Model Output Discussion 01/09/17

[Cheshire Freeze]

Just now, blizzard81 said:

Absolutely, I realised my bad choice of words so edited my post. I know you have always been sceptical about the current output but I was referring to today's posts. 

Working all day, finished at half 10 this evening and have no data left on my phone. I have only had time today to take a couple of minutes on my breaks to view the output.

[iamgazza]

1 things for sure - It's been a great start from a model watching perspective for the upcoming silly season. Awaiting 0z with interest. 

[blizzard81]

Just now, CreweCold said:

Working all day, finished at half 10 this evening and have no data left on my phone. I have only had time today to take a couple of minutes on my breaks to view the output.

Lol, you don't have to answer to silly old me Anyway, normally nobody is more sceptical than me but at least we have something more seasonal at the moment. I for one am very happy with that after the last few years. No doubt this will change as we go into December but there is always hope that it won't

[Man With Beard]

The first potential period for discrepancy is T144-T168, and particularly with the low approaching the UK. EC clusters show a wide range of possibilities, including one that virtually eradicates it.

Clusters 1 and 4 most favourable for a colder back-edge to the trough, clusters 3 and 5 bit more like the GFS 18Z.

T240 clusters already posted above but just to add, the control run cluster appears like the GFS 12Z, and the op run cluster closer to the GFS 18Z. The other cluster is closer to the control run, so slight favouring still towards something colder D8-D11. (Incidentally, the EC control run sinks the high so slowly that winds stay from the north or east until D14, resulting in some fairly cold and dry days.)

[nick sussex]

I wonder whether lack of data coverage in certain parts of the Arctic is part of the cause for these Arctic highs which more often than not get downgraded .

In terms of tonight’s offering from the GFS before the helpline gets over run one should bear in mind the GFS flat bias upstream .

Thats not to say the ECM is promising much in its later output but its more amplified with the key low pressure over the USA at T168hrs and US forecasters suggest although the progressive  pattern might last till next Friday they think more amplification will feed through after that with the possibility of  some correction west of features upstream.

Overall however we do seem to be losing the better NH set up but might still manage to get the ridge toppling towards Scandi.

An issue even with some of the more recent outputs has been the lack of any deeper cold to draw on although of course at this time of year the Continent can cool rapidly under the right conditions so a ridge towards Scandi could help that.

 

 

 

[Cheshire Freeze]

18z GFS ensembles for Cheshire...

After previous runs grouping around the -5 at the 850hpa level, the 18z loses this signal.

[Geordiesnow]

I think its always too easy to read into one run too specifically but it does seem like we are moving away from anything too significantly cold but how  it all play out is not certain. Hopefully we can get the polar WNW'ly and a proper Atlantic ridge to follow but if recent history of the modern day weather pattern is anything to go by, then we just simply won't and the pattern will end up a lot flatter.

[geordiekev]

4 hours ago, chrisbell-nottheweatherman said:

Indeed, but the individual members diverge around the 17th, so making bold pronouncements on the expected situation beyond then is, IMO, pointless; one can speculate or discuss the possibilities, but I've read at least one "nailed-on" comment here today regarding the 18th and 19th which seems premature given the uncertainty from Friday onwards.

Sorry,  can you point the finger at the nailed on comment, 99pc of NW subs are well aware this is a weather interest forum. We all know nothing is nailed on till 2 hours ahead and nothing wrong with persons having positive, fairly sure, thoughts things are getting colder,  and giving all of the evidence in hand, yes the fact that the next 2 weeks is different to the Ian Browns norm is nailed on,  the UK will have snow post 1995 thoughts 

[geordiekev]

3 hours ago, CreweCold said:

Not really.

If you step back and look at the bigger picture, you will see even the more learned on here have preached caution with the upcoming spell due to lack of supporting background signals, along with the longer range seasonal models which have almost unanimously and consistently pointed towards a +NAO tendency for the upcoming months. 

Of course you may say 'just one run' but it's pertinent to note that the flatter runs are closer to what we can expect given the stratospheric state at the moment, amongst a plethora of other factors to consider. With that in mind, you have to prepare for something many of us do not want to see i.e a more Atlantic driven outlook rather than one affected by an abundance of N blocking.

CC with all due respect, whenever a cold spell appears in FI,  many posters appear with the words, it's day 10 or FI, or I told you so, I warned you. Warned against what,  that a PC chart trying to predict a 1000 variables, may be taking out of context as snowmageddon.

Truth, it's getting v cold, there's no zonal in the offing, snow is repeatedly forecast, no ones getting ahead of themselves, despite continued posts suggesting that people think that snowmageddon is nailed on, cmon, stop with the devils advocate.

Edited November 12, 2017 by geordiekev

[Mucka]

Mornin' all.

The models don't seem to have a scooby Doo how to resolve the Atlantic trough/Sceuro ridge.

GFS/UKMO 144 comparison

As we can see UKMO has all the energy heading NE and so does away with the ridge and pushed the trough through with no polar air getting across England while GFS disrupts the trough giving a more amplified pattern.

Both are represented in GFS ensembles with p10 and p11 summing up the uncertainty.

P10/p11 144 comparison.

Hard to know what we will end up with frankly.

 

 

 

 

[knocker]

Today first thing yesterdays front is still hanging around the far south with cloud and light rain but that will quickly clear and leave the whole of the UK in a cold northerly which will be quite strong in Scotland. Thus plenty of showers many of a wintry mix in N. Ireland, Scotland and down the coasts but they will also encroach inland. These will tend to become less as the day progresses and the ridge moves east but still likely down the east coast.

Overnight calm and clear conditions in most areas leading to widespread air frost Monday morning and a cold bright start to the day but fronts and cloud and rain quickly spread into the north west suppressing the ridge.

The fronts clear east during Monday and with the High pressure now to the south east the UK is generally in a light and moist west/south west drift so quite cloudy with some light out breaks of rain in places with temps a little above average.By Thursday 00 a deep upper trough is situated in the Iceland area with a pathway to the trough around the Azores  This pathway is acting as a conduit for a low that has formed on the front in the Azores area to track north east and by said time is 977mb south east of Iceland and the front is already encroaching N. Ireland and Scotland with cloud and rain and quite strong winds. The front duly tracks south east to be clearing SE England by early Friday morning by which time the aforementioned low has deepened to 959mb NE of Iceland and is dragging colder air down in it's circulation and some quite wintry conditions are affecting Scotland with strong winds and frequent snow showers on the higher ground with possibly some quite heft falls which continue through Friday.

From this point it gets quite messy and I suspect one should view the detail with some suspicion. There is again some amplification with the HP ridging NW and the negatively tilted upper trough on it's western flank but a little surface low shoots out of the trough to bring some quite wet weather to all on Sunday

Best left here but a quick look at this morning's GEFS anomaly which is indicating less amplification in the Atlantic. It's really a matter picking  out the bones at the moment.

Edited November 12, 2017 by knocker

[Mucka]

 

GFS/UKMO/ECM 144 comparison

 

ECM actually manages some undercut which reinforces the Arctic block.

Obviously the more the trough disrupts then the more the pattern will be backed up and amplified in the Atlantic.

[Paul_1978]

7 hours ago, CreweCold said:

The speed of it was always inevitable, as we saw last year. It's what happens when you have an strat profile non conducive to blocking. Relying on the perfect trop pattern for wave breaking to occur successfully is risky and can quickly go wrong. It's the reason I have been ultra cautious all week.

The signs were there yesterday and perhaps the day before that the AO may not go as negative as first thought. This was owing, in the short term, to a decrease in vertcial advection Pacific side. After that, it's a domino effect.

 

 

You're a glass half empty chap CC, seems to be always doom and gloom from you. Anyway, are you now changing your thoughts having seen the 00z runs, of which the GFS and ECM are very good and a world away from the 18z's. 

[knocker]

The ecm does vary in detail for the end of the week but is along the similar lines (very roughly). At 1800 on Thursday the deep low is over Iceland with  the fronts already over the UK with heavy rain over N. Ireland and Scotland.brought about by a frontal disturbance. This tracks quickly east and by 12 Friday is over southern Norway leaving Scotland and N. Ireland in gale force westerlies and frequent wintry showers of snow on the higher ground..These tend to veer slowly as the main low fills and moves SE to be near Thurso by 00 Sunday with more trouble approaching from the south west.

Edited November 12, 2017 by knocker

[carinthian]

A mixed outlook view from todays main models. GEM goes recycled Tm circulation as the mildest outcome for many in Europe and ECM as the most progressive model to introduce the coldest Pm air mass. However, most models showing something out to the Atlantic and development out to the SW that could be causing problems with its 10 day forecast models. The shorter term excellent ARPOP model picks this up in the picture below. So much of the mid week period looks quiet and settled for most but surface temps will probably be in single digits as the flow will be from a colder continent. Thereafter, the million dollar question is how far south will the polar trough progress? According to UKMO not much with high pressure holding on a to the south. It has been consistent with this pattern for some days but ECM seems to have other ideas. However, all the main models do show something brewing out to the SW later in the period that will no doubt throw some extra uncertainty into the equation.  Still think we are into a colder scenario looking at the models with a block shown to form to the NW , that apart from the GEM which is the extreme outcome for rinse and spin mild stuff.

C

 

Edited November 12, 2017 by carinthian

[Frosty.]

The Gfs 00z brings some early wintry cheer which is nice to see!?

 

Edited November 12, 2017 by Frosty.

[northwestsnow]

Looking at the 00z runs i dont think i have a clue how this will pan out.

EC again looks mainly dry, and cold.

It does look however that next weekends NWly has been watered down- meaning snow will likely be reserved for even higher up than 300m-

Pressure remaining too high across Europe - a seemingly perennial problem for NW europe when it comes to cold.

Not entirely sure what to make of EC at day 10

 

Dry and cold yes, but what happens next? Can the UK high ridge north? Will the Atlantic allow for it.

edit cant post the image AGAIN  keeps showing yesterdays day 10 !!!

Edited November 12, 2017 by northwestsnow

[carinthian]

9 minutes ago, northwestsnow said:

Looking at the 00z runs i dont think i have a clue how this will pan out.

EC again looks mainly dry, and cold.

It does look however that next weekends NWly has been watered down- meaning snow will likely be reserved for even higher up than 300m-

Pressure remaining too high across Europe - a seemingly perennial problem for NW europe when it comes to cold.

Not entirely sure what to make of EC at day 10

 

Dry and cold yes, but what happens next? Can the UK high ridge north? Will the Atlantic allow for it.

edit cant post the image AGAIN  keeps showing yesterdays day 10 !!!

Think you are right NW. Weird looking end to ECm run. Chart at 216t from ECM below shows a NE ly flow, however the chart at 240t abruptly switches the flow to come from a more Southerly quadrant. 

C

Edited November 12, 2017 by carinthian

[northwestsnow]

10 minutes ago, carinthian said:

Think you are right NW. Weird looking end to ECm run. Chart at 216t from ECM below shows a NE ly flow, however the chart at 240t abruptly switches the flow from a Southerly quadrant. 

C

The pick of the big 3 at 144 is UKMO in my opinion.

Surely the only way forward from there is retrogression?

That said, and in the interests of balance im not sure how much stock im placing in UKMO at the moment, seems to be having wobbles.

Edited November 12, 2017 by northwestsnow

[northwestsnow]

EC mean looks mainly dry and cold-

Nothing to complain about really- 

[Cheshire Freeze]

2 hours ago, Paul_1978 said:

You're a glass half empty chap CC, seems to be always doom and gloom from you. Anyway, are you now changing your thoughts having seen the 00z runs, of which the GFS and ECM are very good and a world away from the 18z's. 

This is where many in here let themselves down. 

It's nothing to do with being a 'glass half empty' or 'glass half full' person as hopes, wishes and  subjectivity shouldn't even come into the picture when analysing the NWP etc. All the cheeriness in the world will not promote the outcome you desire and this thread is no place for misguided hope based optimism. 

My thoughts remain unchanged from last night. After all why should one set of model runs change my view?? That would be a bit 'knee jerk' wouldn't you say. 

Edited November 12, 2017 by CreweCold

[Geordiesnow]

25 minutes ago, northwestsnow said:

EC mean looks mainly dry and cold-

Nothing to complain about really- 

Think your posting the mean charts there? Pressure certainly is not that slack and I would not really describe it as mainly dry either. Still shows the trough trying to dig in but then gets complicated with height rises in the Atlantic, one of those where what happens next is a bit of a surprise. The ECM at least has a stronger arctic high and its  closer to svalbard which make things a tad more interesting. 

[northwestsnow]

1 minute ago, Geordiesnow said:

Think your posting the mean charts there? Pressure certainly is not that slack and I would not really describe it as mainly dry either. Still shows the trough trying to dig in but then gets complicated with height rises in the Atlantic, one of those where what happens next is a bit of a surprise. The ECM at least has a stronger arctic high and its  closer to svalbard which make things a tad more interesting. 

Yes they are the mean charts as it says at the top of my post

Looks cold and mainly dry for most IMHO.

Certainly nothing to suggest Atlantic domination but NWP  seems very chaotic at the moment.

[blizzard81]

The gfs and ecm 00z op runs both show the most potent north to northeasterly flow out of any model run to date. The 18z gfs wobble of last night is well and truly behind us. 

[Chesil View]

Bearing in mind that nothing was really looking like happening until the final week of November any way I,m quite happy with the ECM 240 northern hemisphere chart this morning. High pressure across the pole and Greenland and the jet digging south of the UK.