Model Output Discussion 1200 hrs 15/11/14

[Midlands Ice Age]

 

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.

Knocker

I do not think that Shunter's post is trying to say ALL posts talking about the medium term are irrelevent just the ones posted this morning due to the changes or uncertainties up-stream.

MIA

[knocker]

And it what way did my post exclude this mornings comments?

[Nick L]

Ok guys let's drop it please and not derail the thread.

 

Cheers.

[knocker]

It's not really derailing the thread, merely shunting the irrelevant posts into a siding.

[SMU]

http://www.meteociel.fr/ukmo/runs/2014112700/UN144-21.GIF?27-05

 

My lost post for the week before Winter forecast...-

 

UKMO ;looks like one of those historic charts a few days before things go mad with bitter NE winds - lets hope so!!

 

Models have pushed a tad further East today, so the cold continental air is held at bay, looks like an average start to Dec!!!

 

Enjoy!

[Paul]

The Netweather winter forecast has been issued - 'A cold hearted winter'

 

https://forum.netweather.tv/topic/81904-netweather-winter-forecast-201415-a-cold-hearted-winter/

 

(please don't discuss in here!)

[TonyH]

The three main models means at D10:

 

gens-21-1-240.png EDM1-240.gif gens-21-1-240 (1).png

 

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:

 

get_legacy_plot-web248-20141127083908-17763-0341.gif

 

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

 

test8.gif

 

Subtle differences but the overall pattern mirrored.

I am always amazed why people feel a model would be biased. Surely with the vast amount of expense and detail of programming that goes into them they would have ironed out this bias?

[TonyH]

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.

Agreed Mushy, that aspect did confuse me, I have not been reading of a 'zonal train' etc for a long time on here except from those accusing 'mildies' of doing so 

Edited November 27, 2014 by TonyH

[warrenb]

Indeed the zonal train is in fact to the north of Scotland.

[Gibby]

The 6z GFS op shows an intense displaced Azores High just off SW Britain at the end of it's run supported by a strong and flat Jet stream much too far North to nudge it away and it is an increasing and worrying trend for the start of Winter because such synoptics can prove stubborn to shift once formed and and can also become a repetitive pattern as past Winters can testify too It is at least shown very early in the winter and is way out in la la land at the moment. Let's hope it is removed in subsequent runs.

[Weather Boy]

I am always amazed why people feel a model would be biased. Surely with the vast amount of expense and detail of programming that goes into them they would have ironed out this bias?

 

It's because many of them clearly are. Even to a casual viewer like me can see that the GFS (prior to its upgrade) is always looking to bring back Atlantic dominance, summer or winter, to our latitude.

 

The better question is exactly how you have put it except deleting the words "people feel"!

 

They are biased, but I do agree that such things should be ironed out.  Maybe the GFS P is an attempt to do so.  The jury is out!

[bradymk]

Just a quick look at how the models but the GFS in particular really tend to underestimate the influence of a block to our east, such as the one we have had recently. 

 

10 days out (17th November GFS)

Positively tilted trough, overestimating the atlantic

 

At 6 days out, it still was underestimating the block with a positively tilted trough.

 

Current Chart - Much stronger high to our east, negatively tilted trough, very different outcomes.

 

Just something to bear in mind when viewing charts days ahead with a situation like this. It is almost always continually corrected westwards as we approach reality.

The atlantic barraging through, closer to the time has actually turned into a mainly dry south easterly air flow before a mid lat high builds in to bring an average start to December and much more seasonal than this time last year with plenty of fog & frost for most at times. We await the second part of December with interest.

Edited November 27, 2014 by bradythemole

[mountain shadow]

The 6z GFS op shows an intense displaced Azores High just off SW Britain at the end of it's run supported by a strong and flat Jet stream much too far North to nudge it away and it is an increasing and worrying trend for the start of Winter because such synoptics can prove stubborn to shift once formed and and can also become a repetitive pattern as past Winters can testify too It is at least shown very early in the winter and is way out in la la land at the moment. Let's hope it is removed in subsequent runs.

If we had a raging Polar Vortex then I would agree with this, however, the PV is fragmented and a displaced Azores High towards our shores is not necessarily a bad thing. Many a cold spell has began with a UK local mid latitude high.

 

As the 6z GFS P shows, it can retrogress weswards and then Northwards in reaction to the East moving trough to give a Northerly. Again the 8th December showing a possible cold snap.

 

One thing we always need to get rid off before a cold spell can kick in, is the Greenland vortex segment, hopefully this is the start of a trend to increase upper height in the Greeland area.

 

https://max.nwstatic.co.uk/gfsimagesnew/gfs.20141127/06/264/h500slp.png

[ukpaul]

A very promising GFS 06z*, just the sort of pattern that breaks up the PV. It's a shame we don't get any ensembles, as you can see below it parts company with the existing set early on (and has been doing so consistently, suggesting a notable change in the modelling). Are they available anywhere, I presume from verification stats that it is running?

 

 

Parallel is the yellow and black line, at 72h it separates and from then on is developing from a different scenario.

 

 

* (the parallel that is, why some are still persisting with the lame duck version I don't understand)

 

The ECM ensembles clearly show a split with the op now not just towards the warm end but being the warmest out of all of the runs at 120-144h

 

Edited November 27, 2014 by ukpaul

[nick sussex]

After my enforced absence due to a squirrel chewing on my telephone cable which led to no internet I'm back! lol Seriously though France is great but rural phone services leave a lot to be desired.

 

Surveying the latest outputs is rather underwhelming as low heights to the north don't allow for an easterly to really advect anything deeper cold in and its a case of the mid latitude high being the more likelier option.

 

There are still some more favourable ECM ensembles but they're in the minority cluster, the question really is how long lower heights will remain in the Med, this is important to stop the high sinking too far.equally the degree of amplitude upstream has been quite volatile so far this Autumn, the case has generally been more in the longer range than initially progged by the models and ensembles.

 

It's not the worst outlook and really anything is preferable to mild rain.

 

So will it be a long drawn out mid latitude high then a sinking or will it be the former morphing into something better later.

[mountain shadow]

The MJO could be supportive of Greenland heights rises from around the 8th December onwards as it should progress towards Sectors 8 and 1 which aid blocking the Greenland local.

 

Clearly the further away from the centre the better.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/foregfs.shtml

[mushymanrob]

I am always amazed why people feel a model would be biased. Surely with the vast amount of expense and detail of programming that goes into them they would have ironed out this bias?

 

 

It's because many of them clearly are. Even to a casual viewer like me can see that the GFS (prior to its upgrade) is always looking to bring back Atlantic dominance, summer or winter, to our latitude.

 

The better question is exactly how you have put it except deleting the words "people feel"!

 

They are biased, but I do agree that such things should be ironed out.  Maybe the GFS P is an attempt to do so.  The jury is out!

 

i dont see it as 'bias' as that suggests a deliberate human input, i believe ALL the models are honest and produce predictions based on the data received. its just that some interpret the data and reach differing conclusions. like the gfs is quick to bring in the atlantic, probably because thats the most likely outcome for the uk.

[IDO]

i dont see it as 'bias' as that suggests a deliberate human input, i believe ALL the models are honest and produce predictions based on the data received. its just that some interpret the data and reach differing conclusions. like the gfs is quick to bring in the atlantic, probably because thats the most likely outcome for the uk.

 

 NOAA has a wealth of verification charts and they are all titled as "bias". Bias in statistics is: 2.Statistics: A systemic inaccuracy in data due to the characteristics of the process employed in the creation, collection, manipulation, and presentation of data, or due to faulty sample design of the estimating technique.

Read more: http://www.businessdictionary.com/definition/bias.html#ixzz3KH4A7rud

 

Of course the models are not designed to show bias, its inherent in the algorithms or data, as you highlighted.

 

I am always amazed why people feel a model would be biased. Surely with the vast amount of expense and detail of programming that goes into them they would have ironed out this bias?

 

The mean bias for GFS at D7 provided by NOAA: 

 

I have never suggested the programmer has intentionally built a bias into a model, it is a statistical bias from reanalysis. All models have some sort of bias; ECM over does heights after D7, GFS overdoes lower heights around Scandi and GEM blows up lows.

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

[Bristawl Si]

The 6z GFS op shows an intense displaced Azores High just off SW Britain at the end of it's run supported by a strong and flat Jet stream much too far North to nudge it away and it is an increasing and worrying trend for the start of Winter because such synoptics can prove stubborn to shift once formed and and can also become a repetitive pattern as past Winters can testify too It is at least shown very early in the winter and is way out in la la land at the moment. Let's hope it is removed in subsequent runs.

"such synoptics can prove stubborn to shift once formed"

 

I think i've read this statement about every type of synoptic pattern since i first joined NW.

No offence, but it really is a most over-used phrase on here.

[festivalking]

"such synoptics can prove stubborn to shift once formed"

 

I think i've read this statement about every type of synoptic pattern since i first joined NW.

No offence, but it really is a most over-used phrase on here.

 

Problem is though this particular type of weather became very common towards the end of the last century up to 2008......if you were there you'd be worried too

[Ali1977]

I've booked to go skiing 03rd of Jan, and to be honest with this set up even the alps don't look to good for snow...dry for the foreseeable too so I'm sure the resorts their are starting to worry.

[carinthian]

I am really interested to see how the development of the Med low pressure evolves over the coming days. These can be very unpredictable regarding the amount of precipitation to expect.

The first depression is now giving heavy rainfall in Southern Spain and the secondary depression expected to develop over the Med Basin into the weekend. A strong moderately baroclinic sub tropical jet lays to the South and East, this should enhance development. More than likely later in the weekend a upper level trough would seem more likely as colder air is increasing engaged to the north. So a welcome snowfall to the Eastern Alps seems now likely by the beginning of next week. How well the various numericals deal with this situation will have to be seen. The general consensus of the main models is for it to sink and fill. I for one is not too sure about the speed of this to happen. Into the middle of next week there remains some doubt about the influence and engagement of the polar maritime air mass mix into the continental feed, that's the view over here. There still remains the chance of increased precipitation in the SE of the UK in associationn with the development of the upper trough.

C

[mushymanrob]

"such synoptics can prove stubborn to shift once formed"

 

I think i've read this statement about every type of synoptic pattern since i first joined NW.

No offence, but it really is a most over-used phrase on here.

 

i think that phrase is most apt when dealing with high pressure and possibly only applies to high pressure as anticyclones do tend to sit in one area for a long time. just look at how long the euro-block has been there or thereabouts, and the bartlett high isnt often refered to as 'the slug' for nothing.  all indications are that we are entering a period of high pressure domination, and the exact orientation and position could produce anything from a benign overcast mild regime, to a deep freeze.

id have thought that those of you looking for cold would be happy enough with the prospect of high pressure nearby, because it could always eventually bring cold, and wouldnt the chances of something cold outweigh the chances of something mild?

[IDO]

"such synoptics can prove stubborn to shift once formed"

 

I think i've read this statement about every type of synoptic pattern since i first joined NW.

No offence, but it really is a most over-used phrase on here.

 

IMO I will be very surprised if we get trapped in the upcoming pattern for more than 2-3 weeks, due to the state of the PV. The upcoming pattern is a result of a couple of factors, one being the release of the meridional pattern created by the mid-latitude forcing of Nuri. This includes the release of energy from the anomalous heights as well as the Greenland energy created in that amplified pattern. So an up ticking in the Atlantic highs and lows is almost a natural progression. Once released (after D15?), because of the disorganised PV we should develop a more meridional flow again as highs build into the gaps left by the disorganised polar vortex. Whether this will lead to a trop led cold spell, or just aids the warming towards the strat, we will have to wait and see. In the interim we have to go through a westerly flow, and the models are currently evolving as to where the polar jet sits and therefore what surface conditions the UK arrive at. They are my thoughts on the developing situation and I have always expected a period of Atlantic weather once it overwhelmed the block to our east, which has held firm longer than I hoped.

 

Saying that JMA have just released their current update for week 3-4, taking us up to Christmas and it is in line with Gibby's worries concerning the Greenland vortex and a continued flow from there towards the UK:

 

 

This was not dissimilar to the EC32 and the CFS mean for December: 

 

So knowing our luck of obvious concern for December's outlook.

[The Post-modern Winter]

The 6z GFS op shows an intense displaced Azores High just off SW Britain at the end of it's run supported by a strong and flat Jet stream much too far North to nudge it away and it is an increasing and worrying trend for the start of Winter because such synoptics can prove stubborn to shift once formed and and can also become a repetitive pattern as past Winters can testify too It is at least shown very early in the winter and is way out in la la land at the moment. Let's hope it is removed in subsequent runs.

 

 

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY TUESDAY NOVEMBER 25TH 2014.

NEXT UPDATE WEDNESDAY NOVEMBER 26TH 08:00

THE CURRENT GENERAL SITUATION A wave depression is forming over the English Channel, moving NNE through the next 24 hours towards the North Sea later tomorrow.

MODELS-2 WEEK HEADLINE Generally changeable conditions look likely across the UK though the emhasis should be on more dry weather than wet with temperatures close to average though below where any mist, fog or frost patches develop later.

THE JET STREAM ENSEMBLE FORECAST The GFS Jet Stream Ensemble forecast shows the flow remaining weak around the UK and Europe for the remainder of the week. The trend thereafter remains for it to increase and push further East over the Atlantic, UK and Northern Europe in the second half of the period.

GFS OPERATIONAL The GFS operational this morning shows disrupting Low pressure to the West of the UK by the weekend following the slack and Low pressure across the UK over the next few days. This disrupting Low pressure then is split into a cut off Low over Iberia while another portion moves harmlessly away to the North allowing a ridge of High pressure to reform over the UK from the European High pressure block at the weekend. Later in the period High pressure remains the driving force of the weather over the UK gradually forming a centre either over or close to the UK with some cold and frosty conditions likely to develop for many as a result with patchy fog problems too.

THE GFS PARALLEL RUN The GFS Parallel run is in unison with the operational in the first half of the period before High pressure develops more towards the SW allowing the Jet flow to override and collapse the European High pressure. This then makes for a milder WSW flow across Northern areas extending South at times with some rain at times, more especially across the North. Later in the run a deep Low diving SE over the North Sea introduces a plunge of cold Polar air across the UK with keen North winds and showers or longer spells of rain, sleet and snow in below average temperatures to end the period.

THE GFS CONTROL The GFS control run this morning closer resembles the Parallel run in sequence with a slow transition towards the High to the East giving way to more control towards High pressure close to Southern England. This of course as indicated before allows the Jet flow to cross East into Europe at higher latitudes and allows temperatures to rise on a WSW flow across the UK with rain at times in the north. It is supportive thugh of some form off attack from the North, albeit temporary on this run late in the period with some rain and snow in placesfor a time.

THE GEFS ENSEMBLES The GEFS Ensembles this morning show the most favoured point likely to be held in two weeks from now is the UK to be locked in a trough from Low pressure close to or over the North of the UK with the Jet flow quite well South with unsettled and at times chilly weather with rain at times and snow over Northern hills, though this brought about on a mostly Westerly flow.

UKMO UKMO today shows a strong ridge of High pressure across Eastern Europe, all the way West through the British Isles and with a new centre well out in mid Atlantic at Day 6. Low pressure lies across Spain and over a point North of Iceland. The resultant quiet weather with West winds in the far North and East ones in the far South will leave most of the UK benign with some bright spells along with mist, fog and frost patches developing again with time.

THE FAX CHARTS The Fax Charts show a developing Low pressure over the English Channel over the next 24 hours with a complex array of troughs across the South and East gradually transferring NE in the wake of a strengthening SE flow later in the week as a deep Low complex develops near Spain. pressure is then shown to rise across the UK as a ridge develops across the UK from Europe.

GEM GEM this morning also shows the theme of disrupting Low pressure slipping down over our western Sea areas and arriving over Spain. This sets up an Easterly flow over the South of Britain while a ridge from Europe and later the Atlantic disects te UK with a slacker west flow over the far north. Towards the end of the run pressure falls from both the SE and NW with a complex Low pressure area bringing rain and rather chilly conditions to many before the end of the period in slack cyclonic winds then.

NAVGEM NAVGEM shows a much more marked push of Atlantic weather East across Northern Europe next week as the High over Eastern Europe collapses and allows a displaced Azores High to lie just to the SW of the UK then to become the dominant player in UK conditions with strong Westerly winds with rain at times across the North while the South sees some more lengthy drier periods between very occasional and lighter rain events in average temperatures for all.

ECM ECM this morning also shows a cut off Low feature over Spain at the weekend while the UK lies in centre ground to a ridge from an European High to another one over the Atlantic. On this run there is strong support for the Atlantic High to eventually form a UK based feature with all the attendant Winter issues of fog and frost, widespread, persistent and dense likely to develop across Britain as a result later in the period. This would make conditions very cold locally. Before this develops though a band of cloud and rain from the North is shown to move down over the North and East of the UK towards the middle of next week.

THE ECM ENSEMBLES The Ensemble run shows strong support for much of the UK to be under quiet and anticyclonic conditions in 10 days time with much of the UK likely to have surface air pressure values in excess of 1020mbs. The centre of High pressure will be of paramount of importance as to what conditions will be experienced in any one place at the surface in terms of frost and fog amounts.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS There is still an element of indecision between the models of developments beyond this weekend though the overall general trend is for High pressure is one shape or form to be the overriding factor close to the UK later in the period.

MY THOUGHTS The pattern this morning remains a very complex one with many factors coming into play over and around the UK which could all shape our weather very differently over the period if one factor overpowered another. As it is the models do vary considerably in detail once we leave this weekend which looks like being benign under a ridge from the East. The general belief next week is that there will be a gentle shift towards a new High from the Atlantic playing a more dominat role in the UK weather over the remainder of the period. The positioning of this will be instrumental in the weather type at the surface with differences in opinion on this shown across the models this morning. If the High makes landfall over Britain which is shown by a number of runs then the net result will be quiet and fine weather for the UK but it could well become cold and foggy with frost widespread. This could be reluctant to shift through the day in the light winds. If, however the High is held to the South as is shown by some other output then the Jet flow will overide the system and flatten the pattern to make for mild Atlantic winds to affect the UK with rain at times chiefly in the North. There is also some opinion that the High could move East of the UK and allow Low pressure to slip South over or to the East of the UK later bringing a plunge of colder polar air down from the North for a time late in the period. It really is a case of you pays your money and takes your choice on which theory if any proves correct come the time. It does look increasingly unlikely now that unless the current High pressure over Eastern Europe can gain assistance from a new High pressure centre elsewhere the block over Eastern Europe will probably not deliver anything cold to the UK this time but with plenty of High pressure floating around at our latitude over the next few weeks there is always a chance that these could be drawn to a position more favourable for bringing cold weather to the UK sooner or later albeit home grown anticyclonic cold or from a cold source either from the North or East. As I hinted at yesterday the pattern is far from set at the moment and there remains plenty of interest hemispherically to induce or maintain interest for coldies with I anticipate a cold period likely at some point over the next three to four weeks looking quite likely for the UK perhaps with some snow though that word 'patience' is going to have to take frontstage.

 

This is no way intended as a slight Gibby, but just two days ago you were saying that you were confident of a cold period over the next three to four weeks. Now you're looking at the absolute opposite end of the spectrum where a set up may occur with absolutely no chance of cold going into weeks 3 and 4 and one which you infer could eat further into winter. You're a poster renowned for objective analysis of the models so I'm slightly confused. 

 

Was your talk of cold over the next 3/4 weeks in reference to next weeks high pressure led cold and nothing more substantial. Obviously there has been a shift in direction over the past two days, but not to this degree that I can see?

Edited November 27, 2014 by The Post-modern Winter