Model Output Discussion 1st Nov.2013

[BlueHedgehog074]

Considering it's a Monday, ECMWF is clearly in a good mood this morning and has seemed to have listened to what Steve Murr has said with a Low (that's cut off from the big one to our North) tracking Southwards/South-Eastwards through the UK feeding cold North-Easterly winds on its Northern flank.

In summary keep your eyes on 20/21 November- watch for a low /trough digging SE over the UK & fingers crossed for enough weakness in the zonal wind to allow heights to build towards Scandi afterwards.... Chow.S

(I suppose, to be fair, the ECMWF run last night was not a complete disaster for the cold potential since these changes from run to run are all part of the models trying to get the hang of the likely more amplified pattern change. Plus, that 12Z run was apparently encouraging for Polar Voetex disruption (although admittedly I didn't take a proper look at the whole Northern Hemisphere chart)). I wonder what other little tricks the models have cooked up for us? ;-)The next few days though should see Southern areas, in general, settling down as High Pressure tries to creep in from the West/South and sits over the Southern parts of the UK. The North will likely to stay more unsettled as Low Pressure systems to the North bring in further spells of rain and/or showers. But brighter weather is possible here at times too. Thursday, though, could be much cooler for the UK with that cool/cold North-Westerly flow.

[legritter]

Possibilitys still there for a colder shot but still only showing towards the end runs ,so at this range a fair chance of a pressure rise but locations of any high still far from sorted . 

[Tom Montalbano]

Overnight model runs again hinting at just enough amplification in the pattern to allow ridging, from a mid-Atlantic high, up towards Greenland, as the PV eases away from that area. A colder NW flow looking likely, at the moment, around this time next week, albeit a brief affair, models then suggest the mid-Atlantic ridge toppling over the UK.

As sometimes happens in these synoptic situations, an initial attack from the NW turns out to be a weakish affair and a few days later a more potent wintry flow develops from the NW, if there is still enough amplification and the Greenland area isnt threatened by the PV. 

Its not unheard of to have a colder NW/N spell develop around the 3rd week in November, as was mentioned last night, Nov 2005 produced such an outbreak.

 

http://www.wetterzentrale.de/pics/archive/ra/2005/Rrea00120051125.gif

 

This spell lasted the best part of a week but blocking around the Greenland area was pretty robust, at this time.

With the notable exception of Nov 2010 and the example above, prolonged cold spells are not the norm, in late Autumn. 

Those cold weather junkies amongst you, needing an early season fix, might want to look at the archives from Nov.1965, if you havnt already, an exceptionally cold and snowy final month of Autumn ensued, with a CET of 4.5c.

 

As suggested in those excellent posts from Tamara and Steve last night, we should temper any thoughts of anything of note from a wintry pov, just yet. With background signals as they are, a colder interlude could well be just a brief affair and the PV could then reorganise in the Greenland area once more, closing the door on any further colder outbreaks from the NW/N, in the next few weeks.

 

Certainly an interesting period of synoptic watching though, as we close in on December.

 

Tom.

Edited November 11, 2013 by Kentish CZ

[Frosty.]

Good to see an improvement in the Ecm 00z op run compared to that messy 12z op last night, more improvements to come i'm sure which will bring the southeast into the colder outlook. I think the overall chances of high pressure becoming centred in the mid-Atlantic during next week and colder air moving down it's eastern flank towards the uk is gaining momentum but it's still a work in progress, at least we have a good chance of the first of hopefully many cold snaps / spells at least a full week before the meteorological winter commences..it would be a nice BONUS.

[shedhead]

its amazing how just a few days ago people on this thread were saying there is no sign of cold weather on the way and novemeber is going to end up being very mild.well within the last couple of days the models have done a nice flip out of nowhere and now we are staring at a potential cold and hopefully snowy snap within the next two weeks. Just hope the ecm does a turnaround this morning.

Very true, but with any possible cold spell still over a week away things could just as easily flip back again, indeed the charts of the last 24hrs have been nowhere near as cold as previously.  That in a nutshell sums up the model watching rollercoaster that we all enjoy riding, so expect plenty more chopping and changing this week...as per!

[Captain Shortwave]

ECM mean is not too bad this morning, still showing an amplified Atlantic ridge with mean uppers of -2 over the whole of the UK from days 8-10

 

GFS similar, just showing the same time frame for comparison

 

Certainly looks like it might turn rather chilly into week 2 from this mornings output. Widespread frost and showers which will be wintry over hills and perhaps down to low levels in the north.

Edited November 11, 2013 by Captain shortwave

[Frosty.]

ECM mean is not too bad this morning, still showing an amplified Atlantic ridge with mean uppers of -2 over the whole of the UK from days 8-10

 

The Ecm 00z ensemble mean looks even better than the 12z last night, and that was pretty good.

[radiohead]

The 0Z GEM shows stronger blocking. Though it wouldn't be particularly cold due to how things are set up here, it is interesting to see the heights reaching right up into Greenland.

 

Edited November 11, 2013 by radiohead

[Summer Sun]

Latest from Gibby

 

All models show a West to SW flow over the UK with a warm and cold front crossing East and SE as I type with a period of rain and drizzle clearing slowly from the NW to sunshine and scattered showers. Tonight a wave s shown to run East across Southern Britain with an enhancement to the rain for a time. Tomorrow and Wednesday will become dry and bright for many apart from the odd shower across the North as winds swing more towards the NW. A ridge crosses on Wednesday ahead of a new front passing quickly SE over Britain with another spell of rain followed by colder and fresher weather through Thursday with some sunshine. Pressure is shown to build quickly behind this and though Friday and Saturday will be technically dry and relatively fair days with plenty of cloud areas of fog and frost could form under the light winds should skies break overnight.

 

GFS then ends next weekend with a frontal band sinking South under High pressure with some rain and very murky conditions across Southern areas with the brightest conditions further North. Next week then shows pressure falling steadily over the UK with Low pressure deepening as it sinks South to a position South of the UK by midweek. This sets up a cold and strong Easterly flow across the South with rain or sleet at times in dull conditions. Further North High pressure will build strongly and this will extend South slowly to all areas by the end of the run with light winds allowing widespread frost and fog to form at night and failing to lift for many through the day making it very cold.

 

UKMO on Sunday shows slack winds and grey and misty conditions most likely across the UK. Pressure will be falling and a weakening trough caught up in the slack flow will deliver some rain at times across the South despite High pressure over the top.

 

GEM this morning indicates rather cold and unsettled weather developing next week as pressure falls after the weekend with Low pressure close by delivering rain at times for all in cyclonic and fresh winds. High pressure builds strongly over Greenland late in the run which could have implications on the UK after the term of the run.

 

NAVGEM too shows pressure falling over the UK from next Sunday at the same time as it builds north through the Atlantic towards Greenland. The weather would become unsettled and rather chilly with rain at times once we move into the new week.

 

ECM shows a trough sinking South over England next Sunday followed by falling pressure as Low pressure migrates South over the UK  early next week. As it deepens a temporary but cold NE flow looks likely with some rain and sleet possible on this Low's northern flank. Drier brighter weather over Scotland early next week would then extend South. It then looks like a return to changeable and milder air would be knocking on the door of the UK soon after the end of the run.

 

The GFS Ensembles show a very mixed bag this morning though the overall trend does appear to be a downward trend in temperatures. As usual there is a lot of scatter between members later in the run and the operational was a mild outlier in the North late on. Rainfall events would be frequent but not particularly noteworthy.

 

The Jet Stream shows the flow over Scotland currently, moving further North after this week before it buckles back across SE Britain at the weekend which possibly sets up a new flow running WNW to ESE across the UK or further South at least for a time early next week.

 

In Summary today the models seem to have picked up on a new trend this morning for about a week's time. The build of High pressure across the UK at the weekend is quickly dissolved as Low pressure near the Meditteranean provides a catalyst for Low pressure to the North to move down to join or absorb it. This brings a quick change to wet weather for a time early next week especially in the South and with cold air entrained on a NE flow it would feel very raw with some snow possible on the highest ground. The pattern thereon become less clear with ECM wanting to bring milder Atlantic air quite quickly back in with a reset of the Azores high. GFS,GEM and NAVGEM are less supportive of this, instead building pressure strongly to the West, NW or over the UK with more sustained cold pressure with widespread and persistent fog and frost problems likely should GFS evolve. In the interim period before all this happens we have a week of rather changeable and benign weather with occasional rain alternating with drier, rather chillier and brighter interludes.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[March Blizzard]

Thanks for frequently posting Gibby's assessments, Gav. Much appreciated.

[Summer Sun]

Looking at this mornings output's and any colder air looks temporary lasting 3 or 4 days before a return to milder air

 

GFS

 

 

ECM shows the colder air coming down at t216, looking at t240 the colder air is getting squeezed

 

 

GEM has the 850's no lower than 0 for most

 

 

So the period of the 20th to 22nd ish could deliver the first cold snap of the season before a return to mild air from the west.

 

The met office text forecast from the 15th to 24th also hints a something colder before a return to "fairly typical conditions" for the time of year

 

Through the first part of next week, northern parts will turn colder and remain unsettled with a mix of cloudy periods and rain or showers, which may be wintry over high ground. This will be interspersed with clearer spells too.

 

Further south will likely be settled, though some rain at times, and turning colder with an increasing risk of overnight frost.

 

Later in the week and into the following weekend, conditions look fairly typical for the time of year, with the greatest risk of strong winds and heavy rain in the north, and the best of any drier weather in the south.

 

The first cold snap of the season is gather pace now, its just a case of watching how things pan out over the next 7 days or so

Edited November 11, 2013 by Summer Sun

[radiohead]

Looking a little colder at T180 on the 06Z GFS.

 

 

At the end of hi res, -10 uppers are just about reaching Scotland.

 

 

And then into low res (T216)

 

Edited November 11, 2013 by radiohead

[shaky]

Definitely a colder and more amplified gfs 06z!!hopefully that continues on the 12z!!things are looking better by the minute peeps!!

[garbagebags]

Substantial upgrade in the cold for early next week. Really nice run.

 

Pressure

 

Temps

 

[Frosty.]

Nice cold blast on the Gfs 06z op run this morning, indeed, the 6z is very close to lining up reload after reload with the nw-se angled jet profile and high pressure well out to the west. It would be fantastic if we end up with repeated cold snaps with wintry weather flooding south, progressively more potent than before....polar express here we come..choo..choo...BRING IT ON  

[legritter]

I just cant keep this bottled up anymore ,i think by about 19/20 th november a fairly major change in our fortunes could be taking place .iv looked at charts  and data read other forums looked at canadian forums etc etc so for once im gonna stick my kneck out and say i think some form of block could set up ,early days yet and positioning will be critical ,i know this isnt that scientific but i can feel it in my water ,iv got the straws ready and prozack is in the cupboard, if it doesnt materialise i will throw my toys at the dog ,chears gang 

[garbagebags]

I just cant keep this bottled up anymore ,i think by about 19/20 th november a fairly major change in our fortunes could be taking place .iv looked at charts  and data read other forums looked at canadian forums etc etc so for once im gonna stick my kneck out and say i think some form of block could set up ,early days yet and positioning will be critical ,i know this isnt that scientific but i can feel it in my water ,iv got the straws ready and prozack is in the cupboard, if it doesnt materialise i will throw my toys at the dog ,chears gang 

 

I really don't think it will be a "block". Definitely some sort of cold flow wind directions and potential for snow. But I don't see a block anywhere.

[Frosty.]

I really don't think it will be a "block". Definitely some sort of cold flow wind directions and potential for snow. But I don't see a block anywhere.

A block could form though, some experts were writing november off as a completely mild month recently but the final third could potentially be much colder with reload after reload of polar maritime / arctic air...I HOPE

[AWD]

I think in the longer term we could be looking at a west based -NAO pattern emerging, albeit slowly. We are obviously seeing support gain for a mid Atlantic ridge to become established during week 2, allowing some more seasonal pM air to influence the UK, with (if things go well) some brief shots of arctic air too. This all thanks to the emerging likelihood of a Mid Atlantic ridge;

However, the ridge looks like it could continue it's journey west towards the Eastern Seaboard, albeit slowly, eventually putting the UK the wrong side of the amplified PFJ, and setting up a west based -NAO;

The EC ens also show a moderation in temperatures after the initialisation of the mid Atlantic ridge in week 2, with temps possibly back up, fluctuating around the average mark to see out November;

Obviously regional variation will become a factor here.

A spell of colder weather looking likely in week 2 then, which could possibly provide the first frosts and morning ice for some of us. Doesn't appear to be anything too lengthy though, although with an amplified Atlantic pattern, it does provide reload possibilities as we enter winter proper, although of course, that's pure speculation at this stage.

[garbagebags]

A block could form though, some experts were writing november off as a completely mild month recently but the final third could potentially be much colder with reload after reload of polar maritime / arctic air...I HOPE

Yeah most definitely. A block could form, I'm just not seeing it yet. I do hope so though.

[Man With Beard]

I think on the face of it at the moment there is the possibility of parts of the UK being on the cold side of the PFJ for a time, but there isn't anything to suggest High Latitude blocking, with general factors seemingly against this happening. The negative anomaly does seem to persist over Europe though hence the GFS is settled in FI.

This may well happen, but there seems a trend to disrupt the flow away from being "flat", so the possibility now exists of a pattern change within 14 days - whether this leads to colder or settled weather, or not, we'll have to wait and see

[Chris K]

I think in the longer term we could be looking at a west based -NAO pattern emerging, albeit slowly. We are obviously seeing support gain for a mid Atlantic ridge to become established during week 2, allowing some more seasonal pM air to influence the UK, with (if things go well) some brief shots of arctic air too. This all thanks to the emerging likelihood of a Mid Atlantic ridge;

image.jpg

However, the ridge looks like it could continue it's journey west towards the Eastern Seaboard, albeit slowly, eventually putting the UK the wrong side of the amplified PFJ, and setting up a west based -NAO;

image.jpgimage.jpg

The EC ens also show a moderation in temperatures after the initialisation of the mid Atlantic ridge in week 2, with temps possibly back up, fluctuating around the average mark to see out November;

image.jpg

Obviously regional variation will become a factor here.

A spell of colder weather looking likely in week 2 then, which could possibly provide the first frosts and morning ice for some of us. Doesn't appear to be anything too lengthy though, although with an amplified Atlantic pattern, it does provide reload possibilities as we enter winter proper, although of course, that's pure speculation at this stage.

 

Good post and I believe similar to the thoughts of others such as Snowking. Seems perfectably reasonable considering the outputs being shown.

[Cecil Hogmanay Melchett]

Maybe im being grump but I see very little away from the higher pennines and Scottish mountains to be excited about.

The Polar profile looks poor going through November and to my eye HLB is progged to be fairly invisible in our locale.

[Barry12]

Parts of Scotland could be getting snow to low levels in just 8 days if the 6z verifies.

 

 

Best chart of the 6z though is in 9 days, with parts of England possibly getting snow, and Wales and Northern Ireland too

 

 

Edited November 11, 2013 by Barry95

[Frosty.]

I think the Ecm 00z ensemble mean is an upgrade compared to the 12z last night, it looks even more amplified with winds trending more northerly, the polar front jet plunges southeastwards early next week with the uk becoming enveloped in a cold pool, it's only around a week away, give or take a day, hopefully we are in for a potent blast in 8 days time onwards with reloads galore.