Model Output Discussion - cold spell to end Autumn

[Polar Maritime]

Nice to see a slack Easterly into the 6z.

[bobbydog]

4 minutes ago, snowfish1 said:

Can't see anything wintry for the South East as high crumbles just in time to stop the flow the favoured northern members. YET AGAIN

 

eh? whats this then?

candy floss?

[shaky]

9 minutes ago, JamesL said:

Gfs 6z looks like a rinse and repeat. Seems the cold always appears just before a weekend

Oh my days i was just saying to my wife other day that most of the cold snaps this autumn have come at the end of each week!!crazy cycle lol!!

[Froze were the Days]

06z gives and it takes it away and then it gives again in FI :)...gets progressive around 180z with lows coming from off the eastern seaboard of the States and the pattern looks to flatten but on a slightly more southerly jet. The key is that low pressure gets well into Europe/Southern Scandinavia and the Azores HP ridges far more than at the same time as opposed to the 0z (which doesn't look good in the same time frame).

It is FI but something to keep an eye on...

[Sky Full]

39 minutes ago, snowbunting said:

Me.. rubbing me hands in Glee... lol.

Minor changes for us in the North as the area of low exits the Uk bring gales or severe gales. Not convinced about the timing of the arrival of the snow on thursday... I think it will be earlier on thursday not later.  

Fully expecting cold weather to bring blizzards and drifting snow to us in the North. 

 Great!  I'm on my way!  What time should I arrive at your place??    (on my reindeer, of course!)

[ACCOUNT DELETED]

Some decent snow accumulations for parts of Wales but as always much less here on the coast although many coastal towns would at least see some snow except parts of the Gower & South Pembrokeshire if this chart is correct!  

[gottolovethisweather]

26 minutes ago, Ed Stone said:

But I do think that a lot of model-related heartache would be avoided if Admin would swear-filter the word 'accumulation'...and maybe change it to 'puddle'?

And "energy" to "post-Brexit", "shortwave" to "tantrum".  Getting back to the models, at least the mid-range outlook is certainly still well and truly blocked and far from bolocked, or maybe that's our Brexit talks.  D5 remains a thing of beauty and beautifully describes just what I mean.

 

Edited December 3, 2017 by gottolovethisweather

[Weegaz]

Us across the water will take this all day long.....we’ve started polishing the sledges already 

things still look interesting this weekend and hopefully upgrades over next few days

[Sperrin]

8 minutes ago, Weegaz said:

Us across the water will take this all day long.....we’ve started polishing the sledges already 

things still look interesting this weekend and hopefully upgrades over next few days

I'd run to the bank all day with that. My Xmas work do that night. 

A lock-in may be an unavoidable scenario, ah well 

[carinthian]

On ‎01‎/‎12‎/‎2017 at 13:31, carinthian said:

This latest chart from GEFS has put our resort of significant snow alert for weekend 9/10 th December. Further discussion with portal service providers talk of a increased chance of Scandinavian block to form by possible as early as Mid month with Western Europe in the firing line of a battle zone. Asked for further clarification ( sign of strengthening cold block to the NE ). All sounds good to me if goes to plan.  

 

How about an Easterly developing for Blighty towards Christmas ? ( NH chart 850MB ). You not had one of those for a long time. Looks like an old school winters chart to me ! Defo cold block on this chart.

C

 

[Iceaxecrampon]

GFS 06z

LP off the tip of Greenland but at t+195 one to watch?

Nearer time frame first ppn t+105

Bit further off but a massive amount of blocking.

[comet]

Must admit to feeling a little deflated now that snowmaggedon is off the table although it all looked a little to good to be true. Mind you if the models correct east a couple of hundred miles over the coming week then many areas could be in line for a decent snow event.

[Iceaxecrampon]

17 minutes ago, Froze were the Days said:

06z gives and it takes it away and then it gives again in FI :)...gets progressive around 180z with lows coming from off the eastern seaboard of the States and the pattern looks to flatten but on a slightly more southerly jet. The key is that low pressure gets well into Europe/Southern Scandinavia and the Azores HP ridges far more than at the same time as opposed to the 0z (which doesn't look good in the same time frame).

It is FI but something to keep an eye on...

Agreed - but someone mention the Jet was too strong?

[Iceaxecrampon]

1 minute ago, comet said:

Must admit to feeling a little deflated now that snowmaggedon is off the table although it all looked a little to good to be true. Mind you if the models correct east a couple of hundred miles over the coming week then many areas could be in line for a decent snow event.

Happy and surprised with this output for December and the start of winter  - time yet - but it still  could go both ways -  one thing the ensembles were  all very much in agreement (well yesterday they were.....)

[nick sussex]

I think there maybe too much obsession with the finer detail at longer range which is causing an emotional rollercoaster for some members who will be carted away suffering from exhaustion before the northerly even appears!

The broad pattern remains stable that's why the GFS doesn't deliver what many feared after T192hrs. The positive PNA will ebb and flow buts expected to be re-loaded which is what the GFS shows.

As long as this happens you cannot lose your cold and snow chances.

The ebb and flow will see energy shoot east across the Atlantic, occasionally the PV will get closer and then as the next amplified wave moves east to re-inforce the positive PNA this will pull the PV and lower heights back nw.

The pattern over the ne USA is complicated not in terms of trough setting up but shortwave energy running east and how that disperses into the Atlantic.

The uncertainty currently is not whether the positive PNA will suddenly disappear, that's currently expected to last until at least the middle of the month.

In the meant time the place to watch is the ne because you might eventually develop a stronger high.

 

 

[Methuselah]

Can't for the life of me understand why so many folks are disappointed this morning, as it looks to me as if we are about to have our first really cold (and possibly sustained) blast of the season:

Initial NW'erlies will bring wintry showers to all western & northern parts, and possibly to the Midlands via the Cheshire Gap; the subsequent northerly will put more northern & eastern parts into the firing-line with showers likely to be more widely of sleet & snow...

After that...who knows? 

[raul_sbd]

32 minutes ago, Draig Goch said:

Some decent snow accumulations for parts of Wales but as always much less here on the coast although many coastal towns would at least see some snow except parts of the Gower & South Pembrokeshire if this chart is correct!  

How I can get to that chart info on weather Us?

[Summer Sun]

10 minutes ago, raul_sbd said:

How I can get to that chart info on weather Us?

Under Select parameter click snow depth (in)

https://weather.us/model-charts/euro/england/temperature/20171203-1200z.html

[blizzard81]

To be taken with a pinch of salt as it is the 06z run, but many more colder ensembles in the 12 to 16 day period. The previous couple of runs saw the ens edging upwards at this time. Hope the 06 set is onto something. Would be nice to see an exciting period as we approach Xmas ? 

[Duane S.]

An interesting evolution on the 06z. If only only to show it's not necessarily game over if this come weekend doesn't bear fruit snow wise.  As Nick says, it is starting looking a tad complicated upstream and this is going to obviously effect how the models are interpretating that day to day, run to run. It does look like the +PNA profile remains.

the 06z has a different jet profile off the eastern seaboard...

 

and shows that early undercut of the Azores high is actually counter productive as it leaves an isolated low to our SSW, propping up the high and the jet is forced way further north than it would've done if not. 

The 00z by comparison undercuts the small wedge of heights to our NW instead, allowing the Azores high to orient itself much more favourably...

and the jetstreak rides over the top on a perfect SE trajectory, into Central Europe, just where we want it, with the wedge intact as a result

 

 

[AWD]

4 minutes ago, blizzard81 said:

To be taken with a pinch of salt as it is the 06z run, but many more colder ensembles in the 12 to 16 day period. The previous couple of runs saw the ens edging upwards at this time. Hope the 06 set is onto something. Would be nice to see an exciting period as we approach Xmas ? 

Looks like the Op was one of the coldest in the D12 - D16 period to me;

Not that it is worth analysing the GEFS that much at such a range.

The Control looks like it's gone "Darren Bett" mad in its later stages.

[blizzard81]

1 minute ago, AWD said:

Looks like the Op was one of the coldest in the D12 - D16 period to me;

Not that it is worth analysing the GEFS that much at such a range.

The Control looks like it's gone "Darren Bett" mad in its later stages.

I guess this just highlights the uncertainty as we move further out. Always the case though I suppose. 

[pdiddy]

3 minutes ago, blizzard81 said:

I guess this just highlights the uncertainty as we move further out. Always the case though I suppose. 

Yes, Control looks an outlier, but it's relatively flat, suggesting no return to zonal.  Control moves more towards an Easterly in FI

[nick sussex]

NOAA State Forecast for Connecticut explains a bit more as to the differences upstream.

This is the main cause of the UKMO versus the ECM/GFS at T144hrs, also note their overwiew:

 Overview...

From midweek till the foreseeable future we will find ourselves in a
cooler, more active pattern. Fairly apparent and well known, will go
with a short and sweet overview. N Pacific split flow with MJO phase
5-6 implications as energy piles up over the N Atlantic buckles the
flow across N America creating a high amplitude ridge-trof pattern.
Warm air surging towards the pole, both Arctic air and energy are
displaced at times as individual impulses sweep S/E through the H5
trof over Central/E N America, bottling up and slowed over E/SE
Canada as there`s little room to escape across the N Atlantic.
 

The high amplitude trough ridge pattern is the hallmark of the positive PNA.

Now in terms of the differences upstream at T144hrs between the UKMO versus the ECM/GFS below is  part of those in terms of handling of shortwave energy:

2.) Individual disturbances. Apparent that individual waves through
the aforementioned H5 trof will reload colder air S/E. However what
is not well known is how individual waves evolve and respond, how
they modify the H5 trof ( steepness / amplitude / tilt ) and as to
what draw and amplification individually they bring about in respect
to conveyor belt motions / thermal wind response as they rotate thru
the flow. Isn`t with any certainty that we`ll see an east coast snow
storm for those wish-casting. Especially from 120 hours and beyond,
run to run model guidance continues to sway such that little to no
confidence can be gained. Have to wait and see how things evolve
with later forecast guidance.
 

The re-loading is as the shortwave moves through it pulls the colder flow further south again, as that happens the PV is also pulled back nw.  You can correlate in these circumstances cold digging further south over the east USA corresponds with more amplification upstream and which downstream is similar in the UK.

 

[blizzard81]

3 minutes ago, nick sussex said:

NOAA State Forecast for Connecticut explains a bit more as to the differences upstream.

This is the main cause of the UKMO versus the ECM/GFS at T144hrs, also note their overwiew:

 Overview...

From midweek till the foreseeable future we will find ourselves in a
cooler, more active pattern. Fairly apparent and well known, will go
with a short and sweet overview. N Pacific split flow with MJO phase
5-6 implications as energy piles up over the N Atlantic buckles the
flow across N America creating a high amplitude ridge-trof pattern.
Warm air surging towards the pole, both Arctic air and energy are
displaced at times as individual impulses sweep S/E through the H5
trof over Central/E N America, bottling up and slowed over E/SE
Canada as there`s little room to escape across the N Atlantic.
 

The high amplitude trough ridge pattern is the hallmark of the positive PNA.

Now in terms of the differences upstream at T144hrs between the UKMO versus the ECM/GFS below is  part of those in terms of handling of shortwave energy:

2.) Individual disturbances. Apparent that individual waves through
the aforementioned H5 trof will reload colder air S/E. However what
is not well known is how individual waves evolve and respond, how
they modify the H5 trof ( steepness / amplitude / tilt ) and as to
what draw and amplification individually they bring about in respect
to conveyor belt motions / thermal wind response as they rotate thru
the flow. Isn`t with any certainty that we`ll see an east coast snow
storm for those wish-casting. Especially from 120 hours and beyond,
run to run model guidance continues to sway such that little to no
confidence can be gained. Have to wait and see how things evolve
with later forecast guidance.
 

The re-loading is as the shortwave moves through it pulls the colder flow further south again, as that happens the PV is also pulled back nw.  You can correlate in these circumstances cold digging further south over the east USA corresponds with more amplification upstream and which downstream is similar in the UK.

 

Knowing our luck and also going by previous painful experiences, the ukmo will be on the money.