Model output discussion 24/01/21

[Troubleatmill]

8 minutes ago, Daniel* said:

No that’s clearly not based on ECM 12z which definitely would be snowy across fairly extensive area.

 

Stand corrected, it has just updated, what's the bet it will change anyway

[Battleground Snow]

3 minutes ago, WINTRY WALES said:

Do we think it’s a done deal for midlands south to see no snow at the weekend?!

No at 72 range it can be 50-100 miles out. 

Last Sunday even the hi Res models were wrong at 24 hours out by at least 50 miles .

They also underestimate the block, so more areas could be brought into play, also evaporative cooling may help too.

[MJB]

9 minutes ago, Richard Fisher said:

Yes very poor ECM for Midlands south cold rain. Can someone explain why the borderline between snow or rain seems to be consistently modelled to change to snow around the midlands north?

Doesn't look that poor 

[Mike Poole]

8 minutes ago, TSNWK said:

Genuine question! Why do the overnight runs 9 times out of 10 fail to deliver and then like today we recover for coldies. 

I've lost count of times over the years I've woken to poor overnights..

 

 

2 minutes ago, Sweatyman said:

I've asked a million times. Nobody can tell me!

I’ve wondered about this for ages.  I think it is best approached by ruling out things that cannot be causing it, and then seeing what is left.  For a start the verification stats for all major models are basically the same for the 0z and 12z runs for the northern hemisphere.  There is no statistically significant difference between them over a very long period of time.  So one set of runs is no better than the other.  (There is also no statistically significant differences between the 4 GFS runs, but that is a slightly different question).  

Obviously, the 0z and 12z runs are seeded with different data measured in the hours running up to them - and the most obvious thing would be the difference between day and night in different parts of the world.  Which may lead to a slight bias one way on the 0z and the other way on the 12z, but basically cancelling each other out when it comes to verification.  That’s my best guess, and is pure conjecture. 

[bluearmy]

How can midlanders moan about snowfall?

Btw, control has -13 uppers post day 11.....

[BLAST FROM THE PAST]

2 hours ago, BLAST FROM THE PAST said:

The UKMO is the run of the lot imo it’s got snow written all over it for the South.  Battleground we will be, with cold getting the upper hand.  
 

BFTP

I missed the ECM roll out as I was looking at GFS ensemble members.  I was looking at pert 9 and thought how incredible it was and can’t get colder....then I looked at the insane pert 11....they both signal the end of GW .  Quite a few v cold ones in there.

ECM synoptically lovely, we’ll worry about the cold for my part of the world if it pans out that way

Pert 11

BFTP

 

 

Edited January 27, 2021 by BLAST FROM THE PAST

[bobbydog]

7 minutes ago, Sweatyman said:

I've asked a million times. Nobody can tell me!

To be fair, its not the models that fail to deliver, charts we don't like may be the ones that verify. More often than not, its the weather that fails to deliver.

Its all here in this book-

[JamesL]

11 minutes ago, WINTRY WALES said:

Do we think it’s a done deal for midlands south to see no snow at the weekend?!

A blend of the ECM and UKMO would give parts of mid/se wales and the s midlands some snow. Also EC particularly highlights snow into Home Counties too 

It will not be resolved yet but IMO any high ground above 200m in the south of the UK highlighted above would probably see falling and settling snow and maybe a transient event lower down (snow to rain or vice versa) 

Edited January 27, 2021 by JamesL
Change text

[damianslaw]

There are times when your interest is raised more significantly when you see UKMO, ECM and GFS all seemingly coming into line at the 120 hr range after days of divergence, more so when ECM and GFS are the same thereafter until 240 hrs - more often than not this is not the case..

In the immediate the models are showing heights to the north digging in deeper, this has the effect of elongating the atlantic trough on a negative NW-SE alignment, and marked temperature boundary between the north and south - look at how the 534 dam line sticks to N England for the next 5 days.. 

ECM and GFS then show more robust height development to our north, this is the trigger to a more amplified atlantic flow and we end up pulling in a cold NE/E floe, possibly very cold.

Whether this is a one off moment or a new trend remains to be seen, but my hunch is that they are now going to run with it, and eyes may soon be looking to the NE for our weather.

[Snowman.]

Knit picking a D10 ECM is only going to end in tears! The trend today has been incredible and I stand optimistic with regards to the next few days.

We have snow events coming this weekend which are looking to be the catalyst for further blocking north, whether we win and who wins is to be decided but its so far away that it will continue to change run to run.

Below is 3 charts from the ECM for the 3rd of Feb. Oldest 12z run first with the latest last.

 

Clearly models have underestimated heights to the north and trough disruption has been a severe weak point.

 

 

[Timmytour]

12 minutes ago, WINTRY WALES said:

Do we think it’s a done deal for midlands south to see no snow at the weekend?!

I think a general theme of this winter has been for the models to overplay the extent milder air makes it north and east. It wouldn't surprise me to see corrections to accomodate this again over the next couple of days, possibly to the extent that we are moaning it's all gone too far south!

[Tim Bland]

49 minutes ago, Gadje said:

Is that Svalbard just north of the map you posted.

Eh? I posted a chart of England and Wales to show the band of snow on Saturday as it lies across the centre of England and Wales? It’s nothing against Scotland When I referred to the snow piling up in Scotland tomorrow I didn’t post an image of England

[chionomaniac]

Anyone in the south, who says this is a poor run for us, needs to look at the bigger picture and look at the synoptic evolution and avoid the 850’s. We have a wonderful looking NH profile, very post SSW look to it.

Just look at the Arctic high being matched by the eastern Iceland high. Great alignment to deliver long lasting deep cold to all areas of the UK. The Atlantic low here is set to trigger the colder air further south, and encourage a deep cold air flow across the warm North Sea.

Of course this wonderful scenario may not come to fruition, but lots of variations would still deliver.  A good day with the models, and one I have been waiting for ( expecting) for a while now.

[Battleground Snow]

ECM may even be a mild outlier for the south?

Not quite but very close.... Attached is for Brighton

Edited January 27, 2021 by Battleground Snow

[winterof79]

8 minutes ago, bluearmy said:

How can midlanders moan about snowfall?

Btw, control has -13 uppers post day 11.....

Should know better than quoting post 11 days. 

[Noob]

As a complete noob ( yes we were all one once ) but do the models share each others data when coming up with their charts ?

[bobbydog]

2 minutes ago, chionomaniac said:

Anyone in the south, who says this is a poor run for us, needs to look at the bigger picture and look at the synoptic evolution and avoid the 850’s. We have a wonderful looking NH profile, very post SSW look to it.

Just look at the Arctic high being matched by the eastern Iceland high. Great alignment to deliver long lasting deep cold to all areas of the UK. The Atlantic low here is set to trigger the colder air further south, and encourage a deep cold air flow across the warm North Sea.

Of course this wonderful scenario may not come to fruition, but lots of variations would still deliver.  A good day with the models, and one I have been waiting for ( expecting) for a while now.

Some cracking charts over the past few days really Ed, if people as you say, look at the bigger picture. A bit 'knife edge' for us in the south but I would take the risk for some potential big rewards....

[Mike Poole]

Eyes down for the home strait then!  Some considerations:

The strat, here the NAM chart as of todays GFS 0z:

We’e now seeing at the surface the -NAM/-AO signal at the surface, and the forecast up top is a return to westerlies/+AO - and I think I remember reading somewhere that this could have an effect of sealing in the trop response...not sure about that, maybe @chionomaniac might know.   The SSW likely to be influential for 2 months since 5/1/21 anyway.  

AAM and MJO:

AAM forecast by CFS to rise, and the MJO progression will be a big part of that.  The MJO GEFS plot shows an awful lot of scatter, but that isn’t all noise, as the starting point is now in phase 7 at decent amplitude.  So we should take thoughts of a La Niña style atmosphere end to winter out of the reckoning for the time being.  

It’s timely to look at SST anomalies, given we may have an easterly within the next 10 days:

Warmer than average in the North Sea specifically, which would lend itself to convection with the kind of cold uppers which the models are suggesting are coming our way.  

Likelihood of cold February increased further on today’s output I would suggest.

 

[Tim Bland]

38 minutes ago, Beano said:

These low dew points Sheikhy? Not sold on it yet mate but it will swop and change

Try midday onwards which is when most of the snow falls....

[BLAST FROM THE PAST]

On 25/01/2021 at 10:11, BLAST FROM THE PAST said:

Well I don’t see any major issue yet.  I actually overall like what is before us and what is still on the table to develop.  It may turn out that we have another chilly month in Feb with some cold shots and less cold back and forth with no deep freeze and no particular mild spell.  That is very much on the table.  But also is a big shot and a blow out...making it very interesting watching.....there certainly is plenty of serious intensely deep cold floating around the NH to ‘share out’.

For me this morning I looked at GEM, then UKMO and thought...nice little upgrades.  GFS I thought yep that’s keeping the interest and in the game. I then looked at the ECM and up to t120 I thought ...very nice going forward....then it changed.  The t144 not too dissimilar to UKMO but roundness and angle of the LP approaching moreso on ECM not looking like it would disrupt/slide/shunt SE.  It pushes through us with the core sat above Scotland to bring westerly flow but then hits a wall in North Sea and goes nowhere and it has no follow up trough from the Atlantic to assist it so it stays in situ and becomes flabby.  The block to far NE in arctic Russia initially subsides at t168 to allow the trough to push through us then re-asserts backing/ridging west.  It is this point at t168 where I believe that we will see the ECM back off and the trough won’t push through but will start to disrupt and slide over us, at worst, or to our West.  The op is not an outlier I know but as we’ve seen that has meant diddly this winter....it could very well be right but I don’t think it will be.

ukmo t144

ECM t144

 

similar but for me UKMO doesn’t have the same t168 and 192 as the ECM written on it.  And looking at GFS ensemble and GEM ...well let’s see where this goes.

 

 

t168

t192

t216

 

going nowhere but look at the Atlantic, nothing and look around Svabard on t240...block re-asserting

Imminent deep freeze I’m not projecting...remaining well within the game I am.

BFTP

Want to come back to this....here is today’s ECM at t120 which was the t168 in above post.

looks so much better doesn’t it ?

Here is the t168 from Monday

BFTP

Edited January 27, 2021 by BLAST FROM THE PAST

[Paul]

5 minutes ago, Noob said:

As a complete noob ( yes we were all one once ) but do the models share each others data when coming up with their charts ?

Welcome to the forum

The models will share a lot of the same input date (from weather stations, flight data, satellites, balloons etc) but will use differing amounts and some different types. They'll also use different methods for feeding that into the model, then the models themselves each have different physics etc. 

Hope that helps. 

[Methuselah]

10 minutes ago, chionomaniac said:

Anyone in the south, who says this is a poor run for us, needs to look at the bigger picture and look at the synoptic evolution and avoid the 850’s. We have a wonderful looking NH profile, very post SSW look to it.

Just look at the Arctic high being matched by the eastern Iceland high. Great alignment to deliver long lasting deep cold to all areas of the UK. The Atlantic low here is set to trigger the colder air further south, and encourage a deep cold air flow across the warm North Sea.

Of course this wonderful scenario may not come to fruition, but lots of variations would still deliver.  A good day with the models, and one I have been waiting for ( expecting) for a while now.

It's a stonker. But I'll nae get over-excited just yet; this time tomorrow, perhaps?

[in the vale]

43 minutes ago, Cold Winter Night said:

they all have those heights to our NW-NE, the low heights in N-America and in Siberia/Ural, and that persistent Arctic High

This is the key point for me. I know we're all looking for snow, (ECM = great weekend for me) but, if these bigger pieces of the jigsaw actually fall into place (and there are increasing hints that they might), we could be looking at something quite spectacular. Actual and forecast PV stress is dropping that chunk into our half of the globe and the forecast disturbance of those persistent heights over the Urals could create mayhem here if the die all fall right. Unlikely, but it would be fun. 

Edited January 27, 2021 by in the vale

[Lord Grogon]

25 minutes ago, Richard Fisher said:

Yes very poor ECM for Midlands south cold rain. Can someone explain why the borderline between snow or rain seems to be consistently modelled to change to snow around the midlands north?

My non scientific guess is that it hits a sweet spot of elevation + distance from sea + the definition of “Midlands” being quite a large area.

It’s also only really a factor for fronts approaching from a W/SW (ish) direction which there have been quite a few of recently.

I’m sure there is a better way of explaining this though.

[Noob]

Thanks for the replay Paul, so if thats the case how come models can show complete opposites at the same time frame ? Is there some human input involved or more a case of models see outcomes differently ?