Model output discussion - Closing in on Christmas

[Mucka]

2 hours ago, bluearmy said:

So you’re agreeing with me then mucka .....although I think you mean more ridge on its eastern flank ??

Yes of course less amplified upstream mean less amplified downstream but then hopefully the upstream block then deflects the jet se if the upstream is flattish and won’t do the job for us 

Yes except I think you left out an important factor when putting everything on the upstream pattern post 144. 

I am just saying the downstream pre 144 affects the amplification upstream because the more S the low drops the more the Azores high is displaced (squeezed) NW which affects the angular momentum of that low and amplification whatever is being modelled for it upstream.

Take this GFS run as a comparison.

Look at the angle of high/ridge in the Atlantic (I do mean to the W of the trough to our N) and how far South the trough is . The further S that pushes the more it displaces that high NW which means the next low running against a more amplified pattern

Now compare that chart with ECM this morning

Look at the same things. The trough is not as far S and moving a little more E rather than S because the ridge in front of it is stronger and deflecting it which means the high isn't squeezed NW.

The upstream lows have pretty much the same timing but one is being forced more NE because the Atlantic ridge is further N.

Yes that low will have slightly different angular momentum run to run as well which complicates things but basically the further N the Azores high gets displaced initially then the more likely that next low is forced up the NE coast of Greenland and not sneaking through to its SW to flatten the pattern.

 

[Tim Bland]

Still remarkable to see that chunk of the PV so consistently modeled to sit over us!..

[Scott Ingham]

Another thing to consider although miles away and probaboy mute for that reason is with the heights being so low the 850s around -3 to -5 will be sufficent for snow this time of the year. We wouldn't be looking at convection either as its an area of low pressure coming south from the pole. I think we need to stay on the fence but be glass half full here. Worse case scenario is a seasonal spell of weather with more oppoprtunities for upstream to play ball and a ssw (which i think is 85-90%) to come.

 

Wed have taken this when seasonal models were spewing out doomday +NAO scenarios. REALLY interesting set of 12z to come

[Scandinavian High.]

2 minutes ago, Tim Bland said:

Still remarkable to see that chunk of the PV so consistently modeled to sit over us!..

With that pv sat very close over uk what sort of weather conditions could uk experience thanks.

[Drifter]

Bizarre that so many on here are feeling downbeat this morning. Remember last winter vs what is projected here?

Edited December 19, 2020 by Blessed Weather
Unnecessary word removed

[Ice Day]

Now into FI, so just for fun, but we're possibly going to see the run of the winter so far here!

  

Proper cold approaching from the ENE

[bluearmy]

1 minute ago, Scott Ingham said:

Another thing to consider although miles away and probaboy mute for that reason is with the heights being so low the 850s around -3 to -5 will be sufficent for snow this time of the year. We wouldn't be looking at convection either as its an area of low pressure coming south from the pole. I think we need to stay on the fence but be glass half full here. Worse case scenario is a seasonal spell of weather with more oppoprtunities for upstream to play ball and a ssw (which i think is 85-90%) to come.

 

Wed have taken this when seasonal models were spewing out doomday +NAO scenarios. REALLY interesting set of 12z to come

Surface Thicknesses under the slow moving deep trough days 9/0 in the low 520’s ........  definitely suitable for snowfall without an onshore flow to moderate the temps near coasts

[Radiating Dendrite]

6 minutes ago, I remember Atlantic 252 said:

A bit like 4th Dec 2020? uppers look pants! FI I know

From memory we had uppers of around -2/3 on the 4th. These are a few degrees cooler with much lower heights. 

 

[snowice]

Not bad for just a week away.

[bluearmy]

Just now, Scandinavian High. said:

With that pv sat very close over uk what sort of weather conditions could uk experience thanks.

It’s no longer part of the pv but it contains some air that once was ........  have had this discussion before on here - some think it still is part of the pv but I think description of it as such misleads people as to what conditions really would be in winter actually under part of the vortex ....

[Scott Ingham]

4 minutes ago, bluearmy said:

Surface Thicknesses under the slow moving deep trough days 9/0 in the low 520’s ........  definitely suitable for snowfall without an onshore flow to moderate the temps near coasts

Yeah compeletely agree! Those thicknesses bring down the freezing level without the need for sub -8 upper air temperatures

[Methuselah]

So, here we are at Day 10... and what a right bloody mess, but at least it'd be a sleety, snowy mess?!

    

Could we tap in to that deep cold that's away to the NE? I certainly hope so! Though, for balance, we might end up with a 2018-19: Yes, yes, yes, yes, yeeesss... Oh dear - 21C in February?!

[Tim Bland]

6 minutes ago, Scandinavian High. said:

With that pv sat very close over uk what sort of weather conditions could uk experience thanks.

With low pressure systems spinning around and such low thickness then there would be some snow. Might not be ice days and could be a bit marginal at times but still a good chance die most

[Man With Beard]

Worth recalling a couple of things.

First, it is a good thing that the low at D8 is being modelled a little too far west for optimal cold - corrections are far more likely to push the low further east than west. Check some of model archives in the run up to 20-25 December 2010 - there was worry on here the pattern would go too far west, but come T0 it was bang on target.

Second, a deep low is like a mini altitude boost - 970mb allows snowfall at slightly lower levels than 1000mb, which is part of the reason some SE areas saw snow earlier this month with modest uppers.

No guarantees of course, but I think this pattern has legs

[Ice Day]

New Years Eve on the GFS 0z and 6z - I'd happily take either!  GFS sticking to its guns for now, let's see how the 12z's go

  

[nick sussex]

A nice GFS run but issues with the low not getting sufficiently se .

If that’s modeled to be a weaker affair and can centre further to the se then that would up the ante .

Regardless the infamous shortwave which tracks across the USA doesn’t support the UKMO solution and that’s a reason to be cheerful ! 

[Scott Ingham]

5 minutes ago, General Cluster said:

So, here we are at Day 10... and what a right bloody mess, but at least it'd be a sleety, snowy mess?!

    

Could we tap in to that deep cold that's away to the NE? I certainly hope so! Though, for balance, we might end up with a 2018-19: Yes, yes, yes, yes, yeeesss... Oh dear - 21C in February?!

That small low off the east coast which wont of course end up this way would in theory bring a swathe of snow across the isles on its western flank

[sheikhy]

Control going the same way

[Battleground Snow]

2 minutes ago, sheikhy said:

Control going the same way

Indeed and more importantly there are a few more ensembles following the OP compared to the 00z run... Could improve the long term mean slightly going forward

Edited December 19, 2020 by Battleground Snow
Typo

[feb1991blizzard]

We still can't seem to draw that -16c air over Norway towards us, no matter how good or poor the ridge is, not on ops or any ensemble members.

[sheikhy]

Just now, Mucka said:

I think the 00z ensembles were probably the best mean so far so let's see if we can beat it.

GFS Op runs have been very consistent but the ensembles have been dragging their heels.

Ensembles look better!!!if gfs 12z shows the same then i expect ecm to show a brilliant run this evening!!to be fair ecm was not far off at 168 hours!!

[BLAST FROM THE PAST]

GFS shows a strong ridge but doesn’t hold onto the true GHP and is gone come New Year.....but for us at that point it makes little difference for the Xmas week. It’ll just affect going into January....and that is still well into FI.  Very good run again, little details still to adjust but overall very good

 BFTP

[Scott Ingham]

4 minutes ago, feb1991blizzard said:

We still can't seem to draw that -16c air over Norway towards us, no matter how good or poor the ridge is, not on ops or any ensemble members.

Its not needed mate. See posts above. If it was february id agree we need it but not at this point of winter. 1963 didnt have the mega 850s the majority of time. In fact the best snow events were those with higher 850s

[Methuselah]

Well, I'd certainly take this... were on offer for tomorrow! All the ingredients are there: low heights, light winds, wintry precipitation and freezing fog... What's not to like?

    

[fromey]

Something else to add into the mix!!

Will it happen?? Only time will tell!

Edited December 19, 2020 by fromey