Model Output Discussion 1200 hrs 15/11/14

[BlueHedgehog074]

And its there again, let's keep watching this IMO as its the route to our 1st potential real cold blast. I know its GFS AND the 18z but you get the idea.

Looking forward to the next few days modelling....well actually the next 3 months

BFTP

Kind of a shame it's locked away in FI. But I must admit, it's nice to see some of the operational models continue the signal of Low Pressure digging down to the East/South-East of the UK with High Pressure amplifying to our West to help allow these cold Northerly or North-Westerly flows. It could definitely be something to keep an eye on should the models continue this idea, and especially if it makes it into a more reliable time-frame.

Along with the likelihood of High Pressure settling over the UK within a few days time (with Southern/South-Eastern areas probably being exposed to some kind of (slack) cool Easterly flow from the High Pressure system's Southern flank), it could help to make things feel seasonable.

Edit: Will certainly be interesting to see what sort of journeys the models lead us through along the path of Winter.

Edited November 26, 2014 by DiagonalRedLine

[Mucka]

18z ensembles the first to really show decent amplification in FI with a strong Atlantic ridge and WAA toward Greenland on a few runs.

Hoping this signal grows and we can get more than just a Northerly and toppler if the output goes that way.

Edited November 26, 2014 by Mucka

[blizzard81]

I fully understand your point, my point was that back then, we might not have seen that coming. That the logical evolution is not necessarily the actual outcome. Even the highly respected Met office are frequent victims of natures defiance of logic

 

It looks like we both understand one another's point of view and that can only be a good thing

[knocker]

A quick glance at the GFS and P this morning can be summed up thus. From about T132 the Atlantic dominates. That is the strong HP from the SW which forces the jet north of the UK producing a north/south split. Temps revolving around the average but generally slightly below.

Charts courtesy weatherbell

 

[Captain Shortwave]

Model output at day 6

UKMO

GFS

Parallel

GEM

All pretty similar at this stage with the Azores high pushing eastwards towards the UK. Will the preceding polar maritime flow deliver some wintry potential? GFS/Parallel and UKMO bring 850s of around -4C through the UK, so definitely some snow over the high ground and maybe some hail and sleet briefly to over levels. The GEM barely drops 850s below 0C though. ECM is similar to the GFS/UKMO solution.

The GFS ensembles show high pressure holding (especially) over the south for a good few days whilst rain might push into the north west at times. Beyond that, the GFS continues its rather volatile output so it's again not worth looking beyond day 10 really even on the ensembles.

Edited November 27, 2014 by Captain shortwave

[knocker]

A look at the GEFs anomalies.

 

At T240 Troughs Pacific, Canada aligned east and another pole aligned south eastern Europe. HP north America and Atlantic, By T312 much the same except the Canadian trough extends into Scandinavia and the one in eastern Europe disappears.

 

The upshot of this is the UK continuing under the influence of the Atlantic HP with the lows zipping north of the UK with the jet. Before anyone repeats the mantra that it is pointless looking at the charts later than 1800 today this situation will no doubt change but the key to unlocking the door of the time and direction of these changes I leave to higher authority. I will say there is no indication of cold conditions anytime soon.

Charts courtesy weatherbell

Edited November 27, 2014 by knocker

[Polar Maritime]

The GFSP again this morning shows some wintry Pm shots from around the 8th.

 

[bluearmy]

Gefs in week 2 are a 'dogs dinner'. Too many options and too large a spread across the NH to make a stab at a broad solution.

That means anyone saying they know what will happen week 2 is 'avin a laugh'

[Ali1977]

I think the positioning of the high next week needs watching closely and may pave way to some colder weather. The FI in the ensembles shows quite a few members with WAA heading towards Greenland, breaking through the high latitude PV. I still think the models are struggling in dealing with the current strat warming/Azores high and a flip late next week to a Northen blocking isn't out of the question .

[Duane S.]

Still waiting for the long touted start of the zonal train...

 

There seems to be an appetite for an strong poleward-heading Eastern Pacific ridge towards the last week of December. This could be the main catylist to cold with a meridional airflow taking place upstream and with mid-lat high pressure likely to be centred somewhere between us and a thousand miles west, a decent Atlantic Warm Air Advection surge into Greenland has to be a possibility.

Edited November 27, 2014 by s4lancia

[IDO]

The GEFS are still playing with this pattern change in FI and I am expecting the evolution to swing back and forth over the next few days at least. The D13 GEFS are:

 

 

Similar to yesterday with respect to the pattern. Though a subtle change to a less progressive Atlantic. This morning's GEM stalls the second Atlantic high in the Atlantic, and this has little support amongst the GEFS at the moment:

 

 

It's a GEM trait. Its what some of us were hoping to see around the end of FI, once more of the lower heights had drained off the Greenland region. Some of the GEFS do this around D16 (six on the 0z) so this would be promising for trop up-warming to the strat.

 

ECM is like the GFS with at D10 the third Atlantic high entering stage left, rather than GEM's stalling high: 

 

So a settled period especially for the south on this morning's GFS Op; mild till the end of Monday, cooler as the cold front heads through with a band of rain, then dry through till D15 for down here. The GFS P sinks the high during the run and around D10 it is unsettled for most with two shots of cold air, one PM and the other AM. These are the two of the main clusters in the GEFS FI with the more amplified Atlantic ridge the other cluster. Lets see how this develops.

Edited November 27, 2014 by i'm dreaming of...

[shaky]

Gefs in week 2 are a 'dogs dinner'. Too many options and too large a spread across the NH to make a stab at a broad solution.

That means anyone saying they know what will happen week 2 is 'avin a laugh'

something is defo brewing mate!!! Personally i dont even think the models are handling next Tuesday/Wednesday well at the moment! ! I feel there are still changes to come with maybe a bit more westward correction!! Another thing is there a chance of snow aswell next Wednesday as the front coming in from the north west hits the cool dry air from the east? One thing for sure is its gone feel much colder than we have been use to!

[knocker]

But is it actually cool dry air from the east? I would have thought snow unlikely given the temp forecast.

Chart courtesy weatherbell

[Due South]

But is it actually cool dry air from the east? I would have thought snow unlikely given the temp forecast.

Chart courtesy weatherbell

Knocker we need to get the cold in first. The rest will follow.

[ANYWEATHER]

something is defo brewing mate!!! Personally i dont even think the models are handling next Tuesday/Wednesday well at the moment! ! I feel there are still changes to come with maybe a bit more westward correction!! Another thing is there a chance of snow aswell next Wednesday as the front coming in from the north west hits the cool dry air from the east? One thing for sure is its gone feel much colder than we have been use to!

Morning, as I said last night ,that Azores high is the fly in the ointment, we need that to retrogress somewhat and amplify in midAtlantic and then there would be some fun and games. Models are still toying with that idea in a round about fashion, and nothing is nailed at all beyond this coming weekend....

[MR EXTREMES]

But is it actually cool dry air from the east? I would have thought snow unlikely given the temp forecast.

Chart courtesy weatherbell

can i ask in a polite manner who are you replying to ?

and i suspect your right not cold enough yet from the east for snow as i said yet.

 

its looking pretty much as the charts where showing yesterday but the consistent trend over all shows the vortex over the siberian side getting bigger because you can see it draining west to east.

 

 we enjoy sunny fresh frosty wintry days,

 

  some areas where fog will become a feature could be rather cold.

 

very seasonal and im starting to see the gaps where pressure could build north west greenland heights low pressure dominating scandi area so heights into scandi dont look as likely as the vortex will be to close in this area.

 

i think our first blast of cold will be nw then as the vortex cracks on with its holiday to siberia we the start to see areas opening up for blocking to our north or northwest then the next cold outbreak could well be arctic air then a siberian north easter.

 

its not even winter yet and ive seen this type of pattern in the 80s.

slow burner this one 

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY THURSDAY NOVEMBER 27TH 2014.

NEXT UPDATE FRIDAY NOVEMBER 28TH 08:00

THE CURRENT GENERAL SITUATION  A strengthening SE airflow will develop across the British Isles later, today, tonight and through tomorrow.

MODELS-2 WEEK HEADLINE  Becoming mostly dry with just a little rain chiefly in the North at times. Some frost and fog patches in variable temperatures.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast shows the flow simplifying but fairly strong in a flatter pattern across the far North of the British Isles through the latter stages of next week before slowly migrating South towards Southern England later in the period.

GFS OPERATIONAL The GFS operational this morning shows that High pressure will soon become the dominating factor over the British Isles following the passage of a cold front SE early next week. It's centre is shown to lie across Southern Britain innitially before weak cold fronts attack it from the NW on occasion only for it to rebuild in situ over the UK once any front has passed maintaining the dry weather with variable cloud and only very occasional rainfall and periods of mist and fog and local frost issues intermittently over the whole period.

THE GFS PARALLEL RUN The GFS Parallel run keeps High pressure just that little bit further towards the SW and this allows some troughs SE across the UK at times with some rain at times chiefly in the North. On each passage of fronts a slice of colder clearer air will likely deliver frost and fog night and morning in places before the skies gradually infill with cloud off the North atlantic ahead of the next front. Late in the run the High slip further South allowing a more pronounced dig of unsettled and at times colder weather across all areas with some rain and snow on Northern hills.

THE GFS CONTROL The GFS control run also shows High pressure being the dominating factor across the UK. It's centre over the South next week gives rise to frost and fog issues and rather cold conditions as a result for a time. Later in the run as the prallel run the High shifts further to the South and allows a charge of more unstable and Low pressure from the NW to bring rain for all and as this clears to the SE later winds switch NE with cold and grey skies with rain, sleet and snow in SE areas with drier and clearer weather in the NW.

THE GEFS ENSEMBLES The GEFS Ensembles show that the most likely scenario is for a pattern towards Low pressure to the North of the UK and High pressure near the Azores is the most likely place we arrive at in two weeks from now with rain at times for all in average temperatures. In the short term High pressure close to southern Britain next week will keep things dry and chilly here with night and morning mist, fog and frost issues.

UKMO UKMO today shows a trough of Low pressure moving away East early next week having introduced cold and cleaner air to all of the UK with frost by night. As High pressure then moves in over Southern Britain midweek fog will also become an issue in the South while the North becomes rather cloudy but largely dry and less chilly as winds freshen from the WSW.

THE FAX CHARTS The Fax Charts support the models raw data well this morning with a freshening SE flow in a day or two gradually backing Easterly and dying down over the weekend. Complex troughs will gradually decay and move away from the UK for a time before occluded fronts move in from the West late on the 5th day.

GEM  GEM this morning also shows High pressure developing to the SW next week replacing the slack weather pattern of the weekend with a light North or NW flow following a trough East. This will bring a day or two of cleaner air with patchy frost and fog at night. Cloud will roll around the top of the High by midweek extinguishing the frost and fog issues and as the High then relocates to an intense feature in the mid Atlantic the door is open for cold weather to arrive on Northerly winds for all with wintry showers in the North and East together with frost at night for many.

NAVGEM NAVGEM prefers to keep a ridge across the UK from the High over Eastern Europe in a weeks time with dry and benign conditions for all with frost and fog patches in places, slow to clear in the light winds.

ECM  ECM this morning maintains the theme developed yesterday in that High pressure to the SW of the UK looks the driving force from next week. There will be a period of chilly and frosty weather early next week especially over the South as the High drifts over Southern Britain for a time following an early week cold front. From the charts late in the period a rinse and repeat pattern looks likely in the days that follow with another cold front introducing another pulse of chillier and cleaner air with patchy frost and fog in the South following a cloudier and milder interlude for all with a little rain.

THE ECM ENSEMBLES A slightly more encouraging 10 Day ensemble chart this morning shows High pressure further out onto the Atlantic towards the Azores with a ridge to the UK moving SE ahead of a Westerly flow. With a Jet flow sinking South synopticsjust to the East of the UK conditions look encouraging for an impending Northerly flow a few days on.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The theme remains for the UK to lie under the influence of High pressure most likely positioned just to the SW of the UK over the period.

MY THOUGHTS The models continue to theme around High pressure to lie close to the SW of the UK through the period. This makes predicting day to day and place to place conditions at this time of year very difficult but I would have to base the theme as a fairly dry outlook with only small amounts of rain at times as weakening cold fronts make their way SE at times. What is far more difficult to predict is how much cloud is trapped within the High's circulation which can of course have major implications of amounts of fog and frost that occur and how once formed this clears each day as this can have a massive impact on daytime and nightime temperatures. These details cannot be predicted at this stage as the positioning of the High will help dictate this come the time. Basically if it makes landfall across the South which is shown by some output then frost and fog could be widespread and persistent but if it is held to the South and SW as some other output shows then cloud spilling arond the North of the High along with more in the way of a Westerly breeze will keep things milder and benign for many. Then we move on to where we go later in the run with the majority showing some degradation of the High both away from the UK and also to the West which in theory opens the door to cold air from the North of the UK to advance South and perhaps give the chance of some snow for some in the North and East later. With a predicted slow shift South of the Jet flow over Europe in Week 2 this becomes a distinct possibility and is becoming the UK's best shot at cold in the near future so lets see if it develops and gains cross model support in the next few days. In the meantine we must settle down to a period of benign and quiet conditions weatherwise with chasing cloud cover along with frost and fog patches and the odd patch of rain the most exciting it gets over the next 10 days or so I'm afraid.

[snowking]

But is it actually cool dry air from the east? I would have thought snow unlikely given the temp forecast.

Chart courtesy weatherbell

 

No, it's cool dry air from the West:

 

 

In all honesty the outlook this morning is two things

 

1 - Changeable

2 - Extremely uncertain (looks like our friend Shannon is here to stay for a while longer yet, which is not surprising given the present setup)

 

SK

[IDO]

The three main models means at D10:

 

  

 

Broad pattern similar, though as you would expect the GEFS to be flatter, due to their progressive Atlantic bias. The GEM mean not supportive of its op (again) and the control is more in line with the ECM & GFS ops.

 

The ECM at D10 remains very high confidence for an Atlantic high:

 

 

The D8-10 mean anomaly for the GFS/ECM comparison:

 

 

Subtle differences but the overall pattern mirrored.

 

 

[knocker]

 

No, it's cool dry air from the West:

 

That was actually the point I was attempting to make. Plus the humidity is reasonable high.

Edited November 27, 2014 by knocker

[Shunter]

That was actually the point I was attempting to make. Plus the humidity is reasonable high.

 

Given NOAA's latest updates....I think some of this mornings comments on this forum regarding medium term flows are really irrelevant.

 

Quote:

 

  USED THE MOST RECENT EUROPEAN CENTRE ENSEMBLE MEAN AS A SYNOPTIC

BASE AT THE MEDIUM RANGE. NONE OF THE ENSEMBLE SUITES OF THE PAST

FEW DAYS HAVE PROVEN PARTICULARLY ACCURATE OR STABLE, WITH THE

ECENS MEAN THE LEAST VOLATILE. THE OPERATIONAL MODELS, OF COURSE,

HAVE BEEN EVEN MORE SUBJECT TO THE WHIPLASH CHANGES THAT HAVE COME

WITH EACH NEW DATA CYCLE.

 

Shannon Entropy continues

Edited November 27, 2014 by Shunter

[mushymanrob]

im abit bemused by some referrances to 'mild' and 'zonal train' that have been made in the last 12 hours or so.

i dont think anyones touted a mild, zonal, atlantic regime the sort that we has a few weeks ago. theres not much mild to be had at all, but all models are pointing to a high pressure dominated regime, mid latitude high pressure at that.

to me the outlook into early december is largely quiet, largely dry, largely overcast, and largely average temps. and theres as much chance of a mild spell in fi as there is a cold one, but as things stand theres little chance of either.

[IDO]

Given NOAA's latest updates....I think some of this mornings comments on this forum regarding medium term flows are really irrelevant.

 

Quote:

 

  USED THE MOST RECENT EUROPEAN CENTRE ENSEMBLE MEAN AS A SYNOPTIC

BASE AT THE MEDIUM RANGE. NONE OF THE ENSEMBLE SUITES OF THE PAST

FEW DAYS HAVE PROVEN PARTICULARLY ACCURATE OR STABLE, WITH THE

ECENS MEAN THE LEAST VOLATILE. THE OPERATIONAL MODELS, OF COURSE,

HAVE BEEN EVEN MORE SUBJECT TO THE WHIPLASH CHANGES THAT HAVE COME

WITH EACH NEW DATA CYCLE.

 

Shannon Entropy continues

Hi

The NOAA discussion was based on the 0z and 06z from yesterday and models have moved on from then. I would agree 24 hours ago there was more uncertainty due to the probable pattern change. Also the uncertainty related to a possible ridge in the west of the conus in the 8-14 day period. Downstream impact on the UK would be later in that period. Therefore I still believe the next 10 days show high confidence for our region, though surface conditions are less easy to predict with plenty of potential for fog, frost, sun, etc.

[knocker]

Given NOAA's latest updates....I think some of this mornings comments on this forum regarding medium term flows are really irrelevant.

 

Quote:

 

  USED THE MOST RECENT EUROPEAN CENTRE ENSEMBLE MEAN AS A SYNOPTIC

BASE AT THE MEDIUM RANGE. NONE OF THE ENSEMBLE SUITES OF THE PAST

FEW DAYS HAVE PROVEN PARTICULARLY ACCURATE OR STABLE, WITH THE

ECENS MEAN THE LEAST VOLATILE. THE OPERATIONAL MODELS, OF COURSE,

HAVE BEEN EVEN MORE SUBJECT TO THE WHIPLASH CHANGES THAT HAVE COME

WITH EACH NEW DATA CYCLE.

 

Shannon Entropy continues

 

Why should comments made in a very subjective discussion forum be deemed irrelevant. The reasoning or conclusion may be incorrect but to incorporate the thread without them would leave the thread a bit threadbare, so to speak. If sticking to the short term is the order of the one might just as well tune into the METO, the creme dela creme.

[Nick F]

After the weekend, the upper flow around the north hempishere looks alot more progressive than we've seen in recent weeks, where it's been quite convoluted and blocky. The +ve PNA ridge goes across the west of N America, ending the chance for cold arctic shots across the eastern two-thirds of N America as we head through the first half of December.

 

However, we are fortunate here in the UK, that this last of the current trough disruptions will set us up with a stubborn belt of mid-latitude ridging across us (a link up of the Russian and Azores high centres) through most of next week. because the flow north of the ridge will be quite progressive, as it is upstream over N America - with lows ploughing into Scandinavia. The problem for the models is whether this more progressive flow to the north sinks down and/or waves developing upstream amplify the ridging north to allow a cold N or NWly flow.

 

Looking at the ENS, I think the idea of Scandi high bringing cold air from the east is much less of an option now, given the progressivness of the flow and the background of the low heights deepening to our north despite the signal for a +ve anomaly over the North Pole. So those waiting for wintry potential may have to wait for a wave to work through to amplify a ridge north to allow some colder air south.

 

However, the first week of December is looking a lot more seasonal, parts of eastern England will feel some colder continental drift Sunday into Monday, then a cold Pm airmass spreads SE late Monday and Tuesday, the colder air trapped at the surface as HP builds in from the west for the rest of the week, bringing chilly days and frosty nights.