WInter Model Output Discussion 12z- 28/01/2013

[That ECM]

Good evening. Here is the evening report on the 12z output from GFS, UKMO and ECM for today Thursday January 31st 2013.

All models are fairly agreed on the pattern between now and the middle of next week. The current Westerly flow turns Northerly tomorrow as a developing frontal system crosses and exits Southern Britain later tonight and tomorrow morning. Rain will spread East over Southern Britain tonight, clearing away East through the morning as cold Northerly winds usher wintry showers down Eastern Coasts and rain showers down the Western side of Britain through tomorrow afternoon and evening. Clearer weather follows with a cold and bright day likely for all on Saturday with the few snow showers near Eastern coasts early in the day dying out later. A frosty Saturday night looks likely as a ridge crosses down from the NW followed by a warm front which brings a windy and wet day on Sunday in temperatures returning to near normal. The first few days of next week sees a strong WNW flow over the UK with innitial rain clearing SE with increasingly wintry showers penetrating SE over the UK towards the middle of the week when thing could become quite wintry at times with frequent snow showers in a biting Northerly wind, especially towards the East.

GFS then shows the isobars opening out later next week as milder air tries to drift in from the West with High pressure inching close to Western Britain. A light Northerly still predominates at the start of the weekend before milder winds infiltrate into the UK from the NW. The rest of FI shows changeable weather for most with the trend to rather milder conditions later in FI.

The GFS Ensembles show a rather cold picture for the best part of the run before an improvement in temperatures to near normal levels occurs late in the run. Occasional rainfall occurs nationwide at various points throughout the run indicating a persistence of Low pressure close to our shores.

The Jet Stream shows a continuation of the flow over the UK from the NW on the Eastern flank of the ridging over the Atlantic of the Atlantic High pressure area.

UKMO shows Low pressure over Scandinavia with cold North or NNW flow with wintry showers over the UK, heaviest in the North and East and around coastal exposure in the West too.

ECM tonight shows a rather cold second half to next week with a flow from the NW or North with wintry showers at times, especially once more in the North and East. By the weekend a ridge is collapsing SE over the Uk with a cold day for the South and East on Saturday with wintry showers in the SE with a mild SW flow developing over the NW with wind and rain approaching.

In Summary tonight there is a real mish mash of synoptics tonight all of which point to the same general pattern created by High pressure to the SW and West and Low pressure to the North and East with attendant spells of rather cold and showery conditions with some snow over the hills. Sandwiched within these lengthy rather chilly spells are some short milder interludes with some rain. There seems little evidence of any slide into anything very wintry tonight.

Hi. I very much enjoy reading your posts. I would ask if you could expand on the last couple of lines of your " all model summary" and the last line of the post. Not being funny, just a bit confused. Thanks.

[Frosty.]

There seems little evidence of any slide into anything very wintry tonight.

Yes but there is a slide into wintry at least, better than recent times and still potential for a freeze depending on the displaced azores high, there is another cold block forming and no model can tell us for sure where we will be by mid feb.

[Richie V]

Hi. I very much enjoy reading your posts. I would ask if you could expand on the last couple of lines of your " all model summary" and the last line of the post. Not being funny, just a bit confused. Thanks.

he says using the current output there is little chance of a deep freeze, Gibby also doesnt wear rose tinted specticles or contacts... Simples!

[cooling climate]

Must admit to being disappointed at the real lack of SSW heights and blocking over the

northern hemisphere although it is not February yet and since this may still be a couple

of weeks away perhaps it will be a few more days yet before the models show any

significant amplitude.

Also once we get towards the middle of February and onwards -8c does not really cut it

for laying snow unless of course you have altitude on your side. We really need to see

-10c and below for lasting snow cover and at the moment there is little sign of the beast

on its way.

Of course falling snow and a steady thaw the following day may be fine to some and fair

play to them but I thought by now we would be seeing some signs of a much deeper and

meaningful cold spell ( freeze) with a bitter convective easterly in the offering.

Still lets see what the next few days model output has to offer.

Edited January 31, 2013 by cooling climate

[Frosty.]

he says using the current output there is little chance of a deep freeze, Gibby also doesnt wear rose tinted specticles or contacts... Simples!

I agree but there is enough uncertainty to keep cold fans interested, the models could flip towards a mid month freeze and then gibby will go along with it too.

[weather_it_will]

he says using the current output there is little chance of a deep freeze, Gibby also doesnt wear rose tinted specticles or contacts... Simples!

Do you have some charts to back up your frequent comments of no chance on a big freeze?

Edited January 31, 2013 by snow is falling

[phil nw.]

Really little to choose between the big 3 at T144hrs -the main features showing that cold North Westerly Arctic sourced flow.

Quite low uppers going through the UK 120-144hrs around -6 to -8c with snow showers around quite widely.

It`s another key time for how the pattern evolves from there as the vortex is shown to split to our north with some of that Canadian energy draining towards the Pacific side of the pole.

The later frames of the ECM run shows that an Easterly would be possible if enough of the main vortex is held back to the west -it doesn`t quite get there in the end on this run but there`s time for further solutions at that range.

[Richie V]

Do you have some charts to back up your frequent comments of no chance on a big freeze?

Hi There snow, im restricted to android at the mo so am struggling with that. However, all you need to do is go to netweathers datacentre and spend forty mins going through the outputs, do some side by side comps, not a massive divergence out to 120 hrs tonight. After you have done this, make a forecast for next week, write it down and ask yourself, is it realistic and will it varify.

[Froze were the Days]

Much stronger ridge than what the 240z (for what it's worth) shows as well in Feb 12' which did just enough to stop the Atlantic occlusion over the south east but that was a 'will it won't it' episode (again). As mentioned very messy ECM towards the end and not worth fine detailing.

[joggs]

Gp,Chio, In your expertly viewed opinions are we still looking out for HLB brought on by the ssw last month or has the lag time run its course? Cheers.

[weather_it_will]

Hi There snow, im restricted to android at the mo so am struggling with that. However, all you need to do is go to netweathers datacentre and spend forty mins going through the outputs, do some side by side comps, not a massive divergence out to 120 hrs tonight. After you have done this, make a forecast for next week, write it down and ask yourself, is it realistic and will it varify.

At 5 days out there is still suggestion of possible Greenland high and still there at day 6 when comparing all the models at that range,

I still don't see any end to cold as you seem to suggest?

Edited January 31, 2013 by snow is falling

[SMU]

There seems little evidence of any slide into anything very wintry tonight.

Hi Gibby-

Your daily assessments are always well recieved on here- however perhaps that assessment is perhaps a little wide, although maybe the context is the short term.

This isnt in particular relashon to your post, however still people put to much stock in the F/F/S model. - after the last cold spell the UKMO well & truly beat the GFS into submission.- The problem as ever with the GFS is its eastward bias & poor modelling of any high pressure close to scandi- its been that was since 2000 when it was formerly the AVN model.

Perhaps a reclarification of the mid term tonight ( 144-192 ) -

The UK looks to be straddling the battleground of the Atlantic airmass & Arctic airmass tonight, small incriments east or west will have big effects on how cold it stays or how warm it gets, In the latter stages the jet may become favourably alligned for more wintry weather & its in the mix in the ensembles-

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png shown by debilt- that could be slightly warmer than us-

so decending into wintry weather- undecided but a card thats on the table - which should be highlighted as well as the risk of something less wintry rolling in from the west

S

[simon29]

Way off topic guys, but just asking this as im waiting to start my new job in france, it just all depends on the weather, im a paintsprayer and basically its a waiting game until they get hailstorms which could be anytime, are we looking at anyting stormy in the next few weeks, hopefully i wont have to wait to long.

[SMU]

Gp,Chio, In your expertly viewed opinions are we still looking out for HLB brought on by the ssw last month or has the lag time run its course? Cheers.

There is little chance of significant high level blocking within the next 10 days.

the best we do is a wedge or pebble shaped high over Scandi.

JMA so far has been the only model to present any decent blocking - which at week 2/3 is for the middle of Feb-

S

[nick sussex]

Looking at the ECM ensemble spreads little variation over mainland Europe with the area to the west and north of the UK showing more divergence from the mean.

The ECM ensemble mean is solidly behind the overall pattern, its quite unusual to see such minimal dilution from the actual operational run.

So at this timeframe though there is a margin for error in terms of west/east corrections which could make a difference especially later into the output.

Also there is solid support for the Icelandic wedge, now generally we can see the models overdoing the energy going east at this timeframe so if you factor in past history especially during this winter season then its a positive that so many ensemble members actually want to take energy se rather than east.

I think the next few outputs will be interesting to see whether the appearance of that wedge of high pressure starts a domino effect with even more energy heading se further west.

So if you take the output at face value then we don't see a strong signal for deep winter cold but I'd be sitting on the fence for a few more runs now that the Iceland high could throw a curveball into proceedings.

[chris55]

GFS ensembles are a good benchmark for the output at the moment, good agreement for a colder spell next week with the Low dropping to our east, drawing in a Northwesterly, then a Northerly. No major Arctic freeze but certainly cold with wintry showers and some frosts up until the 8th.

The question is beyond this, do we end up following one of the colder members that enhance/sustain an easterly flow, or do we see the Atlantic coming over the top and a flattening out the pattern leaving us back in a westerly flow?

If we can at least get some energy heading south east we may be in position where sliders could keep the cold in place whilst delivering snow on the eastern edge.

Edited January 31, 2013 by chris55

[BLAST FROM THE PAST]

Yes but there is a slide into wintry at least, better than recent times and still potential for a freeze depending on the displaced azores high, there is another cold block forming and no model can tell us for sure where we will be by mid feb.

So take it face value, I think I've 'got' Gibby now in his report. Not necessarily making a call but reporting what is seen on the charts. So on face value we don't lead into a deep freeze, but we are heading into cold as you say.

As Nick and Steve say, t144 is better again, no need to go beyond currently.

BFTP

[chris55]

ECM extended, good clustering to around day 12, some milder options beyond but also some spikes down to -10, also very snowy just to our east.

[Wayneywoo]

Can someone please explain why this "wedge" that everyone is talking about is such a good thing? Does it mean we look at some form of trough disruption with energy going NW&SE of Greenland which potentially allows a HLB to form somewhere around Greenland/Iceland/Scandi?

Haven't seen any posts from Dave here tonight...

[MR EXTREMES]

i think a northeasterly could well be more favoured outcome in later stages.

and the icelandic wedge is something worth keeping an eye on but even from here a shift east and we have a scandi heights.

so its all very intresting and i see chiono is lurking anything on the strat front which could be of benefit?

[Grimsby Snow Lover]

An interesting tweet from Matt Hugo!!

Matthew Hugoâ€@MattHugo81

Jeez, no consistency but all 51 EC ENS members show a block developing to the NW of the UK by Sat 9th/Sun 10th and bring in an E/NE'ly flow.

[SMU]

That comes from a very strong signal for a sharp gradient developing in the mid atlantic caused by a low diving SE & being supported by that wedge-

use this run as a guide with that low diving SE at 192

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=192&code=3&mode=0&carte=1

Note the wedge all bit small seperated away at 228 east of iceland.

S ^^

Edited January 31, 2013 by Steve Murr

[Panayiotis]

That comes from a very strong signal for a sharp gradient developing in the mid atlantic caused by a low diving SE & being supported by that wedge-

use this run as a guide with that low diving SE at 192

http://www.meteociel...&mode=0&carte=1

Note the wedge all bit small seperated away at 228 east of iceland.

S ^^

An interesting tweet from Matt Hugo!!

Matthew Hugoâ€@MattHugo81

Jeez, no consistency but all 51 EC ENS members show a block developing to the NW of the UK by Sat 9th/Sun 10th and bring in an E/NE'ly flow.

Ah fits in with my prediction in my signature Edited January 31, 2013 by Panayiotis

[shaky]

An interesting tweet from Matt Hugo!!

Matthew Hugoâ€@MattHugo81

Jeez, no consistency but all 51 EC ENS members show a block developing to the NW of the UK by Sat 9th/Sun 10th and bring in an E/NE'ly flow.

blimey!!!!!we got all of the members agreeing to something ten days down the line but cant agree with anything before then!!hmmm very weird!!

[I remember Atlantic 252]

An interesting tweet from Matt Hugo!!

Matthew Hugoâ€@MattHugo81

Jeez, no consistency but all 51 EC ENS members show a block developing to the NW of the UK by Sat 9th/Sun 10th and bring in an E/NE'ly flow.

but didnt i read on here that all 51 ECMWF ens showed a beasterly around mid Dec? all 51 ens wrong!