Winter Model Discussion Thread 12Z onwards 5/1/13

[nick sussex]

Well you can say that but many times one was able to look at the models at ranges between T120 and T192 and think 'how can this go wrong ?' And it very often did.

I think its good to keep our feet on the ground until we're more sure of the detail.

IMO its this timeframe which leads to the most anxiety because its close but not quite close enough!

What I don't want to see from the models is a halfway solution between an initial easterly and the Azores high ridging north, we want a clear route either way.

The chance of a pre 144hrs easterly looks less likely than one evolving from the Azores high in combination with ridge to the ne because the models are reluctant to take energy se in that timeframe.

So if it comes down to the latter we'll know our fate with the degree of amplification of that troughing to the west.

[blueballs]

I would just like to express my respect to Stewart who predicted this likely cold spell way back at the start of december, it`s unfolded as he predicted almost to the day. Its great having such knowledgeable people on here sharing their thoughts and answering the questions of newbies like myself.

Solar activity has increased somewhat in the last week in respect of the amount of spots visible on the disc but most of these spots are not magnetically complex and are basically dorment, there are a couple of regions producing m class flares at present but nothing too drastic.Nobody fully understands the mechanism that turns low solar activity into low NH temps but there does seem to be some correlation, my theroy would be high solar activity somehow cools the stratosphere, giving us a warmish winter and vice versa. i think the current ssw is probably due to the very low solar activity in recent weeks and any affects from solar output won`t stop the effects of this ssw and the one predicted later in jan.....bring it on, bout time we had some lovely white stuff

[ChartViewer]

That solar flare has about as much chance of scuppering this cold spell as Westham do of winning the champions league. Why go out of our way to look for obscure and implausible reasons as to why a cold spell which hasn't even arrived could be a no go.

I wouldnt go that far . Looking forward to some cracking charts today....hopefully

[Jayces]

I don't understand why people are looking for ways that it could fail before it's even arrived?

Let's just enjoy the potential for now and if it does go horribly wrong discuss why after the event :-)

[TAFKAP]

We may not get the deep cold and copious amounts of snow that most on here want but the increasingly implausible suggestions as to why such cold may not arrive is becoming laughable!

Given that the Northern Hemisphere is currently in winter and bearing in mind the size of the landmass of the UK, I would imagine that the chances of a forecast solar flare causing our tiny island to become / remain mild are miniscule, and that is being generous!

Why would this flare pick on the UK and not the rest of the Northern Hemisphere? Or is it being suggested that this flare will cause the early onset of spring across the entire hemisphere?!

It's all a conspiracy I tell ya...

Eyes down for the 12z...

Exactly, EYES DOWN and enough discussing incredibly unlikely scenarios for a cold spell failing. It could of course go either way but a solar flare will have as much effect as if we all floated up to the stratosphere and farted simultaneously. Back to discussing the nwp for god's sake.

[fergieweather]

It'll get cold: that is now unquestionable. But our briefing wisdom today from Exeter affords balanced perspective: "Don't go overboard (re snow / extreme cold etc) as yet. It is still winter, after all..."

In other words: high confidence on the trend now but a cautionary note on any public statements re eventual outcome. Nonetheless, make no mistake: all heading very much in the right direction for cold lovers.

[MR EXTREMES]

There is a fair bit of getting carried away with the emotion within these threads at the moment. To me, the form horse at the moment seems to be mild high over us for a few days followed by a less mild high over us for a while later.

As was predicted by myself and others, the ensembles (in FI) have gone haywire and are chucking out a wide variety of solutions - this will continue for the next few days until the next pattern change is nailed down and by this time FI might be as near as +60 or +72.

I like Ian's idea of mapping any cold spell collapse in the models (I nearly started a new thread myself in the General Discussion Area, after THAT Ecm run in December, to map and record for posterity a cold spell collapse and I wish I had now), however I feel this should maybe have it's own thread and is still a little premature on the current output.

if i remember rightly the gfs was front runner in predicting that cold spell and the ecm was close behind we can all sit a pick chuncks out of the models but they are a forecasting tool and i dont remember such a strong cross model agreement than what we are seeing now.

ofcoarse the detail comes later.

[stodge]

Afternoon all

My first chance to look at the model output for a couple of days and the signs for a mid-month anticyclone continue to be evident. As I've said beforthis happens surprisingly frequently (about one year in three) and "can" be the precursor to something more wintry later in the month (but NOT always).

The route to very cold in this country usually starts with very mild and, to be honest, it's not hard to forecast colder conditions than those we currently have. With anticyclonic conditions (assuming the orientation of the HP is favourable) the cooling down process is also gradual with each day slightly colder then the one before it. This time of the year, the nights are still very long and can still get very cold under clear conditions.

The 06Z GFS operational output shows temperatures in my part of the world declining from 10c today to 5c by this time next week so that in itself will be a significant step forward. As for snow, I remain to be convinced - yes, the possibilities are there but it's often a tricky one to forecast. I suppose a prolonged period of cold anticyclonic conditions is an option but one of many.

[The PIT]

if i remember rightly the gfs was front runner in predicting that cold spell and the ecm was close behind we can all sit a pick chuncks out of the models but they are a forecasting tool and i dont remember such a strong cross model agreement than what we are seeing now.

ofcoarse the detail comes later.

Ain't arrived yet. Plenty of time for a dreaded short wave to shunt the cool/ rather cold to another country. Until it's within that T96 time zone I won't do cartwheels. Every the big boys are being told not to get excited yet. Seen it all before, Worn the T shirt, Drunk the booze, tested food until the mild fat lady is singing stay calm.

[fergieweather]

Excellent post by Stodge and the comment re cold, dry anticyclonic outcome versus any truly snowy one in a nationwide sense needs emphasis at this speculative juncture.

[MR EXTREMES]

up to 72hrs block to our south does looking like retreating south not sure if this is a good thing but lets see what mighty charts the gfs brings to the coldie party by t144.

and by t78 there seems to be something building between greenland and iceland.

Edited January 5, 2013 by model rollercoaster

[stodge]

Thank you for the kind word, Ian, and, coming from you, much appreciated.

[TEITS]

I suppose a prolonged period of cold anticyclonic conditions is an option but one of many.

or a combination of cold anticyclonic conditions intially which becomes wintry as the positioning of blocking becomes more favourable for snowfall. The way this is developing suggests a few opportunities for the rest of the month.

Good start of the 12Zs.

http://www.wetterzentrale.de/pics/Rtavn841.png

[ITSY]

Not a bad picture to have 3 days out

Based on previous runs there will be several 'pumps' of advection (otherwise known as WAA) into the north Atlantic region from the south, that should, if things go to plan, develop to form a block to the north (although initially probably on top of) the British Isles. At this stage you can already see that developing around Iceland.

Indeed, by +96hrs, NE Scotland already finds itself in a slack NEly as a result

Edited January 5, 2013 by ITSY

[cold snap]

People concerned about it going wrong is understandable however it's vastly different to dec 2012

It's more likely to go wrong via a Scandinavia high cell than a Greenland one

Now to any newcomers it's simple maths ,a Greenland high blocks the Atlantic making inroads .

However without full ridging to Greenland we might just end up cold and dry with full ridging we could still end up dry however snow prospects would be at a far greater chance.

Cold is banked now

[on the coast]

Well at 96 its looking superb. Cold in the reliable time frame. Just a question of how cold it gets and if there is snow with it as time go's on.

[Panayiotis]

WOW after staying up and being amazed by the 00z, the 06z outdid the 00z and and sent us all the cold uppers, by a similar route (retrogression of the high to Greenland), looking forward to what the 12z has instore and hopefully produces the same thing!

Edited January 5, 2013 by Panayiotis

[MR EXTREMES]

mmmm looking good to our north good timeframe aswell.

[lord stratus]

Models are firming up on the cold spell of weather coming, eventually cold enough for snow, though it will be 15th to 18th jan onwards for the real deal.

[ITSY]

Looking good so far. Based on previous runs, expect the high to flab somewhat and move SEwards (perhaps towards scandi and scotland) before being reinvigorated with possible retrogression towards Iceland and Greenland.

[Panayiotis]

At 108 hrs heights have gained in strength to the north compared to the 06z, reason why is that more warm is being advected into those areas. This should have a positive effect on us.

[MR EXTREMES]

the azores high seems to be holding back the cold keeping it to the northern eastern side for now.

so do we want the azores heights ridging north to aid blocking up there or would a sinker be better we shall see exciting stuff though.

[MR EXTREMES]

maybe a second bite needed but still onboard but still backing the cold evolution but more settled perhaps cloudy cool here in the south.

[ITSY]

Expect to start seeing the Azores ridge northwards in the next few frames (if this run continues the theme of the last 2)

[ITSY]

the azores high seems to be holding back the cold keeping it to the northern eastern side for now.

so do we want the azores heights ridging north to aid blocking up there or would a sinker be better we shall see exciting stuff though.

It's actually progressing at the same rate as the previous run, with additional potential for ridging into Greenland building from NE Canada. That's how I'm viewing it anyway. Could be wrong.