Model Output Discussion - Colder but how cold and for how long?

[Bricriu]

Just now, mountain shadow said:

So, the straight Northerly is now in the bin.

Looks like we're coming to a solution now

1. Poor Northerly with snow confined to NE Scotland.

2. Then mostly dry for a day or so before somewhere gets impactful snow

3. Snow quickly gone as Atlantic returns.

Hardly worth the build 

 

 

1 minute ago, bluearmy said:

That’s the glass half empty end of the envelope - yes 

I am sure someone  will mention ensembles showing otherwise and that there is no trend, but that's two GFS runs, along with the ECM and EC46 showing a more westerly influence for the final week of January.  Also John Holmes indicated this might happen too. On a more positive note any westerly influence  will hopefully be brief. I don't think I could take another lengthy Zonal period.

[mountain shadow]

There has to be a flooding concern for Southern areas, if there is a very heavy snowfall followed by heavy rain and a rapid melt of the snow.

 

[joggs]

1 minute ago, Bricriu said:

 

 

I am sure someone  will mention ensembles showing otherwise and that there is no trend, but that's two GFS runs, along with the ECM and EC46 showing a more westerly influence for the final week of January.  Also John Holmes indicated this might happen too. On a more positive note any westerly influence  will hopefully be brief. I don't think I could take another lengthy Zonal period.

Just hope the next low after mid next week disrupts and keeps us cold.

[Uncertainty]

26 minutes ago, Kasim Awan said:

Edit: not engaging in this, bit of a silly comment, if you want to contest what I am saying then use logic and evidence not bullying tactics.

Kasim your views and knowledge are more than welcome here. I for one have learnt a great deal from your posts since you stated up on here. I think you give a balanced and unbiased view whereas although I do try to I am clearly in the cold crew and post far more frequently when things look good

No sugar coating from me tonight though in the extended - The eps is showing what the 46 has shown for many days. A relaxation -  as I alluded to a few weeks ago - in the pattern and a strong westerly flow. This has been well advertised across all suites and you can look to the mjo in p4 for a simplistic explanation. 

Here’s the p4 Nino composite - never been a good phase for me in winter.

 

should this happen (it really should) it is NOT the end of winter. On the contrary, the signal for blocking to reinitialise end of Jan / early Feb (assisted by downwelling waves from above - the drip on the PCH plots) and the passage of the mjo to the WP is consistent. 
 

In the meantime, next week’s low is the big chance for many. They often go south, but at face value the models are suggesting just n of the m4 is the current sweet spot.

Finally, the 18z mean looks more wedgey ( and colder) but be careful what you wish for - as @Met4Castsays, one more big shift south and you can wave your historic snow event goodbye! 

18z

 

12z

 

[Allseasons-Si]

The control has the low further SE than the 12z

The mean is colder,...probably tracking the mid week storm further south.

the ens for London are colder than the 12z via this midweek storm compared to the 12z...

 

Edited January 10 by Allseasons-Si

[Bricriu]

3 minutes ago, joggs said:

Just hope the next low after mid next week disrupts and keeps us cold.

I hope so too. I would like some snow of course, but I would be happy  if we could hang on to the cold and dry weather at the very least. We just said goodbye to the puddles, so i don't   want to see them back for a good while.

Edited January 10 by Bricriu

[Met4Cast]

Just now, steveinsussex said:

@Met4Cast care to comment?

GEFS are a substantial improvement over the 12z with no mild incursion into much of the south and the mean remaining below -5C during the period of interest. Deterministic run is going up.. the mean is dropping deeper into the cold.

[kold weather]

4 minutes ago, Kasim Awan said:

A significant number of GEFS members now produce a NW-SE runner which originates from energy over Iceland around the 120-150h mark. Some parse it into a front, and some keep it's circulation entact as a shortwave low.

What is also of interest is the fact these GEFS members also struggle to process the potential big snow maker trough further North East, indicating that a more southerly track of the Azores low also increases the chance of this runner to develop well into the UK. 

Just looking through the ensembkes and the amount of runs that don't have any sort of major low at all, and indeed some literally have nothing and just a pure northerly again.

They really are struggling with what is to be fair a hugely complex evolution with about 4-5 different delicate moving parts.

[Cheshire Freeze]

5 minutes ago, mountain shadow said:

There has to be a flooding concern for Southern areas, if there is a very heavy snowfall followed by heavy rain and a rapid melt of the snow.

 

This is my concern.

Some places could be under water by the end of next week.

[Ali1977]

Control sends the low south - it’ll be Sunday by the time we really know 

[markw2680]

Yes personally I’d love the big snow dump but we are talking 7 days away. Things will change every day regarding where will have snow. It’s extremely difficult to forecast snow even the day before. I’ll never forget going to bed one night with loads of snow forcast only to wake up to wet floor the whole lot went further south and we missed the lot.

point is there’s no point in over analysing anything that far out

[steveinsussex]

1 minute ago, Met4Cast said:

GEFS are a substantial improvement over the 12z with no mild incursion into much of the south and the mean remaining below -5C during the period of interest. Deterministic run is going up.. the mean is dropping deeper into the cold.

And the Westerly influence towards the end of January? 

Just now, Ali1977 said:

Control sends the low south - it’ll be Sunday by the time we really know 

This is what ‘normally’ happens in the summer months

[ICE COLD]

The mean is actually really good at day 8 . 

[feb1991blizzard]

1 minute ago, Met4Cast said:

GEFS are a substantial improvement over the 12z with no mild incursion into much of the south and the mean remaining below -5C during the period of interest. Deterministic run is going up.. the mean is dropping deeper into the cold.

Yes, not even hard to spot -  -8c much further south AS A ENS MEAN, not a million miles of South coast.

[seabreeze86]

The APERGE continues to show a much stronger block and a cleaner northerly 

[Purga]

A zonal hell train in FI and a nascent Bartlett. Thank goodness it's all so uncertain as reflected in the ECM ENS!

 

[Ice Day]

I'd say that's a strong signal for cold out to 192 on the GEFS.  Anything further is just not worth worrying about at this point.

[Allseasons-Si]

The gfs was way in la la land on the ens,...bodes well in keeping the low further south...

that is a good ens set for London BTW

Edited January 10 by Allseasons-Si
typo

[Met4Cast]

Just now, steveinsussex said:

And the Westerly influence towards the end of January? 

I've flagged this possibility a couple of times but just to extract a portion of a post I made on Sunday;

Quote

 

Worth noting the MJO is just 1 variable within the broader windflow (GSDM) budget so shouldn't be taken in complete isolation. I flagged the 20-25th on Twitter as a period where the jet may begin to edge northwards as blocking wanes, this suggests to me the potential for high impact snow events as weather systems hit the colder air across the UK (Indeed, Tamara echoed this in her earlier post here). 

With Atlantic weather systems comes the potential for milder air depending on exactly how/where they track and something that wont be resolved for at least another 7-10 days. A waxing and waning of blocking seems likely but plenty to suggest renewed blocking into February as per @Catacol's (I believe?)  post earlier today.

 

The MJO continues eastwards and blocking is never sustained forever, it will relax and that will allow the jet to nudge a bit further northwards, however; I'd not buy into any output beyond Wednesday next week at this stage, we need to see how any wedges left to our north come into play, this could have fairly big impacts for the weather we see in the UK. 

As outlined earlier today by Tamara, Catacol & Matt though, any waning of blocking will likely be temporary with renewed blocking likely into early February. the mid-extended range remains very uncertain and open to substantial shifts within NWP modelling. Blocking WILL relax, but that doesn't automatically mean mild, wet & Atlantic driven, the jet should remain south shifted..

[Rain All Night]

1 minute ago, Ice Day said:

I'd say that's a strong signal for cold out to 192 on the GEFS.  Anything further is just not worth worrying about at this point.

Is that your location?

[ITSY]

Spot the outlier. An excellent set there for the week ahead - remember when people kept shouting about day 10? - and a reminder that the disruptive snowfall may be good for some but for the vast majority, the prolongation of the cold could bring far greater opportunities and interests down the track. 
 

[Met4Cast]

For those mentioning the GFS 18z det being part of a trend..

Yeah, not so much! Very tight cold clustering, det is outlier territory.

[Metwatch]

7 minutes ago, Cheshire Freeze said:

This is my concern.

Some places could be under water by the end of next week.

Perhaps if the low does end up missing the UK entirely it's for the greater good of anyone living close to rivers / is a farmer. It would give some more time to stay much drier under cold Arctic air with any precipitation coming in the form of showers from the sea.

Edited January 10 by Metwatch

[tight isobar]

1 minute ago, Met4Cast said:

For those mentioning the GFS 18z det being part of a trend..

Yeah, not so much! Very tight cold clustering, det is outlier territory.

Cracking set out to the 19th

[Jason M]

We want the low to go south. This is a really pivotal moment in the season and if we can get the low south many more snow chances will follow for all I suspect.