bluearmy

Subject to quite binary sets of clusters on the 00z run ............. best wait for the next couple suites before having a stab .........

A much more preferred route as more likely to verify at this range ...... a split likely to be trop up would rely on patterns quiet a way off whereas even if the top down is a result of trop influences, these would be occurring at a timescale when the trop modelling is far more reliable.

Maybe not by much but they are further north .......the west Russian trough into se Europe is what’s gaining my attention as it begins to sharpen .......

It was there on the 00z run but less convincing and represented the smallest clusters .....hopefully that looks different later

The gfs 18z actually split the vortex from the trop up - or did you mean the gefs ???

Interesting ........ Eps spread at day 10 says that a cluster has a decent griceland height rise and the extended eps are slowly retrograding the pattern of the trough ridge trough and that upper ridge continues to look like it could gain a bit more traction ......

They are high up nick but there are indications that they will increase lower down as any reversal comes into view .......thinking back to feb, we saw the nwp struggling to resolve the slowing pattern once the reversal came into high res .....we are a fair way from that yet ....

That you said it twice! it would be interesting if it did show a strong uptick as that would presumably show that any reversal will also downwell quickly ... (assuming the uptick was strat led and not the result of trop influences - the Berlin data is useful for that but only available to day 10)

That usually happens but if the trop vortex to our ne is less intense then any mid lay block could use that mobility to drive WAA and build a more sturdy scandi block

I have noted that the gfsp continues to show a temperature split but we cannot see the heights re any reversal or split

I think some of you are expecting Santa to be real if you think there will be a favourable response in the trop to events in the strat before new year ...... it’s just about feasible to expect to see a trop response a couple days AFTER a ssw at 10hpa but given that we have seen poor strat trop coupling thus far this winter, thats certainly not a given - the question of whether we see trop zonal flow ease off in week 2 as upper strat flow weakens is also questionable as often, stronger flow is flushed down through the strat ahead of any downwelling reversal ...... at the moment, I think everything the nwp is showing at 500hpa is trop led ..... that may change as we get towards mid week but I note the gfs ops have backed away from a technical ssw over the past few runs

Yesterday’s ec op showed zonal winds at the top of the strat towards the pole upticking and then reversing quite markedly approaching day 10. The uptick appears to be flushing down through the layers ...... probably too crude to assume this could be used as a template for any likely reversal at 60N a few days later. Though If it is the case, expect an increased burst of zonal flow prior to any fun and games

Eps clusters are singular days 5 thru 7 (and this is a consistent rather than wide spread solution). Thereafter, tough to pin a tail on the donkey ......... there is a wintry cluster at 20% ......it’s not out of the question but the mid lat ridge looks a safer bet for the time being ..... I did see that gfs 06z op ended in the same place as the extended eps mean ..........

The mean will of course contain various clusters .......... I would love to see the eps strat data ..... hopefully ventrice uses one of his ‘free tweets’ in the next day or so .....

The 00z eps offer a route forward but it’s a slow burner ......mid lat ridging nw Europe and eastern Atlantic which exerts itself slowly nw towards se Greenland (NOT A GREENY HIGH). at the same time an Atlantic trough dropping just west of the Azores and a developing scrussian trough could lead to an undercut of this ridge note that Europe cools as we reach the end of week 2 which makes me think the trough to our east will be advecting some colder air around the ridge

Btw, the split works up the strat, bottom to top ...

That’s what your mid lat high late on can lead to ......fits ok with eps clusters and also the expected strat developments ....

Let you know after I have seen the clusters .....either big support for mid lat high in our vicinity or something with more traction than that .... could be the start of a new scandi ridge ...... ties in wirh a developing west Russian trough

I’m noticing some changes to the strat height forecasts today .... I wouldn’t be counting any chickens at the moment re size of displacement or any split to follow .... also the eps much more mean upper ridge in our vicinity in the extended ........ a watching brief for a few runs methinks ......

Well it sits with the op cluster from th 00z suite and that went on to produce a mid lat high across us but a growing mid Atlantic upper ridge b6 day 15 .........

I guess it depends if you mean sustained severe cold or a severe cold snap .... sustained is always a tough ask for an island on the western edge of a continent and the eastern edge of a warm ocean .....

Can you change the very likely to very possible ?? A split vortex post the displacement remains unclear and 80% is way too high for January at this range Mike ...... especially ‘severe cold’. Fiona will be even more confused!

Dp’s still sub zero for much of the region ......... intensity of precipitation required but with it so slow moving, seems the heavier stuff will arrive once the dp’s are positive ..........

Going to need to be a huge change around from the current ens guidance at the end of week 2 for week 3 to be right re anomolys in ne Canada

We are fortunate that someone recently tweeted an image of the glosea run from 3 dec for 6 Jan at 10hpa Looking at the 06z gfs op picture for the end of the year higher up (which one would expect to down well over a few days)