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Model output discussion - into the last third of January


Paul

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Posted
  • Location: st albans
  • Location: st albans
30 minutes ago, IDO said:

Yes, the para what @bluearmy was expecting from the gfs 06z till it when to its usual standard deviation post-d10:

anim_fjv7.gif

Nice wedge with the Atlantic undercutting. "The King is dead long live the King" as long as it throws out charts like this!

Yes that’s much closer to what I was thinking ! 

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Posted
  • Location: Sedgley 175metres above sea level
  • Weather Preferences: Any kind of extremes. But the more snow the better.
  • Location: Sedgley 175metres above sea level
1 hour ago, Mizzle said:

Feb 1 2019 and my area (Fleet) was under a pivot I believe ( MetO called it a mesoscale event). We had 11 hrs of snow which gave one of the best snowfalls I have seen. 

Radar from Feb 1 2019 and my street

 

Screenshot_20190201-232008_Chrome.jpg

20190201_191141.jpg

Have I missed something! Did London get flooded and go under the sea..The map seems to think it as   Could we possibly be looking at a similar event on Sunday with the front stalling around the Midlands area..I've got a feeling there could be a few places getting more than they expect.. 

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
13 minutes ago, beefy201 said:

Just a question as much as love the entertainment on here do you guys actually realise that most of the weather and in particular snow has not shown up further than 4 days ahead .... I can point to much of the snow fall last night as an example . Just for fun I have been comparing much of the hmmmm models chat on here for the last 8 weeks and also looking at the bbc country file forecast for the week ahead and to be honest shock horror not one has achieved more than 40% accuracy 

It's a great question . . . I learned how to read weather charts way back in the 1960s, when snow (and thunderstorms) either failed to show, or exploded out of nowhere, with little no warning at all, more times than I care to remember; so, from that perspective (or maybe habit, as short-range weather forecasting has advanced immensely, since then) . . .

But, the models are something else: by combining the 500hPa anomalies and the run-of-the-mill daily outputs, you can get some idea of the extents of various airmasses and upper wind direction, over a much longer time period? But what you definitely can't do, is pinpoint detailed local mesoscale weather-phenomena, thunderstorms, snow showers et. al. 10-days+ in advance... deterministic chaos just doesn't work that way!

But you can have bloody good fun trying!??‍♂️

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Posted
  • Location: Langley Waterside, Beckenham
  • Location: Langley Waterside, Beckenham
1 minute ago, Battleground Snow said:

The wedges seem to be popping up at earlier timeframes now.

Icon 129

 

iconnh-0-129~2.png

Whilst it quiet on here can I ask the significance of a "wedge" What is it what does it do and any good for us in UK?

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
2 minutes ago, Battleground Snow said:

The wedges seem to be popping up at earlier timeframes now.

Icon 129

 

iconnh-0-129~2.png

The models are making a real drama over the attempted milder incursion with constant changes .  The far north could well hang onto the colder conditions with more potential frontal snow . 

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Posted
  • Location: Coventry
  • Location: Coventry
1 minute ago, Biggin said:

Whilst it quiet on here can I ask the significance of a "wedge" What is it what does it do and any good for us in UK?

They are very good for the UK in terms of cold in the winter,  as when they form near iceland they drive the jet stream to our south and take the warmth from the Atlantic south too.

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield
3 minutes ago, General Cluster said:

It's a great question . . . I learned how to read weather charts way back in the 1960s, when snow (and thunderstorms) either failed to show, or exploded out of nowhere, with little no warning at all, more times than I care to remember; so, from that perspective (or maybe habit, as short-range weather forecasting has advanced immensely, since then) . . .

But, the models are something else: by combining the 500hPa anomalies and the run-of-the-mill daily outputs, you can get some idea of the extents of various airmasses and upper wind direction, over a much longer time period? But what you definitely can't do, is pinpoint detailed local mesoscale weather-phenomena, thunderstorms, snow showers et. al. 10-days+ in advance... deterministic chaos just doesn't work that way!

But you can have bloody good fun trying!??‍♂️

Good points GC, I've always listened to my grandad. If the Robbins are flying upside down and heading west a cold spell is incoming. Also do you rember bucannans cold spell in February? The footprint is back going threw feb

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Posted
  • Location: Cambridge
  • Weather Preferences: Cold, snow, heat, sunshine and thunderstorms. Anything severe.
  • Location: Cambridge

By next Saturday the ICON 12z has the majority of the UK under sub -5C uppers again compared to the 00z that had uppers well above 0C still. Another suggestion that the milder spell is still being watered down perhaps?

00z:

CA8C005F-8C1A-4776-9052-2E5CA4FD7F38.thumb.png.f92e0d9d7f7427f4b0dde51d63143362.png

12z:

FB0644A1-DBD9-4B23-812A-74D0DEAEACC9.thumb.png.24306b159f1bb0488a913992a8c13585.png

 

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

Mostly mild outlook?...oh my god?..I think I’m missing something..my brain probably?...anyway, although I’m seeing plenty of wintry / wintery..potential from the models so far today (Gfs / GEFS / ECM / UKMO etc...obviously Exeter isn’t...which begs the question..why do I bother..pffffffffft?

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Posted
  • Location: Sedgley 175metres above sea level
  • Weather Preferences: Any kind of extremes. But the more snow the better.
  • Location: Sedgley 175metres above sea level
7 minutes ago, nick sussex said:

The models are making a real drama over the attempted milder incursion with constant changes .  The far north could well hang onto the colder conditions with more potential frontal snow . 

Hi Nick,and I hope your safe and well in France. What are your thoughts on this potentially milder scenario with Swtly winds spreading North next week which Exeter are highlighting...Jon Hammond was asked about this the other day and I get the impression he was less certain about that scenario..with perhaps the cold giving more of a fight!! TIA

 

 

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
19 hours ago, Catacol said:

Hmmm - poor comment. Easy to pick apart too. Historic January went up the spout when the vortex didn't split[...]

No. You are wrong: 'Historic January' failed to materialise because 'Historic January' was never going to happen in the first place . . . the models (and 'experts') can bicker all they like but, at the end of the day, the weather just does what it does. Regardless of our sometimes fragile egos!?

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Posted
  • Location: Cambridge
  • Weather Preferences: Cold, snow, heat, sunshine and thunderstorms. Anything severe.
  • Location: Cambridge

To my surprise the GFS 12z is sticking with a fairly northerly track for tomorrow’s band of snow compared to the other models. Could be a few surprises!

091736B6-1260-48CF-8B9F-ED7A19F180CB.thumb.gif.e4a520980baef700c37ee7900ca06183.gif68E46881-3740-4B17-BF99-E7EAB55AE179.thumb.gif.ac9446ee99671a4e7880e615fca83863.gif324C60AC-EE96-4CC2-A1A9-87D528C67D2C.thumb.gif.32c291143b1d8a227f6acc98da331983.gif4AC026BE-0AC5-4F70-9384-3386963997DF.thumb.gif.9b71241e91532dc8829a158ead6d3ce8.gif8C0E7451-1A3E-45AF-945D-187836C93BC6.thumb.gif.b127324f4ac27249e0dd31417b2e16b5.gif

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
1 minute ago, MATTWOLVES said:

Hi Nick,and I hope your safe and well in France. What are your thoughts on this potentially milder scenario with Swtly winds spreading North next week which Exeter are highlighting...Jon Hammond was asked about this the other day and I get the impression he was less certain about that scenario..with perhaps the cold giving more of a fight!! TIA

 

 

Good thanks , hope all is good with you . Ask me after the GFS and UKMO! Lol

At the moment there’s some uncertainty as to how far north the milder conditions might get . Even if the milder conditions do clear the UK it might just be a short lived spell. Then the drama begins to plot a route towards something from the ne .

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Posted
  • Location: Sedgley 175metres above sea level
  • Weather Preferences: Any kind of extremes. But the more snow the better.
  • Location: Sedgley 175metres above sea level
3 minutes ago, General Cluster said:

No. You are wrong: 'Historic January' failed to materialise because 'Historic January' was never going to happen in the first place . . . the models (and 'experts') can bicker all they like but, at the end of the day, the weather just does what it does. Regardless of our sometimes fragile egos!?

Thats one way of looking at it Pete..But if that Vortex would have been a clean split we would have been in the game for something more significant! And tbh there were plenty of strat experts talking up the chances of such an event in the first place..But obviously to use phrases like Historic when looking ahead a few weeks is fraught with error. Let's face it the weather makes mugs of the best pro forecasters on a regular basis. And it makes a mug of me several times a day mate

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Posted
  • Location: Essex Riviera aka Burnham
  • Weather Preferences: 30 Degrees of pure British Celsius
  • Location: Essex Riviera aka Burnham
18 minutes ago, swfc said:

bucannans cold spell in February?

I thought 'Buchans' (which I think your referring to) cold spell was related to cold spells/snaps around mid-November? unless I'm mistaking it with another similar spelling one?

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Posted
  • Location: Netherlands
  • Location: Netherlands
12 minutes ago, Tamara said:

 

 

Attempts to fit the MJO to idealistic blocking scenarios is fraught with error risk because it is just one part of the global wind-flow inertia weighting used to calculate ALL probabilistic outcomes in respect of pattern evolution and change.

One has to look at total global wind-flow inertia which encompasses not just the tropics but also within the extra tropics at different latitudes. That is where the GSDM (modelling) gives diagnostic clues as to where switches in the speed and path of the jet stream are most likely to occur. Simply taking an MJO composite that reflects a tropical phase space element (i.e pinpointing the MJO within one part of the tropics) and without looking at the whole atmospheric circulation - is not a ticket to automatically finding blocking (where it is most desired)  Looking at the broad-scale might not provide only the outcomes that are being sought but will be give a more accurate and objective overview.

Lets briefly look at the here and now and put an overview into practice of latest consolidated data we have of the atmospheric circulation, and which compartmentalises the latest position within the upper atmosphere reflecting a period where the polar vortex remains relatively weak, but is nevertheless undergoing some re-organisation before potential further instability.

Relative global atmospheric angular momentum has sustained its New Year slump and is now wholly reflective of the overall Nina base state. The distinct banding of easterly inertia at 30N c/o enhanced trade winds (shaded blue) is overlaid by compensating westerly inertia driving the extra tropical circulation (shaded deeper orange/red). Good support for the NWP advertised downstream jet pattern driving successive troughs eastward vs the disjointed and relatively weak polar field pressure profile

AngM.thumb.GIF.7e2d61e2270313d18b01c3209485c17b.GIF

 

This distinctly Nina-esque wind-flow pattern, following the much more a-typical relationship maintained during late autumn and the first part of the winter. So, since the turn of the year, it is incorrect to try to maintain any position that says that the atmosphere is behaving in any Nino-esque manner. Indices such as the SOI as well as the GWO firmly point to pressure and wind-flow diagnostics well within La Nina territory. the GWO rooted within the low angular momentum La Nina attractor phases, mostly centred around Phase 2.

image.thumb.png.11d662dfcdebd430d7c63de9547d73d8.png401255538_Phase2.thumb.GIF.39e156064992b89d5aedd1d3828d37c9.GIF

 

With this in mind, considerable amounts of -ve wind-flow (easterly) inertia remains present across the Equatorial Pacific, at the same time as the high frequency tropical signal (MJO)  propagate into the Western Pacific and add westerlies (forward momentum). Convergence strength of westerlies, as added by tropical convection, has being mitigated by easterly trades ahead of it .

Potential pitfalls lie ahead.

NWP will be somewhat blindsided by the immediate signal from the tropics to ignite active tropical convection phasing in the Pacific - and context of the maximum bandwidth capacity of any westerly wind additions has to be taken from the existing position of low angular momentum inertia within the extra tropics. There is a distinct risk that a rise in angular momentum tendency, as created by (attempted) eastward propagation of high frequency tropical forcing, grinds to a halt - as trade wind inertia resumes after a pause. The effect of this would be for the high frequency tropical signal to beat a retreat and any programmed blocking signals advertised at distance within NWP be prone to correction in both amplitude and duration -  and/or more energy switched to the polar jet as a result of angular momentum tendency being over-egged. Or any such rally programmed to be sustained for too long a time.

Break in trade winds indicated here (ringed in red) :

1675509391_tradewinds.thumb.GIF.4af005996aefb9c23506c9ae3a83f08f.GIF

If the upstream Pacific pattern quickly returns to increased amplification c/o trade winds buffering increased momentum in association with MJO thunderstorm development  (and weakening it due to wind shear) , then sufficient polar jet flow soon returns on a temperature gradient out of the US and Canada to negotiate the weakly disjointed tropopause. Much as discussed as the default in recent summaries.

Putting all this together, if the numerical models get the modelling wrong, and there is shortfall in suggested upturn of wind-flow inertia, this will be registered by the MJO beating a retreat in Phase 7. This will signpost extended ensembles to trend away from some of the coldest downstream solutions . Any element of retained Pacific ridge is likely to continue to assist some polar jet flow in the Atlantic sector and it is not enough, on its own, to just assume, through bias tendencies, that there will be enough weakness within the polar field to stump up a large blocking high.

Extended ensemble suites which might include scenarios of Scandinavian/Arctic high combinations should ideally be viewed objectively within a wider probabilistic field which may tend to create something of a NE/SW split. Colder and drier to the NE and milder and wetter to the W and S.  Without a concerted push, not just from the high frequency MJO signal eastward into the Pacific (that question mark over trade winds sapping its strength) but also with some deficit of momentum to recover within the extra tropics - then the chances of some retrograding high pressure out of the arctic are reduced and while forecasts of further warmings of the stratosphere will no doubt keep the partisan on their toes, it could equally maintain an average to rather cold type of default winter pattern - and as stated, the coldest conditions further north east and with milder conditions continuing to push into southern and western parts.

Meanwhile, my own eyes remain on fortunes across S and SW Europe, where the unprecedented cold weather of early January has been relaxing to something more familiar for the time of year - with warmer temperatures, albeit attendant with some wet weather. Later this coming week there are signs of some lovely Spring-like temperatures into the high teens Celsius. Its a case of remaining patient until it finally becomes very much safer & possible to leave and enjoy such conditions 

 

 

Okay. I try to understand. It's quite difficult. I try to summarise, i hope you don't mind

The headlines. 1) there is a La Nina in the Pacific and the atmosphere is behaving as it 'should.' 2) Tamara discusses some issues with understanding MJO in a correct way. 3) The models may be to enthousiastic about the rise of AAM and as a result more blocking is shown, than realistic is. 4) The coldest solutions in the extended ENS may trend away 5) it seems unlikely there will be a powerful blocking high 5) She hints on a NE/SW split. With colder/ drier to the NE and milder, wtter to the west and S. 6) WIthout a concerted push from the MJO moving eastwards (questionable development because of trade winds) and a deficit of momentum there will be no Arctic High moving southwards. 7) Tamara doesn't expect the new warming of the stratopshere will deliver real cold weather for all of us.

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Posted
  • Location: Netherlands
  • Location: Netherlands
7 minutes ago, MATTWOLVES said:

Thats one way of looking at it Pete..But if that Vortex would have been a clean split we would have been in the game for something more significant! And tbh there were plenty of strat experts talking up the chances of such an event in the first place..But obviously to use phrases like Historic when looking ahead a few weeks is fraught with error. Let's face it the weather makes mugs of the best pro forecasters on a regular basis. And it makes a mug of me several times a day mate

I think it is better to wait, when it is clear the split will come. But I really like the efforts by everybody to push the limits of what is possible. We learn a lot by doing so.

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Posted
  • Location: Alvechurch 8 miles South West of Birmingham
  • Weather Preferences: Snow
  • Location: Alvechurch 8 miles South West of Birmingham
28 minutes ago, General Cluster said:

It's a great question . . . I learned how to read weather charts way back in the 1960s, when snow (and thunderstorms) either failed to show, or exploded out of nowhere, with little no warning at all, more times than I care to remember; so, from that perspective (or maybe habit, as short-range weather forecasting has advanced immensely, since then) . . .

But, the models are something else: by combining the 500hPa anomalies and the run-of-the-mill daily outputs, you can get some idea of the extents of various airmasses and upper wind direction, over a much longer time period? But what you definitely can't do, is pinpoint detailed local mesoscale weather-phenomena, thunderstorms, snow showers et. al. 10-days+ in advance... deterministic chaos just doesn't work that way!

But you can have bloody good fun trying!??‍♂️

Like you I’ve been reading models since the 70s good old Alt sci days lol but don’t you feel everyone hangs on to the models like gospel is oldies know the best surprises are not even seen 24hrs out (snow of course)

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
1 minute ago, MATTWOLVES said:

Thats one way of looking at it Pete..But if that Vortex would have been a clean split we would have been in the game for something more significant! And tbh there were plenty of strat experts talking up the chances of such an event in the first place..But obviously to use phrases like Historic when looking ahead a few weeks is fraught with error. Let's face it the weather makes mugs of the best pro forecasters on a regular basis. And it makes a mug of me several times a day mate

But it didn't Matt! And, as always, all human observers (me included!) have bias?

I'm sure you'll agree that only if, this, that or the other hadn't fallen the way they did, some of those fanciful 1947, 63, 69, 70, 79, 85, 86, 87, 96... 'reduxes' would have happened? But they didn't, mate...?

Anywho, here's hoping for rerun of February 1947!?

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Posted
  • Location: Leicester
  • Location: Leicester
2 minutes ago, Battleground Snow said:

Ukmo joins the wedge party at 144

 

UN144-21 (22).gif

Wow!!!where did that come from!!think tomorrows snow is playing havoc with the models as well!!

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