Model thread discussion - cold spell looming

[Battleground Snow]

ECM mean, improved from last night, although I thought the spread would go even lower that the end...

In the extended they might I guess 

 

 

[Guest]

8 minutes ago, Battleground Snow said:

I'm saving this chart for 144 on Friday and will post the actual snow depths people attain to see how close it was 

There seems to be a fierce debate in here whether or not the models are  seeing the convection. I am in the camp that they are underplaying streamers, especially with -12 to -14 air moving over water, but we will see what happens

I'm more intrigued by why it shows greater snow depth west of the Pennines rather than east, given orographic influence should, in theory, benefit those east of the Pennines. Many other models show this, after all.

[Uncertainty]

I mean, why shouldn’t this happen?

 

The MJO is firmly in phase 7 at good amplitude.

And forecast to perhaps stay there for quite some time.

 

The multiple strat weakenings still have plenty of time to filter through the levels of the atmosphere. The forecasting strengthening up top may well be relevant for late Feb or March, but it won’t be the driver of the medium term tropospheric situation.

The clusters from last night are quite illustrative of the evolutions on the table:

So either: The Atlantic breaks through, a benign, springlike U.K. high or the GEM.

The GEFS has been keen on options 2 and 3 for quite a few runs, the ONE thing they are v useful for is picking a FI trend and it, the blend of the above EPS clusters are clearly there...

 

A pretty significant mean SCeuro high there, but given the clusters trifurcate as EPS above, it’s only representative of a blend of v cold and quite mild runs. 
 

If winter had been mild thus far, many would be getting very excited about the situation day 7-12, but as it is, most will rightly be far more concerned with the intense imminent cold spell we have inbound in the short term:

Minus 12 850s forecast by the ECM at the range it truly excels at. A very rare spell of weather coming up, call it what you want, it makes no difference. It’ll be cold with very frequent showers .

One highly pertinent point for western areas in this particular Easterly is the question over the westward extent of the lake effect snow showers. Some models, and indeed the MO warnings suggest not very far is the answer, but the UKV and Swiss model seem to push showers, born from the temperature contrast between air and sea, right across mainland U.K.

@SingularityJames I read your excellent article about this spell and you mentioned you thought the snow showers would penetrate much further than most models would suggest, do you think this chart is realistic?

 

What the GEM is showing would have no semantic debate attached and would make February the month of the beast. An incredible period of model watching, payback for cold lovers for the heartache of the last two winters (and the 5 before that). 

[MattStoke]

4 minutes ago, Battleground Snow said:

ECM mean, improved from last night, although I thought the spread would go even lower that the end...

In the extended they might I guess 

 

 

Trouble is, the 850hpa temperatures won’t tell the story if we have surface cold but milder air aloft.

[Tim Bland]

9 minutes ago, That ECM said:

Tuesday/Wednesday for the sw may hold interest also going by that.

Yes, just about makes it into Cornwall but wouldn’t take much of a shirt to bring more of the south into play

[Tim Bland]

5 minutes ago, Steel City Skies said:

I'm more intrigued by why it shows greater snow depth west of the Pennines rather than east, given orographic influence should, in theory, benefit those east of the Pennines. Many other models show this, after all.

Think that’s the snow that falls tonight. As it turns cold and stays cold after. that snow could still be on the ground at day 10!

[IDO]

A clear signal that the Atlantic stalls to our west by Thursday and that we get a pressure rise around the UK, all the gefs at d16 show this:

The gfs op looks about the worst case scenario and has a different upstream development at d8-9 where the HP train cuts through the trough to our west to flatten the pattern, the ECM and gem go under the trough and the energy pushes north via the developing UK high:

The op synoptic has support so cannot yet be ruled out.

GEFS; the three main clusters at d10 on the ensembles are UK high (control and op), mid-lat high to our east or high-lat high to the NE, with a cluster of collapsing patterns. The trend is good but at that range we have phasing and other issues to resolve. Still, we are heading in a good direction and 5-days of cold looks a good call for the minimum length of this cold spell!

Edited February 6, 2021 by IDO

[Battleground Snow]

1 minute ago, MattStoke said:

Trouble is, the 850hpa temperatures won’t tell the story if we have surface cold but milder air aloft.

Indeed Matt, but what I was looking for was to see how many EPS backed the cold pool west like the gem

[PiscesStar]

1 minute ago, IDO said:

A clear signal that the Atlantic stalls to our west by Thursday and that we get a pressure rise around the UK, all the gefs at d16 show this:

The gfs op looks about the worst case scenario and has a different upstream development at d8-9 where the HP train cuts through the trough to our west to flatten the pattern, the ECM and gem go under the trough and the energy pushes north via the developing UK high:

The op synoptic has support so cannot yet rule out.

GEFS; the three main clusters at d10 on the ensembles are UK high (control and op), mid-lat high to our east or high-lat high to the NE, with a cluster of collapsing patterns. The trend is good but at that range we have phasing and other issues to resolve. Still, we are heading in a good direction and 5-days of cold looks a good call for the minimum length of this cold spell!

My take is that the high will retogress northwards adding to the blocking and halt thea Atlantic completely 

[Tim Bland]

20 minutes ago, Battleground Snow said:

I'm saving this chart for 144 on Friday and will post the actual snow depths people attain to see how close it was 

There seems to be a fierce debate in here whether or not the models are  seeing the convection. I am in the camp that they are underplaying streamers, especially with -12 to -14 air moving over water, but we will see what happens

GFS has more for most  (pre breakdown) so will be interesting to see which is correct ...

[BLAST FROM THE PAST]

18 minutes ago, DisruptiveGust said:

Probably been posted a few times already, but here’s the 00z GEM & ECM at day 10 

Just on this.  The GEM was first to  really go for the current set up coming and this isn’t it’s first run to suggest the block holding and winning.  ECM looks to like it too.  One of the great weeks of model watching ahead.....in fact what a great winter for model watching thus far.

I’m surprised it isn’t busier in here

BFTP

[Malarky]

Wasn't Gem first to get fully on board with the cold spell we're just beginning?

 

Edit - BFTP beat me to it.

Edited February 6, 2021 by Malarky

[Tim Bland]

Arome , UKV and Euro4 snow depths for tomorrow...wouldn’t want to be writing the TFL forecast tomorrow!

[ANYWEATHER]

Model output getting really interesting as regards later into next week, just a day or so ago gfs ecm showing the block getting beat up by the Atlantic and while the gfs still shows something akin to that ecm holds the cold block virtually for the entire run......fun times model watching ahead....!

[Ice Day]

2 minutes ago, BLAST FROM THE PAST said:

Just on this.  The GEM was first to  really go for the current set up coming and this isn’t it’s first run to suggest the block holding and winning.  ECM looks to like it too.  One of the great weeks of model watching ahead.....in fact what a great winter for model watching thus far.

I’m surprised it isn’t busier in here

BFTP

Absolutely this, I genuinely cannot think of a better winter for model watching.  There has barely been a week where there wasn't some interest, whether it be SSW related, FI shenanigans or cold and snow events (not so much for my area, but many areas further north have had plenty to enjoy). 

If Carlsberg did weather watching and all that.....  

[bluearmy]

Extended eps trend towards the ec 46 of height rise griceland and sceuro low anoms .....if our scandi ridge does build then expect it to sink away or retrogress based on that mean .....either way the outlook remains blocked and cold 

[Tim Bland]

UKMO has the Atlantic trying to push in fron the south west Thursday brining snow...will it make it in at all though...that’s the million peseta question today

[keithlucky]

8 minutes ago, BLAST FROM THE PAST said:

Just on this.  The GEM was first to  really go for the current set up coming and this isn’t it’s first run to suggest the block holding and winning.  ECM looks to like it too.  One of the great weeks of model watching ahead.....in fact what a great winter for model watching thus far.

I’m surprised it isn’t busier in here

BFTP

Hardcore weather watches we enjoy the battle .But unless snow is involved in the forecast for there area 70 percent of average weather watcher are just not interested .

[Liam J]

12 minutes ago, BLAST FROM THE PAST said:

Just on this.  The GEM was first to  really go for the current set up coming and this isn’t it’s first run to suggest the block holding and winning.  ECM looks to like it too.  One of the great weeks of model watching ahead.....in fact what a great winter for model watching thus far.

I’m surprised it isn’t busier in here

BFTP

Imagine if these day 10 charts are the way forward and this week is just a taster of the next course fascinating model watching.
And all this actually happening in winter and not spring this time!  

[Duane S.]

As @Uncertainy mentions above, much credit should probably be given to the ongoing Pacific forcing, shown by the MJO plot. Assuming the likes of ENSO is playing ball and we are getting a ‘connect’, and it looks like we are.

All too often we are willing it on to hit record breaking amplitudes in P6/7/8 (Feb’18 hit an incredible SD of nigh on 4 if I remember correctly). But as extreme as the consequences could end up being, it also appears to increase the easterly pace of the convection wave? What we have now is the MJO, still at a very decent amplitude, but stalling (and I am only postulating here) I would naturally assume that this is something that is far more conducive to longevity in terms of a potential cold spell for us, again, under the right coupling circumstances.

Thinking back to that very early March’18 cold spell, as ridiculously extreme as it was (for any time of the year, let alone March!), it was scuppered much earlier than had been expected, by the block being pulled too far NW at an eye popping speed. I’m sure this could be traced back to what the MJO was showing. 

[iand61]

24 minutes ago, Steel City Skies said:

I'm more intrigued by why it shows greater snow depth west of the Pennines rather than east, given orographic influence should, in theory, benefit those east of the Pennines. Many other models show this, after all.

Assuming you mean the Lancs/Yorks part then to me it looks like it’s showing it over the Pennines rather than west of them.

the westward “lump” shown is actually the West Pennine Moors and reach a long way across Lancashire to within about 20 miles of the coast.

I know what you mean though as regards orographic precipitation but we often get the same effects here where the western upslopes end up with lighter rain and snow which then intensifies again as it hits lower ground over the other side of the Pennines.

that said, ignore the snow maps, if there’s snow coming from the North Sea you’ll get the lions share in Yorkshire, just let the snow starved North West have a bit though

[Anthony Burden]

Good morning all ECM very interesting at the end of next week no Atlantic take over Euro high

to take over U.K. weather.Possibly no mild break continuation of dry cold and frosty.

[MOF]

5 minutes ago, keithlucky said:

Hardcore weather watches we enjoy the battle .But unless snow is involved in the forecast for there area 70 percent of average weather watcher are just not interested .

I'm still lurking :,-)

[Godber 1]

Day 10 on the GEM is a thing of beauty!  You wait for a severe cold spell [from the east], then two come along in quick succession?

[Garthvader]

13 minutes ago, Tim Bland said:

UKMO has the Atlantic trying to push in fron the south west Thursday brining snow...will it make it in at all though...that’s the million peseta question today

Hoping it does push in to a point.....snow wise for our little corner sheltered from the easterly's