Model Output Discussion 1200 hrs 30/09/14

[knocker]

The ECM monthly update would seem to indicate more of the same with a near zonal flow with depressions tending towards the N. part of the Atlantic relative to the UK and perhaps more influence of the HP in the south but still a fluid and transitory pattern. No great development of the PV. Temps remaining about average but higher over Greenland and to an extent eastern Europe.

 

[Stormyking]

Quite an unsettled look again on the charts this morning, especially going into the end of next week.

 

Though at the start of next week, there still some chilly nights showing with the risk of frost in places

 

[Captain Shortwave]

Before then

22C predicted widely for East Anglia with 20C possible widely across England and Wales. Going to be a cracker of a day. Beyond that near normal conditions rain and temperature wise. Interestingly the ECM op is still keen on building pressure across the UK into week 2, maybe worth watching as a split vortex would probably trigger this as the westerly flow is disrupted.

Edited October 31, 2014 by Captain shortwave

[IDO]

If the 0 line is no bias and below negative bias and above positive bias then that is not really what those charts show.

They show ECM has recently been more accurate than GFS and while it does have a positive bias at times it is no worse than GFS negative bias?

 

 

Hi

 

I was looking at the average for the last 31 days where GFS averages out a bias at +0.172 and ECM averages out at  +4.0. That is a good sample for a direct comparison rather than daily variances. So ECM does increase heights over the NH compared to the GFS consistently. The higher the positive/negative the greater the bias in meters:

 

 

Anyway no resolution this morning as the models still uncertain whether heights will be slightly stronger in the E/NE or the flow will be more westerly.  

 

ECM at D10:   GEM:   GFS: 

 

ECM & GEM the extreme either way and GFS in the middle. Take your pick.

Edited October 31, 2014 by i'm dreaming of...

[knocker]

Middle of next week the ECM develops the upper trough over the UK and a bit candy ball in the north.

 

[Frosty.]

The GEFS 00z mean shows a very unsettled outlook for the uk and a colder spell for much of next week with a risk of wintry precipitation and not just for scotland, I think sleet and wet snow will feature in next week's forecasts to some degree, there is also an increasing frost risk and icy patches on untreated roads early and late. Towards the end of next week the atlantic sweeps in again, a broadly westerly pattern with relatively milder, wet & windy spells interspersed with colder, brighter showery conditions, again with a risk of wintry showers on hills and night frosts during quieter interludes. There is no sign of a widespread return to v mild / warm and benign weather after today, however, the far south / southeast is likely to have the best of any fine and dry intervals between active weather systems...at last we are going to see something colder, even a touch wintry after weeks and weeks of generally very mild mush..if that's run of the mill then bring it on!

Edited October 31, 2014 by Frosty.

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY FRIDAY OCTOBER 31ST 2014.

NEXT UPDATE SATURDAY NOVEMBER 1ST 08:00

THE CURRENT GENERAL SITUATION.A series of cold fronts will cross steadily East across the UK over the next 48 hours displacing the very mild SSW flow across the UK today.

MODELS-2 WEEK HEADLINE  Becoming cooler for all in more unsettled and sometimes windy weather with rain at times. Possibly drier and milder in the South again later.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream forecast from GFS shows the flow moving South of the UK over the coming two to three days where it is maintained for a time. It is then shown to migrate slowly north again across the UK through Week 2.

GFS Today's operational run shows Low pressure gradually slipping SE down over the UK early next week and on down into the Meditteranean bringing a period of cooler and wetter conditions across the UK. A ridge then follows which as it moves SE too brings the UK back into a changeable Westerly pattern with rain at times chiefly in the North and West and temperatures becoming average or perhaps above again later with deep Low pressure close to the NW at times maintaining relatively mild and changeable and at times windy spells of weather through to the end of the run.

THE GFS ENSEMBLES.  A very similar sequence of events to that of the operational model is shown this morning with if anything rather more potency to the Westerly feed with wind and rain at times through Week 2 for all areas.

UKMO. UKMO today shows Low pressure slipping away SE from the UK early next week taking it's chilly mix of sunshine and showers with it. A ridge following SE behind is shown to give an interlude of dry and bright weather perhaps with frost and fog briefly before Atlantic Westerlies from deepening Low pressure to the NW engulf the UK later next week with rain at times especially in the North and West.

THE FAX CHARTS  The Fax Charts illustrate well the expected passage of complex Low pressure SE across the UK early next week with attendant showery weather. Before that happens a series of fronts crossing East and SE brings an end to the current mild feed of SSW winds.

GEM  GEM today maintains an unsettled look under a broad Westerly flow to the South of deep Low pressure crossing East to the North later next week maintaining the sometimes wet and windy spells of weather introduced over this weekend and early next week from the aforementioned Low pressure area slipping SE.


NAVGEM NAVGEM maintains a broad and unstable Westerly flow later next week as Low pressure remains anchored to the North of the UK keeping all areas in a mix of drier and brighter spells mixed with cloudier rainier ones.  

ECM. ECM takes a different slant as it promotes the return of High pressure from the South later next week and beyond drying things up in the South as well as returning temperatures to above average levels. The North and West will remain in a mild and moist SW flow with rain at times from troughs crossing East.


THE ECM ENSEMBLES  The ECM Ensembles today show the UK bathed in generally a mild SW flow. Up until today the 10 Day mean has shown the UK under a trough from Low pressure to the NW but gradually this is shown to have backed further West on successive runs and makes for a backing of winds over the UK towards the South and feeding mild air up across the UK around a large Southern Russian High pressure and another one near the Azores, the worst possible scenario for introducing any cold weather to the UK anytime soon as the Jet blows relentlessy harmlessly well North of the desired position.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS There are still mixed messages from the models on the 7-14 day prospects shown between the outputs this morning though the effects from High pressure to the South building again somewhat later remain strong from ECM.

MY THOUGHTS  Once again this morning the models appear to be struggling over what to do with the synoptics once next week's well assured depression now clears SE away from the UK early next week. The general consensus appears to be the desire to draw back in Atlantic winds across the British Isles following a collapsing ridge but that's where the complications arise. The majority seem assured that there will be enough energy in the flow following the ridge off the Atlantic across all areas to ensure unsettled conditions with rain at times, as always heaviest and most prolific towards the North and West. However, as yet there are some thoughts towards the Jet flow returning North of the UK and pressure rising to the South enough to bring Southern Britain at least into more settled and dare I say it rather mild weather again. ECM is the flagship in this proposal this morning and in my opinion might not be far from the truth come the day. However, it is very unlikely that any shift into this pattern will return temperatures anything like where we are currently with rather cloudy, mild and benign weather much more likely. It may be of course that should this pressure rise not occur that we all feel the full effect of the Atlantic Westerly with rain, gales showers and sunshine all common in average November temperatures for the next two weeks. What all models do show is no shift towards anything remotely wintry at this very early stage of the season with a mix of factors including Jet profile, the persistent Azores High pressure belt stretching into Europe at times keeping the UK on the warm side of things being the main factors in assuring this doesn't happen at the moment.

[knocker]

A quick look at the GEFs and ECM anomalies for D10. Very similar with a split vortex and indicating more influence from the HP re. the UK with perhaps less unsettled weather and average temps.

 

[Ali1977]

Are we about to get some eye candy at day 10!!!

GFS has a Nice high to the North but not tapping into any cold air this early in the year.

GFS parallel looks great at day 9

Edited October 31, 2014 by Ali1977

[Ali1977]

Great run from the GFS for some cold if it was to happen. Big high to the north.

[ITSY]

there's that flip flopping! GFS OP 06Z is not all that cold for us, but synoptically a thing of beauty. Last night's ens were the first in days that didn't have multiple members showing something similar, and with the vortex not as solid as usual, combined with the potential for an upcoming SSW event, i'm actually fairly optimistic for the time of year. Nonetheless, the output is extremely mild today and therein mild or average barring a couple of days next week. Watch this space though.

 

BANK

 

Edited October 31, 2014 by ITSY

[shaky]

Vortex completely and utterly shredded on both the gfs parallel and operational runs!!very unusual for November!!I was saying yesterday with the minor warming coming up in the stratosphere it could bring out some beautiful cold charts in the next couple of weeks! !

[carinthian]

Big tease at the end of the 06z GFS latest run. Massive warm air advection up the west side of Greenland. Ideal for blocking with the Arctic front heading for the UK. Its all a slow progress, but that's we want to see it at this stage. The building blocks are beginning to take shape. Hopefully lets see this continue across a wide run of further runs. Fingers crossed.

 C

[Newberryone]

A very small window for some snow over Scotland next week according to the latest all singing all dancing GFS 00Z run. It looks highly unlikely that snow will be seen anywhere else. But it will only be early November after all.

gfs-2-138.png

gfs-2-144.png

The latest ECM show's HP trying to move in again right at the end of the run, but according to the latest NOAA & ECM / GFS 500MB mean there is next to no chance of that happening with a continuation of LP driven and unsettled weather.

I wouldn't be so sure of that as pressure has been consistently high in the south Atlantic now for quite a considerable period of time and shows no real signs of declining. Ecm really seems to be holding very firm on this and although the day 10 chart indicates a pm incursion trying to make feeble inroads from the northwest, another large high pressure cell seems to be hotfooting it across the Atlantic to continue a similar theme.

[Barry12]

9-10 November is looking cold on the GFS Parallel

 

Edited October 31, 2014 by Barry95

[Man With Beard]

As mentioned above, good winter synoptics from both GFS op and parallel 06Z as we head into FI:

 

 

Doesn't really have support at the moment from other models:

 

 

And too early in the year for a freeze-up, the parallel gets the closest with a northern/western hills snow event only:

 

Edited October 31, 2014 by rjbw

[legritter]

very tantalising charts from GFS in its further outlook ,but being right towards its end these could disapear in a blink ,but perhaps its picking up on some signals .perhaps even a realy good blow later next week so one to watch ,certainly looks like autumn is about to kick off with some action .as i,v already quoted  if Mother nature is soon to balance the books temperature wise we could see some interesting times ahead here on Net weather ,cheers all .

[summer blizzard]

there's that flip flopping! GFS OP 06Z is not all that cold for us, but synoptically a thing of beauty. Last night's ens were the first in days that didn't have multiple members showing something similar, and with the vortex not as solid as usual, combined with the potential for an upcoming SSW event, i'm actually fairly optimistic for the time of year. Nonetheless, the output is extremely mild today and therein mild or average barring a couple of days next week. Watch this space though.

 

BANK

 

 

Think again, deep inversion.  

 

[ITSY]

Think again, deep inversion.  

 

 

I'm not even sure what "deep inversion" means, and I'd really rather not by the sounds of it.

 

Just to clear up for newbies etc, I'm not saying that these sorts of charts are going to guarantee cold. Nor am I saying that they are themselves particularly cold. In fact, there is an ensemble member (I think ens 20) that provides a long fetch easterly from Moscow to New York which wouldn't provide anything close to snow for us, partly cos of the time of year. All I'm saying is that the synoptics are conducive, in these sorts of set up, to provide cold further down the line - and some of the synoptics are very unusual (and therefore, sadly, unlikely to happen). Worth noting though.

 

[nick sussex]

I see the GFS 06hrs run and the GFS P develop some colder synoptics in their later timeframes, ordinarily I'd expect to see more interest going on in here but perhaps we've all become a bit too sceptical especially when its the GFS which suggests this.

 

If you're looking at how recent patterns have developed across the USA then we have seen a flattish pattern develop some unexpected amplification, looking back at the ECM the deep ne USA low was only starting to be seen on the 23rd October, the original ridge to the north was overstated at that range a bias of the ECM in recent winters however the ne low does verify.

 

We could perhaps assume that because the models are reluctant to stick the PV to the north with continued splits that we always have that more amplified possible scenario in the background.

 

So the question is today what happens if the pattern over the USA is more amplified than currently suggested?

 

Assuming that the models do take a chunk of the PV westwards near the pole towards Canada then we need something to drag that a bit further west, this can occur by a more amplified troughing scenario over there, perhaps something to look out for in future outputs.

Edited October 31, 2014 by nick sussex

[Cheshire Freeze]

I'm not even sure what "deep inversion" means, and I'd really rather not by the sounds of it.

 

Essentially lapse rate is reversed I.e temperature actually increases with altitude above ground level. This is because the upper air temp is generally higher than the ground temp due to rapid radiation of heat from the ground (due to lack of insolation at this type of year). The high pressure then acts to contain this cooled surface layer close to sea level (air descends under HP) and there you have your inversion.

[Steve C]

Hmmm I see the parallel GFS model (and the old one too) is showing a possible gale next Friday. Personally I hope this doesn't come off; I'm due to be on a ferry.

Edited October 31, 2014 by Steve C

[Mapantz]

Essentially lapse rate is reversed I.e temperature actually increases with altitude above ground level. This is because the upper air temp is generally higher than the ground temp due to rapid radiation of heat from the ground (due to lack of insolation at this type of year). The high pressure then acts to contain this cooled surface layer close to sea level (air descends under HP) and there you have your inversion.

Yup. Theta-E charts get overlooked quite a lot (The one SB posted) especially in close time frames. A fantastic chart for snow forecasting, just like it is for storm watching in Summer plumes.

Edited October 31, 2014 by Mapantz

[IDO]

I see the GFS 06hrs run and the GFS P develop some colder synoptics in their later timeframes, ordinarily I'd expect to see more interest going on in here but perhaps we've all become a bit too sceptical especially when its the GFS which suggests this.

 

If you're looking at how recent patterns have developed across the USA then we have seen a flattish pattern develop some unexpected amplification, looking back at the ECM the deep ne USA low was only starting to be seen on the 23rd October, the original ridge to the north was overstated at that range a bias of the ECM in recent winters however the ne low does verify.

 

We could perhaps assume that because the models are reluctant to stick the PV to the north with continued splits that we always have that more amplified possible scenario in the background.

 

So the question is today what happens if the pattern over the USA is more amplified than currently suggested?

 

Assuming that the models do take a chunk of the PV westwards near the pole towards Canada then we need something to drag that a bit further west, this can occur by a more amplified troughing scenario over there, perhaps something to look out for in future outputs.

 

Looking at the GEFS there are only 3 other members that support such a synoptic. By far the most common members are supporting an Atlantic flow, just speed and intensity differentials. The mean at D16 (obvious caveats at this range) highlights this:

 

 

Looking at the PV on the 20 odd members there is no pattern forming apart that only one member has the PV over the Arctic in one blob. The rest have all sorts of combinations. I would say that the op may continue to come out with numerous synoptics whilst this uncertainty pervades.

[nick sussex]

Heres last nights ECM:

 

 

And this mornings, note the change over the USA:

 

 

For newbies the circled area is the developing low, this can engage the PV and drag some of that west, you can already see that the flat as a pancacke pattern shows a bit more amplification this morning.

 

So for the timebeing I think we should keep an open mind about the prospects towards November, whilst we continue to see the PV split theres always the chance something might crop up.