Model Output Discussion - Into Winter

[phil nw.]

1 minute ago, Kasim Iberian Heights Awan said:

If this winter is going to deliver we need cold weather firmly within 240H. Today's ECM would likely go on to produce further mild conditions.

We don't know that.Given the chaos in the changing pattern before day 10 maybe it's best to comment on what we can see.

[winterof79]

48 minutes ago, Kasim Iberian Heights Awan said:

The guaranteed cold spell churned out a flat run

Thats the 6th of Jan which guaranteed cold spell was this

[tight isobar]

17 minutes ago, nick sussex said:

The ECM looks a mess with a lot going on.  Day 6 into 8 is a shortwave frenzy. 

I think it’s for the cat litter tray.

I doubt we’ve seen anything close to the correct evolution this evening from any of the outputs .

Too many things going on behind the scenes .

 

 

.. the energy dynamics are on the sauce 12z ecm.. the ens should highlight this!.. 

[mbrothers]

6 minutes ago, Kasim Iberian Heights Awan said:

If this winter is going to deliver we need cold weather firmly within 240H. Today's ECM would likely go on to produce further mild conditions.

That doesn’t make any sense. So we have to have cold weather before 6th of January or winter is done? 

[Daniel*]

Kasim no doubt would have dismissed cold potential in Jan 2013. On occasion things can work in surprising ways under the right background conditions. 

[Kasim Awan]

2 minutes ago, mbrothers said:

That doesn’t make any sense. So we have to have cold weather before 6th of January or winter is done? 

In general we need good consistency for cold within 240H otherwise we'll be after the carrot all winter.

Just now, Daniel* said:

Kasim no doubt would have dismissed cold potential in Jan 2013. On occasion things can work in surprising ways under the right background conditions. 

Not dismissing the potential, only saying that the wheels are wobbly right now, we need more grounding in cold from the NWP before getting excited.

[bluearmy]

good eps

v good extended clusters 

[damianslaw]

Where does the ECM 12z op sit within its ensembles? Outlier or not?

I remember that op run showing ridge / heights to our north for current timescales, I think at 10 days, alas we have a deep low instead.

Edited December 27, 2023 by damianslaw

[AO-]

EC12 looks like a missed opportunity. The low at the second of January should go more South in order to facilitate the hp over Scandinavia to expand south as well. It is no done deal yet. Wait for the EPS to see how the operational fits.

[Daniel*]

No real complaints here.. 2m temp anomaly out to 11th Jan on 12z EPS mean the first week of Jan is looking overall colder than normal especially further north, with cold deepening and becoming more widespread into week 2.

[TSNWK]

4 minutes ago, bluearmy said:

good eps

v good extended clusters 

So ecm op mild outlier? Which would steady the nerves for some 

[josh-weather]

Latest from EC46. So it moved like the EPS did. Though I'm definitely not qualified to say what the implications are!

https://charts.ecmwf.int/permalinks/mean-zonal-wind-at-10-hpa-extended-range-forecast-64400

 

[bluearmy]

Ec46 as expected on ssw

the heights through Jan looking pretty good 

tomorrows met office update will be really interesting as will show how glosea sees the downwelling from the warming irrespective of it not being a technical ssw 

Edited December 27, 2023 by bluearmy

[Kasim Awan]

Just now, TSNWK said:

So ecm op mild outlier? Which would steady the nerves for some 

The op is around 1-2C above the mean, making it a milder solution but not unsupported.

[bluearmy]

1 minute ago, TSNWK said:

So ecm op mild outlier? Which would steady the nerves for some 

Extended clusters are post day 10 

[Mike Poole]

There’s an awful lot going on at the moment, at different timescales and in different places.  Here’s how I see things:

There is a high probability of a significant cold spell starting early in the new year.  There is also a reasonable chance that it may last (with one or two wobbles) into the spring.  But we have some hurdles to get over first.

So how have we got here and what’s in our favour?  Take a step back from the UK for a moment, and this winter has one stand out feature, a weak polar vortex, in the troposphere that is one that can’t find its usual home, in the stratosphere, that is one that has already suffered a Canadian warming, is now under attack, and on the ropes.  We have an easterly QBO, and we have El Niño, which favours cold in the second half of winter.  We add to that (finally) a more amplified MJO in Phase 1, and rising AAM to put the atmosphere in tune with that El Niño.  

There is a timetable as to how this is likely to unfold:

• Forget the next 9 days, there is nothing to see here!
• About 10 days from now, model runs indicate that high latitude blocking will take hold in the European sector.  How exactly that happens depends on luck - where a ridge punches through, we’ve seen all the outcomes on the various op runs recently.  Provided that happens, could be Greenland (more likely, think GFS 12z), could be Scandi, possibly with retrogression (less likely, think yesterdays pub run).
• At about the same time, a warming event in the stratosphere is taking place, it may or may not be a technical SSW, but it will ensure a weak vortex for the foreseeable.  The models are backing off from a split SSW that looked to me a couple of days ago like it could lock in a -NAO until spring; this backing off may mean it happens later - perhaps when we need reinforcements, I’ll come back to that - or it could mean it is less powerful.  There’s also the possibility that a less than convincing split leaves a remnant of the strat vortex near Greenland where we don’t want it.  None of that is likely to markedly impact the next 3 weeks though, for good or bad.
• The AAM surge may continue, the MJO will move away from favourable phases in time, this might be the optimal time to benefit from a SSW, we can’t be choosers in this, but what I am highlighting here is the possibility that things might work constructively if we can get this winter evolution off the ground in the first place.

Finally, I leave you with the ECM extended clusters, at day 15 you have a choice of cold, cold, cold or cold:

[MJB]

1st - 8th 

8th-15th

1st - 8th

8th - 15th 

No point in going further a field 

[Cold Winter Night]

EPS clusters:

120h-168h the clusters are not far apart.

192h-240h there is only one cluster, in line with ECM Operational. I think the Op is overall a good representative of the ensemble.

In the extended we see the Northern blocking truly develop. Clusters 1, 3 and 4 have low heights over Europe and/or Iberia.

The De Bilt plume shows the ECM as middle of the pack for 2m temps, not much spread; the extended is where interest lies.

[london-snow]

1 hour ago, Met4Cast said:

Ensembles ensembles ensembles. 

Det runs will chop & change between runs probably quite dramatically. One early concern is the lack of “deeper” sub -10C isotherm runs we’re seeing. 

Given how favourable background conditions are, if we’re struggling to get deeper cold in despite that then we really are in trouble. 

Could it be that the background signals that may well play a major part into jan is playing catchup? 

[tight isobar]

A few snapshots of the f-12z eps!.. they speak for themselves!! Lat AT block and an open door for arctic/conti- arctic incursion!!.. ..

[feb1991blizzard]

8 minutes ago, josh-weather said:

Latest from EC46. So it moved like the EPS did. Though I'm definitely not qualified to say what the implications are!

https://charts.ecmwf.int/permalinks/mean-zonal-wind-at-10-hpa-extended-range-forecast-64400

 

The implications are the split SPV is a definite bust which probably means we wont see persistent HLB and therefore long lasting severe cold but the Met Office are bullish about spells of below average temps and wintry hazards for from sooner than week 2 for more or less the rest of jan so it doesn't mean winter is over like some on here will no doubt call.

[bluearmy]

9 minutes ago, Cold Winter Night said:

EPS clusters:

120h-168h the clusters are not far apart.

192h-240h there is only one cluster, in line with ECM Operational. I think the Op is overall a good representative of the ensemble.

In the extended we see the Northern blocking truly develop. Clusters 1, 3 and 4 have low heights over Europe and/or Iberia.

The De Bilt plume shows the ECM as middle of the pack for 2m temps, not much spread; the extended is where interest lies.

Day 10 doesn’t  look like single cluster territory to me but day 8 does ….. I’d have expected more than one cluster from that so probably more than six 

[tight isobar]

Just now, feb1991blizzard said:

The implications are the split SPV is a definite bust which probably means we wont see persistent HLB and therefore long lasting severe cold but the Met Office are bullish about spells of below average temps and wintry hazards for from sooner than week 2 for more or less the rest of jan so it doesn't mean winter is over like some on here will no doubt call.

.. with an arctic profile in forward situ.. mlbs will be ‘more’ than amicable- on the swing

[AO-]

6 minutes ago, Cold Winter Night said:

 

The De Bilt plume shows the ECM as middle of the pack for 2m temps, not much spread; the extended is where interest lies.

About that. The EPS for The Bilt is a little worse than this morning. The warmer intermezzo gets more support in the latest run. But it's no done deal. Having said that, there is quite some agreement between GFS and EC 

 

[tight isobar]

Mid southern England horizontals.. we’ll take that… going forward…@12z-EC