Winter Model Discussion 18Z 16/1/13 onwards.

[mountain shadow]

Catacol,

I'm confused by your Phase 8 composite. I thought the best MJO phases for Greenland blocking were sectors 8 and 1?

Surely if the MJO moves into a highish amplitude phase 8 then the chances of proper Greenland heights increase?

[Frosty.]

I wish the Ecm 12z could have gone on and on as it was about to unleash another very cold blast from northeast europe thanks to that vigorous trigger low shooting across the south of the uk. A very wintry week ahead with heavy snow later tomorrow in the southeast spreading north on sun night and monday with blizzards reaching ne england and eastern scotland during monday and continuing through tuesday with gale force Ely winds, midweek onwards things quieten down but it remains very cold with freezing fog and severe frosts, then unsettled weather starts to push into the west and northwest of the uk at the end of the working week with bands of snow pushing east into the cold air but as the cold uppers get mixed out the snow turning more to sleet and rain except on hills in the north, temps remain below average as the main energy from the complex depression stays out west in the atlantic with trough disruption over the uk and a wintry mix of rain, sleet and wet snow, then that vicious little depression spawning to the west races in on a southerly track and sets up a cliffhanger by T+240.

The bbc weatherman this evening said there was no end in sight to the cold spell, this is very true since the changes the models are showing are still in the unreliable timeframe. Hopefully any change to less cold will be very brief and we will soon be back in the freezer.

[mcweather]

Big GP fan here, but actually I am a little concerned at the medium range output at present, in the context of what GP was expecting. His best guess was that the "milder" spell would be here about now.

The concern is that the Canadian vortex is holding its strength, and then when it does weaken it is emptying into the Atlantic with no obvious rise in pressure to the NW being picked up. GFS chart here shows the concern, with too much energy coming off the Canadian segment to allow much of a pressure rise, and loss of low heights to the south.

We might possibly end up with the same situation we had in December when heights then were expected to rise to the NW and didnt. Result? Lots and lots of cold rain, and a good deal of time required to shift the pattern on.

Saving grace is the MJO which looks set to move through 7 and this ought to signal height rises mid Atlantic at least as the composite here shows:

,

However the phase 8 composite is not so pretty:

and I am having trouble shaking off the experience of December and a certain amount of faith in mean anomalies and predicted composite matches has been lost. Disappointing lack of snowfall on Friday down here hasnt helped brighten my mood.

RJS long range forecast of cold in February still a beacon of light...

I can understand your worry on that front Catacol but if I remember correctly GP suggested a Greenland high that might ridge at intervals across to Scandinavia for feb. I think what the far reaches of today ECM''s have shown is a west russian /Scandi high that looks as if it could ridge across to Greenland in effect producing the same outcome a cold attack from the north east.

For all that additional power from the canadian vortex the lows approaching the UK at 198 and 216 stilll end up diving southeast with only modest heights to our north and east.

That said it would be good to get GP'S latest thought at some point. So that we could look out for the signals.

Edited January 19, 2013 by mcweather

[Froze were the Days]

I love your ramping Frosty! always optimistic, have to say what the ECM is showing is a long long way off and will probably change by tomorrow but as you said staying cold for the next few days.

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

if i am looking at it right if there a break down its around Jan 26 !!!

[Frosty.]

I love your ramping Frosty! always optimistic, have to say what the ECM is showing is a long long way off and will probably change by tomorrow but as you said staying cold for the next few days.

It's not ramping, it's what the ecm 12z is showing but in an enthusiastic tone.

[chris55]

http://www.meteociel...H1-168.GIF?19-0

As posted thats a poor chart with strong South westerlies across the UK-

however a bit more energy south & that could once again turn into a great chart...

Another couple of days required-

Also critically for snowcover across the south- how much WAA do we get around the low on Tues ( T72)-

Ukmo wipes the snowcover out- ECM is a tad more gentle...

S

I don't get this comment, I have been away from the models today and am now flicking through on a crappy laptop.

To me at first Glance UKMO looks great for Tuesday??? Where is the snowcover being wiped out?? -5 line well south, ppn coming in from the west, surely that would increse snowcover? Have not really looked at the broader outlook though and not analysied anything in detail as not really able to tonight.

[Snowmad79]

Well, the weather might not be looking fun next weekend but I bet the news will be. All those places getting a good dumping going from Sledges and Snowmen to Canoes and Sandbags

Lets hope for some huge turn around in the output for next weekend hey.

Edited January 19, 2013 by Snowmad79

[chionomaniac]

John... As much as i love your rebuttles- If we take the UK as a whole as opposed to a hill in yorkshire then the picture is a lot less convincing-yes there has been a cold spell, however I am guessing the CET mean has probably been higher than that-But remember - A monthly CET of around 3c which is the ~ norm for the UK does have periods of time above that & below itso for every day you have been at a low CET then the rest of jan has compensated it...for the UK as a whole- probably a GOOD cold spell so far- tipified by a rare frontal ALL snow event ( bar the extreme SW)If it goes out with a whimper Tues then I would class it as a fairly bog standard cold SPELL- however if something like the ECm develops with further undercutting then we could turn it into a great cold spell.remember the whole thing has been ramped up by the Stratosphere thread- however thus far the 500 heights have been far from convincing on an anomaly front but luckily very favourable for the UK....Fingers crossed that it continues....S

Apologies to the other mods and hosts but I feel I deserve the right of reply here.

Steve

Yes, Bexleyheath hasn't achieved snowmageddon, so the fact that the rest of the country has had considerable snowfall and sub zero temps is of little relevence. I take exception to your suggestion that the whole thing has been ramped up in the stratosphere thread. No, in fact all along it has been suggested that the SSW was akin to shuffling the deck of cards and putting a few extra aces in the pack. And so far that has occurred. In fact the tropospheric forecasts have mirrored the stratospheric conditions very well this winter.

But don't ask me - ask the met office here: http://metofficenews...pheric-warming/, or the BBC weather department : http://www.bbc.co.uk.../feeds/20992173, or many others.

However, there is one thing noticeable. It is the fact that you tried to write off the cold spell before it began - and yes it was forecast and based on tried and tested stratospheric theory (that is now becoming mainstream) that earlier in the season you had tried to dismiss in the technical thread.. This cold spell is significant, and whether the SSW delivers further cold or not, it has certainly shaken up the winter from the mild and zonal weather that was taking hold previously and, no doubt, the CET from the onset of the SSW will show this.

Perhaps you will have the good grace to acknowledge this?

c

[Methuselah]

Anyway, the enormous bint is exercising here vocal cords!

[nick sussex]

I don't get this comment, I have been away from the models today and am now flicking through on a crappy laptop.

To me at first Glance UKMO looks great for Tuesday??? Where is the snowcover being wiped out?? -5 line well south, ppn coming in from the west, surely that would increse snowcover? Have not really looked at the broader outlook though and not analysied anything in detail as not really able to tonight.

Even though you've still got the 528 dam you've changed the airmass and dew points.

There is still though uncertainty even at that range.

The UKMO though brings the colder air back at 96hrs before going downhill quickly thereafter.

Edited January 19, 2013 by nick sussex

[Jason T]

ECM also looking at around next Friday/Saturday where we lose the cold upper air and a changeover to that more Atlantic influence.

T144hrs

http://www.wetterzen...cs/Recm1441.gif

The heights easing away from the NE .

Let`s hope for a last minute reprieve but with pretty good agreement on this between the big 3 along with ens,outputs it has an air of inevitability about it.

Hi Phil, Forgive me if im wrong,But Im sure GP posted that there would be a very brief warm up and then back in to the fun and games. Im also sure that Chio posted that at this point reinforcements were already on the way as the SSW was about to show its hand so to speak.

Edited January 19, 2013 by Jason T

[bluearmy]

I don't get this comment, I have been away from the models today and am now flicking through on a crappy laptop.

To me at first Glance UKMO looks great for Tuesday??? Where is the snowcover being wiped out?? -5 line well south, ppn coming in from the west, surely that would increse snowcover? Have not really looked at the broader outlook though and not analysied anything in detail as not really able to tonight.

the flow is sw behind the occlusion and therefore, with dp's likely to be above zero, we would be looking at a period of snow followed by some rain as the front clears through. fwiw, i doubt the snowcover would be washed away - more likely it would just be dank and misty and then the whole lot comes back south as the low heads se into the continent. if there is still precip on the front then there is a danger that it would be rain as it dropped back through. it doesnt concern me too much. infact, the whole trend of the 12z is to put the idea that next weekend sees the end of the cold spell into severe doubt.

[chris55]

Thanks for the info guys, I can see we get a more westerly infuence on the UKMO, but with 850s below -5 (not sure where rhe 528 line is sitting) I'm thinking the majority away from the far south are on the right side of marginal.

Anyway as Im not really able to have a good look at all the info, I'll take the two Nicks thoughts with much appreciation. Cheers guys.

[Gibby]

Good evening. is it going to stay cold or is there a change on the way. read on for tonight's look at the 12zs from GFS, UKMO and ECM for today Saturday January 19th 2013.

All models programme a continuation of the cold in the reliable time frame of 4-5 days. The current overcast and snow grain type weather will continue for a time before a disturbbance moving North over France brings snowfall into the SE tomorrow, spreading slowly north. Near Eastern coastal areas of Scotland snow showers will continue with some brighter intervals in the West. It will remain very cold everywhere. Through the early days of next week things become more complex as Low pressures and troughs all in cold air move into the South of the UK again disrupting and slipping ESE. There would be some further snowfall developing at times with nowhere immune. By the middle of the week and Thursday somewhat drier but still cold weather looks more likely as a ridge or area of slack pressure develops over the UK with a steady reducing of the amount of snowfall over the UK in continuing frosty weather.

GFS then brings the Atlantic through with ease next Friday with deep Low pressure bringing an eventual change to windy and wet conditions is temperatures much closer to average. FI tonight shows a gradual warming of uppers further so that the UK comes under rather mild amd less wet conditions at times as High pressure to the South pushes Low pressure areas further North of the UK.

The GFS Ensembles show the slow rise in uppers that many runs have shown before with good support for a change in the weather late next week. The operational was a mild outlier in the second half of the run. With rain at times shown through the run the Atlantic will be reponsable for the milder uppers.

The Jet Stream shows the flow continuing South of the UK over the coming 4-5 days before the flow moves North to the vicinity of the UK by the end of next week.

UKMO for midday on Friday shows a SW airflow over the UK with milder air spreading to most areas with only the NE seeing any cold weather by the end of Friday. On these milder winds would be a change to rain at times rather than snow with a steady thaw continuing over the whole of the UK where snow still lies.

ECM shows a breakthrough from the Atlantic too by Friday with rain for all with a thaw too for areas covered in snow. However, it looks like a very stormy period would develop as a deep Low moves into the South with heavy rain and strong winds followed by a likely return to colder weather as the Low pulls away SE in response to a strong rise of pressure over NE Europe extending towards Scandinavia later.

In Summary a change to milder weather looks on the way late next week. All models now support this theory with all areas seeing a thaw and the return of wind and rain rather than snow next weekend. It may not last long as ECM shows us a quick route back to cold in the following week.

[ANYWEATHER]

ecm for instance,takes us out the freezer by this time next week then a couple of days later potentially put us back in! Look no further than t+72 imho ,heres the example..

[Snowmad79]

Didn't this cold spell start much earlier than strat/teleconnections and pro's forecast ? I remember all sources saying mid month would be too early. The strat forecasts etc went with the end of January being more favorable for a cold spell yet this current one started on the 13th.

So no, it wasn't ramped up by strat followers but it also wasn't forecast by those very followers either. We were told to expect lots of chopping and changing through mid month into the latter part of Jan before a cold blast would materialise if I remember rightly.

The way I see it is that it was just a fluke that a small wedge oh HP held out to deflect everything SE. No major block as was also forecast.

Edited January 19, 2013 by Snowmad79

[phil nw.]

Hi Phil, Forgive me if im wrong,But Im sure GP posted that there would be a very brief warm up and then back in to the fun and games. Im also sure that Chio posted that at this point reinforcements were already on the way as the SSW was about to show its hand so to speak.

Yes i believe he did Jason-let`s hope that this is the case.

If this change does materialise it doesn`t look like reverting to an entrenched mild pattern not with the jet still going south.

As Chiono has said the vortex is split and we can see the weaknesses over the pole here towards Greenland.

http://modeles.meteo...21-1-192.png?12

Any heights rebuilding to the north could bring the cold back without too many hurdles-much easier than in the case of the jet screaming across the Greenland/Iceland area.

http://www.wetterzen...ics/Rt850m8.gif

see on the mean chart above at T192 the cold just lurking to NE-hopefully waiting to revisit.

Edited January 19, 2013 by phil n.warks.

[nick sussex]

Didn't this cold spell start much earlier than strat/teleconnections and pro's forecast ? I remember all sources saying mid month would be too early. The strat forecasts etc went with the end of January being more favorable for a cold spell yet this current one started on the 13th.

So no, it wasn't ramped up by strat followers but it also wasn't forecast by those very followers either. We were told to expect lots of chopping and changing through mid month into the latter part of Jan before a cold blast would materialise if I remember rightly.

The way I see it is that it was just a fluke that a small wedge oh HP held out to deflect everything SE. No major block as was also forecast.

No theres two responses to a SSW, the initial response to the reverse zonal winds at 60N and then the full downwelling into the troposphere.

Luckily the first has had a big impact on Europe , sometimes this isn't always the case. It wasn't a fluke without the SSW you'd have had no chance of the current cold spell.

People are confusing the actual signal for HLB's with the initial quick response. For some reason there seems to be a reluctance to accept that the SSW is responsible for the current cold.

This seems to have taken on a life of its own because unless people see a huge Greenland high then they think the SSW hasn't had an impact, it has in terms of the initial quick response, we're now waiting to see the effects of the full downwelling.

[UV-RAY]

Apologies to the other mods and hosts but I feel I deserve the right of reply here.

Steve

You are the king of sour grapes.

Yes, yet again little Bexleyheath hasn't achieved snowmageddon, so the fact that the rest of the country has had considerable snowfall and sub zero temps is of little relevence. I take exception to your suggestion that the whole thing has been ramped up in the stratosphere thread. No, in fact all along it has been suggested that the SSW was akin to shuffling the deck of cards and putting a few extra aces in the pack. And so far that has occurred. In fact the tropospheric forecasts have mirrored the stratospheric conditions very well this winter.

But don't ask me - ask the met office here: http://metofficenews...pheric-warming/, or the BBC weather department : http://www.bbc.co.uk.../feeds/20992173, or many others.

However, there is one thing noticeable. It is the fact that you tried to write off the cold spell before it began - and yes it was forecast and based on tried and tested stratospheric theory (that is now becoming mainstream) that earlier in the season you had petulantly gone out of your way to dismiss in the technical thread. No wonder you want to play it down.

Well Steve, this cold spell is significant, and whether the SSW delivers further cold or not, it has certainly shaken up the winter from the mild and zonal weather that was taking hold previously and, no doubt, the CET from the onset of the SSW will show this, no matter how much snow Bexleyheath receives.

Perhaps you will have the good grace to acknowledge this?

c

Actually Steve has a point, yes granted the pattern has changed but only to what I would call bog standard winter synoptics in January for the UK. What we have seen is what we would expect too see at this time of year, with or without any SSW.

[Chess01]

No theres two responses to a SSW, the initial response to the reverse zonal winds at 60N and then the full downwelling into the troposphere.

Luckily the first has had a big impact on Europe , sometimes this isn't always the case. It wasn't a fluke without the SSW you'd have had no chance of the current cold spell.

People are confusing the actual signal for HLB's with the initial quick response. For some reason there seems to be a reluctance to accept that the SSW is responsible for the current cold.

This seems to have taken on a life of its own because unless people see a huge Greenland high then they think the SSW hasn't had an impact, it has in terms of the initial quick response, we're now waiting to see the effects of the full downwelling.

So in theory we havent seen the worst of the cold spell

[chionomaniac]

Didn't this cold spell start much earlier than strat/teleconnections and pro's forecast ? I remember all sources saying mid month would be too early. The strat forecasts etc went with the end of January being more favorable for a cold spell yet this current one started on the 13th.

So no, it wasn't ramped up by strat followers but it also wasn't forecast by those very followers either. We were told to expect lots of chopping and changing through mid month into the latter part of Jan before a cold blast would materialise if I remember rightly.

The way I see it is that it was just a fluke that a small wedge oh HP held out to deflect everything SE. No major block as was also forecast.

If you have read my posts in the model or strat thread then you will recognise the differences between direct and indirect responses to the SSW and how quickly these can effect the troposphere, and that the bolded line is incorrect.

Here is the 500 hPa anomaly chart to date since the start of the SSW.

As ever, one shouldn't confuse anomalies with blocks - but as I have mentiond before, the block is strong enough to deflect the jet south because of the split vortices.

And remember just because the Canadian vortex is set to try and cross the Atlantic due to a further strat warming reducing its upper counterpart, it by no way means that the long term affects of the SSW are over.

Edited January 19, 2013 by chionomaniac

[nick sussex]

Actually Steve has a point, yes granted the pattern has changed but only to what I would call bog standard winter synoptics in January for the UK. What we have seen is what we would expect too see at this time of year, with or without any SSW.

That maybe the case depending on what you call bog standard winter synoptics in the UK but without that reversal in zonal winds caused by the SSW then there wouldn't have even been the chance of a bog standard UK cold spell.

[Kentish Snowman in Yorks]

Actually Steve has a point, yes granted the pattern has changed but only to what I would call bog standard winter synoptics in January for the UK. What we have seen is what we would expect too see at this time of year, with or without any SSW.

At the risk of going off topic I don't think we should 'expect' several consecutive ice days and continuous snow cover in January in lowland UK surely?

Anyway, here are some ensembles IMBY to keep my post on topic;

A few GFS ensembles even keep the deep cold going out into the extended range...sorry I stop clutching those straws now!

[nick sussex]

So in theory we havent seen the worst of the cold spell

Nothings certain terms of the weather, we just have to see how the downwelling shows up. It's for this reason that the UKMO have added that caveat in their longer range update re colder weather into February.