Model output discussion - proper cold spell inbound?

[Purga]

Split the PV nicely in half......

far reaches of FI looks a peach

[Catacol]

A chart of a different nature, but says all I want for the moment on a late Saturday evening:

EPS showing the strongly negative 850 anomalies kicking in around Tuesday. It's no guarantee of snow on its own, but hopefully the start of something notable through the month. Will it or wont it snow on Tuesday can wait until tomorrow evening at the earliest.

Night all. 

[Nick F]

Interesting but more realistic trend on the 18z GFS and ties in with my thoughts of the models finally slowly backing away from the zonal Atlantic flow they were suggesting, with troughs extending from the intense Greenland vortex continually disrupting SE across UK but still supplying cold polar air from the NW while there is still some cold continental air across the south and near continent too. The Azores ridge trying to extend NE next Saturday, which does mean the NW temporarily turns milder, while the south still cold though, before another surge of cold air moves in from the NW on Sunday quickly squeezing out mild sector trying to slide SE.

Looks like the Greenland vortex is having its last gasp at the end of the 18z GFS run tonight!

Edited February 3, 2018 by Nick F

[WalsallWeather123]

I think in the coming couple of days the GFS will come towards the Arpege and Icon with the precipitation dying before it even reaches wales on Tuesday 

[Frosty.]

Looking at the Gfs 18z there are snow showers heading into eastern / southeast england during tomorrow and especially tomorrow night into Mon morning the SE could wake up to a covering of snow..good luck guys..let the fun times begin!❄❄❄❄❄❄❄❄

Looking at the bigger picture, the 18z shows snow falling in parts of the uk on most days!

[Duane S.]

4 minutes ago, karlos1983 said:

What’s annoying is that bully has been quiet all winter until now! Imagine if it was in tatters like it was in Dec/Jan. really goes to show just how unlucky we’ve been this year. We get height rises to our East/N East just when the trop PV has got organised! 

Yep, although it is quite common for it to ramp up (even more so) ahead of a big upper warming. We often see a final surge of westerlies (or at least, attempts of)  before it starts taking the big hits and either displaces, splits or slowly shreds.

[Ice Day]

7 minutes ago, Catacol said:

A chart of a different nature, but says all I want for the moment on a late Saturday evening:

EPS showing the strongly negative 850 anomalies kicking in around Tuesday. It's no guarantee of snow on its own, but hopefully the start of something notable through the month. Will it or wont it snow on Tuesday can wait until tomorrow evening at the earliest.

Night all. 

That is a an absolute beaut of a chart.  The cold is coming this time.....surely?

[Snowman.]

Not surprised by the 18z and the day overall. The GEFS has had these 'less flat' options increasing over the past 4 suites so it was a matter of time before an OP run started showing them.

[inghams85]

As stated yesterday i believe the models were wrong and progressive and the back track starts again like last week! It's comical sometimes the bias when a lump of cold air and extreme tropical forcing are in play...... Can't wait for tomorrow's runs!

[SMU]

18z Mean @150

We have gone from a full on Atlantic assault to starting to look east again-

2012 redux

[Ice Day]

5 minutes ago, inghams85 said:

As stated yesterday i believe the models were wrong and progressive and the back track starts again like last week! It's comical sometimes the bias when a lump of cold air and extreme tropical forcing are in play...... Can't wait for tomorrow's runs!

Indeed, this last week has been a massive see saw.  We've had a few days when outputs haven't been so good but maybe the tide has turned for those of a cold persuasion today.  As Steve stated earlier, the period starting next Saturday could see another easterly chase.  Well I'm up for it.

Edt.  Strat warming getting is still being consistently modelled and within 192 now

Edited February 3, 2018 by Ice Day

[inghams85]

2 minutes ago, Ice Day said:

Indeed, this last week has been a massive see saw.  We've had a few days when outputs haven't been so good but maybe the tide has turned for those of a cold persuasion today.  As Steve stated earlier, the period starting next Saturday could see another easterly chase.  Well I'm up for it.

We could in theory go full circle to what was shown 4 days ago. Have you read the Me to text update it states systems bumping into colder air with snow for some this is what was shown 4 days ago. Systems disrupting and a holding pattern until the SSW and all It's glory

[Mucka]

It isn't just the Op runs that have improved through today but also the ensemble suites.

It is all about the trough disruption and more and more the models are picking up on it and splitting the energy better.

We could see some big changes in the output tomorrow for the run up to mid month, but with noticeable changes from as early as 120h, if indeed the models have been too progressive, with the cold never fully relinquishing its grip and high pressure being modelled further and further East as more energy is split SE instead of pushed NE as the troughs try to more W to E.

Just as a quick example using p13 from tonight's ensembles and yesterdays 18z Op run as a generalisation of the changes we have been seeing in the mid term.

We will have to wait and see if the trend continues tomorrow.

ECM ensembles

[stodge]

3 hours ago, nick sussex said:

February is shaping up to be a very interesting month and the reason this weeks spell might have been cut a little short could indeed be to do with the SSW, any reversal often comes with a last gasp PV show of force before it hopefully implodes!

Nick's comment (picked up by one or two others since) is completely on the ball.

We often see the initial impact of a push on the PV as being substantially negative in terms of "cold" over western Europe as the PV tightens and the zonal winds increase in response.

No one can be surprised if we have to enjoy/endure a 7-10 day period of Atlantic domination (and the best we can hope for within that is cool/cold zonality) before the tropospheric response to the stratospheric response becomes clear. Given the pressure on the vortex from now until the projected split next weekend and then renewed pressure on each of the vortices I'd anticipate a frustrating milder spell mid-month before we see where the pattern takes us later in the month.

Without wishing to sound too downbeat, it's worth pointing out the vortex split offers us only a place at the table - it doesn't guarantee a winning hand of Easterlies. Still, 18Z Control offers one option which will be attractive to many:

Everything I've seen today in far FI suggests a slowing weakening Atlantic and jet as we move past the middle of the month. Obviously, that offers some possibilities which may be from the NW or the East. We'll see.

[Ice Day]

5 hours ago, inghams85 said:

We could in theory go full circle to what was shown 4 days ago. Have you read the Me to text update it states systems bumping into colder air with snow for some this is what was shown 4 days ago. Systems disrupting and a holding pattern until the SSW and all It's glory

It doesn't mean it will happen, we all know that.  But we are faced at least with a chance for a significant cold spell, which is what most of us are here for.

London ensembles are looking good again, with sub -5's out until 180ish.  

Edited February 4, 2018 by Polar Maritime

[comet]

The 12z today showed a correction west in the model output with the 18z continuing apace with better amplification to the east. I would expect to see this continue as the strat split and forcing draws nearer and nearer. We may only be a couple of days away from viewing some mouth watering charts in the mid to extended range.

[shaky]

5 hours ago, Ice Day said:

We are faced at least with a chance for a significant cold spell, which is what most of us are here for.

London ensembles are looking good again, with sub -5's out until 180ish.  

Wow!!!they have flatlined nicely again!!last few had the 850 temps going up to 0 nearly for thursday but its all but gone now!!!

Edited February 4, 2018 by Polar Maritime

[Snowman.]

2 minutes ago, Mucka said:

It isn't just the Op runs that have improved through today but also the ensemble suites.

It is all about the trough disruption and more and more the models are picking up on it and splitting the energy better.

We could see some big changes in the output tomorrow for the run up to mid month, but with noticeable changes from as early as 120h, if indeed the models have been too progressive, with the cold never fully relinquishing its grip and high pressure being modelled further and further East as more energy is split SE instead of pushed NE as the troughs try to more W to E.

Just as a quick example using p13 from tonight's ensembles and yesterdays 18z Op run as a generalisation of the changes we have been seeing in the mid term.

We will have to wait and see if the trend continues tomorrow.

 

ECM ensembles

 

Exactly this mucka when the models flipped to the cold snap ensembles showed the key with the amplification of the low exciting the US. He ho the OPs began to follow with the UKMO leading the way.

 

[Mucka]

I meant high pressure being modelled further West. Second time in one day I have done that, oh dear.

@SNOWM4N yes really hoping for a repeat. Fingers crossed.

Edited February 4, 2018 by Mucka

[nick sussex]

The problem with SSW's is you're never sure whether it will be a quick response or take longer to feed down into the trop.

In terms of tonights runs we are seeing some westwards corrections again after initially we saw a trend to take things further east. If we do see a quick trop response to the SSW then we should start to see some bigger changes appearing within the T240hrs mark.

[Catacol]

Those worrying about GFS runs:

Dont.

[Timmytour]

49 minutes ago, nick sussex said:

The problem with SSW's is you're never sure whether it will be a quick response or take longer to feed down into the trop.

In terms of tonights runs we are seeing some westwards corrections again after initially we saw a trend to take things further east. If we do see a quick trop response to the SSW then we should start to see some bigger changes appearing within the T240hrs mark.

Nick...can an SAW impact in such a way that, if what already exists as it begins to register is a coldie's heaven, it can shift the whole thing in a different direction and bring us mild southerners?

Edited February 4, 2018 by Timmytour

[Daniel*]

Good to see the sun is very mute there were some that claimed big uptick in solar radiation scuppered Dec 2012 which has sound merit for reasons I can’t convey, remember that.  

Hopefully the stars are aligning for once. We have: E-QBO, La Niña apparently now in decline, lag effect of high amplitude phase MJO possibly wiggleroom for 8 injection of AAM, low solar activity this is all setting up for a decidedly interesting later side of February into March IMO. A seemingly big SSW with significant disruption is expected with a split which historically affects Eurasia the most, rather than CONUS I believe, very cold air will feature through month or be nearby which is Exeter’s current thoughts. What with the vortex being of a greater strength this year, my theory is once the balloon pops it will be even more dramatic, with a recovery virtually impossible, I see extreme cold somewhere in the mid latitudes and extensive high latitude blocking, if things align we could be looking at something sensational. The imminent cold spell could be a taster to the big one, as the days get longer the cold grows stronger winter truly is far from done with us.

Edited February 4, 2018 by Polar Maritime

[Mucka]

The trend to back everything West continues this morning with GFS  00z

Yesterday's Op and today's compared 144 - much better trough disruption with some energy splitting SE as opposed to yesterday all going NE. Heights building through Scandi proper.

 

No reason not to expect the next push from the Atlantic to be modified in the output the same way as it comes into range.

If that happens the cold may not get forced East at all and we could be an Easterly before mid month. 

Of course all that assumes the output is going to keep trending this way. Shhhh 

UKMO and GEM not as good.

 

EDIT

GFS FI Atlantic struggling, 

Cold lingering and heading back West (Even last nights improved 18z had the continental cold being pushed away East at his stage)

Snow pushing in from the East into NE England, band of sleet/snow clearing SE England

 

 

 

 

 

Edited February 4, 2018 by Mucka

[Mucka]

I wouldn't pay much attention to GFS FI other than it wants to bring the cold air back West.

The Op from 216 to 240 is a very good reason why, from no Atlantic to 645mb low in 24h 

 

Quite liking ICON's idea of how the second front will turn out for the NW

 

Edited February 4, 2018 by Mucka