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Model Output Discussion 01/09/17

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ECM mean for London looks fairly steady from the 00z

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34534.thumb.png.cc7f8f1b4cd435d3694a01be552511cf.png

Edited by Summer Sun

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1 minute ago, Summer Sun said:

ECM mean for London looks fairly steady from the 00z

graphe_ens3_php.thumb.png.5bf8d45a8fa83f11040d9377d1b2fe32.png

34534.thumb.png.cc7f8f1b4cd435d3694a01be552511cf.png

Mild outlier :rofl:

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Where is ian fergie?!!aint seem him post anything in ages!!back to the models am glad gfs has dropped the idea of the potential west based nao from this morning!!just need an upgrade on the atlantic block on the 18z and voilaaa!!!

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Silly what ifs aside the ECM looks pleasing to the eye but synoptically far from winter nirvana. I mean if the run is fantastic etc etc now, then where do we go if say in a few days time it was showing -12c 850's across the country for example.

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4 minutes ago, shaky said:

Where is ian fergie?!!aint seem him post anything in ages!!back to the models am glad gfs has dropped the idea of the potential west based nao from this morning!!just need an upgrade on the atlantic block on the 18z and voilaaa!!!

It's my understanding that some of the information Ian shared with us last year was used on other social media websites without his permission. I remember him saying that he would have to stop posting on here. Such a shame isn't it.

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45 minutes ago, CreweCold said:

Don't know why we can't all just get on, without the digs and quips- there's one thing that unites us all and that's that we are all weather enthusiasts...otherwise we wouldn't be here.

The day 10 mean chart isn't great IMO and that cannot be denied...so don't be shocked if the 12z GFS is closer to reality or if the 0z ECM is no where near as good. 

However, there is a positive, pressure remains relatively above average across the polar regions and that can clearly be seen. This suggests we may have further opportunities moving forward.

Even if the mean is right.....I believe we will get a cold shot colder than expected and quite lively, but that early Dec westerly regime will kick in.  Right or wrong... Aaron you are right...let’s get on and enjoy together... what we get is what we get...let’s see if we can get more accurate in seeing where we go

 

BFTP

Edited by BLAST FROM THE PAST

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25 minutes ago, bluearmy said:

Both the mean and clusters are of use - after all, how many times have we seen the modelling hone in in on a solution which ends up a half way house between op runs. There are no ‘hard and fast rules’. 

I have enormous respect for your meteorological input (as with many on here) - but from a statistical point of view, surely the clusters will always provide more information about what is going on than a mean - isn't that a pretty hard and fast rule?:)

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Was going to have 72 hrs off from model watching but couldn't resist today, as had a feeling there would be a bit more consensus at least in the medium timeframe, compared to the best part of 10 days or so. Alas, there is quite a bit up until about 144hrs, though GFS is handling developments differently over the eastern seaboard compared to ECM - there does appear to be a theme here, GFS often over-progressive too quickly, and ECM prone to greater amplification - I've learnt to expect somethign inbetween, and its usually UKMO that sits in the middle, but trends more to the ECM as it is now.

What does this mean for the outlook, remaining very changeable, becoming chilly from Thursday onwards, cold in the north with chance of snow down to lowish levels, and return of frost. Next week, it looks like we will sit on the colder side of the jet, with ridge development over the atlantic, jetstream profile forecasts support a NW-SE aligned trough, the north could be locked into quite a cold wintry period, more average in the south as we end November.

Longer term - keeping an eye on stratospheric developments, will the Polar Vortex get organised as we start December... mmm not too sure, could be about to see a topsy turvy start to winter, with perhaps a greater odd for the cold to win out against the mild, just as we are seeing now.

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12 minutes ago, Steve Murr said:

So just to finalise my thoughts / comments on the 12z suite..

We often find ourselves in Winter with an atlantic high ridging into the pole- & the longivity of that wave / ridge remaining in situ before getting flattened ( as well as the final height ) is directly related to the general consistency & strength of the pacific jet - because after all thats what normally comes barrelling over the top shearing the top of the highs-

Its also important to remember that at this usual point in late November the heights over pole @500MB are generally sub 516DAM & this more often than not coupled with a strengthening zonal wind means the tip of the ridge usually gets to the southern point of greenland before the westerly directional flow is already getting to work on moving everything East -

So on a 'typical' Early winter chart we see a Northerly toppler -

Day 1 we have our ridge & 4 days later its been flattened- look at the pacific jet blasting away- no sustainable meridional flow going forward , just a temporary interuption to the sinuous flow...

Also notice the persistent low heights over the pole -

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Now look at the starting point when the second wave of ridging occurs at 120-

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* The all important residual +VE heights over the pole consistent with the original -4 AO ( which is why people like me / Bluearmy always refer to it )

* The fairly strong but still attenuated pacific jet & weak subtropical jet - 

with this attenuation there is now an ripple in the jet over the states which is a sharp +PNA pattern creating a big 'dig' of cold air in the NE is, that dig then supports the returning flow upwards back towards the pole @144

Post this ( from the GEM ) @144 the entire hemispheric jet is rippled & attenuated creating a 'weak' easterly component in terms of a zonal wind. 

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Not only this but the stratosphere is decelerating at the same time - With the detached tropospheric negative anomaly almost upwelling with time-

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This shows a decelerated zonal flow around the pole 

So all the fall out means that based on the starting point of T96 & the rupture to the jet - combined with the persistance of higher heights over the pole makes any eastward progression of the jet a lot Weaker than normal- & with considerably more North / South components - more so than westerly ( moving East )

Its a rare scenario - but based on the starting point at day 4 the continuation of Cold is odds on favourite, maybe not quite to the magnitude of the ECM in terms of outright blocking, but solid in terms of the pattern remaining blocked & slow out to day 10- 

I would go with the final solution being less extreme than the ECM but overall closer to the ECM than the flat GFS ....

best

s

 

Great post Steve it would appear John Hammond agrees !!:D

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5 minutes ago, Devonshire said:

I have enormous respect for your meteorological input (as with many on here) - but from a statistical point of view, surely the clusters will always provide more information about what is going on than a mean - isn't that a pretty hard and fast rule?:)

I didn't say that one outweighs the other - I'm more a cluster man than a mean man ( hence my reliance on the spreads generally). The availability of the Icelandic clusters is a boon for this season. it's just that on plenty of occasions where uncertainty has reigned, we have seen the mean end up closest to verifying as opposed to the clusters or ops. 

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5 minutes ago, Steve Murr said:

Nice ^^ dont really watch tv forecasts !

totally agree:)

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28 minutes ago, Steve Murr said:

Nice ^^ dont really watch tv forecasts !

Its in his blog :D

Anyway...18z rolling...fingers crossed :)

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Eyes down for the 18Z please call BANK for any doozy charts that follow, Thankyou :good::cold:

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Shortwave at 72 hours slightly further south again!!colder air further south aswell!!

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1 minute ago, Day 10 said:

Eyes down for the 18Z please call BANK for any doozy charts that follow, Thankyou :good::cold:

Cheers another Scrabble word! didn't know that one! yes eyes down for the 18Z

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GFS pushes the low further south with a quicker undercut of colder air. Snow probably confined to the hills though with greater chance of back end snow for many. 

gfs-2-78.png?18

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Just now, PerfectStorm said:

GFS pushes the low further south with a quicker undercut of colder air. Snow probably confined to the hills though with greater chance of back end snow for many. 

gfs-2-78.png?18

Modele GFS - Carte prévisions

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7 minutes ago, shaky said:

Shortwave at 72 hours slightly further south again!!colder air further south aswell!!

We need it a bit further north, for any back edge snow chance

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Of all the charts this evening, this one from the American Navy Model caught my eye. Shows the 300hp wind flow with a almost Omega Block set up. This in tandem with lower heights over the Azores looks perfect for direct Arctic feed into Western Europe at t180. Although this model is fairly new it has access to powerful computer data. Certainly an improvement on the old NOGAPS model which I think it replaced.

C

NVGOPEU12_180_21.png

Edited by carinthian

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1 minute ago, stratty said:

Modele GFS - Carte prévisions

Yeah, I'm not going to follow them. I believe they just accumulate any falling snow, which is obviously not always the case.

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Great 18z out to 114

much better flow at 96-114 brings in the -8c isotherm across Scotty & -6C more wisespread across the UK-

Pressure over Greenland better in situ & ridge developing over NE states better vertically alligned :)

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