Model output discussion - 1st December onwards

[bobbydog]

3 minutes ago, blizzard81 said:

Have you been on the happy juice or something! If you read my post properly, you will see that I was making reference to a specific locale!

i did but have you missed the rest of the northern hemisphere?

[damianslaw]

Lots of topsy turvy scenarios from the models today - not surprised given we are in a changing period, with heights building strongly to our NE and the Jetstream forecast to nosedive southwards. What all models agree on is a general move towards more seasonal temperatures with polar maritime air embedding itself into the mix and quite possibly some frontal snowfall in the north (you don't need particularly low uppers to produce low level snow in the north - just an injection of polar air and heavy precipitation and you end up with evaporative cooling - the 12 Dec a classic example which on paper shouldn't have produced low level snow, yet did..)

ECM is showing the cold pool moving into a very favourable position for longer term cold prospects, GFS less so, but it too shows some notably cold air piling in from the NW. Any NW/N airstream here on in will be jolly cold, given how cold things have been to our north and north west in recent weeks - all bottled up and perhaps ready to spill out..

[knocker]

2 minutes ago, PerfectStorm said:

I literally said, the jet is further south than it normally is, which is a good trend. I don't know what you are grasping at here.

Okay it's no big deal I merely thought your original diagram incorrect and I don't think it is further south than it normally is and where it is now is not good. Doesn't really come under the category 'to grasp'.

[chionomaniac]

Those hoping for something from an easterly are probably likely to be disappointed. However, the Scandi block is the game changer for the whole NH profile. It pretty much transfers to a Kara Sea block with an extending arm towards Scandi, but it is disturbance of the whole NH vortex and transference of a strong positive AO to a strong negative AO that bodes well.

 

We are seeing an unusual disconnect between the upper strat and lower strat profiles. How often will we see a strong Kara Sea high anomaly centred directly below the strongest section of the displaced stratospheric vortex? Especially when the vortex has been at almost record strength?

 

 

Very unusual - as is the whole NH profile and this has been mentioned and discussed earlier in the thread. The Kara high will displace the vortex further away from the pole and the corresponding Canadian high prevent any reorganisation. With the MJO entering phase 8, a possible split in the residual lower strat vortex in the offing and the displaced trop vortex I think that we may be looking in the wrong direction. The ensembles are starting to hint at Greenland blocking by day 15 and I really think that this may be the where the block ends up by mid Jan. Lets see if the ECM weeklies can offer any support?

 

 

[The Enforcer]

15 minutes ago, 492 said:

Although I am unable to reproduce the fax charts here I have just toggled between the latest T+96 and the T+120 and was surprised to see such a dramatic westward extension of the cold air towards the UK by Saturday.

By your command:

 

[northwestsnow]

Are the FAX Charts out yet, crucial they look nothingvlike gfs at 96 

[blizzard81]

Just now, bobbydog said:

i did but have you missed the rest of the northern hemisphere?

No, not at all. Northern blocking, whilst increasing our chances of a colder spell, certainly does not guarantee one. We need heights to lower over southern Europe. This happens to a certain degree on the latest outputs but not enough I am afraid and certainly not in a sustainable way.

[fergieweather]

1 hour ago, knocker said:

The ext ecm in the later stages is going for the vortex N. Canada with a trough down the eastern seaboard and positive heights pushing up to the SW of the UK. This would portend drier conditions.

Indeed so. Ditto EC Monthly tonight (that's two or three successive runs offering same idea by mid-late Jan). 

Noteworthy is how over a good number of it's recent runs, GloSea5 has also leaned to the same outcome: i.e., +ve MSLP anomaly centred to SW of the UK, which - like EC Monthly - results in a successive week-by-week reduction in the recent/current/near-term conspicuous +ve PPN anomaly for much of the UK. Equally of note is how some recent deterministic runs of other models have begun showing the same net outcome in far reaches of their output.

EC Monthly has a cold anomaly over the UK by end of 1st week Jan (the first such signal yet this winter!) but then returns to +ve one as Jan continues, albeit rather masking a net NW'ly flow with anticyclonic regime dominating directly to SW/W. Of interest are striking height rises bisecting the pole by mid-late Jan, but these are subsequently lost or weakly reversed in model signal. 

However, there's a fair spread in stamps 17th Jan onwards (like GloSea) so whilst by that juncture we might reasonably steer towards climatology as fair guide for now, confidence is clearly lower thereafter (as you'd expect).  

What can we reasonably deduce?

- continued signal for something drier, at least for many parts of UK, as Jan progresses

- continued signal for +ve MSLP focused eventually to SW/W

- as per recent UKMO assessment, likelihood of any *sustained and/or pronounced* cold weather continues to look generally low over next 2-4 weeks, albeit superimposed over a colder phase early part of Jan, courtesy depression track running NW-SE across UK or just to S (as per some recent deterministic output)

Edited December 28, 2015 by fergieweather

[knocker]

Cheers Ian that saves me making my simplistic overview of the EC32.

Edited December 28, 2015 by knocker

[nick sussex]

Regarding the ECM 32 Ian did this pick up the Russian block? Given that this is catalyst for the jet running more nw/se.  In terms of the GloSea does this factor in the movement of the MJO?

[blizzard81]

6 minutes ago, fergieweather said:

Indeed so. Ditto EC Monthly tonight (that's two or three successive runs offering same idea by mid-late Jan). 

Noteworthy is how over a good number of it's recent runs, GloSea5 has also leaned to the same outcome: i.e., +ve MSLP anomaly centred to SW of the UK, which - like EC Monthly - results in a successive week-by-week reduction in the recent/current/near-term conspicuous +ve PPN anomaly for much of the UK. Equally of note is how some recent deterministic runs of other models have begun showing the same net outcome in far reaches of their output.

EC Monthly has a cold anomaly over the UK first by end of 1st week Jan (the first such signal yet this winter!) but then returns to +ve one as Jan continues, albeit rather masking a net NW'ly flow with anticyclonic regime dominating directly to SW/W. Of interest are striking height rises bisecting the pole by mid-late Jan, but these are subsequently lost or weakly reversed in model signal. 

However, there's a fair spread in stamps 17th Jan onwards (like GloSea) so whilst by that juncture we might reasonably steer towards climatology as fair guide for now, confidence is clearly lower thereafter (as you'd expect).  

What can we reasonably deduce?

- continued signal for something drier, at least for many parts of UK, as Jan progresses

- continued signal for +ve MSLP focused eventually to SW/W

- as per recent UKMO assessment, likelihood of any *sustained and/or pronounced* cold weather continues to look generally low over next 2-4 weeks, albeit superimposed over a colder phase early part of Jan, courtesy depression track running NW-SE across UK or just to S (as per some recent deterministic output)

Thanks Ian. Maybe the beginnings of that showing in the models from day 10 with pressure starting to rise over southern Spain. I guess this then pushes north west into the eastern atlantic. 

[Glacier Point]

12 minutes ago, fergieweather said:

However, there's a fair spread in stamps 17th Jan onwards (like GloSea) so whilst by that juncture we might reasonably steer towards climatology as fair guide for now, confidence is clearly lower thereafter (as you'd expect).  

What can we reasonably deduce?

- continued signal for something drier, at least for many parts of UK, as Jan progresses

- continued signal for +ve MSLP focused eventually to SW/W

- as per recent UKMO assessment, likelihood of any *sustained and/or pronounced* cold weather continues to look generally low over next 2-4 weeks, albeit superimposed over a colder phase early part of Jan, courtesy depression track running NW-SE across UK or just to S (as per some recent deterministic output)

And with a general slowing of the polar westerlies tied into a negative AO, reasonable to assume that the ridge to the near W/SW will unlikely stick around in that position for long. EC week 3 to 4 transition begins to angle the ridge a bit further north and west.

[chionomaniac]

4 minutes ago, nick sussex said:

Regarding the ECM 32 Ian did this pick up the Russian block? Given that this is catalyst for the jet running more nw/se.  In terms of the GloSea does this factor in the movement of the MJO?

Not convincingly at all Nick. And furthermore there is blocking anomalies to the WNW between days 16-20 before the signal is lost. hmm

The Kara Sea block's extending arm slowly fades and the Scandi increased heights are replaced by lower anomalies  but the AO is still negative as the blocking transfers to a more central Arctic area. There is a strong possibility of an Atlantic link up as the low heights transfer across to Scandi.

[Hotspur62]

Well , if  nothing else a drier theme would be most welcome with hopefully a gradual cool  down to average temperatures over next few weeks with a cold snap in early Jan possible. If this  pans out there will be many disappointed people here but we must respect Ian Fergusson"s expert views with the most likely outcome and thank him for sharing them on this forum. fwiw the last 3-4 days have shown there are still quite a few options on the table and looking past 7 days atm seems Long Range!!  

[knocker]

7 minutes ago, chionomaniac said:

Not convincingly at all Nick. And furthermore there is blocking anomalies to the WNW between days 16-20 before the signal is lost. hmm

The Kara Sea block's extending arm slowly fades and the Scandi increased heights are replaced by lower anomalies  but the AO is still negative as the blocking transfers to a more central Arctic area. There is a strong possibility of an Atlantic link up as the low heights transfer across to Scandi.

The AO goes positive after the 19th as does  the NAO.

Edited December 28, 2015 by knocker

[fergieweather]

10 minutes ago, nick sussex said:

Regarding the ECM 32 Ian did this pick up the Russian block? Given that this is catalyst for the jet running more nw/se.  In terms of the GloSea does this factor in the movement of the MJO?

First sniffed it out with higher probability (into New Year period) in run of 17 Dec. By it's next run (21st), the anomaly was looking a dead cert outcome. Re GloSea, yes, it embeds background MJO but I've not heard it (MJO) being currently considered as of key teleconnective relevance for the UK in any medium range assessment from Exeter. But I will ask.

[nick sussex]

3 minutes ago, chionomaniac said:

Not convincingly at all Nick. And furthermore there is blocking anomalies to the WNW between days 16-20 before the signal is lost. hmm

The Kara Sea block's extending arm slowly fades and the Scandi increased heights are replaced by lower anomalies  but the AO is still negative as the blocking transfers to a more central Arctic area. There is a strong possibility of an Atlantic link up as the low heights transfer across to Scandi.

Thanks Chiono . Nice to see that negative AO at last. I'm still optimistic that the astonishingly mild December will be replaced but a much more interesting January for coldies.

[nick sussex]

1 minute ago, fergieweather said:

First sniffed it out with higher probability (into New Year period) in run of 17 Dec. By it's next run (21st), the anomaly was looking a dead cert outcome. Re GloSea, yes, it embeds background MJO but I've not heard it (MJO) being currently considered as of key teleconnective relevance for the UK in any medium range assessment from Exeter. But I will ask.

Thanks Ian, the reason I ask in terms of the MJO is that NCEP forecasters are worried about their January outlook because they think the MJO could disrupt the downstream effects of the El Nino.

[chionomaniac]

4 minutes ago, knocker said:

The AO goes positive after the 17th as does  the NAO after the 19th

Not quite with my eyesight! But to put that another way, the mean AO (and NAO) is negative from the 2nd until 20th Jan ( ie drops to negative in the reliable and then only returns positive in 23 days time) 

[fergieweather]

8 minutes ago, chionomaniac said:

Not convincingly at all Nick. And furthermore there is blocking anomalies to the WNW between days 16-20 before the signal is lost. hmm

The Kara Sea block's extending arm slowly fades and the Scandi increased heights are replaced by lower anomalies  but the AO is still negative as the blocking transfers to a more central Arctic area. There is a strong possibility of an Atlantic link up as the low heights transfer across to Scandi.

Yup: note my comment re conspicuous cross-polar heights in EC Monthly suddenly vanishing. It's possible but untrustworthy,  I suggest.... and over last couple of days UKMO have likewise been stressing spread of solutions later Jan, with expression of caution around this (climatology as fair a guide as anything given paucity of any favoured model signal). I'm unconvinced by anything being modelled post-mid Jan at the moment. 

[Singularity]

Well for what it's worth, I enjoyed the decimation of the tropospheric vortex by the end of the 12z ECM det. run today.

It also hints at how the focus might shift from the NE to the NW longer term, though I suspect that, as hinted at by the EC-32, a ridge from the Azores becoming more amplified and then being cut-off to our NW is going to be needed to produce a blocking feature significant (i.e. close and large) enough to deliver for many. The method illustrated by the 12z ECM det. involves working with the remnants of the WAA driven by storm Fred coupled with a bit of new WAA ahead of a storm to our west on day 6... not particularly efficient.

 

Interesting to read about how strongly the Kara high contrasts with the strat. above. Could this be the most pronounced impact we've seen so far this decade from having surpluses of exposed Arctic ocean and associated high SAI working together to promote blocking features in that region?

 

[Glacier Point]

And to add further to that, the previous update to the EC32 didn't have much of a mean -AO signal at all for week 2 and 3.

[chionomaniac]

2 minutes ago, fergieweather said:

Yup: note my comment re conspicuous cross-polar heights in EC Monthly suddenly vanishing. It's possible but untrustworthy,  I suggest.... and over last couple of days UKMO have likewise been stressing spread of solutions later Jan, with expression of caution around this (climatology as fair a guide as anything given paucity of any favoured model signal). I'm unconvinced by anything being modelled post-mid Jan at the moment. 

Yes, Ian -  day 15 of the latest EPS has piqued my interest. I am wondering with the unusual strength of the Kara high and lack of comparable analogues here, how useful climatology will be. An interesting few days of models watching coming up, pity that it looks wet in the transitional period.

[blizzard81]

3 minutes ago, Glacier Point said:

And to add further to that, the previous update to the EC32 didn't have much of a mean -AO signal at all for week 2 and 3.

Best post of the day  Highlights how quickly long range forecasts can flip.

[Man With Beard]

Methinks we ask too much of the EC32 - isnt it obvious that only macro events can be forecast so far in advance? Yet micro events, such as these random wedges of heights travelling between Greenland and Russia at the moment, cannot be forecast properly even 8 days ahead, and tiny variances with these have massive implications for the UK and the rest of the forecasting period!!

Indeed, I see two possibilities unresolved at just D5 - link up with Euro low, or no link up. One sends us cold for a week, the other keeps us mild. I don't think anyone will put their house on either solution yet. So why bother with 32 days?!!