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Model output discussion - mid-winter

Paul

Please only post model discussion in here & please keep it friendly!

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8 minutes ago, Tamara said:

Any NWP extended ensemble signal showing a height anomaly to the NE has been/is based upon what looks at the moment like something of a leap of faith assumption that MJO tropical forcing successfully negotiates the trade wind wall of easterlies in the Pacific, overcoming in the process a substantial -3 low angular momentum standard deviation from parity, (reflective of the easterly trades swamping the atmosphere) and then manages to trigger a downstream signal for that greater amplification in the Atlantic and European sector.

My take remains exactly the same as of late that the above described atmospheric hoop jumping is a big ask based on simple AAM budget maths. NWP is now awake to those maths.

 Until or if those easterly trades relent some, and change the complexion of the budget maths to allow greater +AAM anomalies c/o MJO tropical convection to scrub out some of those surplus easterlies (to permit greater downstream amplification), the cat is very much in the ascendency of the mouse at the moment and it increasingly becomes a case of whether the mouse can roar during February. Which to those more especially further south seeking some seasonal whiteness implies more 'jam tomorrow' - and assessing that comes against a spectre of ever greater doubting questions vs also the seasonal wavelengths ever shortening.

 

Thanks as ever Tamara.

Sorry to quote just this part of your post but I think it is quite relevant to the ECM clusters that I post - so I'm gathering that the NE height rises suggested for the month end are dependent upon a couple of background signals which, at the moment, are uncertain and perhaps over-optimistic.

@iapennell - it's getting very close to your timescale for an end of January easterly - I would be very interested in your take on this!

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ECMF_phase_51m_small.gif

This move into phase 4 followed by a decline is about the worst case scenario it has to be said. The hope has been that enough knock-on effect from the amplification in phase 3 will occur for AMM to overcome the Nina state. Today through Friday sees the most focused attempt to do this of the current cycle so we should soon know for sure if it's going to make it where we want it or not.

Having tracked these height rises to the NE for next week, they've not matched well to fluctuations in the predicted MJO. Seems to be more to do with trouble analysing the current MJO state due to convection being poorly focused. Well, something like that - I am still getting the hang of certain aspects of this.

I do have a feeling that the timing and arrangement of lows being shown for this weekend is a bit unfortunate and could have been avoided by chance even with the same forcing from teleconnections going on, allowing for a bit more fight back against the subtropical ridge extension. A local complication working for rather than against us, to to speak. Sometimes you need a little luck. Not convinced we're definitely out of it yet though.

Edited by Singularity
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Arome showing the worst gales across the N Wales coast and around the Liverpool area. Less strong through the Bristol & English  Channel. 

image.png

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There are some very poor models out there - here are some examples.

iconeu_uk1-42-96-0_zmf7.pnghirlamuk-45-48-0.png?17-11

 

Also - BBC (so UKV) had the heavy snow symbol over my area for about 2 days incessantly - 1  inch if that lying outside my house, yet the Icon had all of the showers over N.England and most over Scotland falling as rain, yet there are widespread road closures over all the areas that had rain, the Euro4 had decent snow for me for a while but then downgraded nearer the time so at least offered a good forecast but took to T6 to get there, numerous models suggested I should have 8cm lying snow by now, the GFS and ECM regularly in the run up had 10-20cm and in some cases close to a foot of lying snow, and guess what - the BBC location forecasts are at it agin now having me down for heavy snow throughout Friday.

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9 minutes ago, Draig Goch said:

CFS looks poor but suggests March will be our best chance, February looks mild again but thankfully April looks about average or slightly above this year! 

image.png

image.png

image.png

Thank god April is looking good!!! I've been sitting here worrying about how Sunday is going to pan out with all this Model disagreement but I feel better knowing April will be good 🙊

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18 minutes ago, Man With Beard said:

 

@iapennell - it's getting very close to your timescale for an end of January easterly - I would be very interested in your take on this!

 

Its mid-January maybe in 10 days’ time on 27 Jan we can write of his Easterly

Models flip to mild and everything is written off for a month , they can and do flip back

I Have had 10 days of lying snow this winter and I am southerner and saw more snow lying today in Oxfordshire. Look forward to Friday and how it develops and worry at February when it comes along with any Easterly

prectypeuktopo.png

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32 minutes ago, Dafydd Tomos said:

Arome showing the worst gales across the N Wales coast and around the Liverpool area. Less strong through the Bristol & English  Channel. 

image.png

The worst gales are for Holland, not Wales 

Screenshot_20180117-140205.png

Edited by ArHu3
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9 minutes ago, ArHu3 said:

The worst gales are for Holland, not Wales 

Screenshot_20180117-140205.png

Do that mean southeast better lookout now

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28 minutes ago, stewfox said:

 

Its mid-January maybe in 10 days’ time on 27 Jan we can write of his Easterly

Models flip to mild and everything is written off for a month , they can and do flip back

I Have had 10 days of lying snow this winter and I am southerner and saw more snow lying today in Oxfordshire. Look forward to Friday and how it develops and worry at February when it comes along with any Easterly

prectypeuktopo.png

The exception not the rule, while you have done very well (10th), in southern England no one south of M4 has seen anywhere near that - not even a day, except from maybe the highest ground. This tedium seems neverending ever since 13/14. I can’t help but feel disheartened there was me thinking an E-QBO might be a game changer. Perhaps I’m getting too ahead of myself but foreseeable looks woeful hoping for a change of fortune, however it’s been five years now and have we got any luck down here? Surely the laws of probability will mean we’ll have a cold winter before 2020. What with the approaching solar minimum at lesser amplitude than norm, I’m somewhat expecting at the very least a very cold winter within the next 5 years. And well if you go by those GFS precip charts even the SE would have seen snow - funny London and SE get a yellow warning for snow and ice and there’s not a single shower in sight. 

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58 minutes ago, Tamara said:

Allora... e poi?

The whole post is pertinent to the here and now - but special emphasis given to the bolded parts

The answer thus far has been that the extra mile has been/is struggling against another substantial programme of easterly trade winds that have depressed angular momentum to a level that would reflect a robust La Nina base state if it was to be sustained to meet official criteria. That particular scenario certainly seems unlikely looking forward, but nevertheless it does represent a considerable challenge to any +AAM poleward anomalies c/o tropical convection heading eastwards during the medium term at the very least.

Any NWP extended ensemble signal showing a height anomaly to the NE has been/is based upon what looks at the moment like something of a leap of faith assumption that MJO tropical forcing successfully negotiates the trade wind wall of easterlies in the Pacific, overcoming in the process a substantial -3 low angular momentum standard deviation from parity, (reflective of the easterly trades swamping the atmosphere) and then manages to trigger a downstream signal for that greater amplification in the Atlantic and European sector.

My take remains exactly the same as of late that the above described atmospheric hoop jumping is a big ask based on simple AAM budget maths. NWP is now awake to those maths.

 Until or if those easterly trades relent some, and change the complexion of the budget maths to allow greater +AAM anomalies c/o MJO tropical convection to scrub out some of those surplus easterlies (to permit greater downstream amplification), the cat is very much in the ascendency of the mouse at the moment and it increasingly becomes a case of whether the mouse can roar during February. Which to those more especially further south seeking some seasonal whiteness implies more 'jam tomorrow' - and assessing that comes against a spectre of ever greater doubting questions vs also the seasonal wavelengths ever shortening.

But whichever way one slices it, that would all be part of any future rolling programme of seasonal analysis.

Andiamo - attraversiamo,... Ciao:)

Brilliant post Tamara as always. Presumably the cat is the Nina and the mouse is the MJO...

Looking at the strength of those forecast trade winds, it does appear the eastwards heading PPN is never going to make it to the Pacific. Even taking into account that the Maritime area is often poorly modeled.

You posted this recently, I can't find it anywhere, do you have the link for it?

imageproxy_php.thumb.gif.0f20628bce4fc05fdd62999308c04f9d.gif

 

 

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3 hours ago, Paul_1978 said:

Even that's gone quiet in the last few days.... Unless I've missed something.

Can we put to bed now the notion of the stratosphere forecasts being much more accurate? 

At the ens of the day (GFS for example) forecasts are all intrinsically related to the same nwp model runs and therefore prone to the same swings and flaws.

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40 minutes ago, ArHu3 said:

The worst gales are for Holland, not Wales 

Screenshot_20180117-140205.png

Well yes it does look nasty and storm will be the most impactful in the Low Counties, the Netherlands where you are? But this is a forum primarily made up of British weather chasers or nutters or whatever you call it, and our immediate focus is what’s affecting us or near us.

Unrelated lucky Netherlands has some of the best coastal flood defences in the world as much of your country would have been overwhelmed and inundated going by that. 

Edited by Daniel*

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13 minutes ago, Johnp said:

Can we put to bed now the notion of the stratosphere forecasts being much more accurate? 

At the ens of the day (GFS for example) forecasts are all intrinsically related to the same nwp model runs and therefore prone to the same swings and flaws.

No - because they are more accurate - significantly so - but significantly more accurate doesn't mean bang on at 384 - plus they've still modelled the warming well, no run ever had a technical SSW at 384 and also the warming at 1mb hasn't yet really subsided at 384 yet so we don't really know the final outcome.

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19 minutes ago, Johnp said:

Can we put to bed now the notion of the stratosphere forecasts being much more accurate? 

At the ens of the day (GFS for example) forecasts are all intrinsically related to the same nwp model runs and therefore prone to the same swings and flaws.

Nope. They are way more accurate, mainly due to the topographical aspects it doesn't have to deal with.

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37 minutes ago, Johnp said:

Can we put to bed now the notion of the stratosphere forecasts being much more accurate? 

At the ens of the day (GFS for example) forecasts are all intrinsically related to the same nwp model runs and therefore prone to the same swings and flaws.

I think its more down to people not understanding them, they probably should be banned from this thread and left to the technical thread.

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42 minutes ago, Johnp said:

At the ens of the day 

I clearly spend too long on weather forums - my phone is now autocorrecting end to ens 😁

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As long as it's model discussion all is ok, And on we go..

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2 hours ago, karyo said:

Yes Nick, it is very disappointing to think that up to a few days ago the models were showing a ridge developing in the Atlantic towards the end of this week, with a northerly and then a possible pressure rise to the northeast. Instead we are getting the horrid Azores High extending its influence north and east and a spell of southwesterlies next week. My only solace is that I will not miss anything worthwhile when I am away next week. :)

This is what I meant Monday, model output always changes a lot after such storms. They can't really model something which doesn't exist before until very shortly before 24-48h. Unfortunately the surprises were not very pleasant this time. 

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2 hours ago, ArHu3 said:

The worst gales are for Holland, not Wales 

Screenshot_20180117-140205.png

Why is Scotland white on this? Is that because of all the snow we have? :unsure2: :rolleyes:

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Afternoon all :)

Some early comment on the 12Z suite.

ICON shows a milder spell for the south into next week with 2m temperatures rising into the teens from Monday until a sharp cool down on Thursday. More of a blink and you'll miss it affair further north. Looks like the 06Z GFS Control to be honest.

GFS OP much the same - a new storm forming to the south of Greenland tomorrow and Saturday meanders toward Iceland before heading east early in the week and deepening. Looks as though it will pass well to the north of the British Isles - over the Faeroes perhaps - while the Azores HP moves in to Southern France bringing a spell of mild SW'ly winds (in truth not really had a blowtorch spell this winter so far).

GEM develops a large European HP area into early next week with the Atlantic LP much weaker than GFS and displaced further west so once again mild or very mild across southern areas through next Tuesday.

GFS 12Z OP Northern Hemisphere Profile for T+144:

gfsnh-0-144.png?12

UKMO 12Z NH Profile at the same time:

UN144-21.GIF?17-17

 

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GFS rather more flat than UKMO.

 

 

UE144-21 (1).gif

gfseu-0-144 (1).png

Edited by Seasonality

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Going to lock this now, new thread open here

 

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