Model Output Discussion 1200 hrs 15/11/14

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY WEDNESDAY NOVEMBER 26TH 2014.

NEXT UPDATE THURSDAY NOVEMBER 27TH 08:00

THE CURRENT GENERAL SITUATION A slack pressure area across the UK will slowly give way to a freshening SE flow tomorrow and Friday

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 GFS Jet Stream Ensemble forecast shows the flow gradually strengthening over the Atlantic over the next week and crossing on a more direct West to East motion in the vicinity of the UK thereafter.

GFS OPERATIONAL The GFS operational this morning shows disrupting Low pressure to the West of the UK by the weekend with a ridge from High pressure both to the East and to the West of the UK lying across Britain for the latter part of the weekend. Then the High to the West becomes the dominant feature moving into Southern Britain at times and lying just to the SW at others. A strong Westerly flow will lie across the North then with cloud and occasional rain in relatively milder air. The South close to the High pressure will see lighter winds and patchy frost and fog where clearer skies prevail.

THE GFS PARALLEL RUN The GFS Parallel run is in unison with the operational in the first half of the period with the Atlantic High held slightly more out over the Ocean meaning once a few nights of chilly and potentially frosty conditions early next week a West or NW wind would bring rather cloudy winds for all with benign weather types developing when temperatures remain near average or perhaps a little above. A little rain is likely across the North from fronts passing by to the North whereas elsewhere would be mostly dry. Frost and fog would be limited in this arrangement as the UK would be covered in a lot of shallow cloud. the end of the run illustrates an attack from the North with colder and frosty weather likely should it evolve.

THE GFS CONTROL The GFS control run also follows the same basic pattern with High pressure to the SW of the UK looking the most likely option with time bringing rather cloudy and benign weather to all regions in temperatures generally settling close to normal after a few cold days early next week under a brief Northerly.

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 finger of High pressure lying across Central Britain at the weekend and start of next week. A large High is developing in the Atlantic with abroad Westerly flow across the North and a slacker easterly breeze over the far South. Many areas would become dry but probably rather cloudy with patchy frost and fog away from the windier North and far South.

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 as pressure rises later.

GEM GEM this morning also shows High pressure dveloping over the Atlantic next week, although it is further away from the UK which opens the door to the North on this run with a shift towords cold North winds and a temporary burst of wintry showers and overnight frosts towards the end of next week.

NAVGEM NAVGEM today maintains a ridge across the UK throughout this morning's run once the keen SE flow at the start of the weekend subsides. Dry weather would prevail for many with some frost and fog patches at times in locations where skies clear by night.

ECM ECM this morning develops High pressure in from the West too next week and with the centre lying over the UK for a time the lack of a West flow rounding the North of the High is less influential giving all areas mist, fog and frost in abundance. Late in the run a small but vigorous Low to the SW does the UK a favour by preventing the High from collapsing South and allowing it to strengthen North through the Atlantic by Day 10 which would feed a brief cold Northerly down across the UK just outside the term of the run as Low pressure exits East away from the Northern Isles.

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 a strong trend this morning for the UK to become under the influence of High pressure from the Atlantic in one shape or form from next week.

MY THOUGHTS The models seem to be settling down in terms of agreement in that the UK is likely to become influenced by High pressure originating from the Atlantic next week. What is not in agreement is where that High pressure will eventually lie and it is this that will become important in ascertaining day to day conditions in any one place. The one constant is that there will be a lot of dry weather over the UK with only brief flirtations with fairly weak troughs giving a little rain at times chiefly to the North. Apart from that there is little agreed consensus on the resting place for the High with some output including ECM bringing the High across the UK meaning clear and cold conditions would develop with extensive frost and fog issues, slow to clear by day. There is also support for the High to lie or become close to SW Britain bringing an ever cloudy and benign WNW flow over the UK which means the air would infill with shallow cloud off the Atlantic and bring days of anticyclonic gloom but temperatures close to average with small diurnal variations. As usual the longer term models toys with bringing the occasional blast of chill down from the North later as the High relaxes and rebuilds North over the Atlantic but from past experience this just means a reset pattern once the following ridge topples over. The main hindrance of this High should it evolve as shown the Jet stream will be riding East to the North of the UK which will have the effect of suppressing the High South or SW and this theory has acquired some support from the ECM Ensemble 10 Day chart just released so I have to favour the least desirable option of it likely to be lying close to SW Britain with time and ensuring that no real notable weather of any kind affects the UK. There is of course a lot of water to pass under the bridge before the resting place of the Atlantic High is finally nailed as the block to the East has to subside cleanly first and the disrupted Low pressure down over Iberia in the short term behaves as anticipated currently. As a result I anticipate more shifts in forecast for the period of next week onward over the coming model runs as the synoptic pressure pattern changes.

[johnholmes]

The anomalies are not in agreement totally, NOAA being the odd one out to the idea of ridging coming in from either the S/SW or possibly more S/SE showing on EC-GFS. They have shown this idea for the last 2 possibly 3 days but NOAA is still not as keen shall I say up to last evening. There is on the last one a suggestion perhaps of slight ridging showing SW of the UK but not much in the +ve signal so far. The 8-14 shows neither.

see the relevant links below

NOAA

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

and

ECMWF-GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[SMU]

Looking at the D10 means and the ECM op tease has no support (taken as given of late):

gens-21-1-240.png EDM1-240.GIF

I was also reading the Twitter and Matt also reiterated that the UKMO LR Winter forecast takes into account the possibility of an SSW, so I don't know what the strong signal is that is suggesting milder than average DJF? Should be interesting ECM/UKMO -v- the stratospheric undercurrent.

So IDO, its all looking poor no cold for more than 2 weeks, all LRF' & models say mild. -

Forgive me then your saying no cold for north of 2 weeks is AFTER 384 in the models.

Bearing in mind the current pattern for the next 4 days wasn't picked up to 192, & the developing one has just been picked up at 168 / 192 then I find your post remarkably pointless.

PS the ECM mean is pretty good.

Edited November 26, 2014 by phil nw.

[Gael_Force]

Looking at the D10 means and the ECM op tease has no support (taken as given of late):

 

gens-21-1-240.png EDM1-240.GIF

 

I was also reading the Twitter and Matt also reiterated that the UKMO LR Winter forecast takes into account the possibility of an SSW, so I don't know what the strong signal is that is suggesting milder than average DJF? Should be interesting ECM/UKMO -v- the stratospheric undercurrent.

 

In one of the strat thread posts, Interitus linked to a MetO presentation where they said the lead time for an SSW forecast was just over two weeks on the GloSea5. I cannot see a winter forecast, that spans 3 months, having any stratospheric detail, other than broad brush QBO status.

[IDO]

So IDO, its all looking poor no cold for more than 2 weeks, all LRF' & models say mild. -

 

Forgive me then your saying no cold for north of 2 weeks is AFTER 384 in the models.

 

Bearing in mind the current pattern for the next 4 days wasn't picked up to 192, & the developing one has just been picked up at 168 / 192 then I find your post remarkably pointless.

 

Why not go the whole hog & write the whole of December off now, or better still winter is over before its begun...

 

If I woke up as optimistic as you I would stay in bed all day.

 

PS the ECM mean is pretty good.

 

Sorry.

 

I meant no prolonged cold period, I am not precluding a toppling northerly or seasonal temps under a cool high. 

 

As for the ECM, I am not saying it is bad just the mean does not support the op's upper ridge anomaly:

 

 

 

In one of the strat thread posts, Interitus linked to a MetO presentation where they said the lead time for an SSW forecast was just over two weeks on the GloSea5. I cannot see a winter forecast, that spans 3 months, having any stratospheric detail, other than broad brush QBO status.

 

I am sure it is like most model's algorithms  it weighs up the possibility of a SSW occurring this winter with respect to background signals and will build that risk factor within the forecast. It could be that it only sees that probability at say 30% and therefore the influence on the forecast is less than if one was to occur. My opinion is that I have to respect the Professional's output till it is proved wrong. Others on here believe an SSW is only a matter of time and that is another possibility.

Edited November 26, 2014 by i'm dreaming of...

[phil nw.]

A couple of pointers guys.

 

We all have somewhat different views/slants on the outputs so let's keep things polite and respectful please.

The other thing please keep views wrt Met office forecasts and twitter type stuff for other threads,there's plenty to choose from.

 

There's been some good on topic postings in here recently so let's try to keep things that way.

 

Thanks everyone.

[shaky]

What a beautiful split on the gfs parallel run!! Its like slicing a cake down the middle!! Gfs normal run has more of a northerly aswell next week!! This saga around 120 to 144 hours is not over yet! !

[MR EXTREMES]

fantastic model watching far more interesting either a nw flow n flow or easterly flow either way its rather miss leading when you have charts like this

ecm ok so not the day after tomorrow but certainly most of the above average temps have been mixed out.

look at all that cold east northeast west northwest massive arc of deep cold running around the arctic filtering from all angles we are about the only area on this latitude without cold from the chart i posted in any case this chart is most likely wrong even if it is the cold is and has started filtering into areas where sooner or later we will get colder.

how long will it last well id bet a bottom dollar we have more chance of sustained cold once the goods are delivered.

gefs
cold and cold enough for snow in a fair few places although not for the south perhaps on the hills but unlikely.
but certain for the northern half

the gem although not the same time frame as the rest still cold

nav gem
cold although not looking as good as the others

ukmo cold incoming will the azores high be our friend?

replace the higher heights over scandi with lower heights,
push the azores uk heights west or nw,
and a possible northerly then a possible north easterly and easterly depending how far the block can get nw or west.

small differences cause big changes!.

and i dont for the life of me,
see december being above or even slightly above average.

im going to go with what ive seen over the last few days from the models!......

its 50/50 whether its is a uk dominant high pressure or heights to our west,
perhaps beyond fi,

ridging towards greenland either way some nice seasonal charts being thrown up.

latest gfs run split vortex with movement from the eastside segment of the pv coming close to scandi but a gap right up the center of the arctic circle
pv is in tatters.
not the best run lots of things to be resolved but like i said small changes can have big impacts and nothing mild infact snow chances for northern maybe eastern areas has increased more so for the north.

Edited November 26, 2014 by Nick L
Removed deleted quote

[492]

http://www.wetterzentrale.de/pics/Reurmetd.html

Dewpoints have fallen over central Europe over the last couple of days inspite of a southerly component to the wind. The southerly component is modelled to increase over the next few days with warm air being drawn northwestwards form north Africa and the eastern Med. This warm flow is likely to be frustrated somewhat by the mountain barries of SE Europe and the Alps so some modification in likely closer to the surface. Although the days over parts of Europe might be quite pleasant the nights may be quite cold. As the atlantic low slides into Iberia and eventually takes shape in the Med the flow backs and colder drier air should be drawn westwards towards the UK. At the same time the expected elongated ridge across the middle of the country could provide a spell of significant frost and freezing fog.

Edited November 26, 2014 by 492

[Nick F]

 

 

A relative mild negative AO circa -2 driven by the arctic high, followed up by a sharp modality change of the PNA pattern from generally mild positive driving that cold snowy pattern like last year to a very steep negative PNA ridge -

The eastern us goes through a significant of warming which may bear fruit for the UK !

Regards

S

 

 

Yes, the -ve PNA marked by change of the pattern upstream over N America by beginning of December with a trough digging in across Pacific west bringing some welcome rainfall for parched California while we see a ridge of high pressure and a warm up build downstream over eastern USA. This ties in nicely with current phase 3 of the MJO which tends to favour troughing over western N America - the MJO has been steadily tracking east over last few weeks. Although the -ve PNA maybe temporary looking at yesterday's ENS outlook:

 

 

But, the ridge warm up over eastern US will certainly help downstream for the UK while it lasts.

 

On to the 06z GFS op, looks keen to sink the mid-lat high, but what will than wave over eastern N America do when it works downstream?

Edited November 26, 2014 by Nick F

[MR EXTREMES]

bikinis at the ready for the gfs para but as some say its looking bit mild if your a polar bear.

[Nick L]

Just a tip after seeing some posts doing this, instead of posting a couple of charts alongside comments such as "this could be good", how about explaining why it could be good?

[Man With Beard]

Do not write off a cold-bearing Scandi High if this chart sets the trend - many an Atlantic attack has been held back on charts like this by the time T0 is reached:

Edited November 26, 2014 by rjbw

[knocker]

But if you run it on rjbw it becomes a cold bearing Azores high.

Charts  courtesy weatherbell

 

[IDO]

Both the GFS op and P in FI sink the UK high and we get a cool modified westerly flow that should bring snow to the Scottish mountains and a more seasonal feel to the rest of us:

 

 

 

A much flatter pattern, though some variation on the mix of PM and TM flow. I will probably ignore the GFS op as the D16 PV doesn't really fly with recent output:

 

 

The Parallel's NH profile is more what I am expecting: 

 

Though looking at the D16 GEFS the PV looks like its getting its act together and that gives little promise for a cold block to develop.

 

With regard to the D2-5 WAA from Scandi to the Arctic high, there are timing issues but by T150 all but 2-3 members have the ridge closed off by the uptick in the westerly flow from the Canadian PV lobe: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=150. That is a continued downward trend unfortunately (usual caveats apply). Expecting more changes as to how the inbound Atlantic high in week 2 interacts with the lower heights in Iberia and the sceuro/Russian block, though either way more seasonal temps look likely to herald in the start of Winter:

 

Edited November 26, 2014 by i'm dreaming of...

[Man With Beard]

But if you run it on rjbw it becomes a cold bearing Azores high.

Charts  courtesy weatherbell

Yes of course that's what it is showing - but I'm not talking about what the models show exactly, I'm talking about how they might evolve further. I'm suggesting that, given the experience of recent months, the block to the east might turn out to be a little bit stronger, and the easterly flow might hang on a little bit longer and it might even turn into a Scandi block. Might being the important word! I appreciate the models are on the whole suggesting this idea will be wrong. But my concept of a stronger Scandi High is not impossible either - especially when cross-referenced to the NOAA 8-14 day http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php ?

 

My personal feeling, having seen years of Scandi Highs on the models, is that, when models forecast its collapse beyond T144, they only get it right 50% of the time. Having said that, the ECM is usually the first to not collapse it, so I would lower the odds at the moment unless it "comes on board".

 

But how about these charts - ECM T192 two days ago compared to ECM T144 today - that low pressure system to the north of Scandi is already showing signs of being held back:

 

Edited November 26, 2014 by rjbw

[Gibby]

While I admire the enthusiam and anticipation of what could be from charts over 180hrs the overwhelming trend is highlighted well by the GFS 6z run. The Jet Stream is poorly aligned for deep cold to arrive over the UK from next week in anything more than a glancing and shortlived blow from a brief Northerly before the expected large High to the SW which has thwarted many a Winter's hopes in the past rebuilds and topples across the UK to bring back less cold WSW winds to the UK and NW Europe as a whole. I hope I'm proved wrong but that is how I see it from current thinking I'm afraid. It is of course feasible that the High could well be UK based for a time with attendant frost and fog issues but with a Jet flow riding over the top of it's centre the overwhelming odds would favour pushing it South or SW.

Edited November 26, 2014 by Gibby

[No Balls Like Snow Balls]

Taken from Matt Hugo on twitter

26 out of the 51 EC ENS members from the 00Z run show potential blocking to the NW of the UK and a poss N'ly by approx 6th of Dec...

[Gael_Force]

While I admire the enthusiam and anticipation of what could be from charts over 180hrs the overwhelming trend is highlighted well by the GFS 6z run. The Jet Stream is poorly aligned for deep cold to arrive over the UK from next week in anything more than a glancing and shortlived blow from a brief Northerly before the expected large High to the SW which has thwarted many a Winter's hopes in the past rebuilds and topples across the UK to bring back less cold WSW winds to the UK and NW Europe as a whole. I hope I'm proved wrong but that is how I see it from current thinking I'm afraid. It is of course feasible that the High could well be UK based for a time with attendant frost and fog issues but with a Jet flow riding over the top of it's centre the overwhelming odds would favour pushing it South or SW.

 

There are a variety of wind directions on the 06z ensembles - quite a strong presence in the northerly quadrants too.

 

[legritter]

Good afternoon all, having had a good look at all of our current charts and Data it does look to me that high pressure in unfavourable positions [for cold ]will be lurking around our shores .the only Straw being towards the end of the GFS runs Low pressure could move from west to east bringing in colder north atlantic sourced Air .but all this yet again well towards the 10 day range ,This does seem cruel to us cold weather watchers but we must be realistic and hope that mother nature can spring those surprises which she does so often do .The Hunt is on fellow posters lets enjoy the Chase ,

[knocker]

The latest GEFS anomaly has realigned the trough to the east (badly worded) and the Canadian trough so still looking at low pressure Greenland east and HP to the south.

Charts weatherbell

Edited November 26, 2014 by knocker

[Barry12]

While some look at deep FI as proof of a return to mild westerlys, I'm going to look at the reliable time frame.

 

 

Not a bad day 6 chart at all?

 

[terrier]

Looking at the gfs 6z run looks like a mild weekend coming up then we trend colder early part of next week. Then it looks as though we will end up under a cloudy drizzley high. Nothing overly cold or mild out into fi. One thing I've noticed in the last few weeks is the Cfs is wanting to bring in some very stormy and wet conditions from 2nd week of December hope this doesn't verify as it seems to have been a trend over last few weeks.

[Cloud 10]

That's quite a run from the 06z GFS P this morning with its "Arctic slice" at 144 hrs and is a country mile away from the UKMO 00z.

 

gfs p..  ukmo..

 

 

The models generally have difficulties with high pressure in that region,although they are getting plenty of practice at the moment!

 

The 12z's just got a lot more interesting.

[ItNeverSnowsInWindsor]

An interesting comparison between the GFS (the old GFS model)and GSM (the GFS P) has been made on the Metcheck site which uses the current S Scandinavian high pressure as an example. The new GSM model looks like handling blocking to the East a bit better. I'll be ditching the GFS model from now on!