick- as far as i'm concerned GFS /GEFS are pretty poor ..

[Weathizard]

With the Alaskan ridge/polar high coming into play anything could happen, we've seen before they cause absolute chaos in the models. So I wouldn't take too much notice of the ensembles as they are running at a lower resolution than the operationals, which in themselves will struggle.

We shall see, im not convinced by any outcome at the moment, I would say a white Christmas is game over for most but beyond that I wouldn't hazard a guess.

Edited December 19, 2017 by Weathizard

[nick sussex]

Just now, northwestsnow said:

6z GEFS are wet, wet and wet again Nick- as far as i'm concerned GFS /GEFS are pretty poor ..

The GFS 06 hrs run has the jet track about 500 miles further south than the 00hrs and holds the PV further to the nw.

Given the wild swings shown overnight in the ECM op run then I wouldn’t be placing too much emphasis on the GEFS or EPS until the outputs settle down.

I’m reserving judgement for a few more runs.  But so far today I’m more positive than I was yesterday .

 

[tight isobar]

8 minutes ago, northwestsnow said:

6z GEFS are wet, wet and wet again Nick- as far as i'm concerned GFS /GEFS are pretty poor ..

Having just viewd the london 6z ens...

I can see lots to be optimisitic about(going forward).

Cannot post them in here.

Edited December 19, 2017 by tight isobar

[northwestsnow]

1 minute ago, tight isobar said:

Having just viewd the lindon 6z ens...

I can see lots to be optimisitic about(going forward).

Cannot post them in here.

Hope you are right

[northwestsnow]

4 minutes ago, nick sussex said:

The GFS 06 hrs run has the jet track about 500 miles further south than the 00hrs and holds the PV further to the nw.

Given the wild swings shown overnight in the ECM op run then I wouldn’t be placing too much emphasis on the GEFS or EPS until the outputs settle down.

I’m reserving judgement for a few more runs.  But so far today I’m more positive than I was yesterday .

 

I agree about the jet but at every critical juncture along comes another horrid piece of energy carried along by the jet-

Hope your optimism is well placed nick

[nick sussex]

13 minutes ago, northwestsnow said:

I agree about the jet but at every critical juncture along comes another horrid piece of energy carried along by the jet-

Hope your optimism is well placed nick

We’ll see! 

I think it depends on what you’re expecting . Optimism at the moment  doesn’t mean get the sledge out but trying to avoid a spell of mild mush and get something more seasonal .

We need more upstream amplification to get the low track even further south east  to get the UK on the polar side of the jet .

Its no so much the energy upstream but where it’s directed. As we saw from the recent snow event for parts of the UK you don’t need strong blocking to deliver that.

Its a case of small steps this morning , hopefully we can see a couple of leaps in the next few days !

 

 

Edited December 19, 2017 by nick sussex

[ACCOUNT DELETED]

A very wet festive period for western UK but this latest run has a reduction for my location near Swansea from around 3 inches on the GFS 18z to 2 inches on the 6z but nevertheless it looks like there could be some issues with flooding in the foreseeable future although nothing on the scale of the devastating and widespread December 2015 floods is currently expected. 

[joggs]

1 hour ago, jonboy said:

Brutal cold over much of the USA anticipated in 7 days time I wonder what effect this may have down the road for us

It's going to serve to beef up the jet that's for sure.What we need to happen(coldie perspective) is the jet pulling South and hope we can get little slithers of higher pressure to the north of us in between the lobes of PV.

Be interesting how the intense high pressure plays out over the far side of the pole to us,'re moving into the arctic.

[joggs]

2 hours ago, jonboy said:

Brutal cold over much of the USA anticipated in 7 days time I wonder what effect this may have down the road for us

It's going to serve to beef up the jet that's for sure.What we need to happen(coldie perspective) is the jet pulling South and hope we can get little slithers of higher pressure to the north of us in between the lobes of PV.

Be interesting how the intense high pressure plays out over the far side of the pole to us,'re moving into the arctic.

[northwestsnow]

Looking at all the data to hand this morning i think its hard to see any snow away from higher elevations across NW Britain for the foreseeable- EC remains the best hope for something wintry to develop longer term -

GFS at the same time

Exeter still expecting the low on sunday to push through allowing for a colder north westerly with snow perhaps across northern hills and they go onto say they expect the wet and windy conditions to continue into the new year  with confidence low therafter -

'confidence in the forecast remains low, but the trend points towards some longer periods of more settled weather developing, especially in the south. This would lead to longer spells of drier and colder conditions, as well as an increased likelihood of overnight frost and fog.'

The concern for me is i'm getting an uneasy feeling this last paragraph could be suggestive of a euro high with the jet roaring away to the north ie inversion cold- we might well be glad of that come jan but the way i read it means much of lowland UK can forget about any prospects of snow for quite a long while.

 

[Paul]

As ever, can we keep the beeb / meto forecast in the relevant places and not in the model thread please

[Nick123]

Sorry mods I keep forgetting not to post forecasts on here. I just wish we could be told something reliable in a 24hr period. Anyway the models will probably change by tonight anyway.

[danthetan]

Why people are focusing on charts way out in the ontha and not in the semi reliable time frame 144hr is beyond me. The Alaskan ridge surging into the pole on the last few runs is going to play havoc within the models not worth looking past that timeframe.  

[Frosty.]

14 minutes ago, danthetan said:

Why people are focusing on charts way out in the ontha and not in the semi reliable time frame 

The answer is simple, there is no interesting weather forecast until next week when it could become disturbed / stormy..whereas the reliable / semi-reliable timeframe..i.e this week, the weekend into the start of next week is..putting it mildly.. a yawn fest!

Edited December 19, 2017 by Frosty.

[Daniel*]

21 minutes ago, danthetan said:

Why people are focusing on charts way out in the ontha and not in the semi reliable time frame 144hr is beyond me. The Alaskan ridge surging into the pole on the last few runs is going to play havoc within the models not worth looking past that timeframe.  

Why bother having a model output discussion thread? The immediate timeframe is of no interest for most of us, we’ve come a long way from just being able to gauge from a short-medium timeframe. There’s fun in the chase and there’s the hope we’ll see the teleconnections surface in the NWP in the longer term.

[bluearmy]

27 minutes ago, danthetan said:

Why people are focusing on charts way out in the ontha and not in the semi reliable time frame 144hr is beyond me. The Alaskan ridge surging into the pole on the last few runs is going to play havoc within the models not worth looking past that timeframe.  

This is something that is generally accepted wisdom as it’s an unusual evolution that the models are not used to - however, I wonder how much scientific basis there is for this and whether the improvement over the years with each upgrade may have made this viewpoint redundant ??  We don’t have too many chances to see how they do with this feature !!

 

[knocker]

I have to say I'm a long way from being convinced that the pretty weak amplitude MJO is currently having a significant influence on the model forecast pressure patterns, certainly downstream.

[jvenge]

1 minute ago, knocker said:

I have to say I'm a long way from being convinced that the pretty weak amplitude MJO is currently having a significant influence on the model forecast pressure patterns, certainly downstream.

I noticed a little note on the NOAA MJO page regarding those predicted phases. Worth a look.

 

[danthetan]

49 minutes ago, Frosty. said:

The answer is simple, there is no interesting weather forecast until next week when it could become disturbed / stormy..whereas the reliable / semi-reliable timeframe..i.e this week, the weekend into the start of next week is..putting it mildly.. a yawn fest!

I take your point about the uk weather being boring in the semi reliable time frame. But I'm not looking at whats happening in the uk at 144hr my focus is on the alaskan ridge heading into the pole and what effects that has.