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Paul

Model output discussion - 16th Nov onwards

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Is that good or bad Mucka.. For coldies of course.

 

Good if you want a better chance of snow in the South.

The problem is, other than whether it actually verifies, that the cold air needs to be transported South before it arrives and it need to track in a narrow band so that there isn't too much mixing of upper air. If it develops more (seems unlikely) it will likely track a little further North and the midlands would get a snow fest but the South would likely see rain.

If it doesn't develop enough then it will likely just phase with the trough and head SE and keep the South essentially dry.

It is a bit of a golden ticket deal where frontal snow is concerned.

Edited by Mucka

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a strong siberian high has a major influence on northern hemispheric weather during winter. its strength is usually related to the amount of eurasian snowcover as Cohens studies (debated in detail on this forum) have shown. it has been shown to exert a major influence on winter weather in western europe- i.e. colder.

as crewecold says, cohens studies are freely available to read. the OPI (which i should mention was not a failure last year, as many seem to think, it was just in the 20% or so winters which do not correlate to the OPI) was based on said snowcover and the consequential 'siberian high'

 

 

True bg, but if a strong Siberian High never backs west, it can kill any chance of a cold and snowy winter for the uk, leaving us in 'no mans land'  Last winter springs to mind I think?

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Good if you want a better chance of snow in the South.

The problem is, other than whether it actually verifies, that the cold air needs to be transported South before it arrives and it need to track in a narrow band so that there isn't too much mixing of upper air. If it develops more it will likely track a little further North and the midlands would get a snow fest but the South would likely see rain.

If it doesn't develop enough then it will likely just phase with the trough and head SE and keep the South essentially dry.

It is a bit of a golden ticket deal where frontal snow is concerned.

Thank Mucka.. Well I'm in north west Kent and I have just bought a bar of chocolate..nlets see if there is a ticket when I unwrap.

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The latest BBC weather that was published on Twitter mentioned another possible Northerly mid next week...so I guess they have models going with that option also.

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The latest BBC weather that was published on Twitter mentioned another possible Northerly mid next week...so I guess they have models going with that option also.

 

BBC News forecast have just mentioned this, briefly less cold early next week then colder air spreads back down from North.

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a strong siberian high has a major influence on northern hemispheric weather during winter. its strength is usually related to the amount of eurasian snowcover as Cohens studies (debated in detail on this forum) have shown. it has been shown to exert a major influence on winter weather in western europe- i.e. colder.

as crewecold says, cohens studies are freely available to read. the OPI (which i should mention was not a failure last year, as many seem to think, it was just in the 20% or so winters which do not correlate to the OPI) was based on said snowcover and the consequential 'siberian high'

 

I wasn't questioning the influence of the Siberian high merely asking what cc specifically meant by

 

 

We're pretty much at the point now where we will set off a feedback courtesy of the Siberian High we're seeing at present, what will differ is the time when we see the consequences of this manifest themselves into the further outlook. ECM would take maybe 2 weeks, GFS much quicker.

 

 Put simply what are the consequencies that will manifest themselves that will differ so drastically in the two models. I'm not sure why this seems to generate such a defensive attitude. Anyway it's no big deal so best left before this discussion degenerates further,

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GFS 18z looks like sticking with shortwave/channel low

 

gfsnh-0-60.png?18

 

Edit

just clipping the far South this time. Could be interesting if it developed a little more and was a little further North

 

gfs-2-78.png?18

 

Don't think its much interest that channel low in all honestly, ideally you need cold air already bedded in and we don't have that, if anything, I would prefer that channel low out of the way and let the colder air flood down quicker. 

 

Its still hard to say which areas has the main snow risk, I would say, Northern and Eastern Scotland looks a good bet, perhaps Northern Ireland also and parts of NW England at higher levels especially. The problem we see once Sunday comes, the coldest air starts to mix out but with an unstable set up, it should be a sunshine and shower set up but snowfall would be rather limited to higher levels I would of thought. Still time for the minor details to change but for me, this cold snap can only help to lower SST's down a touch which will hopefully helpin any future cold set ups. 

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BBC News forecast have just mentioned this, briefly less cold early next week then colder air spreads back down from North.

 

Well that differs from their update this afternoon.

 

 

Then during the first part of next week milder conditions look set to return for a time with rain and possibly strong winds spreading across most parts. From later next week onwards the general weather pattern is likely to be for unsettled conditions to prevail across northern areas, with periods of rain and showers, whereas in the south it should be generally less unsettled. However even here some rain and showers are likely at times. Localised frosts are expected in any quieter spells.

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A genuine question but could you explain what you mean by "a feedback courtesy of the Siberian High" in simple meteorological terminology? Thanks

no, to be fair you actually asked what was meant by "feedback from a siberian high" you didnt mention specific models. that question i cant answer but yours i can.

Edited by bobbydog

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Just flicking through the gefsp members and the 12z operational gfs isn't so way out. Plenty of members even more split then the op. I recall last November was similar though that was a Nina -QBO winter .........

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The ext ecm anomaly tonight has an Alaskan trough and North Canadian Low with associated negatively tilted trough Greenland SE and HP to the SW resulting in very much a zonal flow and a N/S split weatherwise over the UK. The NOAA 8-14 although not unexpectently not  precisely  the same, is singing from the same page.

post-12275-0-47257800-1447800067_thumb.g

Edited by knocker

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GFS 18Z still going for another brief northerly feed on Thu, but a few 100 miles further East than the 12Z.

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GFS 18z says no to westerly regime.82mph wind gust recorded this evening over the pennines

Pressure on the pole may bring a true split

post-8269-0-90170500-1447800129_thumb.pn

post-8269-0-44447900-1447800300_thumb.pn

post-8269-0-99896000-1447800939_thumb.pn

Edited by winterof79

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Knocker- you failed to make yourself clear. The way I read your first response was as if you were asking about the role of Siberian HP in context to the NW European weather, to which there are a gamut of sites offering Cohen's research. I don't want to labour the issue but at the moment the -EPO signature and the Siberian high pattern are not mutually exclusive. In essence I believe the ECM solution offers a sequence of

 

1) Siberian high

2) -EPO

3) Collapse of Siberian high

4) Continued or enhancement of -EPO

5) Re-emergence of Siberian high??

 

Number 5 is purely theoretical at this point (not shown within the 10 day timeframe) but would fit in to the feedback attempt at repeated Siberian HP due to the antagonistic response of the -EPO and snow cover in the area. Essentially a highly amplified jet stream at the N latitudes.

 

I believe Tamara pointed this pattern out last winter but I could be wrong on that.

 

The GFS runs have shown this well over the past day or so and the 18z is no different

 

gfsnh-0-288.png?18

 

This causes a pincer movement on the tropospheric vortex and possibly could lead to a complete split in time.

I edited my post to state the same Crewe.Re:Split

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Don't think its much interest that channel low in all honestly, ideally you need cold air already bedded in and we don't have that, if anything, I would prefer that channel low out of the way and let the colder air flood down quicker. 

 

 

 

It is obviously a long shot and I don't think it worthy of intense scrutiny as yet either, may well be gone tomorrow.

Very fine margins and that is IF the GFS is onto something but worthy of a mention.  

 

ECM 12z London ensembles

 

ensemble-tt6-london.gif

 

From one of the coldest runs this morning to one of the mildest this evening.

There is a mixed signal in there for another chance of Northerly cold around the 29/30th

 

Just For Fun 18z ens p5

 

gensnh-5-1-192.png

Edited by Mucka

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a strong siberian high has a major influence on northern hemispheric weather during winter. its strength is usually related to the amount of eurasian snowcover as Cohens studies (debated in detail on this forum) have shown. it has been shown to exert a major influence on winter weather in western europe- i.e. colder.

as crewecold says, cohens studies are freely available to read. the OPI (which i should mention was not a failure last year, as many seem to think, it was just in the 20% or so winters which do not correlate to the OPI) was based on said snowcover and the consequential 'siberian high'

 

Having read their original work in 2013- (don't know if it was changed after the paper was pulled) - they were not basing the OPI on snowcover but on geopotential height anomalies. Their premise was that the anomalies created the conditions for snow cover to expand rather than the snow cover being the catalyst. It is all very chicken and egg and only seems to work with certain other factors present - I think solar max of past two winters was a no-no but that's just one laywoman's opinion.

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Knocker- you failed to make yourself clear. The way I read your first response was as if you were asking about the role of Siberian HP in context to the NW European weather, to which there are a gamut of sites offering Cohen's research. I don't want to labour the issue but at the moment the -EPO signature and the Siberian high pattern are not mutually exclusive. In essence I believe the ECM solution offers a sequence of

 

1) Siberian high

2) -EPO

3) Collapse of Siberian high

4) Continued or enhancement of -EPO

5) Re-emergence of Siberian high??

 

Number 5 is purely theoretical at this point (not shown within the 10 day timeframe) but would fit in to the feedback attempt at repeated Siberian HP due to the antagonistic response of the -EPO and snow cover in the area. Essentially a highly amplified jet stream at the N latitudes.

 

I believe Tamara pointed this pattern out last winter but I could be wrong on that.

 

The GFS runs have shown this well over the past day or so and the 18z is no different

 

gfsnh-0-288.png?18

 

This causes a pincer movement on the tropospheric vortex and possibly could lead to a complete split in time.

 

Further to that, we see some concerted pressure further up towards the end of the run, which is not surprising given the fact that the synoptics we see throughout the run are highly conducive to a proceeding SSW

 

 

 

Thank you

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The little perturbation that initiated some interest yesterday is still there but appears to travel east across France. Still looking ar a very candy ball weekend which is good news for the west Cornwall cauliflower growers. The mild weather has had a devastating effect on the winter caulis so they are desperate for a weekend chill. Every cloud..........................

Chats weatherbell

 

I think the precip. detail can be safely ignored as this has still to be resolved.

post-12275-0-07824800-1447824214_thumb.p

post-12275-0-64962900-1447824225_thumb.p

Edited by knocker

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the modelling has a problem going forward. we can see that it builds an impressive Alaskan ridge and we know that there is a strong Siberian ridge in place. We also know that there is a pretty strong p/v. do you see the problem? it's tough to resolve these three features, especially over the polar region where the modelling traditionally struggles somewhat. hence, we see a big variation in HLB ens members on the gefs and gefsp and also some extremely strong p/v members.

I'm afraid, if you want to know the answers now for the early part of December, then you are likely disappointed on a hemispheric scale. I would say that the modelling is going to be progressive wrt displacing the Siberian ridge south and likely to drift in the direction whereby the vortex is pushed to this side of the NH. that's going to generate some pretty wild runs for the Atlantic.

No point in over analysing - just enjoy the ride.

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The little perturbation that initiated some interest yesterday is still there but appears to travel east across France. Still looking ar a very candy ball weekend which is good news for the west Cornwall cauliflower growers. The mild weather has had a devastating effect on the winter caulis so they are desperate for a weekend chill. Every cloud..........................

Chats weatherbell

 

I think the precip. detail can be safely ignored as this has still to be resolved.

In the run up to Christmas, the brussel sprouts could desperately do with some frosts to get some taste into them!

Weather wise this November seems very similar to 1946 to me, with exceptionally mild weather at its beginning and mild and stormy weather in its middle.

Model wise,... there still seems to be comparisons to be made going forward

Rslp19461125.gif

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