Model Output Discussion 19th January 2014-18z onwards.

[chionomaniac]

   which is why we use ens rather than ops beyond day 6. maybe even day 5 is where the ens go ahead of the op. things is, you do need to know when the ens mean is not to be used re clustering and also the general lack of over amplification on the ens mean does give it a head start over the ops re verified height deviance from that forecast.just a note on the ecm 11/15 day mean posted earlier - that is consistent with what was shown for the next 10 days, 10 days ago. its a pattern that allows for some movement west or east (given the behaviour of the scandi block thus far and the likely arctic heights, what direction would you expect to see?). the current pattern would probably have delivered some different surface conditions, had the continent been colder prior to its onset. as steve posted some days ago, its a broad pattern that delivered decent snow events last january. its a high risk snowy option and more likely to disappoint than deliver but it doesnt have to back west very far to be one which makes this place very excited. you have no idea where the circulations are likely to form along the trough track. i am more than happy to see it continuing to be modelled. add to that the extended ecm ens renew the decent split in the vortex after almost bringing it back together in the 6/10 day period and there is no reason to be downbeat.

I don't see Draztiks Exc ens 10-15 chart as a truly zonal setup. For that I would expect to see more of the negative anomaly towards the southern tip of Greenland. And neither is it a blocked set up either. In my eyes it is somewhere in between, which as he says will give us below average temps - and it is a start to a more blocked set up should the strat deliver downwards, which currently is the big 'if' for the rest of winter.

Edited January 21, 2014 by chionomaniac

[Yarmy]

dear goodness, don't get too hung up! How about "favoured"? Is that better?as i cant see the postage stamps from ECM i can only go with the mean, and seemingly a majority of ec members want troughing to our nw into day 10-15, and as bobby points out, the other lr models agree! This isn't a new signal, its been apparent for days now!I have no preference for the synoptics indicated, but the models show what they show!

 

It's a peculiar sort of wet blanketry though. We have genuine interest at last in the short to medium range and some people are on a breakdown hunt before we've even got there. As BA has pointed out above: it really isn't that bad (the ECM EPS mean anyway). There would be plenty of battleground UK scenarios mixed into that mean.

[Frosty.]

There are hints of the weather becoming more settled in the far south towards mid feb with probably more in the way of fog and frost, otherwise it's a very unsettled pattern for weeks to come with periods of persistent rain & gales interspersed with clearer and colder, showery days and occasionally cold enough for the showers to become wintry and hill snow across the north is likely at times.

[stodge]

http://www.dmi.dk/vejr/til-lands/landsudsigten/

 

A straw of sorts for the coldies - yesterday, the Danish Weather Service (DMI) were calling for milder weather to spread across Denmark over the weekend.

 

Not so today, the "cold from the east is winning this round of the battle" to offer a translation of the title. The HP over Finland is, according to DMI, going nowhere and keeping the milder air to the south and southwest of Denmark.

 

Now, that may well mean the UK but that is a significant change in its 3-5 day forecast from yesterday to today suggesting to this observer that the "battle lines" are further west and south west than expected at this time yesterday.

[Tamara]

Then again they could be absolutely right, as were those who wrote off Dec in late Nov and those who wrote off the first half of Jan in mid Dec....not that anyone has seriously written off Winter at this stage of course. Completely concur with your final sentance though, that process has been arrested for now and already it's very clear the models are struggling post T+120hrs in particular - the question is will that continue or will the Atlantic start to smash though once again?  Answers not to far away now imho.

That part of the winter was predicted as a write off very apparent reasons. A very powerful vortex building under a strongly ramping up polar westerly background pattern which relocated the vortex to Canada and Greenland after some temporary attempted amplification of the atlantic pattern (largely failing) while the vortex resided towards Siberia in late November and as a poleward -EPO ridge in evidence at the time broke down.

 

The situation now is in reverse with the dissembling of the vortex in sequence, plus all the other factors in play which I listed in my most recent post. On that basis, for the reasons I gave in that post, we need to be very careful how we interpret current ensemble means. These are, and will continue to prove, fickle and volatile.

 

The dominant signal apparent from those ensemble means, and including the 32 dayer, is very skewed atm by the large quantity of players in evidence, as mcweather appropriately describes them, and as I listed in my earlier post. The atlantic signal is very uncertain in terms of amplification in the days ahead, and in tandem with pressure rising over the pole and further attempted vortex attacks in the pipeline  - then taking ensemble means at face value is playing with fire even more than it usually is. Especially as these are swinging one way to the other, from one suite to the next suite.

 

Its a pattern knife edge and all bets are off at this time

[gottolovethisweather]

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=307&y=139 (South East England)

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=188&y=176 (South West England)

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=265&y=1 (Northern England)

 

Another very good set of ENS. There are some good trends developing in the output at the moment, both in the troposphere and in the stratosphere! Let's see if we can get the trends in place properly and then that's where the specifics start to become relevant. Already we've observed how tiny corrections westwards and eastwards can drastically alter the sort of weather we will see. That's what we get for living on an island next to a vast landmass and a vast ocean!

 

I haven't checked in here too much in the last 24 hours but looking at your ensembles my two snow-watch dates would still have to be the 24th January and 27th January. The 850s aren't too shabby on said dates hence the snowflakes shown on those charts.

 

A note to all, try not to pontificate on the longer-term signals when the nearer-term may well spring a wintry surprise or two beforehand. An intriguing end to January given what we've endured so far, whatever.

 

EDIT: And to add to my thoughts above, whichever type of precipitation is likely, I can't see this being known until later on Wednesday as stated previously.

Edited January 21, 2014 by gottolovethisweather

[TSNWK]

How many times has someone posted that this winter!

Yes.. but this is the BIG! one.....

[Joe Levy]

I haven't checked in here too much in the last 24 hours but looking at your ensembles my two snow-watch dates would still have to be the 24th January and 27th January. The 850s aren't too shabby on said dates hence the snowflakes shown on those charts.

 

A note to all, try not to pontificate on the longer-term signals when the nearer-term may well spring a wintry surprise or two beforehand. An intriguing end to January given what we've endured so far, whatever.

I couldn't agree more! In 2012, late October or early November I think, a front moved across the South of England and, with evaporative cooling and cold northerly surface flow, caused very heavy snow over parts of Somerset and Dorset! If that can happen in Autumn, when conditions are not normally favourable for wintry weather, then the persistent tendency for the models to show cold north-westerlies appearing in the next week or so is even more promising! Sometimes the best winters are about the surprises!

Edited January 21, 2014 by Joe Levy

[shedhead]

That part of the winter was predicted as a write off very apparent reasons. A very powerful vortex building under a strongly ramping up polar westerly background pattern which relocated the vortex to Canada and Greenland after some temporary attempted amplification of the atlantic pattern (largely failing) while the vortex resided towards Siberia in late November and as a poleward -EPO ridge in evidence at the time broke down.

 

The situation now is in reverse with the dissembling of the vortex in sequence, plus all the other factors in play which I listed in my most recent post. On that basis, for the reasons I gave in that post, we need to be very careful how we interpret current ensemble means. These are, and will continue to prove, fickle and volatile.

 

The dominant signal apparent from those ensemble means, and including the 32 dayer, is very skewed atm by the large quantity of players in evidence, as mcweather appropriately describes them, and as I listed in my earlier post. The atlantic signal is very uncertain in terms of amplification in the days ahead, and in tandem with pressure rising over the pole and further attempted vortex attacks in the pipeline  - then taking ensemble means at face value is playing with fire even more than it usually is. Especially as these are swinging one way to the other, from one suite to the next suite.

 

Its a pattern knife edge and all bets are off at this time

Not suggesting it wasn't Tamara, some of us could see that quite clearly, but that didn't stop the constant howls of derision towards anyone who suggested as much at the time. As you, I and many others have said we are very much on a knife edge now, with precious little required to tip the balance significantly in a number of directions, but for now everything that I can see favours W'erly rather than E'erly domination...that of course can and may change very quickly however.

Edited January 21, 2014 by shedhead

[nick sussex]

I think overall the scenarios on offer are as follows:

 

High to the e/ne, low pressure to the se, energy splitting se to the west of the UK with snow on the eastern flank of any low.

 

High further east with troughing over the UK, temps average to cool, occasionally colder, some snow mainly over higher ground in the north.

 

I think I know which scenario most people want in here!

 

There is a difference going forward and that's mainland Europe will be much colder than it has been so it would be easier to tap into a colder undercut.

 

I don't think the output  shows a  bog standard type zonal flow, even if you take just the means they still keep higher pressure to the east/ne, which will force the jet axis more nw/se.

 

I think the nw/se jet axis is very much likely to verify but its just how far west/east the pattern is that's still open to question.The problem I think is that the winter so far has been a let down in terms of wintry weather, there is nothing really wrong with the second scenario if it was coming much earlier in the winter, the problem is that we're now heading to the end of January and so many people want some proper cold and snow, lasting on the ground for a few days with some nice frosty nights and days.

 

For that you do need to see blocking to the north and east and energy disrupting to the west of the UK not over it, and this is why we must have an early clearance of low heights to the nw, to just allow the Arctic high room to edge further sw and get the cut off low well to the se, its likely that a renewed burst of energy will attempt to move east as theres some breakdown in the ridge over the east Pacific, if the pattern is already too far east when that happens then you're more likely to end up with the second scenario.

 

We can just hope to squeeze a bit more amplification out of the Azores high to buy a bit more time and must now I think we also need to see a more developed shortwave engaging the PV on its southern flank, to just help hold it back for even just an extra day, this could make a lot of difference downstream.

[gottolovethisweather]

I couldn't agree more! In 2012, late October of early November I think, a front moved across the South of England and with evaporative cooling and cold northerly surface flow caused very heavy snow over parts of Somerset and Dorset! If that can happen in Autumn, when conditions are not normally favourable for wintry weather, then the persistent tendency for the models to show cold north-westerlies appearing in the next week or so is even more promising! Sometimes the best winters are about the surprises!

 

Indeed and I often reflect on the past to learn from the future, if you get my drift.  It's still a wait and watch of course though.

Edited January 21, 2014 by gottolovethisweather

[shedhead]

I couldn't agree more! In 2012, late October of early November I think, a front moved across the South of England and with evaporative cooling and cold northerly surface flow caused very heavy snow over parts of Somerset and Dorset! If that can happen in Autumn, when conditions are not normally favourable for wintry weather, then the persistent tendency for the models to show cold north-westerlies appearing in the next week or so is even more promising! Sometimes the best winters are about the surprises!

Fair point Joe, anything is better than nothing, but after more than half of a so called Winter that's been mild and soggy I think most in here crave more than a very localised, transient wet snow event.

[Frosty.]

In general terms there has been very little change to the met office outlook apart from a weak signal for high pressure to eventually build across the south so where does that leave us with a pattern change? I think the models so far today are showing more wintry potential than yesterday, especially the 12z output last night which pushed the cold further east but once again there has hardly been any movement from the mo with the type of disturbed pattern we had through dec and early this month being the form horse, so i'm assuming that mogreps is not showing anything significant in terms of snow & ice for the next 2-4 weeks.

Edited January 21, 2014 by Frosty.

[Mucka]

Talking of ensembles I have to say GFS ensembles and indeed the Op runs to some degree are so massively progressive with the NH pattern that they really are of little use at the moment.

I have banged on about this a fair bit I know but the differences between the Euros and GFS is stark and GFS ensembles just accentuate those differences.

 

Let's take the 120h chart of GFS 06z, the Arctic high has moved across the pole and now sits NE of Scandinavia still rapidly moving SE, NE of Greenland pressure ranges from 1005mb to 1020mb with a W/NW flow.

 

 

Now look at ECM and UKMO for the same time.

 

 

Where GFS has low pressure and W/NW flow the Euros have a stonking Arctic high and S/SE flow.

Now if you look through GFS ensembles you will see that they are generally much worse than even the GFS Op's and light years from having the same NH profile as the Euros.

 

This is important because that high can back the pattern West and provide a robust link up with any Atlantic ridge later.

It could make all the difference if we can get a more amplified upstream pattern, just look at these 168h comparisons (ECM 00z, yesterdays JMA 12z and GFS 00z) and look at the difference in strength of blocking to our N/NE. (Also so note JMA models the Arctic high similar to the Euros rather than GFS)

 

 

So either GFS is modelling the NH much better than the other models and they are wrong or GFS is wrong - take your pick.

For me the GFS is very likely wrong and if it is we can't take any of its output seriously beyond 120h, especially its even more progressive low res ensembles, until it falls into line with the other models.

 

Keep an eye out on future runs to see if the other models move toward GFS in racing the high across the pole or if GFS starts to smell the coffee.

If GFS does come on board expect to start seeing better charts from day 7+ and when the ensembles eventually pick it up expect to see more eye candy in FI than currently.

 

Of course the Arctic high is only one piece of the puzzle and if we can't cut off low pressure from moving SE past the SW tip of Greenland with a more amplified pattern upstream then we will likely get a messy mixed bag of unsettled weather rather than any cold spell proper develop but as noted the modelling of the Arctic high can move the balance more in our favour by providing  a stronger link with any attempted Atlantic ridging.

Edited January 21, 2014 by Mucka

[gottolovethisweather]

Fair point Joe, anything is better than nothing, but after more than half of a so called Winter that's been mild and soggy I think most in here crave more than a very localised, transient wet snow event.

 

Any chance you could talk about future prospects Shed? Yes, I too relate to Joe's comments and in part to yours in fact, but what has gone has gone and this place will soon be filled with charts showing further snow inducing synoptics, well one can hope! Eyes down guys n gals and brace yourselves for another round of East meets West type synoptics.

Edited January 21, 2014 by gottolovethisweather

[shedhead]

In general terms there has been very little change to the met office outlook apart from a weak signal for high pressure to eventually build across the south so where does that leave us with a pattern change? I think the models so far today are showing more wintry potential than yesterday, especially the 12z output last night which pushed the cold further east but once again there has hardly been any movement from the mo with the type of disturbed pattern we had through dec and early this month being the form horse, so i'm assuming that mogreps is not showing anything significant in terms of snow & ice for the next 2-4 weeks.

I thing it's very unlikely that the block will get completly blown away Frosty, so the chance of a return to Decembers set up whereby system after system blasted across us, N Europe and even deep into W Russia looks low. However, I don't currently believe the block will extend sufficiently westward to put us into the freezer either, so the best we can probably hope for is enough westward correction to make us rather than the North Sea the frontal graveyard, that way ensuring that some areas, particularly across the east see at least some snow at times.  Up until very recently I was fully expecting a very wintry Feb and to be fair those on a N Sea oil platform might still get one, but now I'm leaning ever more towards normal to rather cold in the east and normal to rather mild in the west. 

 

Edit-: Hadn't seen yer post gtltw, but hopefully the above fits the bill...

Edited January 21, 2014 by shedhead

[Joe Levy]

Fair point Joe, anything is better than nothing, but after more than half of a so called Winter that's been mild and soggy I think most in here crave more than a very localised, transient wet snow event.

Living in Devon, it is always mild and soggy here! We got very little snow at all in 2013, except over high ground. So actually I think you'll find that some of us would just like to see a flake or two! The northwesterly setup showing on the models is pretty good as far as I am concerned, especially with the jet pointing nw/se. Also, any corrections westward and we get quite a different setup! I was born in the mid 90s in concrete and brick London so any snow is frankly amazing for me!

[fergieweather]

Aside from the snow expected tomorrow across the Pennines, the latest E4 modelling of Thursday's system shows WBFL dropping markedly down to circa 400m immediately post-front. Thus, cater for some snow falling to quite low levels in even moderate ppn rates for the N/NW especially.

[Downpour]

@Shed

 

Sadly I agree with you. I can't see this next lot coming off. The one thing that gives me hope for this winter is that a snowless winter here at 150ft asl right next to Epping Forest is as rare as hen's teeth so one would expect it to snow at some point.

 

But potential at days 8-10 does not inspire confidence. The Pest is the form horse, just as the Beast was the form horse in the notable snowy periods in the last four winters, all of which gave widespread snow on more than one occasion here in the capital.

 

Eyes down, look in... 12z rolling out...

[mcweather]

If members want to see how we can get from roughly where we are now to a Mid feb cold spell with snow.

go to the following address on the wetterzentrale kartenarchive and run forward day by to the 18/19th feb.

 

http://www.wetterzentrale.de/pics/archive/ra/1978/Rrea00119780121.gif

 

Not saying it will happen just showing what a late Jan arctic high and a vortex coming under pressure can do.

Edited January 21, 2014 by mcweather

[andymusic]

short term wintriness!

 

[bradymk]

short term wintriness!

 

Not so much if we are talking GFS higher res, northern and western hills. This will be coming into higher res Euro4 now anyway.

[Cecil Hogmanay Melchett]

Thursday could be interesting!

Higher routes across the north in particular could get a suprise snowfall out of this.

First taste of winter?

[frosty ground]

short term wintriness!

 

Not on the high res thou

Thursday could be interesting!

Higher routes across the north in particular could get a suprise snowfall out of this.

First taste of winter?

Seen snow in Oldham already........ (nothing settled thou)

[Man With Beard]

Yes I must admit I wish i had followed these more closely this winter like a mini home 'project' to see how well they verify. Out of interest, do you (or anyone else reading this) know if there are any resources showing verification and accuracy stats for them? (comparing a chart to actual chart 10 days later or something similar?).

I followed ECM ens chart by chart earlier this month, they significantly changed between T96 and T144 - twice in a week! (and not just back to the previous pattern)