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Paul

Model Output Discussion - The Start Of Winter

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I agree with Mucka 'probability' wise the timing of the pattern change through amplification appears to be homing in ( all be it very disjointed ) on boxing day, however models whilst they are progressive can occasionally be to slow in developing A change & at day 10 there is a margin of error of 24 hours either side-

So we are still in with a shout for something colder from the NW on xmas day.

 

the azores high may well support the ridging towards Greenland as it conjoins with the ridge developing over the east coast...

 

either way it should be an exciting run up towards the big day......

 

I like this new restrained Mr Murr, much less kettle boiling.

 

UKMO looks pretty good for this Sat. I have done a bit of Rolph Harris (nooo not that). Easy 3 steps.

UN120-21dec20edit_zps985ccf95.jpg

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People don't comment when a run is ongoing because they want to see it in toto (and those who don't, often find their earlier comments made to look hasty in retrospect - QED)

 

So, now it's fully out, we can see that it is now showing the suggested pattern change. Having been at the warmest end of its ensembles for the 00z it looks likely that this will change for the 12z.

 

ECH1-240.GIF?15-0

 

Edit: and I should add, thanks NIck Sussex for the links regarding  the bias correction on the GEFS. It looks like it deserves to be paid attention to.

Hang on, Knocker says sunbeds at the ready Who do I believe ??

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Looking at the evolution of tonight's GEFs anomalies there is no apparent indication of any major pattern change. Ridging Alaska but de-intensification of the Greenland/Atlantic ridge with little amplification in the US and a flat zonality. Seems to my uneducated eye the similar story of LP to NW and HP to SW.

Charts weatherbell

 

post-12275-0-94194800-1418675244_thumb.p

post-12275-0-90579500-1418675252_thumb.p

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I like this new restrained Mr Murr, much less kettle boiling.

 

UKMO looks pretty good for this Sat. I have done a bit of Rolph Harris (nooo not that). Easy 3 steps.

UN120-21dec20edit_zps985ccf95.jpg

Very nice diagram which would be ideal if happened but it's very unlikely to be honest . there's too much energy in the vortex segment over Greenland to allow the ridge to be pulled up like that . Maybe the Azores can ridge more WWN toward to the east coast of America giving more of a northwest flow but at the minute a greeny high is very unlikely at that time frame .

Maybe just after Xmas perhaps look to our Northwest but not yet . All the same the vortex is going east and the East Pacific Oscilation does look like going negative with time which will drive cold air South into America and normally produce a ridge to the east of that in reply to the pressure distribution over the above areas stated . I think that's where we need to watch but not just yet . But I do believe a pattern stage will show it's hand in the models before Xmas but won't verify until after Xmas which should at least give interesting model watching leading up to it !

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You do realise that your 384 mean is amplified not flat for the UK.... I really do think you are assuming the black contours are the same as the windflow lines,........

 

Thank you I do realise that. But the troughing on the anomaly is very weak so hardly amounts to anything significant on the surface analysis. Are you saying the contours are not the same as the gradient wind?

Edited by knocker

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I am going to say FI as I suppose the jet stream is no different to anything else but finally digs South and is vigorous. This seems timely also which ties in to "theories" of cold near New Year. Sorry no quotes for theories.

 

gens-0-3-360.png?12

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Looking at the evolution of tonight's GEFs anomalies there is no apparent indication of any major pattern change. Ridging Alaska but de-intensification of the Greenland/Atlantic ridge with little amplification in the US and a flat zonality. Seems to my uneducated eye the similar story of LP to NW and HP to SW.

Charts weatherbell

The mean at t384 to me indicates low pressure well South into Europe, the removal of high pressure to our South and high pressure still over west Greenland , aswel as hinting at a more negative AO . Not that I would ever look at the mean at so far out for any guidance tbh .

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There is a change knocker and whereas it may not be a major one globally, it is for part of the world. The lower heights to our south and into S Europe are the giveaway...

 

Thank chio. I had noticed but not the significance. If you could expand a little  please.

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Thank you I do realise that. But the troughing on the anomaly is very weak so hardly amounts to anything significant on the surface analysis.

But a 384 mean chart is rarely going to show anything else. Even fergie mentioned recently that they look at the individual charts rather than the means at longer range. Having looked through the GEFS at 240, 300 and 384 hours tonight there is plenty of interest.

Some better charts moving forward into the days 11, 12 range within the suite as well. nothing certain obviously, but beyond day 10 maybe an uptick in uncertainty which is good news.

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I am going to say FI as I suppose the jet stream is no different to anything else but finally digs South and is vigorous. This seems timely also which ties in to "theories" of cold near New Year. Sorry no quotes for theories.

 

gens-0-3-360.png?12

Again too far out to be taken litterly because it's only indicative of that particular time frame on the GFS so how reliable is it ? But always good to see the jet going South which can promote high pressure to our North !

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Again too far out to be taken litterly because it's only indicative of that particular time frame on the GFS so how reliable is it ? But always good to see the jet going South which can promote high pressure to our North !

 

Remember SSIB, looking for trends ;-)

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I like this new restrained Mr Murr, much less kettle boiling.

 

UKMO looks pretty good for this Sat. I have done a bit of Rolph Harris (nooo not that). Easy 3 steps.

UN120-21dec20edit_zps985ccf95.jpg

It's a shame that the area over Greenland will more than likely be moving in the opposite direction as low heights cycle around to our north. Still signs of a northerly developing between Christmas and New year. How lengthy and potent is of course up in the air, but at this present time it looks transient, the jet does move south but at the moment the pattern over the Atlantic tends to de-amplify which would bring a very unsettled spell of weather to the UK post this northerly. Of course this could easily change over the coming days, especially is positive heights appear just to our north which could indicate wet weather going south of the UK (AKA a cold, blocking pattern).

EDH1-240.GIF?15-0

gensnh-21-1-240.png?12

GFS and ECM ensembles look in good agreement for this amplification to occur, it's a shame it couldn't have been a couple of days earlier.

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Well for what it's worth campers a quick look at the ECM T360 anomaly.

 

Strong ridge Alaska; flattish across the US and eastern seaboard but quite a marked Azores/ Greenland ridge orientated NW/SE just west of the UK. Trough Scandinavia into Europe. Which on a surface analysis would bring the Azores HP into prominence.

Edited by knocker

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Any Scandi trough would extend into S Europe meaning that any cold air on the west side of the trough would extend further south. Effectively, the UK would be in a more predominantly northerly airflow rather than westerly. With it being at T+384 it is well into FI but still a significant change when compared to T+240. No mild sectors at T+384 (such as we will be seeing this week) in that.

 

Thanks I see what you mean.

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Just a polite nod to keep discussion friendly  :)

 

Thanks 

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Well for what it's worth campers a quick look at the ECM T360 anomaly.

 

Strong ridge Alaska; flattish across the US and eastern seaboard but quite a marked Azores/ Greenland ridge orientated NW/SE just west of the UK. Trough Scandinavia into Europe. Which on a surface analysis would bring the Azores HP into prominence.

I think we should all agree to disagree because in my eyes the Azores will not be a player . Low pressure Europe , -AO setting up . Ridge over Alaska but pushing towards west Greenland . Don't see the Azores spoiler .

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