The hunt for cold - Model discussion (late November)

[Nick F]

Some cold trying to sneak in from the north next week on the 06z GFS between system to the west and a that low manages to go west to east over the UK toward the North Sea/Low Countries before coming against a growing high pressure block over Russia.

One thing that looks increasingly gaining traction in the model output  is an uptick in the upper westerlies working through from N America and across the N Atlantic - thanks to sub-tropical westerly momentum from El Nino over the Pacific. Whether this westerly burst in the jet buckles as it hits blocking over the far N Atlantic, as per 00z EC, or goes under the blocking as per 00z/06z GFS as a southerly tracking jet into mainland Europe - is where the operationals seem to be divided. 

MJO moving through 6-8 in coming days would favour northern blocking and -NAO as we head into early December, but this doesn't rule out a west based -NAO, as some output has suggested, unfortunately.

 

Edited November 21, 2018 by Nick F

[Methuselah]

Just now, weirpig said:

Im probably the odd one out   but i like the GFS 6z run  ok its not great for cold lovers, But plenty of weather going on with the low situated over us  with a brisk wind  maybe even snow showers as the low pushes towards the east bringing down a brief northerly    Whatever the Temperature shows it certainlly wont feel that warm.  Interesting weather.

But it gets better (?) in the long term...

Keep an eye on the cold pool to our northeast...It probably won't exist on the 12Z!

[Northwest NI]

16 minutes ago, Weathizard said:

It’s a transient northerly, fairly common practice when a low moves in during winter months... I agree the models are a bit clueless at the moment but I do think we are converging on a less favourable outcome for cold lovers

I am shocked at this.

not.

[summer blizzard]

5 minutes ago, Ed Stone said:

But it gets better (?) in the long term...

Keep an eye on the cold pool to our northeast...It probably won't exist on the 12Z!

As mentioned, the 6z is very similar to the GEM0z. 

We do however need rid of the Salvabard Low which develops at day 6..

Because even if it ensures a longer draw northerly, by day 10 it means there is no high to the north of our low to fight.

[bluearmy]

Eps clusters this morning ........ well we have lost one so down to five .....the op is in cluster 1 out to day 7 and then drops to cluster 5 thereafter ..... none of the larger  clusters is big enough to take precedence 

 the clusters are offering huge variations in upper flow solution and anomaly placement ......... I would forget any forecast past day 5 at the moment .......... put your money on the uk staying under a blocked regime ..... that covers the euro ridge, the scandi ridge, the sceuro ridge, the east Atlantic ridge and even the Icelandic ridge ....... there is a chance that the trough sets in over us but given that Exeter haven’t mentioned this as likely within the next fortnight, I suspect mogreps doesn’t see it 

Edited November 21, 2018 by bluearmy

[carinthian]

On ‎20‎/‎11‎/‎2018 at 07:28, carinthian said:

Morning all , another spell of snow arrived overnight. Think there is a bit more than 10cm accumulated snow in the village. Current temp -7C. Quick view at this mornings models and looks like an improvement from last nights regarding the hunt for cold, especially from ECM latest run. However, the pick again is the UKMO which has shown consistency in its runs out to 144t and that's to hold the colder scenario over much of your part of the world with the flow still backing. Will get an update from the forecast team over here later this morning regarding their further thoughts ( see above post ) for you guys and hopefully some pictures of the very welcome snowfall in these parts. All snow guns working as well for piste preparation that is now well under way. Time for my daily bacon and eggs, Yorkshire tea, which I bring back from blighty in great supplies. Continental tea, crap!

C

 

Model charts  168t-240 t  always fringed with marginal outcomes , especially with an entrenched colder block in situ.  It is a brave call by some to think a Northerly or Easterly is unlikely in this period. As our (gallpohile ) 300mb jet still favours a southerly track into France and Euroland  with possible disruption. Speaking to the team a few minutes ago, their model still shows a low around day 8 or 9 in the vicinity of Denmark. Longer term has lower pressure over Europe and still hold the resilient strong Arctic ridge with possible Scandinavian High cell to form in its latter time span (15 days ) but think low confidence this far out.  In the shorter term, still some movement for change over SW Britain with a increasing prospect of mild v cold scenario to develop  rather than a quicker transient to mild Atlantic flow. We will see.

C

[Methuselah]

There isn't any consistency (run-to run) at all: it's either Snowmageddon or a further delay in applying the winter duvet...Take your pick!

Edited November 21, 2018 by Ed Stone

[Rayth]

Excellent insight again @carinthian , I remember the model you used last winter done well on the face of it , given what you were posting , does the model verify well? 

[bluearmy]

28 minutes ago, carinthian said:

Model charts  168t-240 t  always fringed with marginal outcomes , especially with an entrenched colder block in situ.  It is a brave call by some to think a Northerly or Easterly is unlikely in this period. As our (gallpohile ) 300mb jet still favours a southerly track into France and Euroland  with possible disruption. Speaking to the team a few minutes ago, their model still shows a low around day 8 or 9 in the vicinity of Denmark. Longer term has lower pressure over Europe and still hold the resilient strong Arctic ridge with possible Scandinavian High cell to form in its latter time span (15 days ) but think low confidence this far out.  In the shorter term, still some movement for change over SW Britain with a increasing prospect of mild v cold scenario to develop  rather than a quicker transient to mild Atlantic flow. We will see.

C

Where does this day 8 low come from?   Is it one that has been spewed out by the Atlantic trough and trundled along beneath the block ??  Alternatively, there are model options that show the main Atlantic feature barrelling through to reach Denmark by day 8/9.  Two quite different scenarios played out .....

Edited November 21, 2018 by bluearmy

[frosty ground]

It's a shame we don't have 20 Ensembles like this

 

 

[winterof79]

Reading the thread I would say there is more Shannon entropy with some of  the posters interpretation of the charts than in the models at moment

We're  never going to be far away from a battleground scenario over the next two weeks meanwhile the continent cools further and heights wax and wane to our North

Edited November 21, 2018 by winterof79

[carinthian]

18 minutes ago, Raythan said:

Excellent insight again @carinthian , I remember the model you used last winter done well on the face of it , given what you were posting , does the model verify well? 

Thanks .Its good to have the insight and ear of a forecast team. Their model, I know is singular  and  updated on a daily 24 hour span, which is much less than some of the bigger models (ie ) UKMO. I have no access to verification results but we in resort are very happy as it is all part and parcel of its portal service. We do not have access to view their charts ( apart from those produced by its fine mesh snow model ) but importantly direct access to a member of the forecast team.

 C

Edited November 21, 2018 by carinthian

[mb018538]

ECM ensembles looking fairly atlantic based out to day 15 at the moment - there is still one reasonable sized cluster that promotes stronger heights:

[Methuselah]

7 minutes ago, winterof79 said:

Reading the thread I would say there is more Shannon entropy with some of  the posters interpretation of the charts than in the models at moment

We're  never going to be far away from a battleground scenario over the next two weeks meanwhile the continent cools further and heights wax and wane to our North

Agreed. And that scenario fits nicely between the extreme solutions the models are currently producing? IMO, none of the present evolutions is ever going to verify?

PS: I hope the new GFS keeps beating the others.

Edited November 21, 2018 by Ed Stone

[carinthian]

18 minutes ago, bluearmy said:

Where does this day 8 low come from?   Is it one that has been spewed out by the Atlantic trough and trundled along beneath the block ??  Alternatively, there are model options that show the main Atlantic feature barrelling through to reach Denmark by day 8/9.  Two quite different scenarios played out .....

Hi Blue, that feature of a low around Denmark has been on going for a while, so I would assume nothing to do with what is shown on the latest GFS run. Our model has shown consistency over its 24 hour update spans as opposed to the bigger GFS more frequent runs. . That's not to say it will verify of course.

C

Edited November 21, 2018 by carinthian

[Nick F]

Looking at 00z EPS T2m for London - 00z EC and GFS operationals on the mild side of the ensemble spread between 29/11 and 01/12 - which indicates they maybe too progressive in introducing milder SWly airflow, big spread developing by 29th too.

00z GEFS postage stamps days 5-6 show quite range of evolutions for the Atlantic low to the SW and the high pressure to the N

Conclusion from this mornings runs:

• Increased westerly momentum in upper flow over the Atlantic towards western Europe next week
• Uncertainty beyond day 5 where the increased westerly burst will go against block close to Nern UK next week (over or under?)
• Therefore, low confidence past day 5 on track of lows off Atlantic into Europe next week and resultant flow direction across UK
• Potential for -NAO to continue until end of month, but could become more west-based as block moves west to Quebec = milder for UK

[Derecho]

Well just to confuse things further in here, these are the updated 06z swingometers

After a very poor set on last nights 18z's the 06z's are remarkably now showing more colder options for the start of December then mild. This has implications for further out although it will probably take a while before a consensus emerges here as it is December 6th:

Global temperature anomalies 0.46C above the long term average but cold anomalies building to our east early next week due to the Atlantic being held back:

[snowangel32]

Well first Snow flakes of the winter here. Clear for anyone to see how hard models are struggling with the evolution leading into winter. It looks way better than previous years the PV has took a kicking and blocking still looks the overall theme we would have banked this last winter.

[karlos1983]

I think the EC ENS graph sums up the current output post D7 quite nicely ......

UNCERTAIN! 

Although definitely colder members appear to be growing in numbers, compared to recent runs..

 

Edited November 21, 2018 by karlos1983

[Man With Beard]

1 hour ago, bluearmy said:

Eps clusters this morning ........ well we have lost one so down to five .....the op is in cluster 1 out to day 7 and then drops to cluster 5 thereafter ..... none of the larger  clusters is big enough to take precedence 

 the clusters are offering huge variations in upper flow solution and anomaly placement ......... I would forget any forecast past day 5 at the moment .......... put your money on the uk staying under a blocked regime ..... that covers the euro ridge, the scandi ridge, the sceuro ridge, the east Atlantic ridge and even the Icelandic ridge ....... there is a chance that the trough sets in over us but given that Exeter haven’t mentioned this as likely within the next fortnight, I suspect mogreps doesn’t see it 

Yes you've summed it up well there - here's the past two cluster sets for D9 (30th November)

  

The big dilemma is where to place heights to the N / NE. The ECM clearly has no clue. 

However, the charts suggest quite a lot of precipitation nearby. Probably rain but cold north westerlies, or even easterlies, can't be discounted, so snow sufficient conditions remain on the table, especially for higher ground in the north. That's about the best I can come up with from these.

Oh, and hope this is allowed - for all those who thought the recent synoptics would be insufficient for snow - even the snow-starved Isle of Wight managed a covering of snow last night for a time.

Edited November 21, 2018 by Man With Beard

[Ali1977]

12 minutes ago, karlos1983 said:

I think the EC ENS graph sums up the current output post D7 quite nicely ......

UNCERTAIN! 

Although definitely colder members appear to be growing in numbers, compared to recent runs..

 

Interesting ENS graph , the only real cluster within that mess is a cold one hovering around freezing. Some big swings still possible, although no cold to note on METO long range. 

[tight isobar]

40 minutes ago, karlos1983 said:

I think the EC ENS graph sums up the current output post D7 quite nicely ......

UNCERTAIN! 

Although definitely colder members appear to be growing in numbers, compared to recent runs..

 

As do these...

Massive scatter and uncertainty!!

Clueless as we stand!!!

[Purga]

Not for this thread I know, but worth mentioning that Exeter / MOGREPS are sticking to their guns re: a temporary mobile milder spell up to about mid December. Cold settled (i.e. blocked) conditions resuming thereafter.

The ENS still show the uncertainty.

Even at the end of the GFS 06z run the NH profile shows a disorganised vortex profile which is far away from the standard 'zonal'.

 

[Summer Sun]

The 7-day 2m air temperature anomaly looks fairly close to average for the majority a few areas are marginally above average & marginally below average but on the whole around average for most

The 2m air temperature trend is on the up for the UK and western Europe

Edited November 21, 2018 by Summer Sun

[shaky]

12 minutes ago, tight isobar said:

As do these...

Massive scatter and uncertainty!!

Clueless as we stand!!!

Mate if the 12z gfs goes with one of the colder options around the 27th i can imagine this place to be buzzing!!some of the ensembles get close to -10 around that date!!i think if we are goin to see upgrades it has to start with the 12zs this evening or i think the chances of milder coming through even for a while will be high!!