Model output discussion - into the start of Winter

[mulzy]

The extended EPS looks good to me - low heights over Europe, higher than normal heights to the west and north and way out east.  That's a cool / cold signal for the foreseeable.

[Scott Ingham]

1 minute ago, stewfox said:

Some members are saying it is going to snow from friday based on the charts and some say cold rain. Looking at 850s some say too high and you need -10c some -2c. The PPN requirements for snow have been explained. 

Is looking out the window still the best option on the day ? Or standing on the roof to get extra height ??

 

Its extremely marginal. The dew points and very low heights are catching my eye in particular... its 60/40 on cold rain but it was 80/20 on cold rain yesterday 

[northwestsnow]

1 minute ago, mulzy said:

The extended EPS looks good to me - low heights over Europe, higher than normal heights to the west and north and way out east.  That's a cool / cold signal for the foreseeable.

We could even see a UK cold pool develop ..

[Allseasons-Si]

1 minute ago, mulzy said:

The extended EPS looks good to me - low heights over Europe, higher than normal heights to the west and north and way out east.  That's a cool / cold signal for the foreseeable.

Thanks Mulzy,that's very nice to hear

[Scott Ingham]

1 minute ago, northwestsnow said:

We could even see a UK cold pool develop ..

Every chance mate...

[feb1991blizzard]

8 minutes ago, Weather-history said:

 

For instance, this ensemble gives 26cm of snow for my area

 

 

 

Not sure about your altitude, not sure what it gives for my location but i do know it would be bunkum here, as 6" has happened once in 42 years and anything much more hasn't happened for nearly 60 years.

[northwestsnow]

4 minutes ago, Scott Ingham said:

Its extremely marginal. The dew points and very low heights are catching my eye in particular... its 60/40 on cold rain but it was 80/20 on cold rain yesterday 

Agreed.

Altitude will of course play a part... next 24 hours fascinating model watching...

[Froze were the Days]

It's like pulling teeth watching the ecm currently...going nowhere fast, chilly with rain 2.0 (the cold kind) unless you live on an elevated hill or peak

[West is Best]

3 hours ago, Steve Murr said:

 

All joking to one side those 10-20 mile increments have added up to a fairly substantial change to a colder theme giving way to a higher threat of snow.

 

 

I don't think this is wholly true. The trend has been and continues to be away from cold. The one good bit of news is that the 12z operational was on the mild side in FI, even at one moment a brief outlier. But the ensembles continue to show a wide scatter with more and more mild runs appearing and the cold snap is less sustained as the Atlantic returns. In the short term the operational was less supported, with a significant number of milder runs. The general trend is way from anything too dramatic. A colder snap, certainly, from Friday to Sunday but nothing to get too ramped about. Very early days in winter terms and all that.

Snow will be in short supply with such warm North Sea temps. It will only really be apparent above 300 metres, elevation which doesn't exist in East Anglia. 

 

Edited November 30, 2020 by West is Best
Adding chart

[Allseasons-Si]

NAO/AO tanking

If these upgrades keep on coming in then i might have to change my avatar...

now where's my car

[stodge]

Evening all

On the cusp of winter so we can probably expect raging zonality, a large European HP and long-fetch SW'lies with temperatures well above average. It often happens early in December but will this year be different?

Last night's 12Z output was far removed from that but the evolution from the weekend trough disruption was far from clear. Some were complaining at what looked a less-than-stellar E'ly while hints of a returning Atlantic as a response to a Siberian warming were also evident for mid-month.

What of tonight - seasonal or just "teasonal" ?

12Z GEM - the trough collapses south on cue and is quite an unpleasant figure by T+96 bringing plenty of cold rain and some wintriness to higher ground. We don't get the clean shift to the south we've seen on other outputs leaving the LP to fill at first in situ and by T+144 it's over the northern North Sea. However, the next Atlantic LP duly slides SE to or just over Ireland before easing further south as heights build nicely to the north of the British Isles. By T=240 pressure is rising over Scandinavia with 1035 MB over Norway and a strong ridge west across Scotland to the Azores HP ridging north. Signs of the PV over NE Canada however and the notion of battle to be joined between the conflicting airmasses. Again, there's no especially cold air over the British Isles at T+240 but Scandinavia is becoming increasingly cold which will help block durability.

 

12Z GFS OP - by T+96 the LP is centred more or less over my house (well, east London) so may be a day to stay indoors and stay dry. The next 72 hours sees the LP try to extend south into Europe but retreat back into the North Sea remaining as the dominant feature so keeping most of the British Isles cold and unsettled. By T+240, the evolution has changed. A new LP centre originally forming over eastern Spain has finally pulled the trough into Europe and a weak narrow ridge of HP has developed across the British Isles between the Azores HP and Scandinavia but the Atlantic trough is now showing signs of positive re-alignment and two small LP centres are over Iceland and heading NE. By T+312, an Atlantic LP has crossed Northern Britain with a strong NW'ly flow to its southern and western flanks but signs of cold are fast disappearing with the PV now looking to be back over Greenland and NE Canada. At the end of FI, LP is over northern Scandinavia and between that and the Azores HP, we have a WNW'ly flow - nothing remarkable to be honest. As an aside, the 10HPA stratospheric forecast continues to suggest weak warming from both Europe and Siberia in FI which might explain the re-consolidation of the PV over Canada.  It's also fair to say Control goes a very different route.

12Z ECM - the fly in the ointment or the partridge in the pear tree? No surprises out to T+96 and as with other models the trpugh becomes a complex feature close to the British Isles by T+144 before re-forming over or just to the east of Scotland briefly before finally clearing away. However, the evolution to T+240 is messy and the final frame leaves us many more questions than answers. Is the LP over Iceland going to slip SE through the British isles into Europe? The PV looks nowhere near as strong as on GFS so could we see more amplification in the Atlantic? Control sends it south before building the HP close to Ireland by T+240 so the airflow remains from the north west or north. 

Conclusion - I can't help but feel it's a step back for coldies tonight. GEM is good albeit with little cold air. GFS hardly screams zonality but the Atlantic and the PV are back and we are relying on enough residual heights over Scandinavia to encourage negative alignment. ECM is similar but a notch better and it may be this pattern of the trough sinking through the British Isles may be something we'll see for a while and that's not wholly discouraging. The mid-Atlantic build of heights is much less pronounced tonight on ECM and GFS but there's still plenty of interest. 

[Scott Ingham]

4 minutes ago, northwestsnow said:

Agreed.

Altitude will of course play a part... next 24 hours fascinating model watching...

Very fascinating. Any snow cover will only help any potential cold pool. If we can stay in a holding period week 2 and be patient a snap could evolve into a spell

[Scott Ingham]

7 minutes ago, West is Best said:

 

I don't think this is wholly true. The trend has been and continues to be away from cold. The one good bit of news is that the 12z operational was on the mild side in FI, even at one moment a brief outlier. But the ensembles continue to show a wide scatter with more and more mild runs appearing and the cold snap is less sustained as the Atlantic returns. In the short term the operational was less supported, with a significant number of milder runs. The general trend is way from anything too dramatic. A colder snap, certainly, from Friday to Sunday but nothing to get too ramped about. Very early days in winter terms and all that.

Snow will be in short supply with such warm North Sea temps. It will only really be apparent above 300 metres, elevation which doesn't exist in East Anglia. 

 

There are also considerable members below the op 4th and 5th... this is the time frame we are looking at and the op is a mild outlier in the outer reaches

[Tim Bland]

Even if the Atlantic comes back in a week or so it probably won’t be for long. A weaker-than average stratospheric vortex looks odds on with these zonal wind speeds, some show a reversal by mid mid month..

[SMU]

Hot off the press ECM zonal forecasts showing a continuation of the deceleration of the zonal wind with the mean reaching towards 20M/S late december

Great trend

[Bradley in Kent]

Trend is your friend, although because cold weather goes against the tide I would put more bets on the 3 mildest runs vs the three coldest runs. 

As others have said, if just a few models / runs predict Atlantic dross, they're 9 times out of 10 correct in the end.

[Allseasons-Si]

Latest EPS(i don't have access to the extended) shows just where all the action is taking place(our part of the NH) with strong +ve heights in the Atlantic/Scurasian sector with strong -ve heights disrupting into Europe with trop pv still forecasted over asia and not getting a foothold anywhere near Greenland/N America,interesting times.

  

Edited November 30, 2020 by Allseasons-si

[Scott Ingham]

2 minutes ago, Steve Murr said:

Hot off the press ECM zonal forecasts showing a continuation of the deceleration of the zonal wind with the mean reaching towards 20M/S late december

Great trend

This is why it is so important to keep this scrussian high/Aleutian low combo. Im very optimistic for mid to end of January I have to say

[iceman1991]

8 minutes ago, Steve Murr said:

Hot off the press ECM zonal forecasts showing a continuation of the deceleration of the zonal wind with the mean reaching towards 20M/S late december

Great trend

How reliable is this Steve ? 

[weirpig]

16 minutes ago, Tim Bland said:

Even if the Atlantic comes back in a week or so it probably won’t be for long. A weaker-than average stratospheric vortex looks odds on with these zonal wind speeds, some show a reversal by mid mid month..

Crikey  could be a  bonanza  end of January if that happens   right in the heart of winter      strange goings on this winter.

[karlos1983]

30 minutes ago, West is Best said:

 

I don't think this is wholly true. The trend has been and continues to be away from cold. The one good bit of news is that the 12z operational was on the mild side in FI, even at one moment a brief outlier. But the ensembles continue to show a wide scatter with more and more mild runs appearing and the cold snap is less sustained as the Atlantic returns. In the short term the operational was less supported, with a significant number of milder runs. The general trend is way from anything too dramatic. A colder snap, certainly, from Friday to Sunday but nothing to get too ramped about. Very early days in winter terms and all that.

Snow will be in short supply with such warm North Sea temps. It will only really be apparent above 300 metres, elevation which doesn't exist in East Anglia. 

 

 

30 minutes ago, Allseasons-si said:

NAO/AO tanking

If these upgrades keep on coming in then i might have to change my avatar...

now where's my car

Upgrade or trend away from cold... which one is it the newbies scream.?

personally I’d say it’s neither, short term it’s been quite a consistent picture for the end of the week, we are in the almost cold enough for all category, but it’s going to feel a lot colder than of late. Question remains where we go next week, but currently a mild outlook looks unlikely, as does anything remarkably cold & snowy. 
 

lamp posts definitely on standby for some as we approach the end of the week though. That’s good news for week 1 of Winter in my book
 

[Allseasons-Si]

Latest clusters...

[SMU]

13 minutes ago, iceman1991 said:

How reliable is this Steve ? 

Seems better than CFS

ICON 18Z Gives the ENE a big thwack of snow- although I wouldnt rule out corrections SE still

[sheikhy]

1 minute ago, Steve Murr said:

Seems better than CFS

ICON 18Z Gives the ENE a big thwack of snow- although I wouldnt rule out corrections SE still

Looks same as 12z although maybe slightly deeper low and further south!!

[weirpig]

4 minutes ago, sheikhy said:

Looks same as 12z although maybe slightly deeper low and further south!!

Plentyof precipitation around on the icon   pivoting  from the east across the midlands   in -4  to -6 uppers  across the sine of the country    

Edited November 30, 2020 by weirpig