Model discussion: Hunt for cold - into mid-January

[Lukesluckybunch]

Just now, Staffmoorlands said:

The ECM has support from the UKMO. The GFS will be all change by 18z as usual in these circumstances 

well it is a shame that the ECM didnt follow the gfs,perhaps its just lagging a little behind it on catching up with the possible new trend from the gfs..however the fact the ECM and UKMO were similar is quite frustrating,perhaps in the next day or 2 they will come on board with gfs and GEM

[SqueakheartLW]

I'll take GFS 12z P15 for the period between Thursday January 20th at 18:00h through to Monday January 24th at 12:00h

I make that a total of 44.9cm of snow for Scunthorpe between those dates

Fri 21st 00:00 +252h

Fri 21st 12:00 +264h

Sat 22nd 00:00 +276h

Sat 22nd 12:00 +288h

Sun 23rd 00:00 +300h

Sun 23rd 12:00 +312h

Mon 24th 00:00 +324h

Mon 24th 12:00 +336h

BANK. 44.9cm of snow coming my way.

P15 IS going to verify ....... I wish

[Ali1977]

Well I think it’s clear to see the ECM doesn’t go the GFS route, much more Ridgy than earlier though but not where we need it. 

[Lukesluckybunch]

ECM mean looks very bad,high to south no signs of ridging north

[Mike Poole]

ECM clusters in that key timeframe T120-T168, and there are 5, all bar one chart has purple border - so Atlantic ridge regime.  We kind of know that from looking at the op runs, the devil is in the detail.

The ideal one (which will include the GFS and GEM evolution) is cluster 2, which puts up a proper ridge and brings down the northerly.  10 members, so 20% chance of that one.  Cluster 1 never clears the high from the UK and doesn’t ridge north into Greenland, clusters 3 and 4 look too Far East for the UK to benefit, op is in cluster 4.  Cluster 5 looks the weakest blocking.  So the proper cold outlook, at this early timeframe looks to be about 20%.  

I should remind some people that 20% is not 0% as it is regularly cracked up to be by those who are 100% certain (for some reason I cannot fathom) there is not going to be any cold blocked evolution in January.  And to be honest, in all of this chase, no-one has to my knowledge claimed more than about a 1/3 chance of a cold blocked evolution, obviously that fluctuates with the model runs.  

There are 6 clusters showing all sorts for the next T192-T240 timeframe, so I think all predictive capability is lost by then so i won’t post them!  

Edited January 10, 2022 by Mike Poole

[DAVE_ALLEN]

46 minutes ago, Anthony Burden said:

ECM going in a totaly different direction tonight collapsing the high pressure at 8 to 9days out yet 168 hrs

high pressure showing strongly to the northwest.Looks odd to me,we of course will see if correct or not 

but find it unusual to see high pressure collapsing so quickly.possible outlier.

If i am correct, were the charts not similar to this set up in the day or so before Christmas where the High Pressure slid away SE into Europe when  days earlier it had not been modelled to do so.

[Trom]

2 hours ago, Mike Poole said:

It’s doing quite well at day 5 in 3rd place at the moment, 0z:

12z:

It's worth remembering that the models are pretty good at forecasting the poles and equator but much worse at modelling the mid latitudes.  The models accuracy for the UK being next to a big pool of water and mid lat was woeful in a post Catacol made prior to Christmas.  It was a bit of an eye opener for me.  ECM had a -0.2 to 0.2 correlation of anomalies to actual for the UK, which is more or less random.  So those verification stats are skewed heavily by the equator and poles.

Here's a link to Catacol's post 

Basically the models are better in winter than the summer - this seems to be due to greater confidence in predicting the polar regions (presumably due to the vortex).  The models are great for the equator and decent for the polar regions in winter.  Poor for mid lats and woeful for the UK.

 

Edited January 10, 2022 by Trom

[stodge]

Evening all

Just catching up on the modelling of the American storm system at the end of this week and into the weekend.

T+144 charts from the 12Z suite:

ECM, GEM, UKMO, GFS OP, NAVGEM

Plenty of divergence still and this is far from resolved. The key is whether the storm system takes the bulk of its energy north towards western Greenland which will provide a break from amplification downstream over the mid Atlantic or whether enough energy is spilled east to prevent that and maintain the strong energy in the northern arm of the jet.

Oddly enough, ECM and GFS OP keep the storm cleaner and shift the energy more to the north - GEM splits the storm in two while UKMO and NAVGEM tile the exit of the storm to a positive alignment and pushes more energy north east and east. Also worth noting how mild the USA is next weekend with any real cold isolated to the northern plains.

[BLAST FROM THE PAST]

1 hour ago, SqueakheartLW said:

I'll take GFS 12z P15 for the period between Thursday January 20th at 18:00h through to Monday January 24th at 12:00h

I make that a total of 44.9cm of snow for Scunthorpe between those dates

Fri 21st 00:00 +252h

Fri 21st 12:00 +264h

Sat 22nd 00:00 +276h

Sat 22nd 12:00 +288h

Sun 23rd 00:00 +300h

Sun 23rd 12:00 +312h

Mon 24th 00:00 +324h

Mon 24th 12:00 +336h

BANK. 44.9cm of snow coming my way.

P15 IS going to verify ....... I wish

All way too soon….but hang onto them

 

BFTP

[Cambrian]

Self-styled  48 hour GFS ensemble “slidograph” to illustrate the maintenance of the period of below average uppers modelled by the 12z GFS over the last three days. 

GEFS T850 spread at 12z Saturday, 12z Sunday and 12z today, the lines link the same time on each graph, staggered to account for the intervening 24 hour intervals. 

The arrival time of the colder upper air for the 15th has not changed, tracked as it crosses the 0 degree line and long term average, and if anything, the duration of below average uppers has extended by around a day in FI to the end of the 24th, besides a brief period around the 18th, although the mean is consistently closer to the long term average throughout compared with Saturday’s run.

Two points - i) criticism of the GFS for being all over the place is a bit unfair if we look at the means and the consistent timings; Ii) following surface cold during that initial period of elevated uppers, reference to the GFS pointing towards a mild outlook is not currently supported by the evidence of the full pack.

One more point! The spread of today’s 12z ensembles is wide from day 5. Here is the spread chart for 144h, so Iceland to Greenland, even just by day 6 is still highly ambiguous. 

and look to where the main ambiguity extends by day 8 - substantial variability around the mean at the base of the Scandinavian trough.

 
If the base of the broad Scandinavian trough extends into that region, then things could get interesting. 

[Ali1977]

T96 and the GFS already looks quite different to the last run In the Atlantic

[ICE COLD]

Just now, Ali1977 said:

T96 and the GFS already looks quite different to the last run In the Atlantic

Yer was just going to post that . Bloody gfs

[ICE COLD]

T120 maybe just a tad slower than the 12z 

[Ali1977]

T132, heights not heading to the west of Greenland this run and no real trigger low, so I think as expected the very cold northerly isn’t happening - it’ll be interesting to see what can be made from this set up  

Edited January 10, 2022 by Ali1977

[Ali1977]

3 minutes ago, Ali1977 said:

T132, heights not heading to the west of Greenland this run and no real trigger low, so I think as expected the very cold northerly isn’t happening - it’ll be interesting to see what can be made from this set up  

Although saying that it’s really trying to send heights into central Greeny and it’s not getting much pressure fromthe Canadian LP

Edited January 10, 2022 by Ali1977

[ICE COLD]

2 minutes ago, Ali1977 said:

T132, heights not heading to the west of Greenland this run and no real trigger low, so I think as expected the very cold northerly isn’t happening - it’ll be interesting to see what can be made from this set up 

Yep the block has pushed further east on the 18z compared to the 12z . 18z first image

[Ali1977]

1 minute ago, ICE COLD said:

Yep the block has pushed further east on the 18z compared to the 12z . 18z first image

It’s waaaaaay better than I thought it would be to be fair. Interesting , maybe more support on the suite this run hopefully 

[bluearmy]

Trying to work out how the Atlantic amplifications will verify remains very difficult. Basically it’s down to upstream trough and Arctic blocking together with the tpv temp split and how those features come about re timing. Absolutely impossible to put any detail on the broad pattern.  What I have noted is that as runs are coming within the 5/8 day timeframe, the amplification of the MAR is increasing somewhat. How sharp is now the question. Currently looks a bit too flat with the deep cold more likely to be to our east than across us. But it remains fluid.

[Staffmoorlands]

18z predictably more in line with the European models now. Wouldn’t be surprised to see a colder run on the 00z though!

[Allseasons-Si]

Hi gang

whilst we have the tpv to the NE of UK(where we want it)then there is every chance that we are in the game here,the timings of a daughter low/shortwave ejected S/SE on the periphery of the main parent vortice to our north is proving a big headache to the NWP's IMO plus the added headache is the low off the NE'ern states of USA/Canada,we need this to sharpen up and pull back N/NW and at the same time split the flow SE ,...instead it engages with the mid Atlantic low then sends a short wave northeast towards the UK and scupper the chances of a build of heights NW of the UK,...we need total separation of these to allow heights in between to ridge north,a fine balance to be resolved with more runs needed.

 

[Ali1977]

Whilst the Op isn’t as good as the 12z, the ENS look like being a sizeable improvement!! Much to be resolved as mentioned above .

T138 mean below, much sharper trough into Greenland here suggesting more ENS have heights heading towards the west of Greenland , like the 12z Op!! 

[Kasim Awan]

9 minutes ago, Ali1977 said:

Whilst the Op isn’t as good as the 12z, the ENS look like being a sizeable improvement!! Much to be resolved as mentioned above .

T138 mean below, much sharper trough into Greenland here suggesting more ENS have heights heading towards the west of Greenland , like the 12z Op!! 

Again, with the ecm / icon not catching on, the gfs is very unlikely to verify and it's op / control have moved away. Still a slight chance so we look to the 00z.

[CoxR]

17 minutes ago, Ali1977 said:

Whilst the Op isn’t as good as the 12z, the ENS look like being a sizeable improvement!! Much to be resolved as mentioned above .

T138 mean below, much sharper trough into Greenland here suggesting more ENS have heights heading towards the west of Greenland , like the 12z Op!! 

looks like a downgrade to me, looking through perturbations

[Snowman.]

Control is close to something decent here

OP is pretty bonkers FI. Either way, don't feel it will be a one and done ordeal, even if they end up being mostly topplers looks like it could be an almost repeating pattern.

[northwestsnow]

The thing is we want as much energy digging south into Europe as possible..

This assists with incoming lows off the Atlantic..

18z shows this as we end with another bitter Northerly ....