Model Output Discussion 01/09/17

[phil nw.]

24 minutes ago, Man With Beard said:

Don't think anyone posted an image of yesterday's EC46 (D14-21), so thought I'd throw this in to whip up the frenzy a bit more

one of the strongest Greenland height anomalies I've seen. Even more significantly, EC ensembles have been pretty much rock solid in this direction for nearly a week now.

FWIW - I think it's now pretty inevitable there will be some strong northern heights in the second half of November. But far less certain that it will bring cold to the UK - could be shifted east or west. It's worth taking a step back to remember just how far out this is in meterological terms - we're talking D10-D20, when the reliable is, of course D7 at best.

Looking at the thickness lines though we are still seeing a west to north west flow there through Atlantic ridging,It looks more like a ridge followed by trough setup.Yes it's better to see those anomalies as they signify a weaker Greenland vortex but those Hts need to be much stronger to replace low pressure up there with a high.  

All academic at that range of course-just an observation.

[Man With Beard]

1 minute ago, phil nw. said:

Looking at the thickness lines though we are still seeing a west to north west flow there through Atlantic ridging,It looks more like a ridge followed by trough setup.Yes it's better to see those anomalies as they signify a weaker Greenland vortex but those Hts need to be much stronger to replace low pressure up there with a high.  

All academic at that range of course-just an observation.

I quite agree with all this, but just considering the chart in isolation, most ensemble members are likely to have even stronger ridges as it only takes a few opposing outliers to even out the mean

e.g. 10 + 10 + 10 + 10 + 0 = 40 divided by 5 = a mean of 8 - but is the likely outcome "8" or "10"?? Probably "10", because 4 out of 5 show this value. In other words, the likely outcome is more extreme than the mean.

[Daniel*]

31 minutes ago, booferking said:

Early December anomaly from ECM weekly.

Perhaps a tad more revealing - week 3 & week 4 -ve height anomalies across Southern Europe - a pretty critical necessity for cold advection. Unusually wet here however it will help drought stricken affected areas. With +ve heights strong blocking in the Iceland/Greenland locale not out the realm of possibility we could pick off a flow off the continent. What's interesting is the stubborn nature of the Greenland blocking being depicted one would think it will turn progressively colder. Those that went for a mild November CET will be kicking theirselves. This signal has been caught up for about a week now so it’s not as if it is getting further away, I think folk should be somewhat optimistic. It has not been this way for a number of years. 

Edited November 7, 2017 by Daniel*

[bluearmy]

3 minutes ago, phil nw. said:

Looking at the thickness lines though we are still seeing a west to north west flow there through Atlantic ridging,It looks more like a ridge followed by trough setup.Yes it's better to see those anomalies as they signify a weaker Greenland vortex but those Hts need to be much stronger to replace low pressure up there with a high.  

All academic at that range of course-just an observation.

That’s a weekly mean chart Phil - I’ve looked through the days and if it were a few weeks on we would be guaranteed countrywide paralysis if it verified. In third week November we could still get lucky.

[phil nw.]

7 minutes ago, Man With Beard said:

I quite agree with all this, but just considering the chart in isolation, most ensemble members are likely to have even stronger ridges as it only takes a few opposing outliers to even out the mean

e.g. 10 + 10 + 10 + 10 + 0 = 40 divided by 5 = a mean of 8 - but is the likely outcome "8" or "10"?? Probably "10", because 4 out of 5 show this value. In other words, the likely outcome is more extreme than the mean.

I will leave the maths to you MWB-it's been a long time since i was at school!.

I just say what i see and i really can't comment on ens suite as i have no access to them.

Edited November 7, 2017 by phil nw.

[Met4Cast]

I agree. Using ensemble means that far out is about as useful as asking the local garden slug what he thinks the weather is going to do. Ensemble means are drastically washed out and don't really offer anything of use.

The operational runs have continuously gone for Siberian High/Greenland high for the past few days, there have been changing details with regards to whether the UK gets cold or stays mild but the main trend for heights to the North have remained the same. Not much change on the 12z GFS so far either, could be on for another stella FI.

[phil nw.]

1 minute ago, bluearmy said:

That’s a weekly mean chart Phil - I’ve looked through the days and if it were a few weeks on we would be guaranteed countrywide paralysis if it verified. In third week November we could still get lucky.

You have the advantage over me as i can't see anything other than the chart posted Blue.

[coldwinter]

5 minutes ago, Daniel Smith said:

I agree. Using ensemble means that far out is about as useful as asking the local garden slug what he thinks the weather is going to do. Ensemble means are drastically washed out and don't really offer anything of use.

The operational runs have continuously gone for Siberian High/Greenland high for the past few days, there have been changing details with regards to whether the UK gets cold or stays mild but the main trend for heights to the North have remained the same. Not much change on the 12z GFS so far either, could be on for another stella FI.

The Siberian high and Greenland high have been present in the extended on the ENS for days. Of course seeing the ensemble mean clusters always helps but they are extremely useful. 

[lassie23]

1 hour ago, Ed Stone said:

Are the 'building blocks' in place yet?

They have been in place for four years Ed

[Singularity]

 

Yeah okay, GFS is really digging for the spanners now with that vigorous low racing onto the scene from the Eastern Seaboard days 7-10 which leaves us waiting until it's had its fun with the UK before we can start to tap into the cold air again, but the alignment of the flow west of Greenland is great for building a strong ridge from the mid-Atlantic to link with the Greenland block so the rest of this run should be increasingly tasty to look at .

Yes... getting there, through shortwaves and everything. Quite a spell for Scotland possible while things arrange themselves, but of course such specifics are not worth much at such range.

[Cheshire Freeze]

20 minutes ago, bluearmy said:

That’s a weekly mean chart Phil - I’ve looked through the days and if it were a few weeks on we would be guaranteed countrywide paralysis if it verified. In third week November we could still get lucky.

My main concern Nick in reply to your earlier question.

It looks like we're heading towards a period of trop vortex disruption, but looks to be just a couple of weeks too soon...which is why I'm a bit dismayed that it doesn't look like it will be 'sustained'. We got pretty lucky at the end of November 2010 with the depth of cold available and I'm not sure that we have the luck to push this time. However we'll see. It'd be nice to see something pop up in the strat forecasts to add another attempt to the pipeline for mid-late December.

[Singularity]

What do we call this - a Greeberian Block? 

Man, the trop. vortex is hurting on this run, much as it was on the 06z. Trying for the trop. led wave break too. Fantastic stuff but still all in the virtual realm. Hammered-in wariness still standing strong for now.
 

I underestimated GFS' capacity for making a dogs dinner from fine ingredients in the trop. but look - the wave actually appears to have impacts all the way up to 30 hPa on this run. First one to take it that far - trend or fluke? Edit: starts looking stretched as early as day 11 which gives it more chance of being meaningful. Will have to watch ECM output on the Berlin site for any signs of such behaviour. Or look out for BA's handy updates .

Edited November 7, 2017 by Singularity

[Cheshire Freeze]

3 minutes ago, Singularity said:

What do we call this - a Greeberian Block? 

Man, the trop. vortex is hurting on this run, much as it was on the 06z. Trying for the trop. led wave break too. Fantastic stuff but still all in the virtual realm. Hammered-in wariness still standing strong for now.
 

I underestimated GFS' capacity for making a dogs dinner from fine ingredients in the trop. but look - the wave actually appears to have impacts all the way up to 30 hPa on this run. First one to take it that far - trend or fluke? Edit: starts looking stretched as early as day 11 which gives it more chance of being meaningful. Will have to watch ECM output on the Berlin site for any signs of such behaviour. Or look out for BA's handy updates .

Yes I was somewhat encouraged when looking at the 30hpa level on this run. That's the sort of stuff we need to see more of in upcoming runs.

[Polar Maritime]

The GFS again continues to show a N/W flow turning Northerly as fronts pass.

[knocker]

The gfs takes the frontal wave a tad further north on saturday across N. Ireland so a fair bit of rain for the latter and England as it tracks quickly south east into northern Germany. This preempts the amplification and time to slip something warm under kilt on Sunday.

EDIT

Sorry PM hadn't seen your post

Edited November 7, 2017 by knocker

[Gael_Force]

56 minutes ago, Daniel* said:

Those that went for a mild November CET will be kicking theirselves. This signal has been caught up for about a week now so it’s not as if it is getting further away, I think folk should be somewhat optimistic. It has not been this way for a number of years.

All 4 weeks have negative temp anomaly on the latest EC monthly but see no signal for excessive rainfall.

http://www.met.hu/en/idojaras/elorejelzes/europai_elorejelzes/

 

[booferking]

Control run is a beauty for heights into Greenland right to the end of the run no let up if only.

[I remember Atlantic 252]

My thoughts at the moment is how wet this Sunday is looking for this location, and areas close to it, GFS shows a shocker washout, UKMO though better, HP slightly closer, looks mainly dry inland, just hope UKMO closer here

Edited November 7, 2017 by I remember Atlantic 252

[bluearmy]

1 hour ago, CreweCold said:

My main concern Nick in reply to your earlier question.

It looks like we're heading towards a period of trop vortex disruption, but looks to be just a couple of weeks too soon...which is why I'm a bit dismayed that it doesn't look like it will be 'sustained'. We got pretty lucky at the end of November 2010 with the depth of cold available and I'm not sure that we have the luck to push this time. However we'll see. It'd be nice to see something pop up in the strat forecasts to add another attempt to the pipeline for mid-late December.

Fundamentally, I agree with your sentiments re depth of cold available. However, late November has low solar input and if we can draw in a continental feed then we might just edge the right side of any borderline scenarios that arise.

[knocker]

The ecm still tracking the wave south east further west than the gfs and at 06 Saturday has it, and the rain, over southern Ireland and Cornwall.At the same time the north of England, N. Ireland and Scotland are in strong, showery, north westerly.

[knocker]

Digit trouble

Edited November 7, 2017 by knocker

[swfc]

Nobody think the ecm at 240 hrs is at odds with the gfs 12z???

Edited November 7, 2017 by swfc

[blizzard81]

Dartboard low in the Atlantic last few frames of the ecm doesn't look too pretty with regards to long term cold for our shores. If this comes off then we can only hope it is forced south-eastwards under pressure from the Arctic high. That would open the floodgates to proper cold. 

[ITSY]

Ens flip like anything, but 17/20 go for significant height rises either in scandi, Iceland, Greenland, or a combo thereof, by the end of FI. ECM eats up the trop vortex too so very interesting, esp after last night's wobble...

[feb1991blizzard]

1 minute ago, blizzard81 said:

Dartboard low in the Atlantic last few frames of the ecm doesn't look too pretty with regards to long term cold for our shores. If this comes off then we can only hope it is forced south-eastwards under pressure from the Arctic high. That would open the floodgates to proper cold. 

Yes you need to see it elongating whilst disrupting and sending energy into France with a stonking big elongated ridge to the North of us and into scandinavi and hope that there would be enough frigid air to come round the back of the high and make its way westwards.