Model output discussion - into the start of Winter

[Hotspur62]

4 minutes ago, Allseasons-si said:

Latest clusters...

You have to say they look pretty good for the UK And think some parts of the Uk have a fair chance of seeing some snow in the first half of December.As ever the devil will be in the detail and the models are already struggling with events on Friday!!Just nice to start winter with below average temperatures something which has been lacking in the last 5 or 6 decembers.

[Mike Poole]

23 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

Yes, this is very interesting and to some extent expected given the persistent Aleutian low, Russian high in the trop output.  But two major winter forecasts came out today, the MO contingency planners one, which is awful both because it predicts a mild wet winter and because they’ve changed the format so dumbed down it’s now the ladybird book of a 3 monthly forecast, see my post in the MO thread.  The other major forecast is of course the netweather one, and while I agree with the idea of a colder December, I was struck by the absence of any real discussion of effects of a SSW for later in the winter, and I think a SSW is a very real possibility.  The disconnect between the strat and trop seems to be growing stronger rather than weaker at the moment:

ECM mean still absolutely resolute about keeping the trop PV away from the Greenland / Canada area, euro trough exactly where we want it as others have said.

Personally I think it would be very foolish to give this winter a 5% chance of being in the coldest quintile, but what do I know

[nick sussex]

The ECM looks a lot better this evening and starts to develop low pressure to the south further east towards northern Italy .

Earlier quite a sustained spell within a slack flow of sub zero uppers . It’s quite a complex set up , the main thing is no deepening of any shortwave energy over the UK which could mix out the surface cold which normally develops in these types of set ups during the winter.

By day ten low pressure tries to move in from the west , that should disrupt and send energy towards that low pressure in northern Italy nearer the time.

Models tend to send too much energy ne at longer range so as long as you keep low pressure anchored in northern Italy and some blocking to the east then closer in they should start resolving that .

Overall although there’s not the deep upper cold to draw on certainly potential is there for an interesting spell of weather coming up.

[bluearmy]

34 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..

This is now a consistent forecast from the 46.  No model is likely to strongly predict a reversal a month or more out but this likely weak upper vortex should allow blocked patterns in the trop to continue (or reform if we go zonal for a period in December)

it should be noted that the 46 maintains a low height anomaly of some kind to our south out to new year ....

[Matt H]

The ECM monthly is looking tasty!

[weirpig]

Icon  brings  snow  showers into Wales  early thursday morning  pushing into central areas  and northern areas by midday Thursday  

[damianslaw]

Short term - complex set up. Models showing the trough dropping directly through the UK, trend ever so slightly further east, and my hunch is it will be a bit further east than currently projected. Models appear to be backing away from a deepening situation, more of a stretched low pressure splitting in situ somewhat and heading south towards central Europe.

Longer term - heights look like building somewhat to the north, with the jet aligned NW-SE so any further  frontal attempts will most likely head on a NW-SE alignment, meaning a generally cold spell.

 

[northwestsnow]

5 minutes ago, bluearmy said:

This is now a consistent forecast from the 46.  No model is likely to strongly predict a reversal a month or more out but this likely weak upper vortex should allow blocked patterns in the trop to continue (or reform if we go zonal for a period in December)

it should be noted that the 46 maintains a low height anomaly of some kind to our south out to new year ....

Jesus mate I just spat my night time coffee out reading that last paragraph..

[Allseasons-Si]

2 minutes ago, bluearmy said:

This is now a consistent forecast from the 46.  No model is likely to strongly predict a reversal a month or more out but this likely weak upper vortex should allow blocked patterns in the trop to continue (or reform if we go zonal for a period in December)

it should be noted that the 46 maintains a low height anomaly of some kind to our south out to new year ....

Blimey!!!

a lock-in anyone,not that we are locked in anyway

jokes aside

this is good news for an extended Dec cold spell in my book

not getting excited though as things can put the mockers on this tiny blighty little island but i am slightly excited

[Mr Frost]

Here are the latest ECM monthly temperature (T2m) Anomalies - weekly breakdown below! Anyone for a below average December and a pretty decent start to January? 

07/12 to 13/12

14/12 to 20/12

 

21/12 to 27/12

28/12 to 03/01

 

04/01 to 10/01

 

As ever subject to change!

Lovely to look at though! 

Edited November 30, 2020 by Mr Frost

[Man With Beard]

26 minutes ago, Allseasons-si said:

Latest clusters...

Cluster 1 is a coldies dream - link up of heights to the north, trough underneath.

Other clusters have potential but no knockout.

[sheikhy]

2 minutes ago, Mr Frost said:

Here are the latest ECM monthly temperature (T2m) Anomalies - weekly breakdown below! Anyone for a below average December and a pretty decent start to January? 

07/12 to 13/12

14/12 to 20/12

 

21/12 to 27/12

28/12 to 03/01

 

04/01 to 10/01

 

As ever subject to change! Lovely to look at though! 

18z ukv out yet mate?love your updates!!hopefuly we get a snowy one in your next!!❄!!18z gfs here we go....

[northwestsnow]

EC 46 is suggestive of a UK cold pool IMO, ie stagnant air ....

 

[BlueHedgehog074]

1 hour ago, syed2878 said:

 I think that the GFS today 12 hours run is thought of in line with thoughts from the Met they are going for slightly above average 10th from mid December onwards let’s hope the four once are wrong mind you they did stress it’s a low confidence forecast

Low confidence seems to be the main thing really. Don’t have anywhere near the knowledge of that of the Met Office, although anything could happen really during that period. My personal feeling though is that we will continue to see the Azores High displaced to our West with further Low Pressure dropping down towards us and into the nearby continent. 

That ECMWF mean is encouraging with the area of Low Pressure maintained to the South-East of the UK and should keep the Azores High held up to our West. Although I would have loved to see a little less in the way of cyclonic activity to our North-West, the fact the blue and purple monster remains stuck on the other side of the Northern Hemisphere is a plus. Should prevent the Jetstream upstream on our side of the Northern Hemisphere from powering up too much throwing constant beastly Lows towards us from the Atlantic keeping the pattern as flat as a carpet.

It is a little bit of a delicate balance I feel. Any over estimation of the trough signal over Europe and the under-estimation of low heights over Greenland and Canada, then there’s a risk of the pattern getting shifted further East with a milder, Westerly, Atlantic drivern pattern trying to spill back through. (Unless the Scandinavia or Russian High puts up a big fight, or the Azores can manage to directly ridge over the UK).

Despite the mean not going out as far as mid-December at the moment, I think there is more in favour of some kind of cool and meridional sort of  pattern continuing, than a raging Atlantic one. With other charts posted above supporting further blocking opportunities. Is far away to get too preoccupied about and things can quite easily change, but is nice to see and fun to discuss. 

[weirpig]

few images from the 18z icon. Just for fun  but a quick rundown  of the snow showers  for the end of the week.  Turning from rain to snow  across east of the country   and then turning heavy  as it makes itsway across  west and North   quite a few  could see heavy snow   away from lowland east  anglia  and the south east  which could be rain.

Edited November 30, 2020 by weirpig

[feb1991blizzard]

11 minutes ago, weirpig said:

Icon  brings  snow  showers into Wales  early thursday morning  pushing into central areas  and northern areas by midday Thursday  

 

 

And brings a countrywide tonking of epic proportions a day later.

[sheikhy]

Icon gives 15-20cms of snow widely across england just 3 or 4 days from now!!!surely not

[Snipper]

I look at this thread every year. Quite happy to caught up with the excitement. 
 

How does this year’s prognosis compare with others at this time of the year in recent times?  So often much enthusiasm at the start of the winter when sadly later on it is often a matter what if or what could have been. Then where is my therapist. 
 

Is anyone brave enough to take a punt at us having a cold winter of note?  Bookmakers have reduced the odds for a white Christmas I believe. 
 

 

[northwestsnow]

1 minute ago, sheikhy said:

Icon gives 15-20cms of snow widely across england just 3 or 4 days from now!!!surely not

I'd be a little wary of that mate...

[Daniel*]

The colder signal is strengthening EPS now showing a maximum of 3C in London on Friday. 
 

[northwestsnow]

1 minute ago, Snipper said:

I look at this thread every year. Quite happy to caught up with the excitement. 
 

How does this year’s prognosis compare with others at this time of the year in recent times?  So often much enthusiasm at the start of the winter when sadly later on it is often a matter what if or what could have been. Then where is my therapist. 
 

Is anyone brave enough to take a punt at us having a cold winter of note?  Bookmakers have reduced the odds for a white Christmas I believe. 
 

 

first half Dec will come in cold...rest of winter no idea ! 

[Allseasons-Si]

1 minute ago, Man With Beard said:

Cluster 1 is a coldies dream - link up of heights to the north, trough underneath.

Other clusters have potential but no knockout.

Yes it is and in the minority too,i hope this continues

we deserve this after so so long without a cold spell,well maybe not that long ago but it feels like an eternity

but let's not get ahead of ourselves just yet,yes there are some snow chances/potential at the end of the week and into next weekend and this is the focal point at the moment,what happens after that,who knows,one hurdle at a time i would say but there is certainly better looking prospects going into next month

[northwestsnow]

1 minute ago, Daniel* said:

The colder signal is strengthening EPS now showing a maximum of 3C in London on Friday. 
 

Yes thats cold,esp for the city .

Rural areas lower, esp further North ...

[Eskimo]

Be careful with the latter stages of the ICON precip charts - they switch to low-res and blow up the precip rates. 

[Mapantz]

I think @Mr Frost posted this earlier today, but to reiterate, take any models showing snow accumulation with absolute caution: