Model output discussion pm 13/01/2016

[Mucka]

2 hours ago, gottolovethisweather said:

Indeed the forecast 850s aren't astonishing in truth though. Bar the weekend when parts of the East of England will feel genuinely bitter with Maximum Temperatures around of only 2c or so, especially on Saturday. The main story other than a dying front moving through will be the dry frosty crisp picture, overnight minimums of -10 or lower in some parts.  Come Monday the warming uppers (relatively speaking) very very slowly transfer their way Eastwards to all parts come Thursday. During Monday the only snow-producing 850s left are out towards the North and East of the UK. However, I ask this of you Mucka and perhaps one or two of the more experienced posters in here, am I painting a realistic picture here?

 

The 850s aren't everything, they are simply one of eight suggested requirements needed to guarantee snowfall yet, there is so much hope and excitement at this prospect (which is still 60-72 hours away) which is why I'm not following the hype just yet. Taking the ECM control literally (not a wise thing to do in isolation btw) the -6 850s have vanished from the UK which suggests rain by then but again, am I likely to be correct in my analysis?

 

I am NOT being deliberately unrealistic or realistic here, yet it looks such a difficult forecast ahead, I'd still suggest a slow demise of the cold by mid-week is the main certainty in all of this. Should the snow fall and more appropriately settle during the early part of the week, what with stalling fronts and all that, I guess the inevitable Atlantic breakdown will be a slow-burner itself, a week NOT to be a media forecaster.

 

 

 

Hi GTLTW

When things are nailed down a bit more  there are people here better than I to give a detailed analysis. The problem at the moment is that we just can't get any cross model agreement so getting into the fine detail is a bit of an irrelevance because it will be invalid by the next run.

Forgetting Saturday night and looking ahead to the possible main event we will a trough sliding SE so what happens is the cold upper air doesn't get mixed out quickly by Atlantic air because we will be drawing in a SE feed ahead of the front and only behind (to the West) does the upper air get truly mixed out, You can see an example of this if you run through GFS 12z with 850's and how the colder air hangs on in the SE. Even where the cold upper air gets more mixed out it will remain cold at the surface though DP's will rise somewhat.

So with a situation like this you are more likely to get snow further East but you are also more likely to get lighter ppn or stay dry but we just don't know the angle of attack or how far North and East any front will get before stalling.

On current output I would say it is likely there will be fairly widespread snow from the first attempted breakdown but the further Northeast you are the more likely it will stay dry and the Further Southwest you are the more likely you will get sleet or rain or snow turning to rain before it clears (but that is a generalisation going off current output)

After that things will briefly dry up and stay quite cold at the surface but it is unlikely we will be able to renew our cold pool of 850's, especially further West so the next attempt of the Atlantic to get in will more likely be rain, especially in the West though we need to know how the first attempt will go before making any predictions about he second because there is so much run to run variability in the output and even the first event is open to some quite big changes as  far as the weather we actually experience is concerned.

Sorry I can't be more specific but the 850's should be cold enough to produce snow for most from the first attempt at a breakdown but much less likely to be for any second attempt as things stand (Cannot emphasise enough that things may be different tomorrow)

[Jason M]

2 minutes ago, I remember Atlantic 252 said:

I need -10 off a NW'ly

and had just rain off these uppers, but ad snow off -1 uppers off battleground style setup

Which sort of proves the point really. For Stafford (which I know as I'm from Crewe originally) -6 from what is really a PM airmass isn't going to cut it :-). 

[DAVID SNOW]

1 minute ago, bobbydog said:

he said "all the models in FI land" (which includes the whole range of their output) so as i said- not strictly true.

As you wish, but I think he was of the opinion that FI  is a lot closer in the models than it usually is. Enough from me .

[John Badrick]

8 minutes ago, lorenzo said:

Fantastic debate today, Stewart, Steve, Tamara - great to see such a meeting of minds here. So different in approach, so absolutely impassioned to see the weather people want and examine the evolution - hat's off to you all.

Love the fact that there are so many factors rolling around that can impact short term, medium term, mid range and long range.

Wave One standing impact on vortex from El Nino
Brutal chain reaction of the Kara High and previous wave break on boxing day - this is a beauty complete atmospheric cascade of chaos.
Composite lift out of strength in Canadian climate home for vortex.
Projected AAM dip - not being an AAM dip at all in big scheme of things with baseline AAM simply outrageous. Relative AAM with a drop that would make La Nina state sing vs. our current state that threatens re-cycle and game on for blocking.
Our Polar Vortex - completely off the grid cold vs. Anomalous off the grid blocking ( Kara / NAO via Davis Strait - yes Davis strait blocking is at 90th percentile of climatological mean).
Siberian High evolution on modelling - huge hit to vortex vs. zero hit within 6 hrs on GFS. Chaotic atmospheric dynamics, via,
Ex-Alex- if ever something needed to write a signature for this winter then Alex is it. Ignore the record breaking vortex dynamics for cold temps. Ignore the record breaking Nino temps for regions, the weather is apparently a spin doctor ( no pun intended)..

Cue Alex, model curveball and gives us the best short range modelling cannonball I have ever seen.

So, with that what can anyone predict, would hazard a guess at ' not a helluva much'  that's speaking politely!

Couple of other thoughts - the GWO Jan Feb - hope to analog these over the weekend with new composites.= - daily modes considering MJO Waves and GWO cycle.. will post as soon as built.

The strat trop disconnect - fascinating this year, W1 Nino vs. the oddness of Kara and now potentially Siberia leaves a layer of the atmosphere modified not by upwelling or down welling but by other factors. Forget OPI or SAI or QBO, this year I feel brings EPF to the fore, there is a possible mode here similar to the QBO. It originates in the mesosphere so beyond our science right now, however it is there.

Here are a few chart to display the awaiting roller coaster

Angular momentum nuclear - 

Oh it's on it's way down...

No worries - it is still rampant....

That is one hastened atmosphere and we have an up and coming monstrous torque event. This winter is not done with it's chaos yet. 

As far as looking for cold, we have it, as far as timing, it's here not withstanding 5-7 days and technical descriptions re SSW, and quantification. Amy Butler for her Strat Trop pathways should be relatively happy with skill. Loosely fits forecast so will take that - especially in the face of all the elements outlined above for near term modelling.

The reduction in move to SSW outlined earlier this week - am wondering if this has been reduced due to classic tightening of the vortex and AO profile, with a pulse of relaxation to follow, hence the move away from u reversal. Maybe will relax in 24-48 hrs as the wave recession and drop occurs, if not I feel it is academic as of more interest is the perturbation created by the AAM state.

Over to the close up models !

Did anyone see Ed's tweet today of backwards air trajectory from last Friday - cold air we have now originated in Svalbard, incidentally round about the same time he predicted it. good work !

 

 

 

bloody good post sir,

a fantastic round up of whats happened in the last couple of weeks 

 

[damianslaw]

Another day and more twists and turns in the short term making for exceptionally difficult forecasting. All eyes on the atlantic vs continental battle, looking like a slow burner with snow in the mix for some, but the eventual winner most probably the atlantic, this is shown in preety much all the models, but could take until Thursday before the change is done.

In the meantime, gone is the nationwide dry weekend, and instead western parts will see one of two halves, Sunday now looking unsettled.

Longer term - wouldn't be surprised if the atlantic breakthrough is temporary.. A good example of a shortlived atlantic breakthrough was late Jan 2013, the cold quickly came back and held itself together.

[Steve_Alltami]

27 minutes ago, lorenzo said:

Fantastic debate today, Stewart, Steve, Tamara - great to see such a meeting of minds here. So different in approach, so absolutely impassioned to see the weather people want and examine the evolution - hat's off to you all.

Love the fact that there are so many factors rolling around that can impact short term, medium term, mid range and long range.

[...]

 

To be fair, I've been a lurker for years - but I've loved the model watching over the last few weeks. 

I've had 4 days with falling snow, two mornings with snow on the ground and not a clue about the conditions in  48 hours. 

Good times - and here's to more :-).

Edited January 15, 2016 by Steve_Alltami
Removed large parts of quote

[SnowBorder]

its difficult to comment on all of the model output, when it's behaved in such an unpredictable manner for well over 5 days. It's been a bit of a lottery as to what might appear next. 

A watered down solution to the UKMO was always probable without the back up from the other models, although I have to say that the UKMO has performed well without the fluctuations of others .

Based on the current unpredictability and the attempted FI height rising, I suspect (gut feeling) an eventual snowy cold spell around the 1st / 2nd week of February. Not a Feb 2009 affair; a northerly with less snow. I favour a weak Greenland rather than a Scandinavian high. Better than the 5 days to come, but far from epic.

Others (elsewhere) have mentioned that early March will deliver the goods; I think it's very possible. El Niño has pushed our winter back circa 6'weeks. 

cheers 

 

 

 

 

 

 

[Spah1]

I keep seeing this posted and people getting excited by it. 

For the amateurs on here please can someone just give a basic explanation of what it is showing and how it may impact our weather. 

thanks

[Ali1977]

Tomorrow evenings moisture and chance of some snow seems on a slightly different track this run, more Wales and SW region rather than NW England down to Midlands.

[bradymk]

Interesting shift south of the snow early Sunday on the GFS 18z. Has snow now affecting parts of SE Wales, parts of the south west and central southern england.

[Weathizard]

With ensembles like this(IMBY) it's amazing there is such uncertainty really.. Everything appears still up in the air with models showing different things yet GEFS pretty much all in agreement bar a few rogue members after the crucial unknown period

[Nick L]

Ridiculous model disagreement going on at the moment. Even tomorrow night it's EC/Euro4 vs GFS with regards to where this snowfall is going. I've never seen anything like this.

[Mucka]

front stalls on the West coast on this run,

 

[jvenge]

6 minutes ago, Weathizard said:

With ensembles like this(IMBY) it's amazing there is such uncertainty really.. Everything appears still up in the air with models showing different things yet GEFS pretty much all in agreement bar a few rogue members after the crucial unknown period

Maybe I'm dim witted, but there appears to be quite a big scatter there and I don't know how it can be said they are in agreement.

[I remember Atlantic 252]

Atlantic miles further west on 18Z GFS, looks like front won't make it as far east as midlands, but means cold will be upgraded

[Chris1986]

At 500 PM AST (2100 UTC), the center of Post-Tropical Cyclone Alex was located near latitude 43.0 North, longitude 27.8 West. The post-tropical cyclone is moving toward the north near 40 mph (65 km/h), and a turn toward the northwest and west with an additional increase in forward speed is expected over the next 36 hours. Maximum sustained winds are near 70 mph (110 km/h) with higher gusts. Little change in strength is forecast during the next 36 hours, and the post-tropical cyclone is forecast to merge with another extratropical cyclone by Sunday.

 

Courtesy of National Hurricane Centre , interesting all the same  

Edited January 15, 2016 by Chris1986
Path graphic added

[Woollymummy]

18 minutes ago, Spah1 said:

I keep seeing this posted and people getting excited by it. 

For the amateurs on here please can someone just give a basic explanation of what it is showing and how it may impact our weather. 

thanks

Am I right in thinking it will also make our days a bit longer as periods of high angular momentum make the earth spin a bit slower? Is that right?

[feb1991blizzard]

2 minutes ago, Woollymummy said:

Am I right in thinking it will also make our days a bit longer as periods of high angular momentum make the earth spin a bit slower? Is that right?

It will ever so slightly affect time and the clocks will have to be reset one day, but it will be in billions of years time as the effect is so minute,

Edited January 15, 2016 by feb1991blizzard

[snowice]

7 minutes ago, Nick L said:

Ridiculous model disagreement going on at the moment. Even tomorrow night it's EC/Euro4 vs GFS with regards to where this snowfall is going. I've never seen anything like this.

I wonder can they reprogram the models to take into account the current input so in future they learn from the current pattern as to were the Shortwaves go when there is blocking pattern.

Edited January 15, 2016 by snowice

[BLAST FROM THE PAST]

11 hours ago, Steve Murr said:

All I would say about Stewarts forecast ( without being accused of trolling ) is both he & Tamara put a forecast out for 17 jan - end of jan delivering 1983 synotics + quote 'a classical -NAO showing' Yet no review on that ( or at least commentary on how that period is set to look ) just move onto the next projection of cold - with the caveat of 'strat allowing' - surely thats the caveat of the whole of the winter -

 

Anyway back to the models - NAVGEM & JMA performing well ATM - I would also throw the Aperge in the mix 

Snowline 72-84 is the key

Brilliant post.  In it to win it

 

BFTP

[Nick L]

13 minutes ago, Weathizard said:

With ensembles like this(IMBY) it's amazing there is such uncertainty really.. Everything appears still up in the air with models showing different things yet GEFS pretty much all in agreement bar a few rogue members after the crucial unknown period

I would hardly call those ensembles in agreement, they're all over the shop just a few days ahead!!

[Mokidugway]

Think it's quite small compared to ocean dragg.

[Weathizard]

5 minutes ago, jvenge said:

Maybe I'm dim witted, but there appears to be quite a big scatter there and I don't know how it can be said they are in agreement.

There is a scatter long term as usual but look at the relatively tight grouping after Monday/Tuesday all taking the 850's up to around 5c with mostly high pressure in charge.

 

[Rocheydub]

2 minutes ago, snowice said:

I wonder can they reprogram the models to take into account of the current input so in future they learn from the current pattern as to were the Shortwaves go when there is blocking pattern.

They are learning all the time!

[Eskimo]

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