Model output discussion - 1st December onwards

[knocker]

You could say this is a two pronged attack and then there was a trough in N. America (the HP to the NE is a constant) and it becomes one.

 

Edited December 4, 2015 by knocker

[BLAST FROM THE PAST]

Short and sweet from me.  What an ECM......landing point 10-14 Dec looking really promising with correct theme....let's get this in the reliable before we worry about detail but us coldies have earned this.  Am I optimistic or confident?   Those who know my style over the years know the answer........come on!!! we deserve this 

 

BFTP

[Ali1977]

So another GFS coming, back towards the ECM or another very average run...ECM my bet.

[knocker]

8 minutes ago, BLAST FROM THE PAST said:

Short and sweet from me.  What an ECM......landing point 10-14 Dec looking really promising with correct theme....let's get this in the reliable before we worry about detail but us coldies have earned this.  Am I optimistic or confident?   Those who know my style over the years know the answer........come on!!! we deserve this 

 

BFTP

Well optimism is a wonderful thing and not to be decried but I'm afraid I know not from where it springs. I can't see anything apart from periods of quite wild and wintry weather from Pm incursions, particularly in the north. And if you take the ext ecm you could probably add in spades.

 

[bluearmy]

Extended ECM eps beginning to look very troughy for  n Europe in general.  The jet digs south in tandem with this developing feature.  

[Nick F]

What I find interesting about the 12z ECM det. by the end of next week/following weekend is the development of the split jet stream over the Atlantic. The split jet has been a common feature over N America this autumn, but with the Canadian block drifting NE and the strong Pacific jet piling in across N America, the jet's forced to bifuricate, with a stronger southern stream undercutting the block over the U.S, typical of El Nino climo, and increasingly so the Atlantic days 8-10 as the PV retreats:

The 12z ECM det. and the 12z EPS control teleconnection forecasts both take the NAO and AO slightly negative from around the 11th, EPS mean falling to neutral with both NAO and AO, so an interesting step in the right direction.

The often optimistic extended EPS control kicks the Canadian ridge out into the Atlantic days 12-15, with deep trough over Europe, as Bluearmy mentions above too. But it remains to see whether the Canadian block sits too far west or spreads east. Even so, the southerly stream EC det. advertises will help pull colder air south towards mid-month.

Edited December 4, 2015 by Nick F

[london and south east kent]

Hi all  it looks like high pressure rise over Scandinavia on gfs tonight well it tries to ..

Edited December 4, 2015 by abbie123456

[Hotspur62]

23 minutes ago, abbie123456 said:

Hi all  it looks like high pressure rise over Scandinavia on gfs tonight well it tries to ..

And right to the end the GFS obliterates the Azores High so that has got to be a start lol!! ( I would how t384 but don't know how to attach could someone tell me how to do this as never been good on PC ). 

[damianslaw]

GFS seems to be doing its usual all over the place job today with the 12z and 18z offering wildly different evolutions as we move further beyond the reliable timeframe, quite often it does this, i.e. picks out the right theme longer term  only to drop it as it nears a more reliable timeframe, but only for the ECM to pick up on it, only for it to then fall back into line with the ECM and show what is was showing at the outset.. GFS is always a roller coaster ride it seems, ECM tends to hold its nerve much more.

The Jetstream forecast is still for a more southerly drag as we approach middle of the month which should enable colder PM air at least to nudge out the omnipresent tropical maritime airstream - which has been the dominant player since late October now..

Edited December 4, 2015 by damianslaw

[snowking]

4 hours ago, nick sussex said:

Overall some signs of a change towards colder conditions but it looks very messy and unconvincing. The PV chunk left over Greenland is a nuisance.

Temperatures look like edging towards average or slightly below which will feel a lot colder given the very mild conditions of the last few weeks.

Unless that PV chunk over Greenland departs the scene then it will be difficult to tap into any much colder air as blocking will be unable to get far enough east.

The overall NH pattern shown on the ECM T240hrs does have some scope, the Euro slug Spawn of Satan high does depart the scene for a few days but its equally vile sibling is waiting in the wings to the sw!

I think its difficult to read too much into any detail given how complicated the set up looks and its crucial that any phasing with those southern stream lows only happens once the pattern is sufficiently east or better still doesn't happen at all.

 

As exciting as the ECM 12z may be, I've been fortunate enough to follow and learn from Nick's posts over the years dating all the way back to the days of BBC Snowwatch, and yet again as on many occasions through the years, Nick's is the post I would really urge members to pay attention to.

We've seen numerous times in the past couple of years modelling really struggling with  'energy clearance' from the Greenland locale. Generally the trend has been for the 'FI' timeframes to show a clean transfer towards the Siberian side of the hemisphere, when the eventual result has actually been for a limited amount of energy to remain (frustratingly) in situ across the Greenland region.

Thats not to say that's what will happen in this particular instance, just that this has been the form horse in recent years. When this is added to the present state of the PV above our heads (and a little to the north!) I would suspect that longer range modelling is perhaps being a little too clean in the energy transfer across the northern hemisphere.

As my username would suggest, I very much hope to be proven wrong here, but I would suggest remaining cautious for the moment might be the best way to go. It's also worth pointing out that spikes in various teleconnecive indicators right now may be playing their part in adding to the model chaos, another reason to remain cautious.

SK

[Costa Del Fal]

51 minutes ago, snowking said:

As exciting as the ECM 12z may be, I've been fortunate enough to follow and learn from Nick's posts over the years dating all the way back to the days of BBC Snowwatch, and yet again as on many occasions through the years, Nick's is the post I would really urge members to pay attention to.

We've seen numerous times in the past couple of years modelling really struggling with  'energy clearance' from the Greenland locale. Generally the trend has been for the 'FI' timeframes to show a clean transfer towards the Siberian side of the hemisphere, when the eventual result has actually been for a limited amount of energy to remain (frustratingly) in situ across the Greenland region.

Thats not to say that's what will happen in this particular instance, just that this has been the form horse in recent years. When this is added to the present state of the PV above our heads (and a little to the north!) I would suspect that longer range modelling is perhaps being a little too clean in the energy transfer across the northern hemisphere.

As my username would suggest, I very much hope to be proven wrong here, but I would suggest remaining cautious for the moment might be the best way to go. It's also worth pointing out that spikes in various teleconnecive indicators right now may be playing their part in adding to the model chaos, another reason to remain cautious.

SK

Yes I would like to concur with these thoughts re Greenland. Very much like northerlies to the uk. In FI they look like clean beauties but as higher resolution kicks in the short waves kick in and it all becomes much messier in general most of the time. The same happens here and I have seen it much myself. Unsurprising given the locale around Iceland-Greenland is practically an area of semi permanent low pressure. I always think for most things nothing is impossible and hence with the weather especially there will always be times a clean shift of the PV towards Siberia will occurr but as the time nears, it can't help be favoured that bit more, a chunk of PV reimagining stubborn near Greenland and effectively, bottling the cold air or the true interest up north still.

[Mucka]

UKMO looking full of potential again this morning (GFS on right for comparison)

It still doesn't want to develop low pressure off the Eastern seaboard which GFS and to a lesser extent ECM have consistently modeled.

 

GFS 00z is actually quite a cool run as we get trapped under cold ridge but that kills any ppn and anyway it is not quite cold enough for snow to low levels.

It may be FI and not always develop cold but blocking is very slowly but steadily being modeled more frequently within GFS ensembles.

 

Also, it may be somewhat under the radar, but we may well be heading toward chilly/cool spell of weather in just a weeks time.

 

Considering how December has been so far and some of the dire predictions writing the whole of December off for cold, we are in a fairly good place though tbf no firm cold signal just yet and things could still flatten out again.  

 

Edited December 5, 2015 by Mucka

[knocker]

I'll start off with the premise that the weekend storms will be adequately covered elsewhere.

As already stated this morning's gfs is the usual mismash of Pm and Tm air with a number of quite cold incursions that will bring with them some quite wintry weather particularly in the north. Having said that Monday again introduces some very mild air from the SW but mitigated I'm afraid by some strong winds. But the main aspect of the run is that there are no major wind storms UK bound. This of course could well change by the next run and no doubt will. In the meantime the only one to keep an eye on in the near time frame is next Thursday and that looks like passing too far to the north, just brushing the Hebrides.

Charts weatherbell

Edited December 5, 2015 by knocker

[Iceberg]

Interesting set of runs this morning meto again screams potential Ecm bring a northland followed by a bit of an easterly and a snow storm for England at T216 thanks to s channel low. 

Gfs brings utter chaos. The models are all very different though and looking through the gefs I can't find a single run which models the energy at t72-96 in Canada in the same way at the meto and Ecm equally they all the gefs members are wildly different even by t144.

given all this end means are next to useless. In the past the models always behaved like this when a pattern change was occurring. What it will lead to is unknown but pretty good agreement it will be different to the current weather.

 

[Mucka]

ECM 00z is quite a cold run and underlines what I was saying earlier about a possible cold spell being just a week away - let's hope it sticks or even upgrades.

 

 

And best of all it has those tweaks I talked about in yesterdays 12z to allow for possible snow. (note the low tot he South and the cold upper air.)

 

 

Not long lived as the Atlantic attempts to move back in but likely some frontal snow before turning to rain if it were to verify (which of course it wont at this range) and perhaps more importantly the pattern upstream remains amplified so another cold shot would be likely not far away.

 

 

Edited December 5, 2015 by Mucka

[bluearmy]

Anyone have a pin.? I can supply the tail and the donkey.

[knocker]

Regarding the low next Thursday the ecm has a interesting different take on it.  It has the low south of Iceland at T120 and then another perturbation forms in the southern quadrant of this which twelve hours later is over Stornoway. If this pans out which is unlikely it could bring gusts in excess of 70kts to Scotland.

 

[northwestsnow]

Well im delighted with this mornings runs.

Something much more seasonal from the euro models with the brakes finally being applied to the Atlantic steam train.

Potential for some snow across parts of the south on this mornings ecm I would suggest.

[Frosty.]

Well the Ecm 00z will cheer up the coldies down south who are currently enduring  very mild mush with temps of 13/15c, the good news is the ecm shows a nationwide change to much colder conditions from next friday with wintry showers and then more settled with widespread frosts becoming increasingly sharp...let's hope the ecm is on the right track.

[carinthian]

Good Morning all. Some good news as all 3 main models show much of the British Isles in a colder regime by this time next week with the source of Airmass Pm. Also good news the last of the prolonged train of Atlantic depressions show a rest bite with a fragmenting and weekening jet stream. Can the colder conditions take a hold ? this will in all purposes will depend on where the main rise in pressure locates during this period after next weekend. The general thought is a rise to the southwest and retrogress NW as with GFS output or move towards the continent as ECM indicates, either would provide a much more settled colder spell for all. Crucially, the UKMO post 144 hour forecasts may provide the answers later today.

 C

Edited December 5, 2015 by carinthian

[damianslaw]

Models all showing a more amplified flow by this time next week. Crucially this will mean a brake on the constant mild flow and wet atlantic flow. This change is just outside the reliable timeframe, if the models continue to show it over the next day or so then we should be seeing a much more seasonal spell of weather come middle of the month.

[Captain Shortwave]

Whilst the operationals offer some cold here and there, no sign of anything particularly prolonged, the enesembles and anomalies continue to offer a rather mixed message but ultimately are struggling.

The ECM ens do move the trough east towards Scandinavia

The signal looks pretty weak by day 9 and 10

GEFs

The GFS later on builds a weak ridge east of the UK with the trough back in the Atlantic

 

Rather unsure at the moment, a lot of uncertainties caused by some discrepancies in the earlier timeframes, again the development of an area of low pressure off the eastern seaboard around day 5 at its future track being one of these.

Overall cooler conditions do look likely to occur at the end of the coming week, but how cool/cold or how long is the major debate here.

Edited December 5, 2015 by Captain Shortwave

[Polar Maritime]

Yes the ECMWF & GFS both seem to go for some kind of Northerly around the 12th. With Lows taking a more Southerly track into the 2nd half of December bringing cooler temps, And a continuation of storms tracking off the Atlantic but with more of a N/W Pm influence than West. Will the 6z hold the same theme..

 

Edited December 5, 2015 by Polar Maritime

[knocker]

Looking at the outputs this morning I cannot find any substantial reasons that indicate any major change. To be honest the det. runs are such a dogs dinner that anything after about five days is a guessing game or wishful thinking. The anomalies are broadly consistent with the upstream pattern although downstream they do play around a bit with weak ridging around the UK and the trough mid Atlantic around mid run.

In the ext period the ecm settles down. At T288 It has HP NE Canada (funny that) LP over the Pole. the vortex NW Greenland with a trough mid Atlantic with weak ridging to the south of the UK.  No significant change in all of this by T360 except the Atlantic trough becomes negatively tilted over the UK

The upshot of all this IMO are periods of unsettled weather with a few Pm shots bringing some very wintry conditions of wind, rain and snow in the north interspersed with some periods of more settled conditions particularly in the south as the HP pushes  in from the SW/S. This fluid changeable outlook will result in some big swings in temp but around average on the whole.

 

Edited December 5, 2015 by knocker

[shaky]

Atlantic completely different again on the 06z!!low is no where near as deep!!not heard from fergie on this thread for a few days!!maybe something is brewing then lol!!!