Model Output Discussion. 3/12/2022. How cold will it get?

[Alexis]

Just a reminder that it was the mighty Navgem that was the first that refused to believe that pseudo hurricane would steam in!

[Bats32]

1 minute ago, Alexis said:

Just a reminder that it was the mighty Navgem that was the first that refused to believe that pseudo hurricane would steam in!

I only trust the NASA and Navgem models

[northwestsnow]

MOGREPS looks bitter Thurs +Fri night in Manchester!!

Probably knock a couple of degrees off for my more rural and elevated place ,could be looking at -8 here !!

Not many members bring surface temps above zero out to the 13th ..

Bye bye Atlantic 

 

Edited December 5, 2022 by northwestsnow

[nick sussex]

Looking at the NCEP extended forecast discussion they do mention poor run to run continuity which we’ve seen over the last few days .

They have low confidence in the pattern across the USA and this down to the different handling of trough energy moving east from the Pacific .

You can clearly see the major differences this causes downstream over Western Europe .

The GFS essentially moves the main blocking much further west and then you rely on height rises to the ne .

The ECM keeps the main blocking further east at the critical time .

You can further see those differences over Greenland at day 7 .

The GFS is dropping shortwave energy about 800 miles further west compared to the ECM !

What you don’t want is a middle ground solution here . So either shortwave energy drops south over sw/s Greenland or much further east so that essentially heads south into the UK troughing .

So whilst today’s outputs are encouraging for coldies the timeframes involved mean we are unlikely to have found the definitive solution yet .

 

[Anthony Burden]

Morning all,ECM 00z now showing the intense low pressure system from the Azores heading into the Mediterranean a major adjustment all due to the intense cold heavey column of air to the north.Looking possible for a long protracted cold/ very cold period for the U.K.,in regards to the white stuff that will depend on Arctic trough’s heading south,but Scotland and the north of England looking likely for a descent amount.

[Mike Poole]

ECM clusters - well the first two timeframes, there is only one cluster.  This does not mean certainty!  Usually, it means there is so much uncertainty the clustering algorithm gives up!  So no point posting them, on to T192-T240:

Here, the op in in cluster 2 (18 members) with that door wide open to cold from the north direct.  Cluster 1 looks very good in terms of the UK trough (25 members), and cluster 3 sticks with the original source of cold coming round now from the east.  All’s good here.

T264+ there are 5 clusters with the jigsaw pieces thrown all over the place, pick the bones out of these:

[Catacol]

GEM/ECM/UKMO now all showing the atlantic low sliding E/SE and stalling/fading. Both ECM and GEM showing some dramatic cold gathering to the NE as the second wave prepares to land. Both are tentatively playing around with height rises over Scandy, but in distant low resolution and therefore at 192h+ everything turns to mush in terms of coherent modelling. In setups like this mushy modelling is standard.

A good start to the day...though it is surprisingly mild here in Lincolnshire this morning. Won't last long...

[Matty88]

Very unusual (for us) to be getting upgrades just prior to a cold spell, but I half suspected it was on the cards as many have been saying the models have a tendancy to over-inflate low's especially with cold air in place and the Greenland Block. 

With the LP flow dominating I think we all need to be keeping a close eye on little disturbances/surface lows as this will be the key driver for snowfall events over the next week or so - I would not be at all surprised to see some decent falls pretty much anywhere. The one I'm particularly interested in at present is over next weekend Saturday into Sunday as a LP sweeps SE - albeit likely very localised (as is always the case with snowfall) this could really deliver for some in Southern counties and will likely develop/change over the coming days.

Some lucky ones could be in for a very snowy scene by Sunday/Monday - no doubts! Fine detail to be resolved.... 

[northwestsnow]

JMA building a Scandy high ....

[Derecho]

Very happy with the output this morning after the operational scares yesterday evening.

Don't think we are completely out of the woods yet, the EC is on a knifes edge but they Azores low holds off and the cold stays! UKMO more progressive but the cold puts up a fight.

GFS fantastic, EC also super but is balancing a fine line between success and failure.

It would be nice if we could get more cold reinforcements into Scandi so even if a deep Azores low comes towards us, we can see further entrenchment of the cold here.

[northwestsnow]

For those worrying about snow I've just watched Carol Kirkwood suggesting snow Northern Scotland on Wed and snow showers for NW England on Thurs...

Although EC/UKMO have us bone dry ...

[E17boy]

I really hope those of us here in London we get to see some white stuff as well. Usually with a northerly we down here don’t get much unless it’s an entrenched feature coming down. The North Sea facing coasts tend to be in a better place rather than inland areas. What we need here is a good convection easterly to push showers in. Just had a thought it’s a BIG DREAM us winning the World Cup then celebrating in the falling snow outside Wowww that would be a 1 million chance but what a celebration that would be a lifelong memory. 
 

Have a great day all my dads 2nd death Anniversary today so trying to keep chins up. 
 

regards 

[LRD]

Good progress (if it's cold you're after) this morning

I still don't like the last frames of both UKMO and ECM. Iberian heights trying to build again on ECM's last frame but nothing to worry about at this stage. UKMO 168's pattern is still a bit far north for my liking and the trough to the north west of Spain isn't elongating enough but it certainly could do so, eventually, while giving us some battleground snow in the south

GFS is very good

One caveat, ECM is amongst the very coldest run in its ensembles for 850s. 

And the GS op is also a relatively cold run although, it looks to me, they have trended colder overnight

No bitter cold but it'll be cold enough for snow

[summer blizzard]

A rare potential victory for the GFS as the Euro and GEM capitulate and keep the cold through day 10.

Signs also that the UK/Scandi Low will weaken and turn the flow more easterly.

[Kasim Awan]

1 hour ago, Nick F said:

Does look very dry away from coasts on the 00z EC out to day 10.

EC and the UKV don't bring any ppn for most from the cold front that drops south on Thursday too. Though GFS does.

But with clear skies likely for many most nights, a widespread hard frost likely. Going to keep the Dec rolling average temp decently below I suspect.

EC and UKV cannon fodder at this stage with troughs. Thursday morning itself should do 1-4mm inland. Plus those 1-2mms in the east should be more like 4-5 with that level of convection in the north sea.

[BlueHedgehog074]

Looking at various operational models at 96 hours, and they all showing well the blocking High over the Greenland/Western Iceland area combined with the Scandinavian trough to the North East of the UK. With some of that troughing reaching South-West towards the UK. Shows well the established cold conditions that will have invaded the UK from the North earlier this week.

GFS 00Z

 

ECMWF 00Z

UKMO 00Z

 

GEM 00Z

 

Considering the timeframe we’re dealing with, wasn’t expecting much differences between the models at that time. You could argue, such as is the case of the Scandinavian troughing, that it’s a touch deeper (slightly darker blues) on the GFS, ECMWF and GEM compared to the UKMO. GEM is perhaps the furthest West with the light Northerly over the UK on Friday, but all essentially show some very cold weather. Cold weather enthusiasts really are in an interesting place.

And while the details are still likely to change, nice to see the operational models make that mad Low to our far South-West less of a trouble maker. Many either significantly squashing and sliding the Low towards/through to the South of the UK, or some just keeping it just slow moving to our South-West. The Icelandic ridge (or wedge I suppose) seems to help put pressure on that Low and make it squashed and pancake-y on some of the models, such as in the example below:

 

One way that can help keep the cold weather going through the UK (even though that Low could provide some snow chances for the UK at some point, so not a totally enemy for cold weather fans). 

This might have already been posted below, so apologies if so, but the 00Z ECMWF ensemble mean at 192 and 216 hours shows that bad boy (stormy Western Atlantic Low) staying squashed keeping the UK in an Easterly to North-Easterly flow. A slidey look it has about it, although with the mean of the lowest pressure out to our South West. 

 

In regards to extending this cold spell, the models overall are in a good mood this Monday morning. I think that is the thing, to be fair, as longs as their is some kind of High Pressure somewhere between the North-West and North-East, possibilities of cold weather can continue to pop about. 

[TEITS]

What a bloody mess these models are in. As soon as we move away from the default weather patterns then chaos occurs and that is because in my opinion the computer models have been coded with historical data. The change in the 0Z ECM is hardly surprising as the 12Z was probably the biggest outlier I have ever seen from this model. The 0Z is at the other end of the scale with this being at the bottom of the ECM ensemble mean, but not an outlier.

Due to this uncertainity I go back to my old method of looking at this from a forecasting instincts perspective. The only problem with this though is the warming planet has changed our weather patterns but now we have the added complication from all of these volcanic eruptions. I admit my knowledge is poor in how all this ash going into the atmosphere affects the weather especially the stratosphere.

So all things considered I would say the cold is here to stay because the same trend of blocking to our N/NW/NE and the low pressure systems in the atlantic tracking S of the UK is constantly appearing in the models despite the varying output. The question is how cold? will it be dry cold? snow showers only around exposed coastal areas? or heavier, widespread snowfall via a convective NE/E,ly?

I am sticking with the colder, stronger flow from the NE/E, more widespread convective snowfall from the 12th Dec onwards.

[Duane S.]

Great runs this morning again  

Worth remembering the dice analogy at these times. If the atmosphere, backed up by background signals/teleconnections, do NOT have a predisposition to cold, we need to roll a double six.

This is one of the rare times when we genuinely have an atmosphere primed for a lengthy cold spell and snow. A double six now gets us nirvana, a 9,10,11 is enough for a memorable spell, 6,7,8 gets us a decent cold spell with snow for some, 3,4,5 gets us a watered down version of what could’ve been and a 1,2 gets us snow on the tops of hills with a quick breakdown. Dice is a good analogy also, because with EVERY incoming cold spell we need a bit of luck as well.

And to boot, you’d be a brave person to bet against an SSW (or as near as) taking place by mid January at the latest.

[Catacol]

I'm still in love with GEM today. 144h - so many tantalising potential next steps... 

[Alexis]

Just a quick note that sea temperatures have really plummeted around the UK over the last week. They are very close to average in most areas now, so I think we need to dispense with the notion that they are particularly high now.

https://seatemperatures.net/europe/united-kingdom/

Edited December 5, 2022 by Alexis

[Frigid]

GFS and ECM for the most part more inline with their ensembles now. Looking good for prolonged cold has to be said! 

[bluearmy]

Gotta love the way a cold fi leads to Dickensian winter posts and a mild one that ‘winter is over’ 

if it’s after day 7 then it’s really doesn’t exist 

all the nwp is a degree of fantasy as it’s all in the future but once you get a week away, you really are pinning the tail on the donkey. 

note that the ec00z looks far more aligned to the  day 7/10 day clusters it was put in yesterday rather than the actual run we saw. 

note that the gfs is still pretty much in line with what it was offering in that same period last couple runs 

note that the Ukmo now wants to meander the Azores low towards us but might it slide if there was a day 8 ??

extended ens means output are flattening the Atlantic somewhat but still retain n high anoms which still have to settle on a general locale so little to deduce atm.  A second wave of scandi troughing is certainly on the table (as is a more zonal offering) 

all just observations - nothing more 

[Nick F]

4 minutes ago, Kasim Awan said:

EC and UKV cannon fodder at this stage with troughs. Thursday morning itself should do 1-4mm inland. Plus those 1-2mms in the east should be more like 4-5 with that level of convection in the north sea.

Yes, I think the models often underestimate the amount of shower activity that gets inland from coasts and they often won't pick up on convective disturbances that form or convergence zones at this range, which can be a big players in bringing precipitation inland in these polar flows.

[ThamesStreamer]

4 minutes ago, Alexis said:

Just a quick note that sea temperatures around the UK have really plummeted around the UK over the last week. They are very close to average in most areas now, so I think we need to dispense with the notion that they are particularly high now.

https://seatemperatures.net/europe/united-kingdom/

This is a great spot, and bodes well.

[Kasim Awan]

1 minute ago, Nick F said:

Yes, I think the models often underestimate the amount of shower activity that gets inland from coasts and they often won't pick up on convective disturbances that form or convergence zones at this range, which can be a big players in bringing precipitation inland in these polar flows.

If the modelled wind speeds are right, then at least during this week snow accumulations from north sea showers really will be confined to a 15 mile coastal strip (for the first phase of the cold snap - i.e. up to Friday). The nne wind tends to push showers down the coast rather than inland. Inland areas will likely be relying on troughs

The western side is a different story, more instability and wind is more directly inland so more interesting for streamers & inland snowfalls here