Model Output Discussion 13/11/13 >

[Catacol]

Latest from Gibby on the models

 

In Summary the Northerly of next week still looks like there is an opportunity of a day or two when snowfall could be seen by some parts of the UK chiefly in the North and West and over the hills. Thereafter High pressure looks likely to build in from the West or NW with a chilly and raw day or two possible in the South on a ENE flow around midweek. It looks likely the High will migrate East then into Europe and maintain a ridge West or NW over Northern Britain.

 

This sets up a SE flow over the South and with falling pressure down to the SW rain would make progress into these parts with time to give dull and uninspiring late November conditions down here with some rain at times while Northern locations stay largely dry and bright if on the chilly side. most output does suggest High pressure in the Scandinavian region later in the run and this could be the catalyst for more blocking conditions for the UK which could in time result in further cold outbreaks developing as we drift deeper towards Winter official from December 1st. For now though all of the above suggests typical November weather for the UK.

 

 

 

A much better summary from Gibby today - thanks. Yesterday was curiously downbeat.

thats a bit fussy CH. after all, we would have decent surface cold after week 3 (if it verified).

 

Yes - maybe you are right - but some of the eye candy on the op and ensemble runs of the last few days has been much better. I'm just getting greedy... :-) - and I pre ordered Xmas Turkey today - so greed is in the air!!

Edited November 16, 2013 by Catacol_Highlander

[johnholmes]

Looks like a frosty end to November then.

 

frosty should be pleased then!

 

and there is nothing from the 500mb anomaly charts to suggest any major change in upper air wavelength to affect the UK into early December. So unless they are really missing something the colder type of weather is set to remain. Obviously there will be variations in it, depth of cold, where it comes from, will it be dry or otherwise etc.

Edited November 16, 2013 by johnholmes

[Gavin Hannah]

FI on the 06z very curios today.  HP setting up over the UK pulling in Euro air but never getting far enough east to bring in the really cold stuff. As for next week, cold and snow are the order of the day especially for the north and high ground. 

 

Really enjoying watching the models right now. We could be primed for 'Beasterly' to kick off December. Considering how zonal the last few weeks have been, the chance for some proper wintery-ness to kick off the festive season would be an early Xmas present.  Just hoping the ski slopes open during this week coming.  

[Captain Shortwave]

For the moment I calling the whole 06z GFS suite a rogue run. It's ensemble mean is completely different to this morning with the polar vortex remaining organised over the pole. The PV blow up shown on the operational has moderate ensemble support including the control. 

If it throw this in the 12z run and the other models start pushing the pattern south then I would start to worry.

[Frosty.]

 then I would start to worry.

don't worry be happy, all coldies should be this morning, the high res is guaranteed to be dominated by arctic air  plunging south with the PFJ down near north africa. No sign of mild air coming back anytime soon, once it's banished in a day or two.

[bluearmy]

there is a feature showing on the T84 fax in the atlantic which develops into a shortwave as it heads se into w france on the UKMO GM.  reading the text forecast on meto website, it seems they are not expecting it to develop too much as it heads se but it needs to be watched as it could deliver quite a surprise, especially over high ground and possibly lower down if it comes through at night.

[lorenzo]

Put these in the Regional thread, best to share here too.

 

ECM Ens & Spread

 

Interesting reading Matt on Twitter mentioning the 84 hrs Fax chart and the problematic potential development of a low currently in situe SW of Iceland. Will be something to watch in the next 12-24 hrs.

 

From NMM on NetWx, some damn fine looking cold air.

 

Progression of the 850hpa temps,  I like this view as you see exactly what is going on with the WAA over Greenland, earlier in the week this was more inclined to Baffin Bay versus over the peninsula itself.

 

After this a close watch to see where the high goes, GWO giving credence to the Scandi Block and then backing West again, am hoping it cycles as projected and we get something like this..

Edited November 16, 2013 by lorenzo

[bluearmy]

just a thought - presumably, if there is an ecm ens upgrade in the offing then they will be running a parallel suite. it may not just be mogreps that makes the 15 dayer look out of kilter with the ens we see until implementation. i wonder if ian can help to confirm if this is currently the case ?

[radiohead]

06Z NAE T48 showing rain just about to turn to snow at the Western Isles.

 

[Tim Bland]

Models firming up on that feature running SE on Weds. For most it looks like sleety rain with snow on the Pennines etc. our friend Ian F has hinted that the met office currently think it will be wet rather than white. Even if nothing comes of next week we should be greatfull for the bigger picture heading into winter

[fergieweather]

Maybe just covering their backs in case the forecasts go belly up or vice versa?,poor though as you say.

BBC Website directly driven by raw UKMO-GM & UKMO 'Best Data' (temps). No forecaster interventions. Exactly same data feed driving UKMO site-specific web forecast. In the past we could intervene and tweak. We can't now. Conversely, TV gfx fed by modified NAE (at least for now) and GM. Hence at times will differ from web forecasts as represent directly Chief Forecaster's modified fields.

[fergieweather]

don't worry be happy, all coldies should be this morning, the high res is guaranteed to be dominated by arctic air plunging south with the PFJ down near north africa. No sign of mild air coming back anytime soon, once it's banished in a day or two.

UKMO go for easterly synoptics dominating next 10-15d:NE initially; SE later. Limited wintry PPN for S especially but rain at times... in a nutshell. The Weds model conundrum remains problematic but EC remains most favoured broad-brush approach. Mostly rain; perhaps some snow N'rn flank and where heavier PPN runs-through. But they've no real concern on impacts from latter (if any falls). Depth temps still way too high, especially by day, for any profound issue from lying snow. Overnight ice from melt-freeze somewhat more a concern, but due to low forecast confidence by Weds it's a short-lead gig re anything possibly worth issue of warning(s).

[bluearmy]

UKMO go for easterly synoptics dominating next 10-15d:NE initially; SE later. Limited wintry PPN for S especially but rain at times... in a nutshell. The Weds model conundrum remains problematic but EC remains most favoured broad-brush approach. Mostly rain; perhaps some snow N'rn flank and where heavier PPN runs-through. But they've no real concern on impacts from latter (if any falls). Depth temps still way too high, especially by day, for any profound issue from lying snow. Overnight ice from melt-freeze somewhat more a concern, but due to low forecast confidence by Weds it's a short-lead gig re anything possibly worth issue of warning(s).

Ian, do you have any insight on the ECM ens upgrade due this month?

[Mucka]

Our Atlantic ridge gets flatter every day it seems and the initial cold plunge (Arctic air) is now just 24 hours or so with snow prospects very limited (though we do get a brief reload of cold uppers) so in that regard it is a bit of let down this morning but then it was also to be expected given yesterdays move away from a more amplified pattern in the near term.

 

Certainly nothing zonal or mild in the charts though and staying chilly or cold at the surface although snow prospects look limited at the moment with high pressure so close to or over the UK.

So plenty of mid latitude blocking over the next week to 10 days but too far East and/or South to draw in a good feed of cold uppers and help with snow chances though we will likely be pulling in some cold dry continental air later. (always a chance of upgrades from these positions)

 

There is no way to tell whether we will get some undercut of the block from there and have high pressure retrogress to draw in  much colder upper air from the NE or we get the Atlantic riding over the top and sinking the block. We are looking at about day 8 here for developments but currently ECM wants to undercut with GFS a little more hesitant.

Some will say GFS tends to send too much energy NE in these situations which can be true but often when we see a disparity with how energy is distributed between GFS and ECM, when low pressure comes up against a block , the end result is somewhere in-between.

 

ECM undercut. We can see here ECM sends most of the initial energy under block.

 

 

While GFS has more energy in the Northern arm of a split jet and so sends low pressure over the top rather than underneath which is often the death knell for HLB prospects though it does have a second bite of the cherry later with some nice undercut which is promising even though it goes on to flatten the pattern.

eventually 

 

 

 

So obviously we need more runs but currently we can be hopeful of at least some undercut and some mid latitude blocking or if we get lucky a chance of some high latitude blocking, probably to our NW but that is all a long way out (Likely day 10+ before any worthy HLB begins to take shape proper). Still a mid latitude block will persist through that period and while that is there we could see some sudden upgrades and draw in a decent Easterly flow if things go our way or we may see a cold and frosty set up predominate - likely with some fog and possible ice days, not bad for November. 

 

Phase 1: (0h to day 5) mid Atlantic ridge. Cold plunge.  Phase 2: (day 5 to 9?) mid latitude block close to or over the UK, surface cold, slack Easterly flow likely.  Phase 3: Day (10+?) Elvis rides in on Santa's sleigh 

 

Okay enough crystal ball gazing for now, enjoy the ride.

 

PS

I know GFS 06z had very little undercut with the jet mainly riding over the block but looking at the ensembles and other runs and models it is pretty much out on its own at the moment.

Edited November 16, 2013 by Mucka

[MR EXTREMES]

to my untrained eye I think any high pressure will end up in scandi area in time.

the feature the ukmo is eluding to is a feature id of thought will aid more in a scandi high set up.

 

now the problem is scandi highs don't block the alantic and are prone to shifting to far east,

and all the time low heights run over the top although this aids in bring cold into Europe which of coarse is needed for an easterly to have the desired effect, but also can be problem as we are always on the western side of any cold, I still continue to hold firm on a near miss situation in the later part of November I also feel the ukmo is the model to watch in the realiable timeframe and other models are very much riddled with maybes and 50/50 on any cold developments futher out.

 

the vortex does need to move or fragment or split but even this don't make any futher developments 100% but does help I think the pacific ridge is certainly causing a knock on effect and the all important jet stream is also something to keep an eye on, I hope im wrong but I see a collapse in developments later on due to a strong vortex and holding strong.

 

of coarse there is talk of wave 2 event taking place and this may aid in futher developments over the pole.

 

but this don't discount what we have for next week which has fluctuated from upgrade to downgrade to upgrade on next week cold and this is not abnormal this happens all the time.

 

timing depth precipitation upper air values thickness wind direction depression tracking its the weather and it does what it wants.

 

so there is every reason to be excited next week for some!

as for myself im looking beyond because living on the costa del south coast  theres really not much interest for us down here but nice to see frost a real frost.

 

im hoping to see some exciting ne flow with good convection this winter and of coarse nice deep channel lows not much to ask really lol so looking forwards to this evenings and tomorrows output with deep interest and ive picked up my toys and put them back. 

[Gaz1985]

Looks like snow on the leading edge of the weather front Tuesday night/Weds Morning but it soon turns to rain,

 

For the coldies in the Midlands and Northern England you'd have to be up during the early hours to see anything settling before it gets washed away and even then it won't be anything heavy away from high ground.

 

Also Wednesday not looking as cold now as was showing the last few days, around 5c for this area but was showing 2c yesterday. Scotland however clings onto the coldest air and nothing much has changed in that respect since the last few days. So I think for England and Wales a slight downgrade but not for Scotland.

 

 

Edited November 16, 2013 by Gaz1985

[Man With Beard]

I think Ian F's assessment for Tues/Wed agrees completely with all the free models we are looking at, though a yellow warning for parts of Scotland / NW England might be useful nearer the time if ppn amounts stack up?

 

Longer term: As ever, if you're wanting at a soap opera, look at each model in isolation and panic/salivate in response. But if you're wanting to make a forecast, look at lots of models over the course of a day or so. And, based on several models such as the ones below, I actually think there is enough confidence to call T168-T192 (i.e. next weekend). There will very likely be high pressure centered somewhere between Iceland and Finland, and, even more likely, low pressure centred not a long way from the French Riviera. For the UK, this means that an easterly seems unavoidable (especially in the South), probably persisting for a few days (which fits in with UKMO forecast provided by Ian F above). GFS 06Z slightly different but out on its own. Being late November, the easterly is likely to be cold as it will be sourced through Eastern Europe at the very least, though as yet unclear how cold; precipitation (could be rain, sleet or snow depending on depth of cold) is possible, more especially if the high is centered in Scandinavia or above Scotland.

 

[fergieweather]

Ian, do you have any insight on the ECM ens upgrade due this month?

I saw a note on it. I'll find it and read it again.

[MR EXTREMES]

I think the ecm this morning is a beautiful certainly can see something evolving from the cm if its correct the others are ok but not nowhere near as good as two days ago.

[Frosty.]

This will be very impressive if it verifies, almost 510 dam into the far north, I imagine that frequent heavy snow showers will blitz the far north & northeast of scotland through the first half of next week as they are likely to feel the most bite from the arctic blast but the thicknesses are also very impressive further south and if there is a disturbance running south in that flow, it could be a knife-edge rain to heavy wet snow event, it has been known to catch forecasters out in the past, I think modest hills have a good chance of a decent covering, higher up the better..It's going to feel like winter next week and the latest met office outlook is for it to remain rather cold until well into december with high pressure generally to the north of the uk so northern britain would become settled with widespread frosts but fine and sunny days, the further south you are, more chance of unsettled and chilly weather with low pressure to the east/se.

[Summer Sun]

This mornings ECM ensemble and Op are in pretty good agreement of it becoming more settled from around next Thursday with low pressure heading back to Greenland thus allowing high pressure to set up for the UK

 

 

Temperatures should recover a bit but a likely to still be below the seasonal average for just about all

 

NAO is now showing hints of going back to positive again

 

Edited November 16, 2013 by Summer Sun

[snowmadchrisuk]

The 12z Moscow model is briiliant ... Wednesday would be all snow under the -10's and low pressure forming to our SW

 

edit: I see it is yesterdays .. arhhh was getting excited about upgrades then .. 

 

 

Edited November 16, 2013 by snowmadchrisuk

[Jayfromcardiff]

The 12z Moscow model is briiliant ... Wednesday would be all snow under the -10's and low pressure forming to our SW

 

edit: I see it is yesterdays .. arhhh was getting excited about upgrades then .. 

 

 

 

 

 

Hi mate, how reliable is this model though?

[radiohead]

12Z NAE T48. Rain turning to snow over high ground in Scotland.

 

[Summer Sun]

Hi mate, how reliable is this model though?

 

No sure its not a model I ever look at but its yesterdays 12z

Edited November 16, 2013 by Summer Sun