Model Output Discussion - Into Winter

[Vikos]

1 hour ago, Mike Poole said:

Can’t help feeling that the situation in the USA is massively important if we are to see the current evolution upgrade into an epic cold spell over here (I’m not talking about the Christmas timescale here).  So I hope there is record warm across the pond!

We may be looking down the barrel of a loaded gun… a massive displacement of the tPV towards Eu/scandi may be, and this mild interlude is just cocking the hammer? 

1 hour ago, Mike Poole said:

Can’t help feeling that the situation in the USA is massively important if we are to see the current evolution upgrade into an epic cold spell over here (I’m not talking about the Christmas timescale here).  So I hope there is record warm across the pond!

We may be looking down the barrel of a loaded gun… a massive displacement of the tPV towards Eu/scandi may be, and this mild interlude is just cocking the hammer? 

1 hour ago, Mike Poole said:

Can’t help feeling that the situation in the USA is massively important if we are to see the current evolution upgrade into an epic cold spell over here (I’m not talking about the Christmas timescale here).  So I hope there is record warm acr

Edited December 13, 2023 by Vikos

[offerman]

39 minutes ago, TillyS said:

This remains a stubborn high to our south. Yes, northerly incursions are perfectly possible from this but there is an almost entire absence of northerly blocking at the moment, so don’t hold out high expectations right now. The typical scenario with this would be a couple of days of polar maritime chill before mild air returns from the north-west.

 

No blocking = no prolonged cold

This is often the problem, we need that high to our south to either move far westward or migrate northwest or northeast to bring in the colder weather

[Vikos]

Maybe we need a new thread, this one isn’t loading properly? @admins

[Tim Bland]

Just to set expectations ; I can’t see any models showing widespread snow and ice days over Christmas for the majority away from Scottish / welsh mountains. I’ve seen these “PV sinking south over the uk brining snowy conditions”  many times on the models over the years,  and usually it’s watered down and snow is limited away from usual high ground. 
 

What we are seeing is a mainly north westerly flow (occasionally north) with a mix of rain and sleet showers for most and snow for high ground. Temps around 4-6c during the day for most.   IF we are lucky enough to get a low slipping further south and dragging in a northerly there’s a chance of some snow on the northern edge …

[bluearmy]

12 minutes ago, IDO said:

I have been watching the tPV for a few days, hoping the Arctic high will sink into Siberia/Russia, propping up that high, a trigger block to enable the Euro trough. The D1-D8 GEFS mean highlights this:

 

That retrogresses the Euro high back west. The ebb and flow of the tPV, rather than sub-tropical forcing, that's still MIA. So, it's a bonus.

Lots of uncertainty post D8, macro and micro and a watching brief for the time being. Timing and the reaction of the trough and Euro high could make a big difference to what we experience. As this is the machinations of the cycling of the tPV, I am more inclined to believe that this will be a shorter cold spell for some, but maybe other background forces can increase the longevity...

Perhaps a good time for the spv and tpv to couple with the fairly benign upper strat flow feeding down into the trop  ?  That would help the pattern to stick. 

 

[TauntonRoss]

I think the charts look good this morning, everything is trending downwards to a colder outlook, the PV displacement is good and what is happening in the states seems to be on our side for once.

[E17boy]

Morning peeps,

Well the models are showing something more seasonal as we run up to Christmas. However we need to sit tight on our seats. People in the south will probably be wondering what the sudden fuss is all about and right so as down here eg London we don’t normally benefit from a NW airflow. 
 

So the way I am seeing this is yes if we do get the PM shots it will bring temperatures down and feel more seasonal. However at the moment I am not seeing any sign of widespread snow or severe cold, especially here in. London. What happens from here who knows but we need to again watch with great caution it may be a 2 or 3 day colder snap and then we have the normal Atlantic coming back. We would all wish that this leads to something more sustained but just got to see how the pattern evolves and where Mr High pressure decides to go.

I will end the above with a slightly cheery note. I can’t remember what year it was but we had a similar patter n a NW airstream covered the Uk with a high out to our W SW.Then that NW airstream turned into a northerly as the and eventually the high migrated the Scandinavia and winds turned to a bitter NE and that bright widespread snow and severe cold. Forgive me as I can’t remember how far back this was but this setup did happen many years ago. So where we go in the current model output is up for grabs but things can even from these setups turn in our favour.

Have a great Wednesday all

THE SEARCH FOR OUR WINTER WONDERLAND CONTINUES 

regards

[carinthian]

Morning all, some interesting charts this morning. The incoming cold coming shown at various rates with the GEM the most progessive and ECM slowly heading there. I draw your attention to the chart below (GEM op at 168T) . As also shown on the UKMO extended and ECM  ,there is a formation of what we used to call a "curveball low " that forms along the top  of the Huge Mid - Atlantic High between Southern Greenland and Labrador. It develops where the thermal gradient and pressure gradient is greatest and its this formation that can be rapid as highlighted in the post yesterday by @Nick F. So just another feature to watch with interest over the coming days but from a coldies point of view encouragingly improved charts from all the models this morning. However, for real cold I would like that Scandinavian trough to eventually dig south prior to Christmas   and that would up the snow stakes for many in UK/ Euroland.

C

Edited December 13, 2023 by carinthian

[MattStoke]

18 minutes ago, Tim Bland said:

Just to set expectations ; I can’t see any models showing widespread snow and ice days over Christmas for the majority away from Scottish / welsh mountains. I’ve seen these “PV sinking south over the uk brining snowy conditions”  many times on the models over the years,  and usually it’s watered down and snow is limited away from usual high ground. 
 

What we are seeing is a mainly north westerly flow (occasionally north) with a mix of rain and sleet showers for most and snow for high ground. Temps around 4-6c during the day for most.   IF we are lucky enough to get a low slipping further south and dragging in a northerly there’s a chance of some snow on the northern edge …

Seen snow here almost every time there's a north westerly during the winter months, and I'm far from being up a mountain.

[Mike Poole]

This morning’s clusters from T192:

Not entirely sure what to make of them, so I’ll just make one observation.

I think what stands out is the T264/day 11 charts - there is consensus across the 4 clusters that the PV has moved east and drained from Canada and Greenland.  There has been this trend on the models to properly move the PV east for some days now, we’ve talked about it in here, but it has been uncertain - I think we are now in a position to say this is very likely to happen.  And it may bring with it cold and possibly snow to some in the UK.  But what is of interest to me is what happens next to the PV?  Does it regroup and head back home, in which case it is not clear much has been gained?  Does it remain displaced?  How do the MJO and AAM uncertainties play into that?  Does it pay us a proper visit (can’t discount this)?  What is the role of the strat, and the interesting developments up there (near SSW at the end of last 2 GFS runs), and how does that factor in to the positioning of the trop PV for the start of January?  More questions than answers at the moment.

[TEITS]

Nice to see an improving trend since I last posted. If the output continues then its the type of weather pattern when in locations such as mine you would struggle to acknowledge the cold spell whilst experiencing max temps of 6C and sunshine. However exposed locations to the NW,ly who are at higher elevations could be facing white out conditions and heavy snowfalls. You can guarantee some idiots will need rescuing in the scottish mountains who ignore the likely warnings.

A few more things to keep an eye on.

Wind could be a major feature as some ensembles have much deeper low pressure than the operationals. Any snowfall may not be restricted to high ground as depending on the timing and intensity could bring snowfall to lower levels. Possible low pressure running across the S of the UK around Xmas. Could either bring a snow event or a rain turning to snow as the low clears E.

[booferking]

50 minutes ago, Tim Bland said:

Just to set expectations ; I can’t see any models showing widespread snow and ice days over Christmas for the majority away from Scottish / welsh mountains. I’ve seen these “PV sinking south over the uk brining snowy conditions”  many times on the models over the years,  and usually it’s watered down and snow is limited away from usual high ground. 
 

What we are seeing is a mainly north westerly flow (occasionally north) with a mix of rain and sleet showers for most and snow for high ground. Temps around 4-6c during the day for most.   IF we are lucky enough to get a low slipping further south and dragging in a northerly there’s a chance of some snow on the northern edge …

Best leave that opinion to the people that live in the areas that this type of setup suits im low laying and well inland and will do quite well from this if it pans out like some charts show merry christmas

[syed2878]

Looking at today’s zero hours runs from GFS, and to an extent ECMWF. I think we can have 30 maybe 40% confidence in getting something called for next week it certainly ties in with forts from Exeter in the text forecast from yesterday if you read the text. It also says that chances of cold increases later on in December and beginning of Jan 2024 they do, however state that on balance it could remain mild

[TSNWK]

00z uppers from day 9 - dispite the eye candy synoptics the uppers are rather underwelming.. flatters to deceive in my view..

[Catacol]

1 hour ago, Mike Poole said:

I may be missing something here, but the BOM plot seems to disagree with the ECM 46 plot about - the past, let alone the future.

I'd probably stick to this chart.

 

ECM bias corrected is now broadly in line with the BOM. The difference they have is around amplitude. We wait to see.

[northwestsnow]

All things considered this could be a very snowy  xmas set up for the likes of @Kasim Awan

@MattH amongst others in the community.

Certainly a cyclonic  NWly with uppers around -5 /-6 should in theory produce very good results 250m asl and above ...

[BartyHater]

2 steps forward overnight, but a definite step back on the 06GFS at 162hrs, which is considerably flatter than its 00 counterpart.

Lets see how the rest of the run pans out, but those stubborn Euro heights look like delaying the colder push S a bit on this run.

Edited December 13, 2023 by BartyHater

[warrenb]

The big difference between ECM and GFS is the modelling of the pole, by 240 the GFS has split the PV whereas the ECM has it strengthening. When looking at the charts, don't just look at the Europe view, also take into account the Northern hemisphere view.

What I am saying is (excuse the pun) they are polar opposites of each other and one is going to have to give.

[TSNWK]

12 minutes ago, BartyHater said:

2 steps forward overnight, but a definite step back on the 06GFS at 162hrs, which is considerably flatter than its 00 counterpart.

Lets see how the rest of the run pans out, but those stubborn Euro heights look like delaying the colder push S a bit on this run.

looks ok to me if anything the the trough is making better progress south towards iberia on this run to my eye 

[northwestsnow]

6z brings lots of snow showers to elevated NW Britain and on the 22nd brings a period of snow for SW England

Edited December 13, 2023 by northwestsnow

[January Snowstorm]

Just now, northwestsnow said:

6z brings lots of snow showers to elevated NW Britain and on the 22ns brings a period of snow for SW England

No snow with those uppers other than the very highest ground. Gfs can be quite misleading in its ppn type charts

[TSNWK]

Just now, January Snowstorm said:

No snow with those uppers other than the very highest ground. Gfs can be quite misleading in its ppn type charts

I intially agreed on uppers of around -5 not cutting it for most - however there is something about thicknesses as well that need to considered and might by more important under such low pressure?

 

[bluearmy]

Just now, January Snowstorm said:

No snow with those uppers other than the very highest ground. Gfs can be quite misleading in its ppn type charts

With low heights and slp, the freezing level will be lower than the uppers indicate - where the flow relaxes a bit I’d expect to see snow in the northwest to reasonably low elevations 

[northwestsnow]

Don't be fooled by the moderate uppers  the low thicknesses are at play 

The surface temps with uppers around -5 gives these  surface temps

Look at Ireland as santa prepares his sleigh

[Chesil View]

Interesting little feature runs from western N. Ireland to Paris on the gfs 06z around 240 /264