Hunt For Cold: Model Discussion - Heading Into Christmas

[bluearmy]

41 minutes ago, feb1991blizzard said:

I would like to see the 1mb chart, i dont think the 10mb split is getting any wider from the last run.

A little wider and more notably, it seems to immediately downwell to 30 and 50hpa at the end of the run 

[SMU]

The split getting wider is a VERY positive signal for UK cold !

[northwestsnow]

3 minutes ago, Steve Murr said:

The split getting wider is a VERY positive signal for UK cold !

Yup, and a small improvement on the EC mean tonight with high pressure slightly further north- start of a trend?

 

[feb1991blizzard]

3 minutes ago, Steve Murr said:

The split getting wider is a VERY positive signal for UK cold !

Yes, ideally you want one lobe over canada, the other one right over to Russia, so as it's imprints on the trop, you end up with one of those big long scandinavian highs so you get a nice big long fetch  of air all the way from Eastern Russia and Siberia.

[Man With Beard]

44 minutes ago, Catacol said:

Holding pattern at present. The extent of the hit to the vortex, and whether it splits or not will be a now cast event. However there has been a lot of gloom in here today, and the usual suspects who love to shout “told you so” with little to no understanding of actually what they are telling us have appeared in force. Always makes me chuckle to read posts from those who enjoy pointing out the the UK rarely gets a sustained cold spell and that mild/wet is our default setup....as though we don’t know that already. Really tiresome to have to filter out that twaddle.

We didn’t get our block this week - but it was a close run thing. Torques set to re engage very shortly....and the second bite at Pacific led forcing to shunt a block up to the north will be in the period between Xmas and New Year. The fact that a UK high looks likely to be the end product of the current negative torque phase is good news....a much better starting point for the next +MT impacts to work off than the rather nasty trough we had anchored to our west last week.

All good still. Strong signals very much in place....but angle of any potential vortex split really will dictate whether we get cold shots or the chance of a properly sustained cold spell of easterly feeds. There are no guarantees here....but we still potentially stand on the cusp of a spell of special January wintriness....

Thanks Catacol. It did look like a possibility of turning colder for Christmas at one point ... but can't be restated enough, long-range forecasters speak in terms of general trends, not specifics. A pattern may look a good trend for a UK cold spell at D12, but always needs favourable progression from that stage for a cold spell to firm up by D5.

In that sense, though it ultimately failed, I am fairly satisfied with how my past two week's forecasting panned out - I spotted the potential for a N Atlantic High around this time at the start of December, unsure exactly how influential it might be, with the models at the time suggesting a minor influence, but I saw the opportunity for an upgrade to be within the window of what could be expected. Ultimately, the ensembles were right all along - we are going to get a N Atlantic High in the next few days, but not strong enough to bring down the northerly I'd hoped for. From a forecasters point of view, I was happy that the N Atlantic High I saw as a logical progression from the pattern back then has come to fruition - so a successful forecast in my point of view. The fact that it won't bring snow to the UK was a failure for the pattern to adapt slightly in the way I was hoping it might. It was just potential all along, and potential is not a guarantee.

With this thread being named "The Hunt For Cold" this year, a few of us (like me) are taking slightly more liberties in focusing on cold prospects rather than looking at the whole picture, and perhaps that is responsible for more "told you so"s when prospects fail to become realities. I've no problem with that, but just worth remembering in here that most of us are actively looking for cold in our posts - it might help heart-rates stay more stable if this is kept in mind!

Anyway, preach over, back to now. SSW or no SSW?? Recent modelling has seemed pretty confident it won't mean a quick journey to cold:

but I'm not forgetting February 2009, where after an SSW, the models turned on their heads at D6, producing a good cold spell out of nowhere. 

Probably best to take longer range NWP output with a slightly bigger pinch of salt than usual

[bluearmy]

@Man With Beard 2009 was 9 years ago ..... we should hope that modelling has moved on enough that we don’t get such a turn around ...........

[Met4Cast]

5 minutes ago, bluearmy said:

@Man With Beard 2009 was 9 years ago ..... we should hope that modelling has moved on enough that we don’t get such a turn around ...........

Right get in the bin, they'll be no making me feel old on this forum!

Edited December 20, 2018 by Daniel Smith

[That ECM]

4 minutes ago, bluearmy said:

@Man With Beard 2009 was 9 years ago ..... we should hope that modelling has moved on enough that we don’t get such a turn around ...........

But it also did it in March this year?

[Allseasons-Si]

Just posted this in the strat thread and thought that i would post it here too, it rivals the warming earlier this year,a Dec record?

looking good on the 30hpa now

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/

Edited December 20, 2018 by Allseasons-si

[Man With Beard]

2 minutes ago, bluearmy said:

@Man With Beard 2009 was 9 years ago ..... we should hope that modelling has moved on enough that we don’t get such a turn around ...........

What's getting me is that, in the ECM ensembles, I can't see any sign of a response in the TPV to events in the SSW. Or at least what I am expecting - which is a large areas of low pressure disintegrating somewhere in northern latitudes. Or is supposed to be a slow downwelling? You know more than me about this BA - sorry if this is covered further back in the thread but I don't have time to read everything on here in winter  

[Catacol]

7 minutes ago, Man With Beard said:

Thanks Catacol. It did look like a possibility of turning colder for Christmas at one point ... but can't be restated enough, long-range forecasters speak in terms of general trends, not specifics. A pattern may look a good trend for a UK cold spell at D12, but always needs favourable progression from that stage for a cold spell to firm up by D5.

In that sense, though it ultimately failed, I am fairly satisfied with how my past two week's forecasting panned out - I spotted the potential for a N Atlantic High around this time at the start of December, unsure exactly how influential it might be, with the models at the time suggesting a minor influence, but I saw the opportunity for an upgrade to be within the window of what could be expected. 

I think the signal was evident throughout medium range modelling, and the shunt supplied by the spike in AAM was significant as the driver of this. However I have thought back to a Masiello tweet of around 10 days ago where he mentioned issues with “lifting out” the Atlantic trough. In simple terms it got well and truly stuck....boxed in by heights that caused it to stall, and perhaps the stubbornness of the initial Scandy high that brought the snow/freezing rain event did more harm than good in preventing that trough from pushing east. 

Water under the bridge now - but the key is that everything is interconnected, and the very resilience of the Scandy high that may have helped block a mid Atlantic height rise this week might also be the very vehicle that helps promote a split rather than just a displaced vortex. It is that very complexity that leads some to conclude that the weather is all just random. It certainly isn’t...but the complex relationships on a global scale can make it feel that way sometimes!

Model watching from this weekend onwards is about to get very interesting again. Having a few days’ breather in the run up to Xmas might be a very good thing given Xmas prep to get done....cos once NWP picks up on combined Pacific and Strat forcings this place may go into meltdown.

[The Beast From The East]

35 minutes ago, Steve Murr said:

The split getting wider is a VERY positive signal for UK cold !

Hi Steve, could you tell me as I'm clueless on all this but even if it does split, could it just simply rejoin a few days or weeks later? Thanks.

[bluearmy]

3 minutes ago, Man With Beard said:

What's getting me is that, in the ECM ensembles, I can't see any sign of a response in the TPV to events in the SSW. Or at least what I am expecting - which is a large areas of low pressure disintegrating somewhere in northern latitudes. Or is supposed to be a slow downwelling? You know more than me about this BA - sorry if this is covered further back in the thread but I don't have time to read everything on here in winter  

I don’t have the time to look through 50 runs but I knew you would ! It’s not easy to see a QTR unless the model is moving frame to frame .....  The reversal looks to be around the 29th so a QTR could be showing by 2nd/3 rd jan so that’s right at the end of the eps. The gefs look a couple days quicker on the reversal so maybe that’s why we see one member going QTR

i think a couple more days to wait 

5 minutes ago, That ECM said:

But it also did it in March this year?

I wondered about this .... feb 11th was the SSW. Gfs ops were showing the response late in their runs by 6th feb ..... as it turned out they were a little progressive re the response. The point being that the gfs ops and ec op were showing a response before the warming took place 

[Mike Poole]

14 minutes ago, Allseasons-si said:

Just posted this in the strat thread and thought that i would post it here too, it rivals the warming earlier this year,a Dec rocerd?

 

And this is just the latest thing that leads me to believe that we are on the cusp of something special, one of two things we may not have seen before.  The other being the models inability to get a grasp of what the strat warming looks like at a timescale when they should!  It may be something new...

For the north hemisphere, this event looks highly significant, for the UK that has to be tempered by our location, 'if it can go wrong it will go wrong'  

Having said that where we stand today, I think it's more 'if it can go right, it will go right'.

What we need to see now, is a firm up of the ECM version of the SSW, One warming leaving the residual vortex well split.  This scenario looking more likely by the day to me.  Interesting to watch how (if) it unfolds...

Edited December 20, 2018 by Mike Poole

[Snowy L]

11 minutes ago, bluearmy said:

I don’t have the time to look through 50 runs but I knew you would ! It’s not easy to see a QTR unless the model is moving frame to frame .....  The reversal looks to be around the 29th so a QTR could be showing by 2nd/3 rd jan so that’s right at the end of the eps. The gefs look a couple days quicker on the reversal so maybe that’s why we see one member going QTR

i think a couple more days to wait 

I wondered about this .... feb 11th was the SSW. Gfs ops were showing the response late in their runs by 6th feb ..... as it turned out they were a little progressive re the response. The point being that the gfs ops and ec op were showing a response before the warming took place 

Thing is during the last two SSWs in 2013 and 2018 we were very lucky to see two examples of perfect splits - a displacement followed immediately by a clear split. We still don't know what's happening with the potential split, whether it will be a partial one, a full one or even if it will happen at all. I think it's clear the models are struggling with forecasting what happens after the displacement as the fate of the vortex is still unknown after that.

Edited December 20, 2018 by Snowy L

[thetipster]

Edited December 20, 2018 by thetipster

[bluearmy]

Ec46 weeks three and four due imminently. I would expect the high anomoly to be present across n uk week 3 and possibly edging nw for week 4. The previous run was v progressive moving that block nw week 4 and i expect this run will be a little slower 

Edited December 20, 2018 by bluearmy

[SMU]

23 minutes ago, The BEAST From The East said:

Hi Steve, could you tell me as I'm clueless on all this but even if it does split, could it just simply rejoin a few days or weeks later? Thanks.

Overall the likelyhood is with a split is one lobe will fade away as the main lobe will begin to restrengthen - however if you get a big split through all the layers then essentially thats the engine broken with only mild recovery-

This recover could well be tempered by the ongoing upward assault of wave 1 activity where the strat remains sub say 25M/S for the rest of the winter-

In laymens terms a December warming + Split @10HPA of this magnitude with record breaking heat flux as always precluded 'peak' negativity in the AO, the period of 05/01/19 to 19/01/19 will most likely yeild the most negative AO of the winter - possibly record challenging-

For the Uk the QTR ( Quick troposheric response ) seems at this stage to favour the UK-

What you will see from the QTR is a 1 or 2 wave pattern diving into the pole - This is where because of where I highlighted the split

Alligns nicely to of 2 High pressure that may link into the 2 wave Pattern

The very *Early* prognosis is -EPO & Atlantic ridge to Scandi link up- in that case its a big thumbs up to a QTR-

However there are many other manifestations & pairings that do occur - more common being the cross polar flow coming from a siberian link up with the PNA ridge- Very cold for the Eastern us- no great for us-

The map above highlights all the entry points-

The QTR ( end of Dec ) if it occurs favours -EPO / Atlantic ridge combo....

 

[bluearmy]

Icelandic site not updated yet!

[northwestsnow]

10 minutes ago, bluearmy said:

Ec46 weeks three and four due imminently. I would expect the high anomoly to be present across n uk week 3 and possibly edging nw for week 4. The previous run was v progressive moving that block nw week 4 and i expect this run will be a little slower 

No QTR to the proposed SSW?

[karlos1983]

@feb1991blizzard I must be doing something wrong  can't find the link for the 46 anywhere in there

http://brunnur.vedur.is/kort/ec-ens/2018/

Or i is just fick 

[The Beast From The East]

2 minutes ago, Steve Murr said:

Overall the likelyhood is with a split is one lobe will fade away as the main lobe will begin to restrengthen - however if you get a big split through all the layers then essentially thats the engine broken with only mild recovery-

This recover could well be tempered by the ongoing upward assault of wave 1 activity where the strat remains sub say 25M/S for the rest of the winter-

In laymens terms a December warming + Split @10HPA of this magnitude with record breaking heat flux as always precluded 'peak' negativity in the AO, the period of 05/01/19 to 19/01/19 will most likely yeild the most negative AO of the winter - possibly record challenging-

For the Uk the QTR ( Quick troposheric response ) seems at this stage to favour the UK-

What you will see from the QTR is a 1 or 2 wave pattern diving into the pole - This is where because of where I highlighted the split

Alligns nicely to of 2 High pressure that may link into the 2 wave Pattern

The very *Early* prognosis is -EPO & Atlantic ridge to Scandi link up- in that case its a big thumbs up to a QTR-

However there are many other manifestations & pairings that do occur - more common being the cross polar flow coming from a siberian link up with the PNA ridge- Very cold for the Eastern us- no great for us-

The map above highlights all the entry points-

The QTR ( end of Dec ) if it occurs favours -EPO / Atlantic ridge combo....

 

Thanks for taking the time to answer my question Steve.. . Hopefully it will all turn out cold and snowy for us and for once not at the end of the season but sometime in the early part of Jan. ?❄

[feb1991blizzard]

4 minutes ago, karlos1983 said:

@feb1991blizzard I must be doing something wrong  can't find the link for the 46 anywhere in there

http://brunnur.vedur.is/kort/ec-ens/2018/

Or i is just fick 

Select the month (12) - select the day (20th) then just leave it there and keep refreshing until you see the am time (10:35) - become 22xx  then when it does, click on the 00z, scroll down to the first thing you see that has a 22xx time stamp on it.

http://brunnur.vedur.is/kort/ec-ens/2018/12/20/

Edited December 20, 2018 by feb1991blizzard

[blizzard81]

3 minutes ago, bluearmy said:

Icelandic site not updated yet!

Yep. Almost predictable now. Always happens (not just ec46) when anticipation is at it's greatest. 

[karlos1983]

1 minute ago, feb1991blizzard said:

Select the month (12) - select the day (20th) then just leave it there and keep refreshing until you see the am time (10:35) - become 22xx  then when it does, click on the 00z, scroll down to the first thing you see that has a 22xx time stamp on it.

http://brunnur.vedur.is/kort/ec-ens/2018/12/20/

oh i see, I was just being an inpatient TIT 

Cheers