Model output discussion - Post SSW - Will it turn cold?

[bluearmy]

9 hours ago, blizzard81 said:

But the whole reason we view the ops in high anticipation is the fact that they are run at a much higher resolution. If an op run vears off on a different tangent within the first 4 to 5 days I thought we had always been told to sit up and listen. The opposite advice seems to be dominant tonight. It's 'bin the ecm op' as it is not in line with the rest of the suite. 

and it’s seems we should in this instance. A ridge again getting between the Canadian vortex and the developing system headed ne to prevent phasing and the jet streak from the vortex has to pretty well all go ne rather than be spread se aswell. given that ukmo agrees with this then WAA attempt number one is a fail but number 2 is likely to be fairly close behind. 

The way that the gfs/gefs and ecm op are modelling the strat in the mid term are pretty different with ec far more attentive to to Canadian vortex poking its nose into the Atlantic sector - even moreso then it’s 12z run which is visible this morning on Berlin. 

The icelandic clusters were late last night but now we can see them, there was 52% agreement on the initial WAA making it around day 6. Things remain ok in general for a sustained cold to very cold period though with fi ens generally bringing a strong cold euro trough sw from a developing Siberian vortex and the blocking headed further nw in time, would be nice to get the surface cold in so that any borderline events fall the right side. this is currently looking less like a settled cold period once the cold arrives. The modelling isn’t doing too well with its consistency (as expected during reverse flow and strong vortex remnant upstream) but broadly it’s on a path we can see. that’s clearly getting colder ...........

Edited February 14, 2018 by bluearmy

[winterof79]

30 minutes ago, Banbury said:

ECM @240 needs to get its act together 

Yeah shocking chart

[markw2680]

Although ecm is not as good this morning it still has the high going north eventually so I suppose if we are just looking for trends atm which is the safest thing to do then they all seem to be heading in the right way. Once we get high to the north it will only really go one way I’d think. And we won’t be complaining unless you like mild that is!?

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

Mean not as good as yesterday

[Summer Sun]

UKMO extended has the high a bit further south than GFS does this morning at t168 it might be a bit closer to ECM's run at t168 hard to tell until the NOAA chart updates

[Ali1977]

13 minutes ago, SN0W SN0W SN0W said:

Mean not as good as yesterday

No where near as good, clusters may be more informative 

[blizzard81]

Ecm looks to be watering down and delaying things again. Never a good sign. 

Edited February 14, 2018 by blizzard81

[bluearmy]

The eps further east with the mean ridge as they respond to the op direction of travel and delayed initial pulse of WAA and eventual neg tilted trough. Spreads are big and pretty indeterminate so I would be having a day off from too much analysis of the charts - the lunchtime Exeter 15 day outlook worth a read.  

[pureasthedriven]

2 minutes ago, bluearmy said:

The eps further east with the mean ridge as they respond to the op direction of travel and delayed initial pulse of WAA and eventual neg tilted trough. Spreads are big and pretty indeterminate so I would be having a day off from too much analysis of the charts - the lunchtime Exeter 15 day outlook worth a read.  

As is the existing over-nighter. Fairly instructive, I feel. Certainly favouring the slow ECM evolution for now. 

[Banbury]

1 hour ago, winterof79 said:

Yeah shocking chart

Certainly not as good that's for sure

[Sky Full]

For several days now the models have indicated that the SSW might begin to affect UK weather patterns by around the 23rd February.  Here are the charts for +216h (23/02) as of this morning:

ECM           

GFS            

GEM           

JMA.       .   

Now, correct me if I am wrong, but this looks like four very different solutions in nine days time although the JMA and ECM do have some agreement.  Unfortunately the UKMO does not go out this far so we can't use it to try and get some additional guidance.   I just don't understand how we can know which of these charts is the correct one, or if all of them are wrong at this distance.  Just because one might show the conditions we want to verify does not mean that is the correct prediction.  All the charts imply that cold conditions are likely but there is enough disagreement to suggest it could still go either way.  Whatever conditions I might wish for in late February, I am sitting on the fence until all the charts start to converge which might be a few days away yet.  

Edited February 14, 2018 by Sky Full
.

[karlos1983]

Anyone else got problems with GEFS ens graph on meteociel? Still showing me the 18z from yesterday 

[frosty ground]

1 hour ago, bluearmy said:

The eps further east with the mean ridge as they respond to the op direction of travel and delayed initial pulse of WAA and eventual neg tilted trough. Spreads are big and pretty indeterminate so I would be having a day off from too much analysis of the charts - the lunchtime Exeter 15 day outlook worth a read.  

Only a few days ago the much talked about Extended EPS went off on one, maybe its time we sop taking these things at face value.

[frosty ground]

1 minute ago, karlos1983 said:

Anyone else got problems with GEFS ens graph on meteociel? Still showing me the 18z from yesterday 

I can get them

[Summer Sun]

8 minutes ago, frosty ground said:

I can get them

Check the date bottom right

Today's 00z update

Edited February 14, 2018 by Summer Sun

[That ECM]

13 minutes ago, Summer Sun said:

Check the date bottom right

Today's 00z update

Good trend and arguably less spread at the end of the month as opposed to in 8/9 days time. Playing out the slower route or the quicker route but at this stage the end of the month looking cold.

Edited February 14, 2018 by That ECM

[karlos1983]

10 minutes ago, Summer Sun said:

Check the date bottom right

Today's 00z update

Cheers SS, Control was a peach then! Op went of on it's own little jolly at Blackpool pleasure beach again I see! Generally another very cold set especially towards the end! 

Edited February 14, 2018 by karlos1983

[stodge]

Morning all

Well, it's fair to say this site went through the emotional mangle yesterday. Stellar morning output followed by what seemed to many as huge downgrades but then discovering the Ensembles were even better than before.

Nonetheless, with volatility in abundance and nerves on edge, it all got a bit fraught so where are we this morning ? Whilst being totally aware of the volatility issues, I'm still going to take my medium-range look at the morning's output.

So I'm looking to the end of next week - Saturday February 24th to be exact - and as always I'm starting with the ECM 00Z output at T+240:

Not as strong for fans of snow as yesterday but the evolution to a Scandinavian HP remains albeit with less favourable positioning and orientation at this stage. A strong SE'ly flow across the UK so you'd think settled and reasonably mild (0 to +4 uppers suggesting temperatures well into the teens) but there's much colder air over Europe and heading our way.

GEM 00Z OP at T+240:

A complete change from yesterday. The attempt to push the Azores HP across the British Isles and into Scandinavia never gets started and instead LP develops over Scandinavia. There is strong HLB but it's currently too far away though there is a sign of a ridge building from the south to meet the ridge further north. There's a shallow LP in the North Sea so cold and damp conditions down the east coast and across Scotland but becoming more settled in the west. It's a dog's dinner of an evolution this morning and I'm far from convinced.

GFS 00Z OP at T+240:

This will have calmed a lot of frayed nerves this morning. The evolution is simple - the HP cell from the Azores north and then NW as northern blocking sets up based on Greenland. The E'ly is in place and the colder air is arriving - by T+240 -4 uppers across the country as a whole and -8 uppers crossing the east coast so much colder with the possibility of snow showers further south. Further into FI there's a chance of very snowy weather for the north while the cold lessens slightly and briefly in the south before a new pulse of colder air as the winds switch more NE.

GFS 00Z Control at T+240:

Another very strong chart for the fans of cold. It's slightly different to OP with more heights over Scandinavia but the jet is very far south. Further into FI the output remains stellar with the core of the HP retrogressing to Greenland and a hint of a disturbance developing in the Norwegian Sea and heading SSW toward the British Isles.

Looking at the GEFS for T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

That's a very strong and solid GEFS in support of the OP and Control with just two or three keeping the Atlantic in place. The lack of spread at this time is noteworthy.

By contrast, here's the GEM ENS at the same time:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=1&mode=1&ech=240

Much more variety.

In summary, the morning GFS output will have steadied nerves somewhat and the confidence in the GEFS behind the evolution is striking but, that being said, cross model consistency remains elusive. GEM OP goes a very different route and its ENS still have many options on the table including long fetch S'lies and SW'lies.

ECM is in a different place again this morning albeit with HP over Scandinavia and colder at the gates so I'd say two steps forward for the coldies this morning with the consistency across the GFS a huge plus. GEM OP sits and looks an outlier while ECM may or may not be indicative. Within the overall trend of volatility it's not a bad start to the day for cold fans though not as good as yesterday but a long way from some of the OP-led despair of last evening.

Buckle up, I suspect the ride is just about to start again.

 

[karlos1983]

So it seems the low pressure that exits the Mid Atlantic Coast of America at around +96 is quite important. I wonder what they make of it state side? 

[frosty ground]

14 minutes ago, karlos1983 said:

So it seems the low pressure that exits the Mid Atlantic Coast of America at around +96 is quite important. I wonder what they make of it state side? 

I thought it was the wave that develops on the western flank of the high and is driven around the high and forms a low that was the catalyst. (to drag the cold air westwards later on)

Edited February 14, 2018 by frosty ground

[johnholmes]

If the 24th is indeed the day for the cold to set in then it is a simple task from now on! Just keep checking each model -24 hours each day. If it is consistent then no problems, if not not then lots of temper tantrums I suspect.

My favourites for looking 10 days ahead are not consistent, at least the ECMWF version is not. NOAA looks the most promising if it is cold you crave. As always I check each one every day.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

Both the 6-10 and 8-14 show ridging in the required area

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

EC as commented on is somewhat different from 24 hours ago, GFS less so.

 

[Seasonality]

I wonder when the last time the GFS trumped the ECM and UKMO in such a set up is?

[Gael_Force]

It's like looking at an old picture in the negative! 

[Rayth]

Down down deeper and down 

get down , deeper and down 

I’m partial to a bit Quo

[Glacier Point]

Couple of observations here..

The magnitude and longevity of the stratospheric warming may favour a slower, much more assured downwelling zonal wind signal. Even at day 15 GEFS struggle to get 10hPa winds to revert back to westerly. Think of it as a flushing through the atmosphere - ideally looking for the upper layers to begin to cool in response to downwelling. This argues for a tropospheric response later rather than sooner, more towards month's end (and well beyond).

Like Brexit, the SSW has become the only game in town, but there are other factors we should have bandwidth for.

Angular momentum rose dramatically in January in response to a major MJO wave. The GWO responded with a classical high amplitude orbit.

However, phase 8 composites sifted for the La Nina years aren't what you would expect:

Transference of this to current situation makes this tricky, but the idea of not all of the atmosphere being totally cooperative to stratospheric lead should not be discounted.

That's the bad news out of the way.

The MJO is forecast to be centred over Africa and enter the Arabian Sea during week 2. 

The idea that it will become weakened is sound given the theory that a SSW will impact the tropics and reduce the scope for wave development.

So, a weakening tropical signal centred in phase 1 - 2 looks right. That translates to a loss in overall angular momentum and a more substantive negative tendency in angular momentum. Given we are still at relatively high levels of angular momentum, I would suggest a long phase 1 period upcoming, entering phase 2 final destination by months end into March.

The composites for March phases 1 and 2 sifted for La Nina bear much more resemblance to what extended GEFS and EPS are suggesting:

And factor in the impacts of the strat warming being timed at this time, which will likely excite this pattern.

So bottom line is that expectations in the next ten days may need to be a little reigned in, but thereafter....a strong, convincing signal for a genuine -NAO pattern to take hold.