Model Output Discussion 5/12/2012 18Z onwards - the one after THAT ECM

[MKN]

what time was on that forecast? have you a link?

it was posted yesterday I believe I wouldn't read much into it. Its just a video stating the obvious it COULD be cold or COULD be mild. We all know that cold is a much more favoured outlook albeit not yet certain. If the charts were seeing for next week are the same Sunday they won't be mentioning mild.

[Glacier Point]

As if NWP didn't have enough on its plate with the disturbance to the PV, MJO forecasts consolidating on a phase 2 projection. That will expose the GFS in particular (it has a large bias to tropical convection in the longer range) to greater pressure to turn the jet northward over Iberia. This will be a false bias given that the GWO is in phase 8/1 - and this is the superior measure. That lobe of the pv cut off over NE Siberia also rolling around like the preverbial loose cannon.

GEFS H5 day 10 a reasonable depiction however (huge snow potential btw):

Substantive ridge between Greenland / Iceland / Svalbard. Tonight's CPC 8-14 dayer will pretty much look like this. That will keep the jet well to the south and only when the ridge pulls fsr enough west will it be able to come up from the south. Always the risk however of shortwaves, but these likely to maintain our cold pool in situ by advecting the cold air westwards.

Stick with your ensemble means!!

Edited December 6, 2012 by Glacier Point

[sebastiaan1973]

Lots of EC members have low pressure at the continent at 168h

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2012120600!!/

[Weathizard]

So happy to wake up and there not be a complete capitulation, I'm sticking with a cautious mindset but I think the initial easterly is odds on with mostly all GEFS members giving us one, shame about the 2 rogues!! Still, very happy and lots of time for upgrades post 120. Hopefully for the whole of the uk.

Roll on the fun.

Edited December 6, 2012 by Weathizard

[chris55]

Although ECM may not have the very strong easterly and sub -10 850s of yesterdays, I actually think it would produce a lot more snow for most than yesterdays run.

All models pointing towards a cold and snowy outlook, can't be bad eh.

[BlueSkies_do_I_see]

The BBC know that the moment they issue this forecast there will be an impact on the economy with people changing their plans/ cancelling trips. Bad news for the High Street if this verifies. Wonder if Osborne factors a harsh winter into his economic forecast - I somehow doubt it.

Matt Hugo just tweeted about interesting overnight output and just a case of how cold/snowy now

[Ian Brown]

A continuation of the excellent output this morning, the UKMO finally on board with the pattern. The key timeframes are now at T96, so it is coming closer. We are entering the latter stages of the game and our opponent has played all it’s big guns to no avail. We would have to be very unlucky now not to get a decent easterly of some description.

Little point in worrying about breakdowns or where the block may end up.

[loafer]

The Gfs 00z looks fantastic for a very wintry spell until well into FI and increasingly snowy, early in the cold spell it looks like snow showers would be mostly coastal but some would spread inland but it would be very cold with persistent frosts and a high windchill as that easterly has a sharp cutting edge, as pressure falls, we would have a potent mix of unstable air and increased snowfalls, later in FI turns milder and messy but some incredible cold being bottled up to the north and i'm not concerned about what an op run shows at T+300 onwards.

The models have a general grasp on next week but lots more fine tuning to come.

Great post, Frosty.

Tuesday looks to be a very interesting setup for a Kent Streamer, particularly with the North Sea remaining comparatively warm at this time of year.

[Frosty.]

This is all at the T+96 range now, that trigger low spreading southeast on sunday and then we are into the incressingly cold air which will turn colder and colder with severe frosts and snow flurries/showers, eastern uk probably having frequent snow showers during next week which could merge into longer periods of snow and drifting in fresh to strong ENEly winds.

[weather eater]

Top post Ian, OK so this morning’s runs are not as good as last night’s ECM but only a fool would expect them to be. The building blocks are in place and we are going to see a huge variety of evolutions promoted by the models in the coming days. Remember the models will pick a trend run with it, drop it and then maybe go back to it, meanwhile I need to get out and get some work done before the snow arrives which will be about one o’clock, if this mornings BBC forecast is right.

Edited December 6, 2012 by weather eater

[snowking]

Lots of EC members have low pressure at the continent at 168h

http://www.ecmwf.int...t!2012120600!!/

Yes now 4 main clusters developing

Cluster 1: HP to the north, LP running west along southern britain

Cluster 2: HP to the north, LP running west slightly further north than Cluster 1

Cluster 3: HP dominant over the UK

Cluster 4: HP over the UK but attack from the SW looks likely

Out of all 51 clusters

- ALL of them show some form of easterly flow (one or two go either SE or NE)

- Only 2 members don't have the -6c 850mb line over almost all of the UK, and these two members suggest an attack from the SW

So to echo Matt Hugo on Twitter, Easterly is coming, cold/snowy potential remains to be seen.

These are how the clusters number:

Cluster 1: 20 (+control)

Cluster 2: 17

Cluster 3: 9

Cluster 4: 5

Cluster 1 & 2 (the most likely) deliver the sunshine and snow showers from the east type scenario that would likely get better and better with time given increasing convection potential over the north sea and potential for longer outbreaks of snow given the LP in the equation

Cluster 3 would give us mostly dry away from some coastal counties but bitterly cold

Cluster 4 would give us a very snow potential breakdown (or stalling situation)

SK

[chris55]

ECM and GFS mean at 120

[AWD]

In the short term, the NAE shows a period of heavy rain today for all, with hill snow in the north;

With some strong winds running down the east coast and around the channel;

Could be blizzard like conditions across the Yorkshire moors & Pennines for a time.

Unwelcome rain in the South West where we still have scenes like this;

Edited December 6, 2012 by AWD

[Gibby]

Good morning. Here is todays report on the 00zs from GFS, UKMO, GEM and ECM for today Thursday December 6th 2012.

All models show the pattern as before for the period today until midweek next week. Today sees a Low pressure area moving SE over Scotland and down the North Sea in the next 24-36 hours. A band of rain and snow will move steadily SE clearing away tonight to leave a cold Northerly flow with wintry showers across the UK by dawn tomorrow. After a windy and cold day wintry showers will die out from the West as winds sie out as a ridge of High pressure builds in from the West for the weekend. This would mean a dry and cold weekend with frost and freezing for overnight, especially in the South. By Monday a new Low passes SE to the NE declining the ridge North as a NE flow develops on the back side of the Low pressure as it moves SE over Europe. The cold flow will begin to pull wintry showers in from the NE early next week intensifying by midweek with widespread night time frosts.

GFS then shows High pressure to the North with Low pressure close to the South with a cold and unstable East or NE flow over the UK. There will be snow showers or snow at times with some appreciable falls possible over the hills. In FI details are unimportant at this range but the trend of the operational is for a change to slightly less cold conditions with rain or sleet at times in cyclonic winds.

The GFS Ensembles show a cold spell to come with the operational a milder outlier at the end. Rain and snow is shown to occur at times thought as usual in cold spells no huge amounts are indicated.

The Jet Stream shows a SE moving flow over the UK and on down over the Med where it turns East over Southern Europe. Later next week the flow ridges High over the Atlantic with a flow moving East over the Arctic Circle while another arm travels East over Southern Europe. The UK sees Scotland see a returning if weak Westwards moving flow from Scandinavia later and an equally weak Easterly moving flow over Southern England indicating a complex Wintry Low pressure system near Southern Britain.

UKMO for midnight on Wednesday shows High pressure from Iceland to Northern Russia with Low pressure over the Baltic and the SW approaches. A cold and wintry look to the weather would be had with sleet and snow in places most likely in the east and SW.

GEM shows a complex area of Low pressure over or close to the UK, trendding down towards the SW. An increasingly wintry picture would develops with outbreaks of sleet and snow expected for many at times.

ECM today shows an unstable cold pool developing over the British Isles as an Easterly flow pulls it in from the East. Low pressure develops over and around the UK with sleet and snow a common feature of the weather over the UK later next week. The pattern does show sign of moderating later as the block to the NE weakens.

In Summary things look very wintry this morning. The longevity of the cold is open to debate and we need the Low pressure areas mixed in the cold pool to locate in the right place to allow the risk of sleet and snow to continue but the theme even far out is for cold weather to be still in place and though details will change I think we can safely say that a week or two of cold and wintry weather looks likely from early next week when there is a more than evens chance we will all see some snow.

[snowking]

Whilst we continue to focus on the slightly longer term, the potential for a bit of a 'sting in the tail' for eastern areas tomorrow as we get a wrap around of the LP:

The NAE has been pretty consistent with this now for the last few runs, with it moving very slightly further west with each run

SK

[EML Network]

That's the GEM though ?

DOH !!

so it is..here's the UKMO..sorry

[Methuselah]

Earlier this week, I was saying that we'd need wait until after mid-month for any sustained, deep cold...

I think I can quite safely say, here and now, that I WAS WRONG!

I certainly hope so, anyway. Roll-on the 06Z!

[Lynxus]

The 06Z is already showing that today's event ( IMO ) may bring more widespread snow.

I think further south has a better chance than it did also as it will reach during the darker hours and will be slightly colder.

I suppose it will very much be a wait and see event but certainly anywhere with some higher ground could be in for something fun ( And then rain )

Obviously the cold uppers are not around but its still "chilly" and ive seen snow with ground temps of +5c before.

Edited December 6, 2012 by Lynxus

[Neilsouth]

Don't understand the despondency! The ECM is still very good in terms of wintry weather, and the 240 chart would result in me not being able to land at Heathrow that morning that's for sure. There was no improving on the 12z runs, let's be realistic here.

The winds are much slacker on the models this morning, not good we really do not want the winds to drop off anymore otherwise the cold air will struggle to push across the north sea.

A downgrade as far as i'm concerned and I wanted to see really good blowing snow as well

[Thundery wintry showers]

The model output agreement on a "sunshine and snow showers" type of east to north-easterly flow, with the possibility of organised snowfall at times via troughs and southerly tracking depressions, has strengthened further this morning. From T+168 to T+240, the ECMWF ensemble mean suggests an east to north-easterly flow slowly swinging around to the SE, but with continental air established and fronts stalling against the continental block which could well mean frontal snowfalls. The key timeframe is now around T+96, for where we get to at T+96 on the GFS, ECMWF and UKMO there can only really be one outcome. If the model outputs still look like this tomorrow, and more so Saturday, with the key transition remaining on Monday, then you might see me starting to indulge in some ramping. However I have seen these easterlies toned down somewhat between T+72 and T+120 so I'm just holding onto the very top of the "ramp" at the moment.

I agree with the posts re. flooding in the South West- some serious rainfall in many places today. There is the chance of some snowfall from this system too, but it will be very marginal and I suspect that most of us won't see significant accumulations. The second low for Sunday/Monday looks like it will produce rather less precipitation but at present it is modelled as the "trigger low" that is followed by the aforementioned east to north-easterly regime.

[Gibby]

Worth me emphasising why UKMO still remain a tad cautious on outcome into 10-15d trend period especially:

" 5. Discussion : Both ECMWF EPS and MOGREPS signal the colder than normal blocked regime through the period but with MOGREPS emphasising stronger S’ly component in the flow bias diagnostics while ECMWF favours a dominant E’ly type. The two ensembles diverge more markedly going into the trend period with ECMWF signalling a shift to a cold SE’ly type while MOGREPS veers further round and pulls in potentially milder SW’lies. On balance prefer a continuation of the colder scenario but with low confidence."

Cheers Ian. Must be nightmare with all the different evolutions being thrown out run to run at the moment. I can of course appreciate the caution in the Meto at the moment despite the hysteria between us on here at times.

Edited December 6, 2012 by Gibby

[ITSY]

Good news then, so far Ian.

On the 06Z, everything seems in line with where it should be by +66. Atlantic low slightly stronger but may not come into play..

[snowking]

Worth me emphasising why UKMO still remain a tad cautious on outcome into 10-15d trend period especially:

" 5. Discussion : Both ECMWF EPS and MOGREPS signal the colder than normal blocked regime through the period but with MOGREPS emphasising stronger S’ly component in the flow bias diagnostics while ECMWF favours a dominant E’ly type. The two ensembles diverge more markedly going into the trend period with ECMWF signalling a shift to a cold SE’ly type while MOGREPS veers further round and pulls in potentially milder SW’lies. On balance prefer a continuation of the colder scenario but with low confidence."

Ian further to my post yesterday regarding the MOGREPS, has it ever been noted to be particularly slow at dropping an idea?

It seems pretty at odds now with most operational and ensemble (inc. mean) NWP output

I could be completely wrong but i'm sure I remember the MOGREPS ensembles being the last ones to drop the signal for the more developed easterly some modelling had suggested last week

SK

[BLAST FROM THE PAST]

Worth me emphasising why UKMO still remain a tad cautious on outcome into 10-15d trend period especially:

" 5. Discussion : Both ECMWF EPS and MOGREPS signal the colder than normal blocked regime through the period but with MOGREPS emphasising stronger S’ly component in the flow bias diagnostics while ECMWF favours a dominant E’ly type. The two ensembles diverge more markedly going into the trend period with ECMWF signalling a shift to a cold SE’ly type while MOGREPS veers further round and pulls in potentially milder SW’lies. On balance prefer a continuation of the colder scenario but with low confidence."

MoGREPS then does not see a transfer of HP towards Greenland then Ian?

BFTP

Edited December 6, 2012 by BLAST FROM THE PAST

[chris55]

Worth me emphasising why UKMO still remain a tad cautious on outcome into 10-15d trend period especially:

" 5. Discussion : Both ECMWF EPS and MOGREPS signal the colder than normal blocked regime through the period but with MOGREPS emphasising stronger S’ly component in the flow bias diagnostics while ECMWF favours a dominant E’ly type. The two ensembles diverge more markedly going into the trend period with ECMWF signalling a shift to a cold SE’ly type while MOGREPS veers further round and pulls in potentially milder SW’lies. On balance prefer a continuation of the colder scenario but with low confidence."

So this is the trend BEYOND the entire ECM Det run. How are the ensembles (mogreps) looking within the 5-10 day period as that looks to be the most interesting for now.

GFS op siding more with MOGREPS i guess in the 10-15 day range.

http://www.wetterzen...s/Rtavn3001.png

But interesting to here EC ens continuing the cold beyond day 10, De blit showing lots of scatter in the extended range but with more cold clustering.

Edited December 6, 2012 by chris55