Model output discussion - proper cold spell inbound?

[Frosty.]

My goodness it's exciting isn't it, waiting to see how the SSW impacts on the uk and mainland europe..will it be like flipping a switch seeing the models change suddenly?..the anticipation is growing..

in the meantime, enjoy the cold during the next few days and the upcoming cold zonality, hopefully like the ukmo 12z which would be colder than usual from the w / nw..potentially lots for coldies to look forward to this month!

Edited February 5, 2018 by Frosty.

[chionomaniac]

24 minutes ago, That ECM said:

Interesting, not showing on gfs. Something to watch out for on future runs. Due to that high and therefore moving PV towards us hence causing more of a nw flow for a period? TIA if an easterly is to happen, how in your opinion do you think this will happen?

In all honesty I'm not sure at the moment. But from that chart I would expect the trough over us to decline and heights start to build to our NE. Then we need to see if the second phase strat warming can obliterate the stronger Hudson bay daughter vortex.

[ghoneym]

Operation runs of 12z available models from meteociel up to +144 (to keep them in line with what we can get from UKMO) and also the 10mb strat for +144

   UKMO   GFS    ECMWF   GEM    JMA    

Navgem    CMA   CPTEC     ICON   GFS 

The main trop vortex segment is similar in structure to me anyway, on UKMO, ECM & GEM. The pacific ridge is played out slightly differently in most models however the most detailed look to this is from the American GFS and NAVGEM. A fair difference in heights and navigation of the AZ high especially in the main 3 with the UKMO maintaining it east at this timeframe, whilst the GFS and ECM have began retreating Westward. All models show an Atlantic influnece on our shores, typically NW /W flows with a strong vortex still present. For how much longer? 

Overall broad-scale patterns appear similar across the board with split trop vortices, the main vortex Straddling the USA /Canada / Greenland. The Strat vortex split in two and being tag team blowtorched. 

What comes next? The teleconnections are favourable, the split and warming location is apparently favourable, solar activity is minimal and the experts (twitter & netweather) are excited. All looks tilted in the favour of a notable cold spell post mid month. Of course the alternative would be a slower trop response and with the days of winter ticking down could just be a somewhat expected cold winter period with interludes of mild conditions.

On a knife edge indeed.

P.S apologies to the seasoned enthusiasts and the like on here for using some of the lesser known models that are typically ignored but I think it will be interesting to see how they each individually handle the SSW in their outputs. Soon see 

[Chevron12345]

56 minutes ago, chionomaniac said:

The first signs of the SSW trop disturbances are there on the latest ECM 12Z by day 10 #arctichigh

That to me is the starting point.

Hasn't a artic high already been modelled in the later stages of output quite a few times already this winter? Why is that one different in relation to a SSW?

Edit - is it because of split pv?

Edited February 5, 2018 by Chevron12345

[Snowjokes92]

Just took a peak at the uppers for ukmo 144hrs and was shocked at how cold they were! Didnt expect that. I wonder if thats something to do with the upper atmosphere changing  and pushing the cold to mid latitudes. Can see big swings this week. Hold on to your hats and scarves!

[Frosty.]

Well, we know that winter 2017 / 18 has an Ace up it's sleeve which could mean a Blockbuster late winter for the uk and in the meantime, tonight's Ecm 12z ensemble mean shows plenty of cold zonality with a predominantly wintry flavour to our weather until mid month and then hopefully getting into high gear during mid / late Feb!

[chionomaniac]

18 minutes ago, Chevron12345 said:

Hasn't a artic high already been modelled in the later stages of output quite a few times already this winter? Why is that one different in relation to a SSW?

Edit - is it because of split pv?

You have answered your own question correctly. Any previous Arctic highs may not have been in line with background expectations. This one certainly is. When the models are in line with background signals then we take more note. The EPS AO has dropped like a stone so this shouldn't be a surprise. It may not be there on the next run but I suspect the blocking signal will be, somewhere.

[ITSY]

Guys, has anyone actually used their eyes tonight?!  we’re looking for trends not the holy grail...

 

[bluearmy]

4 minutes ago, chionomaniac said:

You have answered your own question correctly. Any previous Arctic highs may not have been in line with background expectations. This one certainly is. When the models are in line with background signals then we take more note. The EPS AO has dropped like a stone so this shouldn't be a surprise. It may not be there on the next run but I suspect the blocking signal will be, somewhere.

Sod’s law that the 12z eps back off somewhat on the neg AO although they still go neg.  the gefs and gems seem to be getting lower on it, run by run 

[snowice]

Just so you know  the gfs snow charts are wrong for over here the precipitation over Ireland was for snow its just grains its now evaporating the cold is killing the front i wouldn't expect much over the UK from this. So hard to model. 

[chionomaniac]

22 minutes ago, bluearmy said:

Sod’s law that the 12z eps back off somewhat on the neg AO although they still go neg.  the gefs and gems seem to be getting lower on it, run by run 

I must admit that is a bit of a surprise.

[BLAST FROM THE PAST]

Interesting, current sunspot is crackling with B and C class flares.  Not unusual in solar max but of interest as we close in on solar min.  Talk of SSW ahead too so interesting indeed..

I’m cautious of this potential period ahead, inasmuch Scandi Height rises look like a very good bet but I have concerns on the shape/positioning of it.  It hasn’t gelled this winter, but getting Height rises / blocking system there certainly puts us in with a shout.  

So midmonth, block forming in place, jet meandering wildly, will we get an LP system going underneath ‘enough’.......watch time.

 

 

BFTP

[damianslaw]

1 hour ago, Snowjokes92 said:

Just took a peak at the uppers for ukmo 144hrs and was shocked at how cold they were! Didnt expect that. I wonder if thats something to do with the upper atmosphere changing  and pushing the cold to mid latitudes. Can see big swings this week. Hold on to your hats and scarves!

Yes both ECM and UKMO are showing very cold uppers advancing east through north atlantic, sub 510 dam air encroaching, colder than what we saw a couple of weeks back, all down to the very cold air that has been in residence over NE Canada all winter, and I wouldn't be surprised if the stirrings in the strat are having this effect, there is potential for an almighty surge of frigid uppers to spill out from the Pole somewhere into the mid lattitudes once the warming does its trick - an arctic snow bomb perhaps.. oh gosh I'm normally more restrained than this..

Back to the here and now, lots going on, cold for the foreseeable, a very brief milder phase on Thursday blink and miss it, chance of further snow showers later in the week from the NW, similar to 17-19 Jan.

 

[snowfish1]

1 hour ago, Snowjokes92 said:

Just took a peak at the uppers for ukmo 144hrs and was shocked at how cold they were! Didnt expect that. I wonder if thats something to do with the upper atmosphere changing  and pushing the cold to mid latitudes. Can see big swings this week. Hold on to your hats and scarves!

Do you think more snow is likely then based on the outputs?

[snowice]

5 minutes ago, damianslaw said:

Yes both ECM and UKMO are showing very cold uppers advancing east through north atlantic, sub 510 dam air encroaching, colder than what we saw a couple of weeks back, all down to the very cold air that has been in residence over NE Canada all winter, and I wouldn't be surprised if the stirrings in the strat are having this effect, there is potential for an almighty surge of frigid uppers to spill out from the Pole somewhere into the mid lattitudes once the warming does its trick - an arctic snow bomb perhaps.. oh gosh I'm normally more restrained than this..

Back to the here and now, lots going on, cold for the foreseeable, a very brief milder phase on Thursday blink and miss it, chance of further snow showers later in the week from the NW, similar to 17-19 Jan.

 

Sounds like a ramp lol. 

Be interesting to see the 144 chart on 18z and  if the flow is more North westerly than the 12z.UKmo looks good. 

[Mucka]

2 hours ago, stodge said:

I don't follow this at all. No one was expecting the cold air to come back west as early as mid month.

The PV is under attack and a split vortex is still on course for the 9th-10th after which the two vortices will themselves be subject to strong warmings.

It's a hugely significant event but its immediate tropospheric response isn't yet clear. We are going to have to endure a final Atlantic onslaught next week and all the models tonight have a very deep LP around or to the south of Iceland at T+240.

From there, of course, there are any number of possibilities and as I've said from the start, the SSW doesn't guarantee cold or snow - all it does is buy us a seat at the table not a winning hand. 

I'm NOT going to say a SSW will lead inevitably to colder conditions over the British Isles - it COULD but I'm not saying it WILL.

There is a lag as we all know - ten days from 9th-10th takes us to 19th-20th and the very edge now of GFS FI - look at the GEFS of T+372 off the 12z and you'll see plenty of interest.

We may finish up with benign boring dross or we may not - it's going to be an interesting few days of model watching.

No one? I was and it was modelled here and there as well with just that trend withing GFS ensembles until the last 24h where that has been reversed.

Also at no time in any of my posts did I mention the reasoning being the upcoming SSW event.

I explained precisely why I expected better height rises to the NE - much better trough disruption with some energy heading SE instead of all heading NE. (currently around 120 through 144) with eventual undercut of any blocking to our East.

I expected the output to begin to explore that by this evening but it isn't the case so it seems it was a wrong call barring a sharp turnaround.

 

 

Edited February 5, 2018 by Mucka

[Catacol]

Not too much to add tonight really... but with an eye straining at the 10 day prognosis the EPS looks on track. 

Note the Azores/Euro high anomaly wiped clean and the cold trough in place. The question is - where from here? Low pressure anomaly to dig further south into Europe with pressure rising to the north? Both ECM ops today hinted at this.

In the meantime let's not forget the cold air in situ and pulses of very cold polar maritime incoming throughout the next 7 days as the trop pattern over the north atlantic kicks the vortex where it hurts. These may spring snowy surprises - whatever anyone thinks about polar north westerlies (and I am normally one of the least enthusiastic about these due to my own location) sub -8 850s as currently modelled on Friday and Monday particularly are not to be ignored - they are very cold for a north westerly air stream and snow for many parts is perfectly possible. A bit hit and miss, and warmer sectors likely to bring rain and sleet to the south at times - but I wouldnt rule out snow from this setup even in the south over the next week.

It's all lining up nicely still. Perhaps understandable that the flurry of Sunday posts across multiple online platforms yesterday has not been repeated as everyone gets back to work today.. but nothing has changed overnight to my eye. By tomorrow we will have visibility of 96 hours past SSW on the ECM - and for those predicting a pretty quick trop response to the reversal this might be when we can start expecting the real eye candy to make an appearance.

[Nick F]

EC weeklies just updated and weeks 3 and 4 looking positive for northern blocking, probably factoring the tropospheric response to the SSW.

 

[bluearmy]

Ec 46 shows week 3 and 4 low heights and slp nw Europe and high heights and slp to our north and nw. Tough to see how high heights are over scandi until global picture revealed. What is noticeable is -4c upper across midlands weeks 3 and  4. That’s a long way off for such a mean. 

[Mucka]

18z an improvement on previous runs at least.

 

Edited February 5, 2018 by Mucka

[Mark Neal.]

ECM monthly sounds promising!

@fergieweather Brrrr. An overall cold Feb unfolds according to latest ECMWF 30d modelling, with risk of E'ly flow developing further into the month. An interesting forecasting period ahead, on many levels...

[Steve C]

30 minutes ago, damianslaw said:

Yes both ECM and UKMO are showing very cold uppers advancing east through north atlantic, sub 510 dam air encroaching, colder than what we saw a couple of weeks back, all down to the very cold air that has been in residence over NE Canada all winter, and I wouldn't be surprised if the stirrings in the strat are having this effect, there is potential for an almighty surge of frigid uppers to spill out from the Pole somewhere into the mid lattitudes once the warming does its trick - an arctic snow bomb perhaps.. oh gosh I'm normally more restrained than this..

Back to the here and now, lots going on, cold for the foreseeable, a very brief milder phase on Thursday blink and miss it, chance of further snow showers later in the week from the NW, similar to 17-19 Jan.

 

Sub 474 DAM air over NE Canada! 

[Daniel*]

2 minutes ago, bluearmy said:

Ec 46 shows week 3 and 4 low heights and slp nw Europe and high heights and slp to our north and nw. Tough to see how high heights are over scandi until global picture revealed. What is noticeable is -4c upper across midlands weeks 3 and  4. That’s a long way off for such a mean. 

From what Nick F posted could be quite snowy with potential for elusive channel lows.

[Sweatyman]

2 minutes ago, Steve C said:

Sub 474 DAM air over NE Canada! 

How many fronts crossing us???

[comet]

although I am still of the opinion that this could have been a more memorable cold spell had it not been for the much stronger warming and forcing we are seeing in the strat  I think most would be willing to forsake that if we see real winter wonderland arrive at our shores.

I think over the coming days and runs we will see the heights build more robustly north from roughly our local with the large area of low heights held back further west. Strong heights then developing in the high north east Arctic ( Severnaya Islands) linking with heights from eastern Atlantic ushering in very cold (maybe bitterly cold) north easterly winds etc. This may very well take 20-25 days from now as the models struggle to digest the implifications of such strong strat forcing. I would expect that we will be entrenched in a cold pattern several days before the real cold kicks in with a risk of some snow. 

Here's hoping.