Model Output Discussion 29th December - Into mid-Winter.

[bluearmy]

31 minutes ago, blizzard81 said:

A sobering update indeed. Are you referring to this morning's ext ens?

I was but the 12z is the same ........

[Duane S.]

13 minutes ago, feb1991blizzard said:

Right, cherrs I'm not really that knowledgeable on the MJO, what I would say regarding the west based -NAO though, I would much rather see one modelled at this range than a pattern too far East, I predicted a west based -NAO at the beginning of Dec when a really strong GEFS mean modelled one at serious range, but we always seen to end up with the pattern too far East so I'm never forecasting one again, a lot of people on here always say the models have the pattern too far East, I think the other way, I would rather start of with a West based -NAO, how many times in the last few years have we had the pattern 'TOO' amplified - not often, and how many times has the cold been out of reach and the continent to the East gets it? nearly every time I would suggest

You do realise that it only works one way though don't you?? :-)

Seriously, I do get exactly what you are saying and would tend to concur. Easterly 'drift' over a period of time on the charts would appear to be far more prevalent than Westerly. Implying the models are indeed, on the whole, more prone to over-amplification than over-zonalification (sounds like a real word to me).

[Zakos]

Comparing this pattern to the previous cold shot into Europe in early Jan, certainly looks like the cold is edging closer.

 

 

[snowbunting]

This  looks like a another prospective Nly.. Respective heights over Greenland, PV moving towards Russia.

 

 

[Singularity]

True that phase 8 is not ideal in isolation for us due to the W neg NAO signal:

- but with the real convective signal potentially featuring more of a C Pac component based on hovmoller plots, plus the stratospheric vortex displacement, we may just be able to modify the above in our favour.

Anotjer factor to consider is tje fact we'll be moving ever close to Feb, in which phase 8 places a strong blocking signal close to our NW, and its not uncommon for the tropical feedbacks to take a bit longer to manifest in our sector than the models first show.

While it should be to soon to go all the way to the above, a halfway house between it and the composite for Jan may be achievable. 

In this respect, hopefully the Atlantic component of the MJO forcing won't come to dominate as much as the H-W plots currently suggest, as the result is a less clear cut signal for our sector albeit with an impressive trough signal to our south.

[Met4Cast]

I'm not sure what the fuss is about really? ECM and GFS have us staying very cold throughout next week with potential beyond that, it's certainly not mild. Even Sundays attempt at an Atlantic attack now looks unlikely to make it past the Midlands.

Staying cold with very hash frosts next week, with potential for snow beyond that, not to mention it would only take a tiny correction North to be back in the convection game again. 

[damianslaw]

Significant changes over polar regions being shown by today's models, all wanting to move the PV towards siberia which allows for the first time this season significant heights rises to develop over Greenland - and unlike early Dec these do have a very strong chance of verifying.

It is indeed quite an interesting period weatherwise, a northerly followed by an attempt to bring in a SW flow, but quickly ridging develops over the country heading to our east, with central core of heights Baltic/N Germany producing a cold continental feed mid week, very frosty looking, but limited convection or any long draw easterly - thereafter, signs the ridge will retrogress NW aided by the change in the position of the PV. Hard to say what may happen next, low heights to our SW, low heights dropping down into n scandi, a battleground scenario potentially with frontal activity coming unstuck across the country. Lots happening and far from the default westerly onslaught.

[Duane S.]

24 minutes ago, Daniel Smith said:

I'm not sure what the fuss is about really? ECM and GFS have us staying very cold throughout next week with potential beyond that, it's certainly not mild. Even Sundays attempt at an Atlantic attack now looks unlikely to make it past the Midlands.

Staying cold with very hash frosts next week, with potential for snow beyond that, not to mention it would only take a tiny correction North to be back in the convection game again. 

I agree. I think the fear (and it's not unjustified) from some though is this is the start of a trend to further 'downgrades' (I.e. further slipping south from the high). Unlikely, I think this is, give or take the odd blip, the 'worst' we are going to see the charts as we head into next week's continental feed of sorts. I do fancy the northern arm strength has been a bit over-egged in recent ops

Edited January 12, 2017 by s4lancia

[Catacol]

43 minutes ago, nick sussex said:

So what does everyone think. These are the composites for phase 7 and 1 of the MJO.

Phase 7                                                           Phase 1

Compare that to the outputs of the ECM and GFS towards day ten.

If its something like phase 7 with high pressure over Greenland then we need to see this either central to eastern based not west because a west negative NAO is risky, Atlantic energy will attack the weak point of the blocking, if you're lucky you get trough disruption to the south but theres a risk if the main block is too far towards Canada.

 

You beat me to it Nick - I was just about to post phase 1 myself. Looking at the MJO plots tonight (though Ventrice site is down at the moment and WDT have gone to sleep since Xmas so the rather unreliable WH plots is all we've got....) we have a signal for quite a high amplitude phase 1 burst before a fairly swift rebound to a low amplitude. The high amplitude phase 1 composite looks very similar to where ECM is heading tonight

Velocity potential charts show the clear signal for phase 1, with a particularly sharp negative anomaly off Eastern Australia

In essence that chart shows definite movement in the MJO once again and support for the ongoing nature of a mid lat high in the medium term. Where does it go from there?

I'm not certain where this data comes from.... but sub seasonal MJO predictors would see a swift cycle through 1 - 6 once movement begins, with a return to phase 7/8 in time.

February phase 7 sees blocking to the east continue and then phase 8 is tasty....

 

Based purely on specific MJO forcing and sub seasonal graphs I would suggest therefore that the block wont go too far in the medium term, and then as February nears we may see increasing forcing for a higher latitude position. These MJO forcings are not the be all and end all of course - but they are significant. Overall suggests to me that prospects for an extended spell of cold weather with wintry potential are pretty good. Need to see the long game still here... which from the more negative view of the winter so far seems to be what we have been having to do for weeks!! And, of course, we need to see the block nudge just a teeny bit further north if we are to develop the cold pool GP referred to the other day to have a chance of battleground snow. Very fine margins...

 

 

[nick sussex]

Not a bad start to the GFS 18hrs run, the jet upstream is a bit more amplified at T48hrs. We're looking for the most cut back in the jet sw'wards into the UK and looking to minimize that annoying milder blip at the weekend.

Edited January 12, 2017 by nick sussex

[Purga]

ECM ENS again looking cold with the Op on the milder side.

Warming a bit at the end but the cold option is still strongly represented

 

[bluearmy]

2 minutes ago, Purga said:

ECM ENS again looking cold with the Op on the milder side.

Warming a bit at the end but the cold option is still strongly represented

 

Apart from Monday, not sure the op is on the milder side ?

[Ali1977]

3 minutes ago, bluearmy said:

Apart from Monday, not sure the op is on the milder side ?

Towards day 10 it's heading warmest 

[blizzard81]

5 minutes ago, bluearmy said:

Apart from Monday, not sure the op is on the milder side ?

Probably referring to day 10. Only 3 other members are milder.

[Purga]

3 minutes ago, bluearmy said:

Apart from Monday, not sure the op is on the milder side ?

Well it is for about half of the run right up to tuesday and the hugs the middle of the bunch and is milder bias at the end.

[Ali1977]

Low over the med at 90 is slightly deeper and further North , could help a stronger Easterly feed and snow potential ...apart from that it's very similar.

Edited January 12, 2017 by Ali1977

[Singularity]

Just a quick note on how mid-Atlantic amplification may actually have turned from friend to foe by altering the jet pattern from one firing more or less straight across to the N of Scandinavia and beyond (blue arrows), resulting in a nice elongated high right across to W. Russia with a clean easterly on the other side, to one that tries to arc back around through Norway, almost creating a separate anticyclonic circulation around the UK (red arrows), which pushes maritime air down south that interferes with the continental air and nudges that onto a S of W track.

Goes to show - amplification is as much about where it happens as how much!

[Scandinavian High.]

Cold pushing back west from the east .

[Ali1977]

1 minute ago, abbie123 said:

Cold pushing back west from the east .

Not looking as good as the 12z though, 850s not as good but still cold on surface. 

[jules216]

This is just to lighted up the mood while 18z is trickling along,mods feel free to delete if off topic.

Just want to prove how even a medium term forecast can go horribly wrong, this is one of the most respected senior forecaster in Slovakia showing his views ahead for first few weeks of January towards the end of December(pict1), on picture 2 is a snapshot of real time temperature on the 8th January at 8AM, he was only about 30 degrees adrift! A travesty as they just had their coldest spel since January 1987!

[2810lollypop]

2 minutes ago, jules216 said:

This is just to lighted up the mood while 18z is trickling along,mods feel free to delete if off topic.

Just want to prove how even a medium term forecast can go horribly wrong, this is one of the most respected senior forecaster in Slovakia showing his views ahead for first few weeks of January towards the end of December(pict1), on picture 2 is a snapshot of real time temperature on the 8th January at 8AM, he was only about 30 degrees adrift! A travesty as they just had their coldest spel since January 1987!

[Kentish Snowman in Yorks]

The cold uppers have faded a little more on the GFS 18z but the High is actually quite a bit further West than the previous run so we are under greater influence from the Easterly although still quite slack at Day 7.  Surface cold remains throughout however.

[Hotspur62]

Well 18z has colder air much further West on this run with High slightly further North.Also Lower Heights in Med compared to 12z. Small differences have big implications for UK and it will very cold in Eastern England on this run.Could it be a start of a trend pushing High further North?.Fascinating model watching and be interesting to see ECM and UKMO next runs.

 

[Purga]

Interesting evolution with the GFS 18z

A pocket of pretty cold uppers -8hPa and an decent area of snow across the south of the UK

A long way off of course but still nice to see,

[blizzard81]

I like the gfs 18z run. Shame it's reputation is akin to nogaps!