Focussed Model Discussion

[bluearmy]

7 minutes ago, Broadmayne blizzard said:

but I thought it was wedges what made sledges Blue

They do and I suspect they probably will ........ though it may be difficult to see them doing their stuff until we get closer - assuming we don’t see a further reduction in nwp mobility as the downwelling wave actually reaches the trop ....

[oliverek7]

2 hours ago, Catacol said:

Roughly at the turn of the month - yes. Provided we can get a good long wave pattern in place for cold air supply from the continent at around this point and through the first week of Feb then the prospects for a cold to very cold month are good. We hoped the trigger was going to be in 72 hours.....but it might instead be in 144 hours as the surge of heights occurs behind the second trough event at the weekend. Not a big difference really in the grand scheme of things.

Yes, I have been looking at the ecmwf model and it has been delayed, the original Forecast a few days ago was correct in the sense that the predictions made a few days ago will happen, it is now looking like it will take longer for the blocking pattern to develop due to the us winter storm taking longer to move across the atlantic and down the North Sea into the mediterranean, presumably as a result of the very slow progress of the ssw effects reaching down to the trophosphere.  This was supposed to happen at he middle of next week however the us low is now being taken to Scandinavia first, pushing the high pressure, that would have given us the cold easterly flow, into Russia. After that point, the same low will move down the North Sea (still uncertain though) and into France and then the Mediterranean by the start of the week beginning 28th of January allowing high pressure to re establish itself and build over Scandinavia and then there is the increasing chance of easterly winds so it still may happen, just a little delayed as the ssw event is causing very slow changes this time round as opposed to last year’s one which happened very quickly.

[kold weather]

Quite a few very strong ridges from the Azores in the 00z ECM ensembles actually towards the back end. True Greenland highs are more rarer, but still a few form right at the back end (3-4th Feb).

Also quite a few runs form little secondary lows around the cyclonic LP, this could be a possibility of getting some snow away from favoured spots towards the start of the following week (27-29th). Given there is decent energy in the jet at this point, wouldn't be at all surprised if little features like that crop up as we move closer to the time.

Edited January 20, 2019 by kold weather

[Derecho]

Swingometers have been more volatile then the stock markets recently, almost all the ensembles go for a mild January 25th now, no easterly in sight. Remarkable... this swingometer is definitely for the archives and one to use for future reference.

Luckily further out many runs are still looking very cold to end the month. P9 has a deep cold pool on our doorstep and a snowy area of low pressure.

 

So the easterly isn't too be but perhaps we don't have to wait too long for a shot at something colder.

[Singularity]

Regarding getting HLB to hold steady to our NW, an issue in the longer-term modelling at the moment is that they see the MJO struggling against a trade wind burst in the Central Pacific, hindering progress into P6 & P7 - the ones that help sustain HLB to our NW. It's jet another instance of the strange 'counter-Nino' behaviour that's kept on cropping up this winter and messing with the tropospheric contribution to cold spell setup.

So comes a conflict of signals, because while this interference is likely all-too real for our comfort, I've also seen the majority of such MJO-trade wind battles pan out more in favour of the MJO than modelled at the longer-range. So it's hard to make a call on whether the MJO will help us out or not. At least one thing we do see is little appetite to have the MJO continue to hinder us once it's left P4-P5 behind, which reduces the odds of the strat-forced mean zonal wind reduction failing to produce some usefully aligned flows for notably cold, snowy spells of weather.

Overall, I believe the MJO will be the decider as to whether 90+% of Feb is cold with widespread snow chances, or nearer 50%. 'Nicer problems to have', as some say.

[BlackburnChris]

+144 ECM , showing a linkup with the Arctic High 

 

[knocker]

The currant US storm, now around the tip of Greenland, tracks quickly east/south east and fills but by t108 the next one is over Iceland. The main trough then moves east but the complication is an associated active front linked to another trough away to the south west which brings heavy rain to the north west by midnight Saturday This belt of rain, sleet and snow tracks south east down the country during the day clearing the south coast by 1800 and by Sunday the country is in a brisk northerly. Then a brief ridge before the next front arrives on Monday with strong winds and heavy rain

[stodge]

Evening all

Just as a variation on the usual (and hopefully okay with the mods), just a little analysis of how the models have moved in the past few days.

I've picked January 25th at 1pm as my point of reference and used the GFS 12Z OP as my starting point:

T+288 on 13/1:                                         T+264 on 14/1:                                        T+240 on 15/1:                    

T+216 on 16/1:                                         T+192 on 17/1:                                       T+168 on 18/1:

T+144 on 19/1:                                         T+120 today:

If there's enormous variation here, magnify that four times each day plus the ENS and the Parallel and you can see why seeing the wood for the trees becomes so difficult.

As a comparison, here's ECM 12Z output for the same point:

T+240 on 15/1:                                         T+216 on 16/1:                                       T+192 on 17/1:

T+168 on 18/1:                                         T+144 on 19/1:                                        T+120 today:

It might seem ECM "flipped" yesterday evening but if you look at the previous days there was no consiste3ncy in the modelling either. We finished up cold across the UK and everyone was happy but look at the enormous variation of the North Atlantic profile.

I would argue therefore for all the "Easterly" was nailed on, it never was. Modelling was hugely inconsistent and although the outcome for the British Isles looked good that was a coincidental outcome of a number of inconsistent variables. Shifting the variables or resolving them changed the outcome and the inevitable whining of "downgrade". 

It also seems to this observer GFS called this well - the day to day volatility betrayed the uncertainty. Today, GFS has clearly moved to the ECM solution and we can see if that verifies. 

Lessons - FI is T+120 and occasionally less. The key timeframe for ECM seems to be T+144 for setting the general pattern and we'll see if that proves a good adage especially if the GFS shift this evening is confirmed in the next few days.Further out than that you're better off with other tools such as the Ensembles to provide broad guidance but that's all.

I'll run the comparative analysis down to T+0 to see whether what we are seeing now turns out to be the truth or whether further variation is likely.

[bluearmy]

Interesting post @stodge but to claim GFS or any model called this well is plain nonsense ........... 

ec op is pretty well as expected .....now onto the eps to see if there is any sign of a decent height rise - whilst the Canadian vortex remains, Iceland would be the favourite for an ‘eddy’ generated wedge to set up shop. Meanwhile, @IDO noted a developing Siberian high appearing to ensure the diving trough can’t trend too far to our east .....the day ten chart is a similar evolution to day 3 but it’s backed further west which will help us to stay cold. 

[ICE COLD]

5 minutes ago, bluearmy said:

Interesting post @stodge but to claim GFS or any model called this well is plain nonsense ........... 

ec op is pretty well as expected .....now onto the eps to see if there is any sign of a decent height rise - whilst the Canadian vortex remains, Iceland would be the favourite for an ‘eddy’ generated wedge to set up shop. Meanwhile, @IDO noted a developing Siberian high appearing to ensure the diving trough can’t trend too far to our east .....the day ten chart is a similar evolution to day 3 but it’s backed further west which will help us to stay cold. 

Sorry to ask questions in here I know this forum is for the more knowledgeable posts . But that vortex over to the NW has been there all winter just ruining our chances of a proper block . When will it move Nick ? I thought it was forecast to drain away but it’s still there ? 

[Paul]

Just now, ICE COLD said:

Sorry to ask questions in here I know this forum is for the more knowledgeable posts . But that vortex over to the NW has been there all winter just ruining our chances of a proper block . When will it move Nick ? I thought it was forecast to drain away but it’s still there ? 

You're welcome to ask questions in here, and it's not limited to those with lots of model knowledge, so post away - as long as it's model discussion (or model related questions), it's fine  

[stodge]

8 minutes ago, bluearmy said:

Interesting post @stodge but to claim GFS or any model called this well is plain nonsense ........... 

ec op is pretty well as expected .....now onto the eps to see if there is any sign of a decent height rise - whilst the Canadian vortex remains, Iceland would be the favourite for an ‘eddy’ generated wedge to set up shop. Meanwhile, @IDO noted a developing Siberian high appearing to ensure the diving trough can’t trend too far to our east .....the day ten chart is a similar evolution to day 3 but it’s backed further west which will help us to stay cold. 

Without wanting to get into a dispute over semantics, my point is that anyone looking solely at GFS OP could have had little confidence in the Easterly happening.

Yes, it was a possibility but it never became a probability let alone a certainty. All the factors that needed to happen for the E'ly to occur (primarily the trough dripping cleanly through the British Isles and then heights building behind it and extending SW to the British Isles) were never there in enough confidence for it to be a reality.

For me, the lesson learned is not to look too far beyond T+120 if you want a sense of what WILL happen as distinct from what you might want to happen.

I will continue the comparative analysis of GFS and ECM down to T+0 to see if where we are now id where we end up.

[knocker]

Eastern North America plunged into freezer with this highly amplified upstream pattern

[Weathizard]

2 minutes ago, ICE COLD said:

Sorry to ask questions in here I know this forum is for the more knowledgeable posts . But that vortex over to the NW has been there all winter just ruining our chances of a proper block . When will it move Nick ? I thought it was forecast to drain away but it’s still there ? 

It’s the perfect area for a polar vortex to set up, abundancy of moisture, temperature contrasts, cold land mass, jet stream ect, you can see why it loves to set up shop there. But I don’t think anyone can predict when it will bigger off, it might not...

[Paul]

Thought I'd post this in here too. Monday night and Tuesday looking interesting on the netwx-sr as the cold front moves through. Some back edge snow on it + a lot of wintry showers packing in behind from the northwest. 

Lasting lying snow mainly limited to the hills though.

[stodge]

4 minutes ago, ICE COLD said:

Sorry to ask questions in here I know this forum is for the more knowledgeable posts . But that vortex over to the NW has been there all winter just ruining our chances of a proper block . When will it move Nick ? I thought it was forecast to drain away but it’s still there ? 

I think one of the myths or fallacies we need to tackle is this notion of the PV preventing cold. If it really worked that way, we'd hardly ever have cold weather so it's perfectly possible to have cold weather with the PV.

The SSW reduced the strength of the PV significantly - you'd expect the PV in mid January to have a core temperature of -88c and zonal winds of (I forget exactly - 80 to 90 m/s). We now have a PV with a core of -72 and winds are only now returning back to positive values after a spell of negative or near negative values.

So we have a very weak and disorganised PV which has been split into various lobes but it's still there.

As the PV gets slower, amplification becomes possible in the Atlantic as the zonal wind speed falls and (I believe) that impacts the jet.

Displacing the PV helps - move it a little further west and heights can rise over Scandinavia - move it a lot further west and you can get some Greenland blocking.

[knocker]

Still portending cold or very cold in the ext EPS with high pressure ridging into the Arctic from Alaska and eastern Europe.; vortex northern Canada and the split flow over the Atlantic with one arm running around the Greenland ridge and the other down to the slightly negatively tilted trough adjacent to the UK

.

[bluearmy]

24 minutes ago, knocker said:

Eastern North America plunged into freezer with this highly amplified upstream pattern

Interestingly, it doesn’t hold .....a couple days ago it looked like it would but the mobility continues and the vortex rotates towards the Atlantic ....latest eps suite looks flatter to our west as the vortex continues to  extends its influence in our direction. Less chance of Atlantic ridging and looks like more chance of wedges to the n/ne ....hence not quite as low uppers and not as deep a euro trough but perhaps a more direct nw/se flow would present a better chance of sliders for the uk .... hopefully we get less than six clusters so we can see the variations the model is finding ....the spreads at day 10 are mainly to the sw with the trough potentially further west than the mean on its nw/se routing 

[DanBaynes]

29 minutes ago, ICE COLD said:

Sorry to ask questions in here I know this forum is for the more knowledgeable posts . But that vortex over to the NW has been there all winter just ruining our chances of a proper block . When will it move Nick ? I thought it was forecast to drain away but it’s still there ? 

I'm in the same boat as you @ICE COLDim very much a learner and @stodge post is from a far knowledge person. 

But wasn't the draining of that part of the pv or not as it's turned out so far all down to the evolution of the failed easterly and the pv moving into scandi?

 

[kold weather]

28 minutes ago, bluearmy said:

Interestingly, it doesn’t hold .....a couple days ago it looked like it would but the mobility continues and the vortex rotates towards the Atlantic ....latest eps suite looks flatter to our west as the vortex continues to  extends its influence in our direction. Less chance of Atlantic ridging and looks like more chance of wedges to the n/ne ....hence not quite as low uppers and not as deep a euro trough but perhaps a more direct nw/se flow would present a better chance of sliders for the uk .... hopefully we get less than six clusters so we can see the variations the model is finding ....the spreads at day 10 are mainly to the sw with the trough potentially further west than the mean on its nw/se routing 

I realty worry if we end up setting too far west unless it really digs down far enough, because there is a fair chance your going to be dragging up warmer air from the south on the upper lows eastern flank or we never have enough cold air aloft to begin with if the flow bends. We really need a solid Scandi high for that to work and for the troughing not to become too intense (IE low pressure nort going below 995nbs I'd say, any more and its probably going to start pulling in too much warm air). P12 on the GFS ensembles shows that concern due to not having any major scandi core.

On the plus side, if we do get a decent upper high in the Scandi area, it will help in terms of not needing the cold pool being as deep to still give the goods.

To be fair there is are certainly some ensemble members going down that route on the GFS ensembles, ECM ensembles still going down the mid-atlantic route in the main.

 

Edited January 20, 2019 by kold weather

[jules216]

19 minutes ago, DanBaynes said:

I'm in the same boat as you @ICE COLDim very much a learner and @stodge post is from a far knowledge person. 

But wasn't the draining of that part of the pv or not as it's turned out so far all down to the evolution of the failed easterly and the pv moving into scandi?

 

For what is worth my understanding of why things have not worked out for a -NAO. The noise was more pronounced GWO phase 5-6-7 progression which was advocated my some teleconective experts which would have enhanced chances of HLB. Instead a much lower amplitude event happened which caused a mere MLB or UK mid Atlantic high.Meanwhile Pacific amplified which sent cold down the East Coast of USA and part of the Vortex wants to stay quasi permanently over NAO area despite many attempts of extended modeling to point otherwise so -NAO is yet again being pushed further and further back. Yet again it is down to the fact that as much as tropospheric LRF the other forecasts such as tropical MJO progression,exact placement of ridges/troughs  post SSW is unreliable in long range. It is also a fact that NAO has not been in prolonged negative phase in winter months for a long long time (not counting March as a winter month), like in late 80s early 90s spell.

[Nick F]

Finding the GFS u-wind cross sections rather temperamental with regards to easterly winds propagating down through the troposphere, 00z looked sustained final days of the month and onwards, 12z looks a lot more underwhelming - perhaps why the 12z operational looks much less blocked than the 00z operational did.

00z

12z

Be nice to finally see some stability and sustainability for easterly downwelling into the troposphere, alas the GFS is obviously struggling with this vertical resolution that far out, eventually it may latch on! Been a long time coming much to our frustration.

[feb1991blizzard]

38 minutes ago, bluearmy said:

Interestingly, it doesn’t hold .....a couple days ago it looked like it would but the mobility continues and the vortex rotates towards the Atlantic ....latest eps suite looks flatter to our west as the vortex continues to  extends its influence in our direction. Less chance of Atlantic ridging and looks like more chance of wedges to the n/ne ....hence not quite as low uppers and not as deep a euro trough but perhaps a more direct nw/se flow would present a better chance of sliders for the uk .... hopefully we get less than six clusters so we can see the variations the model is finding ....the spreads at day 10 are mainly to the sw with the trough potentially further west than the mean on its nw/se routing 

Is the ECM graph likely to show higher temperatures in the extended range then as a result? - everything was trending colder on the last few runs

Edited January 20, 2019 by feb1991blizzard

[bluearmy]

2 minutes ago, feb1991blizzard said:

Is the ECM graph likely to show higher temperatures in the extended range then as a result? - everything was trending colder on the last few runs

I suspect it will - yes ....be interesting to see if the snow depths show any increase 

[northwestsnow]

3 minutes ago, bluearmy said:

I suspect it will - yes ....be interesting to see if the snow depths show any increase 

I detected a slight rise in 850s on the mean at day 10, which suprised me, and disappointed me a little..