Model Output Discussion - The Start Of Winter

[Met4Cast]

Polar Vortex? What Polar Vortex. It's gone.

 

[BLAST FROM THE PAST]

Around 10% of the ensemble members go for a lowering of heights over Europe, and HP taking hold to our NE. But 20% go for a Euro high!

 

The predominant pattern is one from the west or northwest, continuing the average-to-cold conditions, while remaining unsettled. The snow over the Scottish mountains could well continue to pile up.

Cheers Nick...Plenty of time Nick say 10 days down the line to develop,  lovely current pattern emerging for early winter

 

BFTP

[Weather Boy]

There have been a couple of posts this evening that have confused me , Nick L replied to SM`s post about what the ECM showed after t+240  and Nick replied there was decent support for a scandi high between 288 and 360 hrs, ( which is understandable as SM is like most of us on here, anticipating a much colder turn mid month.. ie 288= 18th dec to 360= 2nd jan) in turn invariably supports a much hypotheised forecast to high level building somewhere either to the north east or northwest of the UK.  

 

Then, Ian F  replied to NIck L post that all he could see from the ECM clusters were `dartboard` lows in our vacinity for that timescale. 

 

 

Assuming the ECM 12z wasn`t an outlier heres what the ensembles show 

 

T+144

EDH101-144.gif

 

Deep low pressure ` dartboard type` as agreed on all models over or near the UK, a sausage shaped high anomaly stretching way across the atlantic and the USA to the south, and a very flabby high pressure to the east sat over western Russia. 

 

Now lets see what is happening at T+192

EDH101-192.gif

 

Hights across the atlantic begin to weaken and at the same time the deep trough over the UK begins to weaken too.. the flabby heights to the east over russia begin to inflate and literally doubles in size. 

 

So at T+240 we have ....

EDH101-240.gif

 

A weak azores high penned in well to our south , a shallow looking trough to the north of the uk, which has actually been pushed back by a very good looking high to our east which looks like its advancing westwards. 

 

Sorry Ian, but are you sure you are looking at this years charts and not last years 

 

`IF` the ensembles are any where near the mark we can anticipate stalling lows, trough disruption and if really lucky undercutters.   

Either way, PM flows for the time being, with a chance of heights pushing into Scandi ... fingers crossed!!

As always I stand to be corrected but those are anomaly charts which means that they don't necessarily equate to dartboard low or flabby shallow high or whatever: they are average pressure at the time mentioned compared to average pressure generally. Therefore I am not sure that it is correct to interpret them as you have done.

That said I too am extremely confused by Ian's comment compared to Nick L as they seem completely at odds with each other. Ian refers to deep lows North of or even over the uk. This would suggest a generally westerly flow. Whilst that doesn't equate solidly to mild weather, it is very different from the scenario Nick mentioned in his post hence my confusion. I therefore do not think I agree with the "blizzards" comment (much as I would like to) as that would be highly unusual in a mainly westerly flow away from Scottish high ground, especially this early in the season.

The GFS in FI both 6z and 0z before it supported Ian to a degree in giving a westerly flow in FI but no dartboard lows and in any case Ian has previously said that GFS low res is given very little credibility.

The signs more generally seem to point towards a colder evolution as per Nick L but when METO say no, only a fool doesn't listen (although of course they could be wrong).

I am a bit generally baffled by this apparent dichotomy and really don't know what to make of it.

If Ian and/or nick could explain then I for one would be very grateful!

[bluearmy]

Around 10% of the ensemble members go for a lowering of heights over Europe, and HP taking hold to our NE. But 20% go for a Euro high!

 

The predominant pattern is one from the west or northwest, continuing the average-to-cold conditions, while remaining unsettled. The snow over the Scottish mountains could well continue to pile up.

10%? Would that be the same probability that the forecast zonality several weeks ago wouldn't make it and we would see a continental flow instead?

[Dancerwithwings]

What i find interesting is that the GFS didn't have a sniff of this northerly 48hrs ago for in 6 days

Really proves that things can change very quickly... Let's hope things get very Wintry for all

 

 

[bluearmy]

Interesting on several levels

[fergieweather]

Nick and ian are referring to the ECM clusters. The anomolys won't necessarily pick that up and the mean post day 10 definitely won't.

Your best indicator that we can see will be the london graphs in 30 mins

Moreover, I was also referring to 1000hPa clusters. I also did NOT say "all I can see is...". I merely said a repeating (sometimes potentially deeper) cyclonicity signal to N was striking: but bear in mind these are ENS clusters, not DET output! I see nothing in other output to alter that broadscale view: it also tallies with UKMO stance (posted earlier) on strong dipole of low heights to N, high to S, into 10-15d period.

[damianslaw]

Models supporting a more amplified flow over the atlantic as we move through next week aiding the development of more robust mid atlantic heights and conversely allowing a more northerly flow to develop as we head towards the weekend, the outcome of this will be some rather cold weather for December and certainly a significant risk of snow down to low levels where precipitation occurs even in some southern parts I would say - but still a while off.

 

Longer term - well as ever all eyes on developments across to the west atlantic, if we see further amplification take hold this would maintain stronger heights close to the west/northwest which could quite easily begin to ridge NE in the vicinity of Norway..  allowing lower heights to take hold over Europe.

 

Lots going on - no obvious signs of an impending very cold spell, nor anything particularly mild neither, indeed odds favour a continuation of near or below average temps as we move further into December.

[bryan629]

20% chance of a euro high... would definately have some on this thread revelling in glory, however, 10% of a scandi high sounds more like a no chance scenario.... what does the remaining 70% show ?

 

A very confusing picture just when i thought shannon had taken a holiday, like the PV is almost about to, Perhaps lets just get to middle of next week , get the storm out of the way, and enjoy the snow wherever it lands , im really certain we will be wheeling out the fat lady before long 

[TSNWK]

image.jpg

Interesting on several levels

Hello BA would you mind explaining a tad please why?

[BLAST FROM THE PAST]

What i find interesting is that the GFS didn't have a sniff of this northerly 48hrs ago for in 6 days

Really proves that things can change very quickly... Let's hope things get very Wintry for all

 

 

Good post, agree wholeheartedly.  That is quite an increase in amplification.  Can't wait for next 2-3 days worth of model watching...maybe some more amplification and probably some more flattening....and the elation and despondency 

 

BFTP

[gottolovethisweather]

Moreover, I was also referring to 1000hPa clusters. I also did NOT say "all I can see is...". I merely said a repeating (sometimes potentially deeper) cyclonicity signal to N was striking: but bear in mind these are ENS clusters, not DET output! I see nothing in other output to alter that broadscale view: it also tallies with UKMO stance (posted earlier) on strong dipole of low heights to N, high to S, into 10-15d period.

 

Ian, re: your final bit above.

 

Am I right to ascertain from this, that you believe the UK will be sitting to the North of the High Pressure area during this timeframe and thereby, largely under the influence of PM airstreams throughout. 

Edited December 6, 2014 by gottolovethisweather

[Polar Maritime]

Good post, agree wholeheartedly.  That is quite an increase in amplification.  Can't wait for next 2-3 days worth of model watching...maybe some more amplification and probably some more flattening....and the elation and despondency 

 

BFTP

 

Yes Blast, Lot's of uncertainty in detail, A few small shifts N/S can make all the difference in these set-ups. For which the Models can change at short notice for these adjustments.

Edited December 6, 2014 by Polar Maritime

[knocker]

 

What i find interesting is that the GFS didn't have a sniff of this northerly 48hrs ago for in 6 days

Really proves that things can change very quickly... Let's hope things get very Wintry for all

 

Very true things do change quickly particularly with the track and timing of these depressions but I think it a little unfair to say it didn't have a sniff. It was sniffing around the day before.

Edited December 6, 2014 by knocker

[bluearmy]

Hello BA would you mind explaining a tad please why?

Supportive of the raw output and the broken fronts in the sub 528 dam flow will deliver something wintry across Central areas on Thursday night.

[gottolovethisweather]

Hello BA would you mind explaining a tad please why?

 

I think he's referring to the 528DAM line snow-maker (give or take a few other required variables) and the positioning of an incoming warm front over Southern Britain bumping into frigid air.

 

Best not look into things too deeply at such a range though. 

Edited December 6, 2014 by gottolovethisweather

[fergieweather]

Am I right to ascertain from this, that you believe the UK will be sitting to the North of the High Pressure area during this timeframe and thereby largely under the influence of PM airstreams throughout. 

Although EC-ENSGrams for e.g. London or Reading show wide-ish but predictably so spread towards latter stages (I recall seeing 2m temps on 12z offering minority member support across anywhere from circa +12 to -3!), it looks broadly average as best my cursory look gauged (not mild) most of the way.

[bluearmy]

Certainly more colder options on the 12z T2m graph than the 00z.

Like I said earlier, trend or anomoly?

[bryan629]

Hello BA would you mind explaining a tad please why?

A long way off in meteorological terms, but a developing warm front pushing up from the southwest crashing into a frigid cold airmass... once far enough inland rain will turn readily to snow (or at least front edge snow), also heavy ppn comes with it. the front also has the potential to stall then pivot south eastwards. 

would be fun and games if it verifies and your underneath wherever it stalls 

[Mammatus]

Tonight's 18z GFS brings back thursday night's/friday morning's severe gales across southern England into East Anglia and Kent.

 

 

One to watch this one.....   

 

Mammatus

[kumquat]

We can see the model flux. The chopping and changing from one run to the next. Tonight coldies are happy. Last night and a couple of nights ago not so.

The Met Office output disappoints the coldies, but then we get Steve back after a hiatus of a few days and we also get Frosty back into the fold. Both buzzing positively just as BFTP (Fred) get's his solar/lunar cycles sorted. Ian F's posts sting with their realism. A real shot of pure science and backdoor insight and welcomed.

Nick S is providing his legendary translation of shortwave dramas, drawing on USA experts and providing exemplary pictorials. John Holmes gathering data and hitting us with upper air flow truths.

BA is right on the money, as usual.  Old Man Met has popped up a couple of times with intriguing foresight into global wave patterns and where he thinks they go.

There are too many people to mention including the regular site posters and forecasters. AWD (from our neck of the woods down in the SW thread) created a beautiful thread today going through all the ins and outs. GTLThisW has been a stalwart in providing great commentary and well thought out predictions.

IDO, Knocker and others provide the counterbalance, with reason.

What a great place to be.

 

PFJ touching Tunisia in the 18z GFS at 192

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014120618/gfsnh-0-192.png?18

 

Vortex almost totally gone from Greenland after this point yet this model is still seeing the Azores High as a major player for us. A lot to happen here but thoroughly fascinating to see.

[BlueHedgehog074]

Tonight's NOAA 8 to 14 Day Anomaly Chart continues the idea of higher than average heights to our South-West towards the Azores area (red dashed lines), with a bump in the green line towards the Azores suggesting ridging to our South-West.

The green line also demonstrates a flow, at the 500mb level, from between a West to North-Westerly direction over the British Isles. Along with higher than average heights towards Northern America with another little bump in the 500mb flow (green line) over Western Northern America suggests areas of ridging High Pressure in that area. Some lower than average heights extending from North-Eastern UK towards Greenland (blue dashed lines) with West to East Atlantic troughing, but perhaps with Low Pressure areas also digging East or South-Eastwards towards mainland Europe. The 'bendy' look of the general 500mb flow to the East of the UK could suggest this being the case. But whether it can help prevent the possibility of the Azores high ridging to our East, which could cut off the cool Westerly or North-Westerly flow, seems uncertain. (It could help, even, to re-amplify the High to our West, though amplification further upstream would probably help, too). Because there's higher than average heights over Northern America, it will probably prevent the Vortex chunks/low 500mb heights to our North-West from backing too far West into Northern America with these getting pushed further Eastwards at times. This would probably help maintain the Westerly driven pattern. And again, with the models showing quite a mobile Westerly pattern, it seems to make sense. Another aspect to note is that there is an area of higher than average heights over the Russian/Eastern Scandinavia parts with possible High Pressure cells in that area. As well as the Atlantic dominated outlook, the idea of High Pressure over the Russian area is akin to what a lot of the models show. This might provide a helping hand to possibly get Low Pressure systems to continue to drop to our East against the blocking High over Russia. Some models, like the 18Z GFS, show a similar sort of aspect for late next week and into the weekend. An example from the GFS at 150 hours:

 

(Low Pressure dropping to East. Amplified High Pressure to our West with a cold Northerly flow pulling down through the UK. Some High Pressure also to the far North-East)

 

It is also admittedly the help of amplification upstream that helps to achieve the outcome that the GFS shows for that time. 

 

But again, it's probably not worth getting too carried away since the anomaly chart I'm using does focus on days 8 to 14. And I think, personally, for now, any High Pressure to our far North-East will likely to be too far away to deliver deep cold to the UK (doesn't necessarily mean it can't happen at some point. Plus, the GFS 18Z run does show the build up of heights to our North-East with weakening of the Vortex to our North/North-West).

 

For the sake of it anyway, the 6 to 10 day version of the NOAA 500mb anomaly chart does seem to paint a colder picture for the UK, with better ridging/amplification to our West and troughing over, or to the East of, the UK. Noticeable UK North-West flow at the 500mb level too. So does fit along with the idea of the models providing us with some cool/cold blasts from the North-West or North later next week. 

 

 

As mentioned by others in the thread, the cold and snow fans do also have the pleasure of a wintry North-Westerly blast today (Sunday) and into Monday, with sleet and snow showers going on a rampage over North-Western areas. Particularly over high ground. 

 

(an example for Sunday evening from the 18Z GFS precipitation type charts)

 

Another thing to still watch out for is that stormy Low for the middle of next week. Still capable of giving some powerful gusts to places, especially those towards North-West facing coasts.

 

(Wind Gust chart examples used from the 18Z GFS for both Tuesday and Wednesday)

 

 

As such, do take care when venturing out during those days as it could be a bit wild out their, particularly also in the rain/hill snow/showers. (Edit: Mind you, there is also that example from Mammatus above for Friday). 

 

Overall, when considering the 8 to 14 day version of the NOAA anomaly chart, it would seem like a Westerly pattern will likely continue with ordinary conditions for December. And when comparing it to the more amplified looking 6 to 10 day anomaly chart, it would indicate the prospect of us loosing some of the amplification to the West and the pattern becoming a bit flatter. Nothing at the moment on the chart suggesting anything particularly cold either, plus the models themselves keep quite a Westerly pattern going in FI. It would probably be fair to say that their doesn't seem to be anything particularly mild either with a variable flow probably between the West or North-West, and with Lows possibility continuing to feed in towards the UK from the North-West. Maybe also, should models like the GEM and GFS continue with some build up of High Pressure to the North or North-East in deep(ish) FI with dissipating Vortex chunks to the North/North-West, then it could help make the Westerly pattern to become more sluggish with weather conditions becoming less stormier. That does, though, start reaching guesswork territory. But is personally how I see things for now.

 

Additionally, while it does filter out a lot of detail towards 240 hours, perhaps it is worth mentioning that the 12Z ECMWF H500 hPa  Pressure Ensemble Mean chart for that time-frame does go for an Atlantic Westerly pattern. Higher heights to South and lower heights to North: 

 

For next week, at least, there should certainly be a variety of weather conditions from blizzards, storms, rain, sunny spells, wintry showers and possible frosts, for various weather fans to enjoy. Up and down colder and less-cold conditions thrown in for good measure, too.

Edited December 7, 2014 by DiagonalRedLine

[MR EXTREMES]

Still a little disappointing for us in the south.

Although many are excited and understandably so !

Us in the south don't look like getting anything here.

Hopefully we can get some real heights nw or ne and channel lows this is possible but unlikely from the outputs seen.

Mind you pretty blowy at times but modified upper air is not to good for us in the sw se and South other than the highest hills.

Although coldest air does not look to be at our East more to our North and northwest.

So I'm hoping for a Greenland or Scandinavia heights but certainly not showing.

[Barry12]

The GFS is still going for the Northerly at day 6, but at day 7 the Azores high starts ridging in and we end up with with a W/SW. Hopefully the ECM continues with it's run from last night.

Also looks like the Azores is would move in at day 7 on the UKMO, so the most likely solution is a brief Northerly followed by some less cold and settled conditions.

There's still time for changes though, hopefully ECM prolongs the Northerly and the Azores is further SW.

Edited December 7, 2014 by Barry95

[Iceaxecrampon]

00Z for today  - 7th December ended up a downgrade to be honest - but travelling over Shap through Cumbria later today to Keswick

(and through Dunmail Raise on the A591) I will see what the conditions really are like.

 

 

All eyes obviously on Thursday

 

 

but a week yesterday

 

 

This is at +126 - was +144 considered reliable?

 

 

Could be a different story -  all in all a very interesting week on here.

 

Ian

Edited December 7, 2014 by Iceaxecrampon