Model Output Discussion 12z 18/10/2012

[johnholmes]

hi IF

Yes notice the difference between the Fax for 12z Thursday from this morning to this evening. Its very much a rather fluid situation as to positioning of fronts/centres etc and indeed further ahead as to how long the cold spell lasts. Perhaps my initial idea some days ago of 3-4 days might not be that far out, we shall know by about this time next week!

[Isolated Frost]

Labrador upper low, bye bye meridional flow. It's obvious from that image that what happens next is it crashes into Greenland, the flimsy 'wave' HP falls and is replaced by a zonal stream. The hemispherical pattern doesn't support a sustained spell.

But it's October- this will happen. The upper air is exceptionally cold for the time of year anyway, so in the end this is an extremely positive early spell. On a side note, doesn't do my 2008-09 composites any bad with a northerly in late October... The stratosphere thread is your best source of knowledge atm, I would tell anyone who hasn't seen it to pop in and have a read, it is absolutely superb and fwiw will influence any MOD thread later on this winter.

[fergieweather]

Re UKMO standpoint: the 12z UKMO-GM proved slower to feed cold air south on Friday compared to previous runs, whereas EC was quicker; consequently, the latest GM was modified more to this solution from T+84 through to T+108. Equally, UKMO-GM has leaned a touch towards speeding up a cut-off of the cold feed from the NW, albeit not anywhere near as fast as GFS. Sitting in the middle is the EC solution and so the UKMO-GM (driving BBC graphIcs at that range) has been modified towards it , i.e. in handling of the system spreading down from Iceland on Fri and over the north of the UK on Sat PM. Latest UKMO-GM PPN output continues notion of snow showers onto NE coastal districts and over the weekend has signal for some as far south as Welsh mountains, as might be expected, but a very muted signal elsewhere aside from Scotland, really.

[Buzzit]

Mogreps is an ensemble suite used by the Met predominantly for short range forecasting. Mogreps-UK is the UK convective Scale Ensemble (36hr duration / 6hr charts) and plays a significant role in asisting with formulation of UK severe weather warnings. Mogreps-G is the Global ensemble (72hr duration / 6hr charts) and Mogreps-15 is the Mogreps-G but run to 15 days, (Mogreps-15 is processed at ECMFW as the Met do not have enough of their own juice) I would not get too hung up on talk about what the Mogreps is showing post 72 hours as my understanding is that it is not really any better than the ECM ensembles after that point.

[IDO]

There is a pattern developing by GFS for a cool/cold 14 day(+) period. The London T850's peak at 13 shortly, but the GEFS mean bobbles around the 0 mark for the rest of the 18z run:

http://cdn.nwstatic.co.uk/ensimages/ens.20121022/18/t850London.png

Today's GFS Op run (0z) continues that theme. Uppers of -5 hit the UK in 2/3 waves, from T60, but are quickly washed out. However this run has us in a trough synoptic right through till late FI so providing plenty of opportunity for a transient wintry spell, more especially for higher ground. Still lots of uncertainty within the ENS from T144 so a colder spell is not ruled out, though cool and wet looks the most likely scenario, with the remaining risk that the colder potential will still stray east.

[lorenzo]

GFS 850 temps looking impressive on Friday morning, much of the country around -4/6 or colder.

Some even more impressive drops the further south you check, one for London looked like an 18-20 degree change.

Further out this from the ECM caught the eye for the 1st November.. the models it would seem want us to have fun this winter watching them... this system threatens to bomb on Halloween to send is for the start of the month.

[Gibby]

Good morning. Here is the report of the 00z output from GFS, UKMO and ECM from my perspective,

All models show High pressure to the North of Britain with a slack and rather warm Easterly drift over the UK. The air is very humid with extensive mist and fog over all higher ground. Over the next few days the winds freshen, especially in the South as the pressure gradient steepens over the UK.. At the same time a cold front moves down over the UK on Thursday reaching the South on Friday with a marked fall in temperatures everywhere with much more broken cloud and sunny spells lifting the mist and gloom but introducing frosts at night. The North and East could see wintry showers over coasts and hills to start the weekend.

GFS then shows a ridge slipping South over the weekend with winds backing NW. A Low pressure area also slips SE to the North of Scotland, running down the North Sea by Tuesday and into Denmark. A band of rain will move SE early in the week followed by a resurgence of a chilly North-westerly flow with a return to night frosts away from windward coasts. A NW flow persists then for the middle of the working week with temperatures slightly below average particularly in the North. Just after the middle of the working week a new Low pressure moves SE from the NW bringing cold and unsettled conditions to all through Thursday and Friday with spells of rain and sleet and snow for high ground of the North by the end of the week. In FI the trend is for the weather to remain cold and unsettled with rain or wintry showers for all as cold Low pressure lies near or over the UK until reprieve develops at the very end of the operational run.

The GFS Ensembles show a huge drop in uppers of 10C in a few days time followed by a slow recovery. The operational is one of the colder options later in the run though not without some support. Rainfall amounts increase with time indicative of more unsettled conditions developing next week irrespective of temperature.

The Jet Stream shows the flow is splitting into two with a weaker arm down over Spain while a stronger arm to the North of the UK tilting SE down over the UK in a week or so.

UKMO for midnight on Monday shows a Low pressure area over the North Sea with a cold cyclonic flow over Britain. There would be rain and showers for all in rather cold conditions with some snowfall over Northern higher ground.

ECM too shows Low pressure moving quickly away East into Europe from the North Sea with a ridge transferring SE over Britain. The weather would see rain and showers next Monday clear away with a drier, rather cold interlude with a frost for most areas Monday night. Further North winds would freshen from the West as Low pressure deepens to the North on Tuesday. This spreads wind and rain across the NW at first and down across all areas by midweek followed by a cold and blustery NW airflow with squally showers of rain and hail, with sleet and snow on the higher hills of Scotland and the North.

In Summary a shot of very cold air will replace the current mild uppers over Britain in the coming days. As skies clear frosts will become widespread for a time. Into next week the weather turns more unsettled and somewhat less cold with rain and showers at times in rather chilly feeling conditions. The unsettled spell then deepens later in the week with Low pressure just to the North as per ECM or complex over Britain as per GFS. Either way the weather will feel unpleasant at times with a high wind chill though any snow will be restricted to the higher hills in the North of Britain.

[BLAST FROM THE PAST]

Big upgrade on the GFS this morning, very good run for cold and UKMO pvery good too. That LP dives down from the north will bring some interesting conditions. GFS has things further east with the LP compared to the ECM hence colder for longer, which will shift?

BFTP

[fergieweather]

Some qualifying thoughts on the snow potential into Fri-Sat from UKMO Ops Centre, issued this morning:

"WBFL of 400m spread south during Friday. This will allow a wintry content down to sea level, so a mix of rain, sleet or hail. Any snow would need to be inland and above 200m. It is very difficult for snow to settle at this time of year given such high depth temperatures. Any temporary accumulations tend to be overnight and very quickly melt after sunrise. Hence, very few, if any, places near eastern coasts will see any lying snow. However, cannot rule out prone east coast high ground such as the North York Moors..."

[snow drift]

Big upgrade on the GFS this morning, very good run for cold and UKMO pvery good too. That LP dives down from the north will bring some interesting conditions. GFS has things further east with the LP compared to the ECM hence colder for longer, which will shift?

BFTP

Much to be sorted as we move forward. The differences between the two outputs you discuss at T200+ will have a big influence on what we would experience. The depth of the low on ECM is greater and is positioned just of NW of Scotland compared to GFS which has it to the NE of Scotland. What we can see from all the output is the trend.

Detail is impossible at this time period but what a start to the season for model watching. So much of interest, so much to be resolved and so much better than just watching the weather role in from the west/ south West.

Only concern is, can we take another 5 months of intense model watching with our partners asking if " we are on that bleed computer looking at the weather again?"

[johnholmes]

http://www.meteo.psu...0z/hgtcomp.html

Both these continue with the same idea as they have shown for several days in agreement too with the NOAA version. Much as I posted last night into the winter thread, there is little sign into early November of any significant wave change occurring. So an upper ridge mostly fairly well west with an upper trough mostly east of the UK but at times pretty close or even over it. Nothing mild on the horizon at the moment into the start of November, possibly even out to mid November looking at the predicted wavelengths. At some point, as always, the wavelength will change but it is impossible to say this far out what will trigger it.

Edited October 23, 2012 by johnholmes

[phil nw.]

GFS 850 temps looking impressive on Friday morning, much of the country around -4/6 or colder.

Some even more impressive drops the further south you check, one for London looked like an 18-20 degree change.

Further out this from the ECM caught the eye for the 1st November.. the models it would seem want us to have fun this winter watching them... this system threatens to bomb on Halloween to send is for the start of the month.

Yes quite a shock to the system when that cold air comes through L.

A chance of some wintry showers in the far NE,especially over high ground. but for many of us a crisp and bright weekend with some sharp frosts overnight.It will be good to get rid of this continental murk.

Later output continues to show trough disruption around the UK with a lot of Polar air still in the mix, as those ensembles suggest.

The models continue to promise an unsettled and rather cold period to follow with the flow essentially from north of west.

The ECM above is typical of the 00z runs for the medium term.

[dragan]

12z UKMO-GM slows cold air south on Friday more than previous runs, i think EC was quicker; bu the latest GM changed more to this solution at T+84 to T+108.

[shedhead]

Big upgrade on the GFS this morning, very good run for cold and UKMO pvery good too. That LP dives down from the north will bring some interesting conditions. GFS has things further east with the LP compared to the ECM hence colder for longer, which will shift?

BFTP

Looking at the overnight runs the potential for a cold reload appears to have increased again during next week, but the trend does look to be an increasingly unsettled one, with rain at times for many and some snow on high ground...especially across Scotland.

Edited October 23, 2012 by Paul
Stop picking fights and just comment on the models please.

[Gavin Hannah]

00Z FI is very pleasant for us cold fans, but it is FI....... Anyway, the 00Z gives us a little more cold air than the 18Z and another decent reload. The interesting bit is working out what will happen thereafter. Towards the end on the 18Z, LP swept in off the Atlantic (Ex-hurricane?) giving us a more mobile outlook. The 00Z shows a decent Northerly flow before the Atlantic moves in right at the end.

[SMU]

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

enjoyable runs today as things drift along with a cold theme-

The first of the winter- a snow spike in the ensembles from the control run..

Things slowly falling into place-

S

[legritter]

Much to be sorted as we move forward. The differences between the two outputs you discuss at T200+ will have a big influence on what we would experience. The depth of the low on ECM is greater and is positioned just of NW of Scotland compared to GFS which has it to the NE of Scotland. What we can see from all the output is the trend.

Detail is impossible at this time period but what a start to the season for model watching. So much of interest, so much to be resolved and so much better than just watching the weather role in from the west/ south West.

Only concern is, can we take another 5 months of intense model watching with our partners asking if " we are on that bleed computer looking at the weather again?"

My wife constantly tells me to get off computer and look out the window ,but do it in the kitchen with lights off ,so no one see,s you .oh well todays mod and data still giving us plenty of action over coming weeks ,with pressure still high around greenland and n atlantic .a fair chance at this stage of low pressure moving south over us or near next week .for us coldies its going to be an interesting and frustrating time ,there is also the possibility of an ex hurricane moving into mid atlantic in the far outlook , so if we still have some v cold air to our north and pressure is high enough it could give us some very interesting modell watching im off to dig me veg patch , so the FROST can break it down ,cheers gang .

[BLAST FROM THE PAST]

Well GFS 00z and now 06z say NOTHING is coming our way unless its from the NW or N for some time. With HP to our WSW arching back to repeated heights building over Greenland, a reload pattern. Thats up to t156 lets see beyond.

BFTP

Edited October 23, 2012 by BLAST FROM THE PAST

[legritter]

Regards my last post ,i mentioned ex Hurricane in mid atlantic , in the far outlook ,not sure where i got that info from ,i could be totally wrong ,i might of dreamt it . think i,ll take a break ,cheers gang

[bluearmy]

'Just a quick one, but latest update of the ECM 32 day model out to the middle of Nov or just after paints a particularly cyclonic and cool, if not cold outlook with low pressure and a -ve pressure anom dominant across the UK and NW Europe in general. Temps look to be around 1C to 3C below average throughout the forecast period, though perhaps temporarily at or slightly above given SW'ly as lows approach. High pressure and a +ve pressure anom exists across Greenland and more particularly NE Canada (Labrador etc), but overall latest update looks distinct unsettled and cyclonic for the UK, but not with a 'mild' signal associated with it.'

taken from Matt Hugo's post in the strat thread this morning. this is exactly the same pattern shown by NAEFS week 2 so seems to show that novemer could see a repetitive theme with us stuck under a mean cool trough. memories of june and july ..........

naefs shows HLB remaining west of greenland and kamchatka throughout.

[snowking]

We also have GP's north pacific low showing in todays runs:

More bering based you could say than Pacific but once again his thoughts perhaps coming to fruition. Any number predictions on the euromillions tonight?

SK

[syed2878]

it then fits in with the mets 16-30day outlook they going 4 below avrage nov.

[Radiating Dendrite]

I like the end of the 6z!

To be fair the whole run displays a situation where blocking over Greenland is a constant option.

[Robbie Garrett]

Polar Vortex setting up shop over Russia, Azores feeding the Greenland high.... now that's a way to start November boys and girls!!

End of the run, but still... a sign of things to possibly come??

Average temperatures into November, still within a colder than average spell.

NAO forecast to remain negative throughout this period.

I suspect over the coming few weeks, we are going to see a lot of Notherly blasts but mostly wet and windy. Probably going to be a massive warming event if anything to kick-start a colder end to November. MetOffice seems to agree with this......

Edited October 23, 2012 by Robbie Garrett

[AWD]

The 06z Ensembles show a lot of the members stay colder than the mean for most of the run.

http://www.wetterzentrale.de/topkarten/fsavnmgeur.html

http://www.wetterzentrale.de/topkarten/fsavnmgeur.html

So after the next few months, below average temperatures seem likely for the foreseeable future, nothing exceptionally cold, but cool & unsettled.