Model output discussion - proper cold spell inbound?

[karlos1983]

7 minutes ago, Stuie W said:

An output is an output. For all the great charts, when you drop in a mean chart, you can`t dismiss it just because it isn`t what you hoped for. Going to be nervy viewing.

Well, a mean chart is just a blend of the model suites members though, not an individual run (to my understanding) So if you’ve got 8 really cold members and 8 reging westerly members there’s probably not going to be a middle ground! One will be wrong and therefore so will the mean! 

My point about the ECM is we don’t get to see without ploughing through that weather.us site viewing each member in isolation what the individual runs are doing. Like that GEFS graph, clearly 2 runs very warm compared to the rest, which will automatically rise the average/mean temperature. Anyway we may derail. 

Edited February 9, 2018 by karlos1983

[blizzard81]

10 minutes ago, mulzy said:

Extended eps stays on track; higher than normal heights to the north, lower than normal heights to the south.  Slight change of emphasis in that towards the later end (days 14-15), the focus of the higher heights is moving west towards eastern Greenland.

Great news I expect a colder set on the debilt ext ens after hearing this. 

[Man With Beard]

Whenever I've seen a mean 1030mb high in a place where it doesn't usually happen, 9/10 it verifies in that place. However, considering the scatter in the diagram for North Sweeden, I won't call it for a few runs yet.

   

NOAA 8-14 starting to see Scandi heights too but still a "work in progress"

[bobbydog]

17 minutes ago, timboy666 said:

what is a ssw?

 

16 minutes ago, Ice Man 85 said:

Sudden Stratospheric Warming. I won't pretend to know what that is though

pop over to this thread - 

it will give you all the info you need on a Sudden Stratospheric Warming and all the implications that come with it. 

that goes for anyone else not sure- it has some excellent explanations in there as to how it affects our weather 

[Stuie]

4 minutes ago, karlos1983 said:

Well, a mean chart is just a blend of the model suites members though, not an individual run (to my understanding) So if you’ve got 8 really cold members and 8 reging westerly members there’s probably not going to be a middle ground! One will be wrong and therefore so will the mean! 

My point about the ECM is we don’t get to see without ploughing through that weather.us site viewing each member in isolation what the individual runs are doing. Like that GEFS graph, clearly 2 runs very warm compared to the rest, which will automatically rise the average/mean temperature. Anyway we may derail. 

Absolutely, Karlos. That is the concern when `everything` is not on board. Let`s hope (unless it isn`t cold you are after) that the individual members are outliers that are skewing the mean otherwise we have to take the output at face value.

[mulzy]

10 minutes ago, blizzard81 said:

Great news I expect a colder set on the debilt ext ens after hearing this. 

I don't think it will be 'super cold' but hopefully trending in the right direction.  Control looks decent.

[ptow]

35 minutes ago, Stuie W said:

I will have you know, after tonight`s output, it is 9 days away just to buck the trend...

Good point 

[Singularity]

1 hour ago, Snowy L said:

I think the ECM evolution (high building from the Southwest with the undercut coming from the east instead of the west) is more likely. The warming is going to push the Greenland vortex lobe west into central canada over the coming week so I dont see any real pressure coming from the Atlantic. I think the GFS was toying with the Atlantic undercutting and now it is in a bit of a no mans land. Hopefully it gets on board with the ECM in the next few runs.

For entertainment value, here is an illustration of what can be considered highly feasible going forward from the ECM day 10 given expected secondary SSW influence.

No kidding around here although yes, the caveat applies that it's just one possibility among quite a few. Fact is though, if it's ever going to happen, it's when we have the ingredients in place over the next fortnight.

So yes, I have come to accept that a faster height rise to our NE with a major block advancing west starting around Thursday is an outside option now, but I won't complain if the ridge from the mid-Atlantic proves to be the start of such a progression!

[BLAST FROM THE PAST]

An excellent ECM again.  FWIW my view is a delayed Spring until April.  On that basis with my LRF I think we may see a slower burner re this SSW on its effect for us in the U.K. and Ireland re lock in of cold blocked set up.  Very interesting chart watching, GFS back in the mix.....best I grow my peppers and tomatoes I just bought from ‘a shop’ indoors for a while 

Come Sunday there will be many happy cold bunnies in W and NW.....and Cheshire Gap....look out!

BFTP

 

 

Edited February 9, 2018 by BLAST FROM THE PAST

[bradymk]

I know all the talk at the moment is about the SSW and the potential impacts starting to now enter the model timeframes, but this has been covered well already today by other superb posts as always.

Just wanted to highlight a wintry Sunday for some coming up and just how cold the air is that has been coming from the west at the moment. 

We have -10/-11c 850 temps from an Atlantic modified air mass on Sunday which is pretty impressive. Wet bulb down to below 100 for whole UK. Thickness also very low. For the majority this setup doesn’t deliver what we all crave the most and it will just be dry and cold. But Ireland and parts of the west could do well on Sunday but regardless these really are some chilly air masses hitting us from the west at the moment considering the modification. ❄️ 

[David Morse]

35 minutes ago, timboy666 said:

what is a ssw?

For a long time I couldn't get to grips with what it means and most explanations, including the MetOff, just say its a reversal of winds high in the stratosphere, which of course is true, but doesn't explain it really.

So analogy time, this is how I understand it

Imagine the polar vortex is a cup of tea and you are stirring it carefully to get the most perfect stable vortex going, as you stir faster and faster the tea moves higher at the edges of the cup, lower in the middle. This well in the middle surrounded by higher tea on the edge of the cup equates the to pressure differential in the Polar Vortex, low pressure = cold, so the centre of the vortex is the coldest place as it has the lowest pressure.

The spoon represents the polar stratospheric jet stream driving the polar vortex. Your hand is chaos. As with all jet streams they're prone to speed up, slow down and at times buckle when pushed. So you're stirring your tea and someone knocks your hand. The jet stream (the spoon) deviates from its course around the cup and cuts into the flow, this disrupts the vortex. If the spoon is deviated enough the vortex stops spinning, the well at the centre fills with the tea from the outside and the pressure in the centre rises, high pressure = higher temps. It warms up. 

[Frosty.]

The GEFS 12z shows some great wintry potential, think I will be posting a lot more charts similar to these in the coming days..lovely stuff!..I know it's deep FI  but it's relevant as it's the range when things could kick off big time..or even sooner if the Ecm is right!!

Edited February 9, 2018 by Frosty.

[kold weather]

ECM ensembles are a right old mixed, some really great looking runs and some runs probably would embed a 2-3 week cold spell. Equally there are certainly more than a few runs which do nothing and indeed a decent minority blowthe Atlantic back up again, a few just have a shortwave nightmare, and the rest have a cold set-up of varying degrees (some have a UK high, some have the classic Scandi, some evolve a stunning Greenland-Scandi monster high.)

 

[bluearmy]

Have to say that the eps are a tad underwhelming given we should be seeing things firming up. The AO/NAO combo less negative than for a few runs. The operational, actually has  less than 30% support with the ridging up to scandi according to the probability charts days 8/10.  Thereafter I suspect another binary look to the extended clusters as per the 00z run with scandi ridge establishing but also an upper euro ridge to our south. 

the strat charts look a little like the Canadian vortex slowly recovering  and perhaps an Atlantic trough as the Asian blocking heads further towards Siberia 

in conclusion, nothing settled yet and possibly a little too much back patting on here after  that 12z ec op! 

lets hope tomorrow retains continuity from the op and ukmo on the mid Atlantic ridge beginning to show 

[Sky Full]

I think it's reasonable to say that there are considerable similarities between these two February charts which are only a couple of days apart:

ECM.      

GFS       

and this one too:

               

Just check out the date of that last chart  

That's just a bit too close for comfort!  Not saying the Thames will freeze over or anything, but if the balls all end up in the right pockets we will certainly need to dig out those thermals....

[lorenzo]

16 minutes ago, bluearmy said:

Have to say that the eps are a tad underwhelming given we should be seeing things firming up. The AO/NAO combo less negative than for a few runs. The operational, actually has  less than 30% support with the ridging up to scandi according to the probability charts days 8/10.  Thereafter I suspect another binary look to the extended clusters as per the 00z run with scandi ridge establishing but also an upper euro ridge to our south. 

the strat charts look a little like the Canadian vortex slowly recovering  and perhaps an Atlantic trough as the Asian blocking heads further towards Siberia 

in conclusion, nothing settled yet and possibly a little too much back patting on here after  that 12z ec op! 

lets hope tomorrow retains continuity from the op and ukmo on the mid Atlantic ridge beginning to show 

The daughter vortex reforming with the parent is quick today, the vorticity transition shows the shear from the split leaving a strong canadian vortex which drags our vortex back to canonical. After this there is literally no vortex to speak of on this side of the hemisphere, with torque and MJo effects due to imprint. It's absolute carnage as far as sensible modelling is concerned, if you consider analogs the MJO alone is creating talk of ushering in Nino at pace later in the year. Subsequent to the lack of any meaningful vortex influence on our side of the hemisphere, we also have the secondary pulse of WAFz at D10 savaging the parent vortex lobe. To such an extent tonight it splits it and throws the pacific into the three wave pattern with another daughter vortice.

Utter carnage - last night the split from the main vortex following SSW modelled to split siberia > pacific ,, tonight it's a weak split, a mere shread of vortex remains in siberia then later on the parent vortex splits at D10 attacking the pacific from not the arctic or west, but the east.

This is no ordinary SSW.

[Sky Full]

7 minutes ago, Sky Full said:

  

Just check out the date of that last chart

That's just a bit too close for comfort! 

Further to my last post, not wishing to be taken for a scurrilous ramper, I would add that we currently have nothing like the extent or depth of low uppers over Europe which were evident in 1962/3 and which contributed to the record low temperatures that year.  There is therefore no chance of similarly arctic conditions developing on this occasion.  And I am not related to Michael Fish, either.....

[bluearmy]

1 minute ago, Sky Full said:

Further to my last post, not wishing to be taken for a scurrilous ramper, I would add that we currently have nothing like the extent or depth of low uppers over Europe which were evident in 1962/3 and which contributed to the record low temperatures that year.  There is therefore no chance of similarly arctic conditions developing on this occasion.  And I am not related to Michael Fish, either.....

Glad you qualified your ramp with some realism  

[ANYWEATHER]

Just now, Sky Full said:

Further to my last post, not wishing to be taken for a scurrilous ramper, I would add that we currently have nothing like the extent or depth of low uppers over Europe which were evident in 1962/3 and which contributed to the record low temperatures that year.  There is therefore no chance of similarly arctic conditions developing on this occasion.  And I am not related to Michael Fish, either.....

And to add Greenland had its warmest winter..  The polar vortex over North America remains relentless adding fuel to the jet stream towards the Uk 

[ghoneym]

Model output minus ICON (keep getting processing error when uploading for some reason) and CPTEC (utter garbage) from meteociel. I snapped the +144 output from Monday. + 144 for 2 reasons, first because it gives us the max UKMO range and second because + 144 from Monday is wind reversal day = official start of SSW.

First the ECM

From Monday   From today   Both for Sunday at 13:00.  

Not a million miles away, misread the pacific ridge angle slightly but main vortex elongation and break away low pressure system shown. AZ high not as regressed as shown from Monday, Downstream similarities good.

Next the GFS

From Monday   From today   Both for Sunday at 13:00

HMMM make your own mind up, not great from GFS if you ask me.

The UKMO

                                              

Really good from UKMO IMO, overall pattern almost nailed from back on Monday

JMA

                                               

Similar to GFS, probably worse, decent effort any smaller vortex evolution. Heights downstream up into Svalbard similar.

GEM

                                                      

Great effort from GEM! Often overlooked but in my top 3   

NAVGEM

                                                     

just below mid table, a kind of Stoke city type effort 

CMA

                                                     

 bit over progreessive in many ways but overall ok.

There you have it, starting conditions are set for the SSW.

EDIT:- I should have waited until Saturdays 18z run to do this but its the weekend folks 

Edited February 9, 2018 by ghoneym
.

[SMU]

3 hours ago, bluearmy said:

An axis on the 850 hpa wind to cheer @Steve Murr

yes

standard vertical profile of a ridge pumping NNE out of the azores.....

Edited February 9, 2018 by Steve Murr

[Catacol]

2 hours ago, chionomaniac said:

So we are making headway at last with both timeframe and suggested evolution. I must admit earlier on in the week I thought we were never going to get there.

So to recap the first stage of suggested post SSW developments is the Scandi block. Now we are seeing strong indications that this is likely to occur with the seeds being set from day 6. The next stage will be the retrogression of the block west depending upon how the residual daughter vortex over NA is affected by the second phase warming. After that the we could be rocking and rolling between the Scandi and Iceland/Greenland blocks until the vortex recovers.

I hope that everyone can see why @Catacol and I were so excited last week. Still a lot of water to run under the bridge but we are on course...

Yes indeed Chio - still drumming on the table top, waiting for the fun to get just a tiny bit closer.

All coming together - Feb 19 now in medium range, and both ECM and GFS coming in line (indeed ECM is day earlier on the 12z...)

This the impact of dual forcings: MJO passage creating high amplitude phase 7/8 and strat vortex split and reversal. These have both been visible for many days now - so many days that if feels as though we have been talking about this impending event for eons. GWO heading on a decent 5-6-7-8 orbit

with MJO sitting in high amplitude phase 7. GFS keeps it there - ECM has it declining and moving to phase 8 more quickly (GFS has been the more accurate in recent days/weeks) - but to be honest we are past the point of no return on this now, and the forcing to a favourable high lat solution is in place - as Tamara hinted at the other day longevity of this signal is more open to question... but that can wait.

Strat split and warming now very well modelled on 11th Feb at 10hpa but also almost simultaneously at lower levels, though the Asian vortex shard at lower levels is further East, opening the door for height rises, as expected, over Scandy

 

 

Strat winds begin to reverse on the 11th, and within 2 days are really very impressive (lots about this all over twitter at the moment....)

 

The end product is difficult to escape - height rises to the north. storm track forced further south due to arctic warming, and an uncertain future for both remaining vortex lobes. For me I'm not especially worried about this particular debate - if the US vortex shard remains strong (ish) then we get more energy to disrupt against the block. High risk, big potential win. If it weakens we get an easier retrogression with energy bumping along to the south. Another potential win. Meanwhile there is only one way the asian vortex shard can drag the pattern once we get the high in place and the winds in reverse - and that's back west. This adds the curious option of undercutting lows coming the wrong way.. something GFS extended started to toy with days ago.

It's all good. 100% certain snow? Of course not. Nobody is daft enough (surely) to suggest that anything is certain when it comes to snow. We are all aware that our geography makes snow chances inherently difficult away from high ground? Nuff said on that. But this is the greatest chance for the most significant wide ranging event for many years... certainly back to 2013.. possibly back to 09/10 - and if the vortex splits and the winds reverse as GFS is suggesting then we could bag a severe 1980s style event. 

Longevity? Irrelevant.

 

[tinybill]

just watch ed  the week  forcaston bbc  news  24  weather  for the week  its gob smacking   the beast of the east is due the end of next week and its going to get  even colder  with loads  of snow

[SMU]

So 24 hours since yesterday can the GFS get the canadian ridge migration right tonight-

East out if Canada, phase with azores high then ridge NNE....

Edited February 9, 2018 by Steve Murr

[Mucka]

Looking better, not miles away from UKMO if memory serves.