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Paul

Model output discussion - proper cold spell inbound?

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27 minutes ago, Roadrunner said:

Was there a SSW prior to February '91? May have been answered previously so apologies if so. I also remember around the time we had the snow nirvana that year, the Eastern seaboard of the USA had quite high temperatures for the time of year. May mean nothing at all - then again my knowledge is very limited! 

Yes, apparently so, as Judah Cohen was comparing similarities with the split vortex then, to the forthcoming one. He mentioned it on Twitter.

Screenshot_2018-02-07-09-34-28_1.jpg

Edited by Barry Reynolds

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56 minutes ago, bluearmy said:

Following on from Dave’s post, the eps control deveiops extensive n blocking and w euro trough but eventually  brings a warm easterly (remember jan)

the eps do show e euro high uppers anomoly through the extended period 

I don’t believe that the ens means have yet found a qtr although individual members and clusters will. I’m sure they will !

Didn't you say low heights to our south on eps a couple of hours ago? Now you mention a euro high?

Apologies if I'm getting confused.

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6 minutes ago, Johnp said:

Didn't you say low heights to our south on eps a couple of hours ago? Now you mention a euro high?

Apologies if I'm getting confused.

Uppers not heights john

euro trough but anomolous high uppers over e Europe. Low ones over w Europe 

i struggle to think of too many qtr’s that wouldn’t bring low uppers to e Europe which led to my comment that the eps haven’t got the qtr yet

Edited by bluearmy

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Just now, Catacol said:

I am becoming a bit worried.... because I'm turning into a GFS op junkie. How is this possible? We all know GFS FI is there to be snorted at... but right at the moment I cant help it.

All 4 runs yesterday progged blocking for week beginning 19th Feb. 3 mainly over Scandy... 1 that had a distinct Greenie flavour.

No change this morning. GFS of early Monday 19 once again showing the pronounced scandy block.

gfs-0-300.png?0

Not interested in details - only in trends. 5 out of 5 since starting this FI block hunt. This is all the result of the vortex split and SSW reinforced by a favourable pacific pattern. The predictability of op runs at the moment is a reflection of the consistency of the teleconnective signal.

And this pattern is likely to build rather than fade. To something like this FI image this morning....... block and reversed undercut. Crikey...

gfsnh-0-384.png?0

Only another 48 gfs runs to the 19th Catacol. Hope your nerves aren't shredded by then Catacol. lol

Things starting to look good though.

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The GEFS 00z mean looks strongly zonal until around mid month but then markedly weakens with pressure rising and a much more flabby slow moving pattern develops.:)

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Well main empahsis being going forwards with atmospheric responces- the shorter term progs, are being missed...the colder air now looking to hold out longer than anticipated!!.

And fridays snow chances again rear...as the colder air quickly digs in as frontal system makes inroads across the country and spark transition.

Many twists and turns shorter/medium term... let alone the potential mass impactual, shenanigans of developng ssw...

gfs-1-54.png

gfs-1-66.png

Edited by tight isobar

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Just now, Broadmayne blizzard said:

Only another 48 gfs runs to the 19th . Hope your nerves aren't shredded by then Catacol. lol

Things starting to look good though.

 

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1 hour ago, nick sussex said:

I’m saying nothing ! :D

Ok then I will! 

Generally in set ups with higher latitude blocking signaled , if the UK is lucky then you do get a repeat scenario developing which alternates between east ne and then northerly . So Scandi high retrogresses you then get a trough dropping south into Scandi which develops a more northerly and then back to an east ne and repeat.

It would be great to see that happen but we haven’t even got to the Scandi high bit yet and it’s some way off.

Following on from NIck S post.

Some members might not be aware of the chart archives. Skip through  late Jan, Feb 1947 and you will see great examples of high pressure alternating between Greenland & Scandi and at times high pressure stretching between both locations.

http://www.wetterzentrale.de/archive/slp/1947/Rslp19470201.gif

Really is a wonderful sight to see such incredible cold winter synoptics.

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Two quick points of note...

Remember 180 hrs point..complete split!!??.we'll see.

And as again...no mild mobility at-all shorter  term fridged pm flow!!!!

gfsnh-0-114.png

gfsnh-1-114.png

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22 minutes ago, bluearmy said:

Uppers not heights john

euro trough but anomolous high uppers over e Europe. Low ones over w Europe 

i struggle to think of too many qtr’s that wouldn’t bring low uppers to e Europe which led to my comment that the eps haven’t got the qtr yet

Agreed, it would be most unusual for a SSW-induced blocking high to take on the kind of orientation needed for much other than a cold flow through E (or at least NE) Europe.

Regardless of the model output, I find it very encouraging that I've not come across any expert input cautioning any mechanisms by which the stratospheric anomalies might not propagate quickly down with an initial focal point for unusually strong and expansive height rises not far NE of the UK.

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Just now, TEITS said:

Following on from NIck S post.

Some members might not be aware of the chart archives. Skip through  late Jan, Feb 1947 and you will see great examples of high pressure alternating between Greenland & Scandi and at times high pressure stretching between both locations.

http://www.wetterzentrale.de/archive/slp/1947/Rslp19470201.gif

Really is a wonderful sight to see such incredible cold winter synoptics.

Absolutely classic example there teits

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Still a consistent signal from GEFS for the tropospheric vortex over Greenland to migrate into northern and eventually NW Canada, this appears to co-exist with a similar shift with the stratospheric PV - as the SSW takes hold.

gefs_z500a_nh_25.thumb.png.a5b33f1bf822307fbfa77afe1eddb4ac.png ------------->>>gefs_z500a_nh_57.thumb.png.325a270025c9c24618347ced7ae2b053.png

As the TPV shifts W/SW, this allows the ridge in the Atlantic to extend NE to link up with the ridge anomaly over Barents Sea/Svalbard, this is also shown by the 00z GFS op, this will rely on some amplification to allow trough disruption into Europe and then allow the ridge to build NE.

Can see beginnings of this at day 10 on the GEFS H500 mean

gefs_z500a_nh_41.thumb.png.f527d05f26ca860ce909daa021665f41.png

The lagged effect of high amplitude 7 transition to 8 of MJO wave calls for some amplification over the Atlantic towards the NE anyway, the SSW forcing the TPV into Canada and allowing +ve heights to manifest to our north over Svalbard from the block already over NW Russia to build and arctic ridge will already be in place, waiting for the Atlantic ridge to join and expand to bring high latitude block which will force the Atlantic jet south.

That seems the logical route to me based on consistent signal from GEFS, whether it plays out as thus remains to be seen.

 

 

 

Edited by Nick F

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3 minutes ago, Nick F said:

[Space Saving]

The lagged effect of high amplitude 7 transition to 8 of MJO wave calls for some amplification over the Atlantic towards the NE anyway, the SSW forcing the TPV into Canada and allowing +ve heights to manifest to our north over Svalbard from the block already over NW Russia to build and arctic ridge will already be in place, waiting for the Atlantic ridge to join and expand to bring high latitude block which will force the Atlantic jet south.

That seems the logical route to me based on consistent signal from GEFS, whether it plays out as thus remains to be seen.

This continues to be an added complication for the 'pre-stratospheric influence' part of next week, and one the models as a whole continue to disagree on. Applying MJO analogues at face value, GFS with its ridging up through the UK linking to Scandinavian height rises matches much more closely to MJO P7 under Nina, while ECM and GEM with a trough sinking S/stretching SE through the UK bears closer resemblance to MJO P7 under a neutral ENSO background, although much weaker with the height rises to the E and NE for some reason.

A fascinating conundrum, if a bit irritating for forecasting efforts :laugh:

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180.. warm flow across the pole as ssw get to work...

Mother lobe feeling the heat force and begins to slide like a melting cube of ice...

10hpa flags the signal...epic latter frames coming up..

gfsnh-0-180.png

gfsnh-10-186.png

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26 minutes ago, TEITS said:

Following on from NIck S post.

Some members might not be aware of the chart archives. Skip through  late Jan, Feb 1947 and you will see great examples of high pressure alternating between Greenland & Scandi and at times high pressure stretching between both locations.

http://www.wetterzentrale.de/archive/slp/1947/Rslp19470201.gif

Really is a wonderful sight to see such incredible cold winter synoptics.

For those more used to using Meteociel format where you animate by running cursor down the time dots.

http://www.meteociel.fr/modeles/archives/archives.php?mode=2&month=1&day=1&year=1947&map=4&hour=0&type=ncep

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17 minutes ago, tight isobar said:

10hpa flags the signal...epic latter frames coming up..

gfsnh-10-186.png

Nice to be seeing those kind of charts at T+186 instead of numerous T+384 postings over the last few months!

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6/6 GFS runs for blocking out in FI, ECM starting to sniff it at day 10 too, perhaps.

Edited by Daniel Smith

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And another run that finishes with an easterly. The thing that makes me wary though is that its just staying out at the end of the run and not getting closer. With the SSW that may be less of a concern than normal but not something that usually ends well.

Hopefully luck will fall in our favor this time with a couple of weeks of cold and lots of snow before the blocking adjusts to bring southerlies and some march warmth!!! 

 

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1 minute ago, Jason M said:

And another run that finishes with an easterly. The thing that makes me wary though is that its just staying out at the end of the run and not getting closer. With the SSW that may be less of a concern than normal but not something that usually ends well.

Hopefully luck will fall in our favor this time with a couple of weeks of cold and lots of snow before the blocking adjusts to bring southerlies and some march warmth!!! 

 

I was gona say the exact same thing!!it might be 6 runs in a row now but lets face it if its not getting any closer then theres a higher chance of things going wrong!!at the moment its all just pretty look at and hopefully it dont stay that way!!

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Models will always try to revert to Zonal as that climatic norm. When a signal is so strong for blocking it often takes the model time to get there.

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1 minute ago, warrenb said:

Models will always try to revert to Zonal as that climatic norm. When a signal is so strong for blocking it often takes the model time to get there.

Why would it revert to zonal when, even with a SSW? Could you just explain the bit in bold..doesn't make sense? Thanks.

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7 minutes ago, Chevron12345 said:

Why would it revert to zonal when, even with a SSW? Could you just explain the bit in bold..doesn't make sense? Thanks.

Models will try to revert climate norms, but when an overriding signal (SSW for blocking) is thrown in the mix, then especially low res it will delay the inevitable basically.

When the blocking comes into high res and remains, then we are systems go.

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Just two scenarios really; Atlantic behaving versus Atlantic being as much of a pain as it can manage.

h850t850eu.png h850t850eu.png

First scenario, blocking response has an easy time starting its journey west. Second scenario, it doesn't.

The latter is akin to what happened in March 2013 with a brief warm spell in the far south, but that was part of a much a slower response to stratospheric events. Atlantic troughs will have to be more of a nuisance this time to bring about the same sort of sequence. Of course we all know how much it loves to be just that :rolleyes::laugh:.

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