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Model output discussion - 5th December 2016 - Into Winter we go

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  49 minutes ago, Hammer50 said:

Could this be a start to a 1963 scenario here's hoping.

and feb 1991 blizzard said this below?

No, that cold spell was well signposted, there was a weak Stratospheric vortex, the GLOSEA1 and the EC24 had strong support for it well in advance and the ECMWF and GEFS modelled it all the way in from 300 hours, it counted down like clockwork and subsequent modelling was very precise throughout that winter.

In 1963, I guess you used the wrong post to talk about these models, perhaps 2010 December??

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Just now, bluearmy said:

With 'a really strong trop vortex' in place and what seems to be a strong upper strat vortex (though again this seems to displace fairly easily towards Siberia with the onset of trop induced wave 1), how do you explain the modelling being chucked out at present which shows significant trop amplification??

a strong upper strat vortex/trop vortex combo surely wouldn't allow such patterns to develop ?? Remember the models are one trop/strat picture. They aren't separate entities. 

The gefs are  bouncing around a bit, the eps a bit more consistent. The Canadian ens now lost the euro low anomolies in the latter part of week 2, whilst the gefs/eps retain them. 

TBH if I was just using my own intuition based on model watching over about 6 or 7 years, I would say that even when there is a strong vortex right the way down in past years, the models (usually but not always the GFS in FI) can find a way to throw out ridiculous Easterlies without any logic or any strat warming event involved in the run but they never actually verify, and my instinct is that any ridging will be toppler / brief(ish) PM incursions and will topple as soon as resistance of the wave break occurs at any reasonable altitude, and with no top down SSW likely any time soon, I would forecast an unremarkable January and probably rest of meteorological winter, but obviously I don't have the qualifications of others.

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Just now, johnholmes said:

  49 minutes ago, Hammer50 said:

Could this be a start to a 1963 scenario here's hoping.

and feb 1991 blizzard said this below?

No, that cold spell was well signposted, there was a weak Stratospheric vortex, the GLOSEA1 and the EC24 had strong support for it well in advance and the ECMWF and GEFS modelled it all the way in from 300 hours, it counted down like clockwork and subsequent modelling was very precise throughout that winter.

In 1963, I guess you used the wrong post to talk about these models, perhaps 2010 December??

My reply was a bit of fun.

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36 minutes ago, bluearmy said:

With 'a really strong trop vortex' in place and what seems to be a strong upper strat vortex (though again this seems to displace fairly easily towards Siberia with the onset of trop induced wave 1), how do you explain the modelling being chucked out at present which shows significant trop amplification??

a strong upper strat vortex/trop vortex combo surely wouldn't allow such patterns to develop ?? Remember the models are one trop/strat picture. They aren't separate entities. 

The gefs are  bouncing around a bit, the eps a bit more consistent. The Canadian ens now lost the euro low anomolies in the latter part of week 2, whilst the gefs/eps retain them. 

Just MLBs in the outputs- inline with climo & a forecast deceleration of the zonal wind-

Past week 1 Jan we need to see where the zonal mean bottoms out & whether that becomes a double dip or works its way upwards- I havent looked at the eddy flux charts however the means have trended upwards again over the last 36 hours ( more inline with UKMO ) which isnt good news-

This is really important:

MLBs can provide the Uk with deep cold as our 2 most cited events ( jan 1987 & feb 1991 ) had neutral AOs 

11th jan 1987 was slightly pos!!

IMG_1171.PNG

4th Feb 1991 was slightly pos...!!

IMG_1170.PNG

So Easterlies are driven by an MLB not always HLB...

cant access Merra data ATM

S

Edited by Steve Murr

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8 minutes ago, feb1991blizzard said:

TBH if I was just using my own intuition based on model watching over about 6 or 7 years, I would say that even when there is a strong vortex right the way down in past years, the models (usually but not always the GFS in FI) can find a way to throw out ridiculous Easterlies without any logic or any strat warming event involved in the run but they never actually verify, and my instinct is that any ridging will be toppler / brief(ish) PM incursions and will topple as soon as resistance of the wave break occurs at any reasonable altitude, and with no top down SSW likely any time soon, I would forecast an unremarkable January and probably rest of meteorological winter, but obviously I don't have the qualifications of others.

The one thing that kept human beings in the survival race was "Instinct". Often far outweighs technology, so stick with it, you'll be right.

Edited by Dorsetbred

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1 minute ago, Dorsetbred said:

The one thing that kept human beings in the survival race was "Instinct". Often far outweighs technology, so stick with it, you'll be right.

Unfortunately though, I don't want to be right!!!!!!

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Merry Christmas all, great posts on here tonight so I'll go for a brief one - my thoughts today are unchanged since yesterday - good chance of a back-edge snow event for New Year followed by a couple of cold days - beyond that, still to be decided. IMO.

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9 minutes ago, Steve Murr said:

Just MLBs in the outputs- inline with climo & a forecast deceleration of the zonal wind-

Past week 1 Jan we need to see where the zonal mean bottoms out & whether that becomes a double dip or works its way upwards- I havent looked at the eddy flux charts however the means have trended upwards again over the last 36 hours ( more inline with UKMO ) which isnt good news-

This is really important:

MLBs can provide the Uk with deep cold as our 2 most cited events ( jan 1987 & feb 1991 ) had neutral AOs 

11th jan 1987 was slightly pos!!

IMG_1171.PNG

4th Feb 1991 was slightly pos...!!

IMG_1170.PNG

So Easterlies are driven by an MLB not always HLB...

cant access Merra data ATM

S

Steve to me those are HLB, I don't really pay much attention to AO and NAO stats, those blocks ridge right the way up near the polar regions the Northern hemisphere is from 0 to 90N.

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2 hours ago, Steve Murr said:

Poor afternoon runs - less ridging on the GFS / ECM means the cold never really gets in-

The Greenland high option was never on the table - however something from the NE / E was hopeful- 

At the very least the deep cold will be close by to the east.-

No more sign of any cross polar flow..

Wow, did you just get a pair of socks and a bottle of 'hai karate'?....

I thought the GFS looked half decent in FI.....

gfsnh-0-360.png

Anyway, just popped on to say merry Christmas to everyone, hope you have all had a good day despite the weather or the models. :drunk-emoji::drunk::santa-emoji:

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15 minutes ago, feb1991blizzard said:

Steve to me those are HLB, I don't really pay much attention to AO and NAO stats, those blocks ridge right the way up near the polar regions the Northern hemisphere is from 0 to 90N.

Not sure really mate - take Feb 91 core blocking over central scandi -60N

HLB should really be north of 75N in the arctic circle

S

 

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Just now, Steve Murr said:

Not sure really mate - take Feb 91 core blocking over central scandi -60N

HLB should really be north of 75N in the arctic circle

S

 

Maybe I'm wrong but I class a high over us that sits there as mid latitude block, it would be possible IMO to get heavy snowfall from a mid latt block for your location but not most of the UK, if there was a really thin sausage shaped high (like a Richmond skinless not like your fat stubby Lincolnshire ones with that seasoning in) with a very steep pressure gradient to the south then it could deliver for you.

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4 minutes ago, Steve Murr said:

Not sure really mate - take Feb 91 core blocking over central scandi -60N

HLB should really be north of 75N in the arctic circle

S

 

An interesting debate - had Feb not posted that, I would have done so. blocks much further north than those two scandi ones are just as  likely not to deliver deep cold to nw Europe anyway!  Anyway, if we can get those euro low anomolies to verify post day 12/13, then we may well not require any blocking further N than 75 anyway. 

Wonder if the pub pub run will chuck out another ridiculous fi. There were plenty of fairly tedious GEFS 12z members so we are due a boring op. 

 

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Re hlb it's not a term I am particularly fond of tbh. But an example and diagram is provided http://climate.ncsu.edu/climate/patterns/NAO.html here 

 

the example is near the bottom where it talks about a hlb being situation over Iceland/Greenland etc. The diagram is over Iceland and southern Greenland. 

I am happy with the general trends in the models ATM. It all looks good latest gfs 18z has a better block and shape again for the 1st of Jan. 

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By the 2nd it has -10 850s in Scotland and -8s down to the midlands. Some serious cold to start the near year. 

IMG_0646.GIF

Edited by Iceberg

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The 18z gfs is more amplified in reliable and semi-reliable timeframe leading to a better cold shot from the north for New Year's Day.

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22 minutes ago, Steve Murr said:

Not sure really mate - take Feb 91 core blocking over central scandi -60N

HLB should really be north of 75N in the arctic circle

S

 

Then when does MLB start and finish then?

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2 minutes ago, Matthew Wilson said:

At least some potential at 168ish:hi:

IMG_0893.PNG

IMG_0895.PNG

As the cold front introducing the cold moves south, the back edge turns to snow. 

174-779UK.GIF?25-18

Edited by SN0WM4N

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Merry xmas  to you all

Spending time with family so my thoughts on models will be brief

Opportunities for cold are abundant, This time last year the models indicated very little for opportunity for snow and many people had spent a miserable Christmas outside of their flooded homes.

This year snow is in FI, This shows if nothing more that its certain runs, some with minor tweaks that the atmosphere could deliver something wintry. 

the jet stream diving south and in doing so pushing the Euro high eastwards is certainly a possibility, with that would also see pressure rises towards Greenland.

This of course does not mean snow is highly likely here in Uk, but it does give the opportunity for cold air to sink south and then possabilities of shortwaves and for the South its crossed fingers for a undercutting low.

Fi will never give you a correct scenario with the complexity of the atmosphere but it can often give trends.

 

i think many forget just how awful it was this time last year, this year is much more interesting at least.

anyway enjoy your Christmas evening and lets enjoy these possibilities in deep fi and hope to see some slowly appear in the more reliable period and become consistent which is the best signal of the trend going forward.

 

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What a corker from the pub run on christmas day

gfsnh-12-324.png?18

Edited by Zakos

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gfsnh-1-324.png?18

Deep into FI some decent cold air across the UK , be nice to get some hard frosts

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gfs-0-324.png?18

Lovely snow event

Oh whats that? Not enough?

gfs-0-348.png?18

Here have an easterly.

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27 minutes ago, SN0WM4N said:

Then when does MLB start and finish then?

There will never be any defenitive locale-

I guess ( for me ) 70N is the very highest amplitude for a MLB - where the 552 contour reaches, but the core of the blocking is further south ( say around 55/60N)

So look at the difference

18z = MLB 552 contour 65N - core 55N

IMG_1172.PNG

2010 = HLB 552 contour 80-85N core pressure 70N

IMG_1173.PNG

 

best

s

 

 

 

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