Winter Model Discussion - Cold Hunting -23/12/12

[Geordiesnow]

Must say, those runs which showed heights from Canada entering into Greenland with higher heights and thicknesses look awfully off the mark now - not that it would make too much difference to our part of the world as it would of end up as a west based NAO anyways.

Getting the detail spot on looks difficult to pin point, the cold through Boxing day has been downgraded now somewhat but the main trend is for Atlantic based weather, any cold air looks most likely to come from the NW and in these situations won't last very long.

Won't surprise me with such a strong jet stream if we see a deep low coming into play, today has reminded me why I love gale force winds from the west, its something we have sort of lacked so far this year.

[Dunstable Snow]

Oh well at least its Christmas.... The last time I posted there looked ot be a real possibility of a west based negative NAO setting up. Whilst I doubt that would have delivered anything worthwhile from a coldies perspective we are now faced with the atlantic conveyor belt and donwstream pressure rises over Western Europe. Perhaps thats what we deserved when we started to wish away the Russian high ! At least most of continental Europe was in the freezer now it looks as though these same areas will also turn very mild for the time of year. Not good I suspect for our long term prospects for winter cold.

The charts at the moment and my football teams (Fulham) rapid descent towards the premier league relegation zone are leaving me a little disheartened this evening. That said I would like to wish everybody on this great site a great Christmas break. Hopefully by this time next week things will be looking up on both fronts but I wont be putting any money on it !

Cheers

[phil nw.]

To be honest Phil, this remains the theme once again for the duration of the GFS 12z, bar the brief west or north westerlys that follow as the low clears east ahead of the next incoming low. The sheer number of lows hammering in over the next 10-14 days must surely lead to records being broken for rainfall. With one of the wettest Decembers on record in some places.

Yes PE it`s looks pretty gruesome for the foreseeable-more rain is the last thing we need.I would even settle for an Azores high ridging up to the UK for now-just to give us a break.

As for cold it`s desperate times when we have to look into later frames for even a toppler.

The only way is up wrt the outputs now.

[Summer Sun]

GFS 12z ensembles

[Cecil Hogmanay Melchett]

GFS 12z ensembles

zonla,awful,not much else to say really,no wionder steve murr has vanished,i wish that zonal conveyor would vanish!

[Geordiesnow]

.As for cold it`s desperate times when we have to look into later frames for even a toppler.

Quick toppler on the ECM run at 96 hours in particular with the -10hpa touching Shetland! To be fair, the models have hinted at a very weak ridge heading se'wards from Greenland which may bring a bit of cold air to Northern parts of Scotland but even if it does come off perfectly, its not going to last very long! One to keep an eye on though because it could deliver some snowfall for some parts of Northern areas at least for a time.

Nonetheless, the trend even on this ECM run thus far is for the Atlantic to come in and there is the potential for a large low pressure area to head for us, large does not always mean deep though so the isobars are not all that tightly packed at this moment in time.

[Paul]

'Winter's over' type posts will be just removed so bear that in mind if you're tempted to type it & save yourself / the team some effort by not doing so! This being the model thread, most of which go out to two weeks or thereabouts, forecasting over 2 months of weather in here is clearly not on topic, and lets face it is most likely to be designed to get a reaction rather than to add anything worthwhile to the debate.

Also. please remember that this is the model discussion thread, so if your post doesn't actually discuss the output and just talks about how depressing/good things are, or how things will hopefully change or not, please post into the mayhem/emotions thread:

http://forum.netweat...n-ramp-go-nuts/

Thanks, and Merry Christmas

[karyo]

The models are having an easy time as the zonal pattern is so easy for them to predict and they are in perfect agreement which is bad news for us!

At 192 hours the ECM is giving us a small window of opportunity for a northerly toppler as the low in the east coast of North America is deepens and slows down.

Pity there is no high pressure further north to give us something more substantial.

Karyo

[phil nw.]

Quick toppler on the ECM run at 96 hours in particular with the -10hpa touching Shetland! To be fair, the models have hinted at a very weak ridge heading se'wards from Greenland which may bring a bit of cold air to Northern parts of Scotland but even if it does come off perfectly, its not going to last very long! One to keep an eye on though because it could deliver some snowfall for some parts of Northern areas at least for a time.

Nonetheless, the trend even on this ECM run thus far is for the Atlantic to come in and there is the potential for a large low pressure area to head for us, large does not always mean deep though so the isobars are not all that tightly packed at this moment in time.

Yes i see that GS in fact Shetland has stayed quite cold up to now and is continually modelled to remain so in the next few days.

Quite stormy up there at times though and it must be feeling raw with 2mtr temps in low single figures.

Other than that the early part of the ECM looks rather unexciting although i notice in the later frames some tendency to ease the jet further south allowing that colder air to ease down a little more into Scotland.

[Geordiesnow]

The models are having an easy time as the zonal pattern is so easy for them to predict and they are in perfect agreement which is bad news for us!

At 192 hours the ECM is giving us a small window of opportunity for a northerly toppler as the low in the east coast of North America is deepens and slows down.

Pity there is no high pressure further north to give us something more substantial.

Karyo

Why does everyone think zonal patterns are easy to predict? Although the main pattern trend looks stright forward, the detail is far from clear cut and it never is so changes in the detail will of course mean changes in the long term etc. Whether they are changes for the better for cold lovers remains to be seen.

[OldMetMan]

I've been sitting back for a few days wondering if the models would do anything with the developing massive northerly blast developing E of Greenland but alas no.

Although the overall 500mb has some noticeable troughing and significant vortices here and upstream, they are all too mobile at the moment, and with no mid-Atlantic ridge and associated HP there is nowhere for that Arctic blast to go but SW and feed yet more LPs.

However, a couple of glimmers of hope as I see it now, there are minor upper highs forming just north of Scandinavia as well as off the Pacific NW which to my mind may indicate the mobility of the 500mb flow is slowing down a bit, to hopefully begin the process of forming a more static wave train.

The models still are changing quite markedly even in the reliable time frame, well at least in terms of detail of LPs and where/when they will develop, so short cold blasts are entirely possible over the coming days. In fact, the GEM is slowing things right down in the long term with some pretty cold air being brought to us in association with the major and complex LP it is predicting by then.

It is worth remembering that occasionally when cold air is being persistently held back from our shores by LP after LP running in from south of Greenland, a slow-down can occur over the US E coast with a more deeper LP forming, allowing the last in the LP train running across us to let,the cold air suddenly plunge S. I have seen this happen a few times.

Meanwhile, remarkable mildness is with us for now. I don't buy the usual GFS stuff with endless LPs in the longer term because that is what it always seems to do, but keep an eye on that incredibly cold stream E of Greenland - it may yet turn out to not have been in vain from our point of view!

Merry Christmas folks if I don't get a chance to say before then and many thanks to all of you for adding so many "likes" to my posts, that means a lot to me.

OMM

[snow1975]

What a great chart this is, a bit like the GFS 6z in FI. Great for the flooded areas. When was the last time we saw low pressure over Iberia? The high looks like it wants to risge north to Iceland/Greenland. Some pretty cold air to the east and north of the UK.

[I remember Atlantic 252]

The models are having an easy time as the zonal pattern is so easy for them to predict and they are in perfect agreement which is bad news for us!

At 192 hours the ECM is giving us a small window of opportunity for a northerly toppler as the low in the east coast of North America is deepens and slows down.

Pity there is no high pressure further north to give us something more substantial.

Karyo

Yeah, last 2 ECMWF charts decent, coldish, 240 chart looks okay, was on last nights 12Z as well, maybe a developing trend for a high pressure start to Jan

[nick sussex]

In a desperate attempt to find something remotely interesting about the output the smallest of chances to develop something a little colder.

What may look like a deep mean low in the ne USA is actually a chance to develop a ridge ahead of it, however its complicated by the low ahead of it which stops a stronger ridge forming earlier.

If the deep low and that weaker feature phase its game over as was the case this morning.

Given the last few weeks they'll probably phase! if our luck has finally changed they won't!

The JMA isn't too shabby at 192hrs, has a similar pattern.

Edited December 23, 2012 by nick sussex

[cooling climate]

Very interesting 12z ECM run this evening loaded with potential(yes that word again).

It also is more in line with what American meteorologist Larry Cosgrave was talking

about in his weather America newsletter with a +PNA and 500mb cut of low over Baja

California.

Will these promising signs still be there in the morning.

[LomondSnowstorm]

What a great chart this is, a bit like the GFS 6z in FI. Great for the flooded areas. When was the last time we saw low pressure over Iberia? The high looks like it wants to risge north to Iceland/Greenland. Some pretty cold air to the east and north of the UK.

Yes, I was just about to post this, shame about the NH pattern being relatively poor at that point but at least the endless train of lows is retreating by this point and there may be a point down the line from this where we might have a shot at retrogression. Certainly beats the current setup at least.

[snow1975]

Yes, I was just about to post this, shame about the NH pattern being relatively poor at that point but at least the endless train of lows is retreating by this point and there may be a point down the line from this where we might have a shot at retrogression. Certainly beats the current setup at least.

The Hemispheric view isn't great. Could do with an Arctic high nosing SSW towards Svalbard. However, I'm sure there was such a high on the output a day or two ago.

[nick sussex]

A little bit of good news from the expected pattern in the USA from the NOAA discussions:

MEDIUM RANGE GUIDANCE IS INDICATING A GRADUAL TRANSITION FROM A

PATTERN CONSISTING OF PROGRESSIVE AND SHORT-MEDIUM WAVELENGTH

SYSTEMS CROSSING THE ERN PACIFIC AND CONUS TOWARD SLOWER MOVING

MEAN FEATURES WITH GREATER WAVELENGTH.

Which turns into a bit of a head scratcher because that goes against a flat upstream pattern which the models have subjected us to over the last few days.

You would expect to see a slower progression of systems with more amplitude.

The ne USA troughing shown by the models is generally agreed on but its how amplified that makes a difference.

Edited December 23, 2012 by nick sussex

[Grimsby Snow Lover]

A little bit of good news from the expected pattern in the USA from the NOAA discussions:

MEDIUM RANGE GUIDANCE IS INDICATING A GRADUAL TRANSITION FROM A

PATTERN CONSISTING OF PROGRESSIVE AND SHORT-MEDIUM WAVELENGTH

SYSTEMS CROSSING THE ERN PACIFIC AND CONUS TOWARD SLOWER MOVING

MEAN FEATURES WITH GREATER WAVELENGTH.

Which turns into a bit of a head scratcher because that goes against a flat upstream pattern which the models have subjected us to over the last few days.

You would expect to see a slower progression of systems with more amplitude.

The ne USA troughing shown by the models is generally agreed on but its how amplified that makes a difference.

Hi Nick, I find reading your posts very interesting and informative, many thanks. However I struggle to understand the NOAA discussions you share on here. In simply English what does this one actually mean for us? Many thanks GSL

[nick sussex]

Hi Nick, I find reading your posts very interesting and informative, many thanks. However I struggle to understand the NOAA discussions you share on here. In simply English what does this one actually mean for us? Many thanks GSL

Lol! thanks.

Well they expect the speed of low pressure crossing the USA to slow down and at the same time a more amplified flow to develop, in this situation this results in a better chance for the UK to get some colder conditions.

[Grimsby Snow Lover]

Lol! thanks.

Well they expect the speed of low pressure crossing the USA to slow down and at the same time a more amplified flow to develop, in this situation this results in a better chance for the UK to get some colder conditions.

Thanks Nick!

Why can't they just say that then lol? Merry Christmas

[Summer Sun]

ECM is following GFS for early January by rising pressure giving the flood hit areas a welcome respite

Not bad agreement even at this stage

Edited December 23, 2012 by Gavin.

[A Winter's Tale]

Good evening. Tonight, it's a much drier picture for Scotland and Northern England with some clear spells, especially in eastern areas. However, to the south a band of rain is moving northwards so in England and Wales that are south of Manchester and certainly south of Cardiff-London are likely to experience some rain from this feature overnight. There may also be some heavy rain showers around the west coast of Ireland. Overall a mild night with lows of 5 to 9C.

Christmas Eve should start off on a wet note in Wales, southern and central parts of England and even western parts of Scotland and eastern parts of Ireland aren't immune from seeing some precipitation. Northern and eastern areas are likely to stay dry with some clear skies in north eastern Scotland.

Into the afternoon, many parts of England, Wales and Scotland should be affected by the rainfall. The south of England and the north of Scotland could end up drier and certainly Ireland looks like staying somewhat drier. Maximum temperatures ranging between 4 and 10C.

For Christmas night, it seem that this area of rain should continue to track north eastwards so rain could continue to fall in north eastern parts through the night. Some drier weather following behind but also some showers in western and southern areas. Overnight lows of 2 to 8C.

And for Christmas Day, it's looking like a cooler day but unfortuantly not a white one. Maximum temperatures typically 5 to 7C in northern areas and more like 8 to 10C in the south of England and Wales. Also it should be a 'drier' day with some showers - especially in southern England, Wales and western parts of Scotland and some areas may see some sunshine, just in time for the Christmas lunch.

Overnight into the early hours of Boxing Day, it looks like turning colder in Scotland with temperatures possible close to freezing in some areas and maybe even some snow for the Shetland Isles. There should be less showers aswell with some clear night skies in places. Minimum temperatures of 0 to 5C.

For Boxing Day, it should be quite cold in Scotland to start off with. However cloud cover should increase from the west as a band of rain arrives in western Ireland. However for eastern parts of England there may be some sunshine. Maximum temperatures ranging between 3 and 10C.

Into the night and the band of rain pushes eastwards bringing rain to many areas but it may hang on in Scotland and there could also be some snow on the mountains. Some showers could follow the band of the rain in western areas. Overnight lows of 2 to 7C.

There may still be some rain hanging onto northeastern Scotland on Thursday whilst the theme is for sunshine and showers elsewhere with a fresh north westerly wind. Maximum temperatures 4 to 9C.

For Thursday night, in Scotland there could be a cold northwesterly flow the potential for snow showers whilst southwesterly wind bring milder temperatures to southern England and Wales. A dry night for most, perhaps not a particulary clear night and there could be some rain in some south western areas.

With high pressure to the south of the British Isles, on Friday we could see southwesterly winds sweep over the British Isles bringing milder temperatures and possibly further persistent and heavy rainfall.

And possibly the mild and wet weather could continue into Saturday.

A colder and showery theme for Sunday, possibly a northerly toppler or a fresh northwesterly. Details will become clearer closer to the time but it'll be interesting to see how things develop regarding this date.

A bried period of cold temperatures on Sunday night.

Certainly the changeable theme looks like continuing for the forseeable and this would mean that details will vary beyond 4 days. But I wouldn't rule out some further rainfall for large parts of the British Isles following Christmas and the door is open to a wide-array of outcomes. It seems like high pressure will be situated for a while to south of the British Isles so this does leave the British Isles somewhat vulnerable to low pressure systems but it's almost impossible to pin-down specific details in the weather. I suppose anything could appear in the outlook beyond Christmas. One thing to look out for is the nature of Azores/Iberian High as time goes by.

For example, look at the positioning of the high at 96hrs ECM 12z

And compare that to 240hrs

Certainly as time goes by, there's a trend for the high to move to the middle-latitudes. If you read LomondSnowstorm's post last night on the Scotland thread and you can see how this northward movement of the high can be precusor to synoptics that favour colder weather for the British Isles and you could say that developments regarding Stratosphere can support this change in synoptics.

[Gibby]

Good evening and welcome to the evening look at the 12z output from GFS, UKMO and ECM for today Sunday December 23rd 2012.

All models show a continuation of the unsettled spell of weather in the reliable time frame tonight. Another wave depression looks like moving NE overnight amalgamating with an occlusion drifting in from the West tomorrow with further rain and showers for all in the next 24 hours following the brief drier spell today. Late in the day clearer air will move in from the West with some heavy showers at times near Western coasts. Christmas Day will see a sunshine and shower weather type in many places with lower temperatures and lighter winds on the big day itself. Some of the showers will be heavy and slow moving giving some large rainfall totals again locally. Boxing Day sees fewer showers as something of a ridge is shown to move across from the West. It will be rather chillier with temperatures near to normal. On Thursday an active front moves East with heavy rain moving West to East over the UK with a short showery spell following before winds back SW and milder air floods back NE over the UK behind a warm frontal band of rain on Friday, preceded by some snow again on the Scottish mountains.

GFS then shows next weekend as being very unsettled with Low pressure crossing East over the UK with rain and showers, heavy in places over all areas in temperatures close to normal. The unsettled theme continues into the New Year with a very zonal flow developing with a sequence of Low pressure moving into the UK delivering rain and wind, followed by spells of rather colder weather with showers falling as snow on Northern hills. It will remain very windy for much of the time.

The GFS Ensembles show a continuing unsettled Atlantic based theme with rain at times throughout as depression after depression approaches, centres over then exits to the East of the UK with undulating temperatures between very mild days and rather chilly days in always rather windy conditions. No real wintry weather is hinted at in any trend tonight.

The Jet Stream shows a continuation of the undulating pattern across the Atlantic towards the British Isles for the foreseeable future.

UKMO for midday on Saturday shows a deep depression to the NW of Britain with a strong to gale SW flow over the UK. Fronts would carry rain NE over Britain to be followed in turn by sunshine and heavy showers, especially near Southern and Western coasts. Temperatures would remain close to the seasonal average for most.

ECM shows an equally unsettled spell next weekend with strong West or SW winds bringing rain at times for most. Towards the end of it's run a brief pattern change is shown again tonight as a cut off Low down to the SW allows a High pressure cell close to the UK to bring a drier and more settled phase in 8-9 days time, though it doesn't look like lasting long beyond day 10 as pressure from the NW causes it to sink away SE into Europe over the days that follow the end of the run.

In Summary it's more of the same in the reliable time frame with rain at times with only brief drier intervals. The rain distribution may shift towards greater quantities falling in North-Western areas later. Temperatures will never be far from normal with some milder than average days in the South at times. The incidence of frost, ice, fog and snow all remain on hold tonight as this zonal train continues. ECM does offer some crumbs of comfort for a drier spell but other than allow for a few transient frosty and misty nights it doesn't look like hanging around long or setting up in any position where a more sustained cold spell could setup or evolve.

[Zenarcher]

Model summary using the GFS, ECM, UKMO, NOGAPS, GEM, JMA.

Christmas Eve - Will be mainly cloudy and wet with mist or fog being wide spread as well. The wind will be mainly calm all day but a strong breeze will be over Southern England so Santa may have trouble landing at night where gusts around 40mph might catch him out. Temperatures will be cold although may reach double figures in the far South of England.

Christmas Day - Temps are expected to be below 7c for most of the UK but the SE of England may see double figure temps again. A white Christmas is looking unlikely now it will be a cloudy start with showers around and later on becoming more sunny in Western and Southern parts. Highlands may see some snow during the evening though. Wind will be mainly calm but in the evening and night gales moving in over Ireland and the Irish sea.

Boxing Day - All models show a low around 985mb just to the West of the UK, the low is expected to move in later, it will bring a heavy band of rain across the UK with heavy snow across the Scottish Highlands. It will bring gale force winds across much of the UK and severe gales over Ireland.

96 hours Thursday - The models show a low pressure sitting over the North of the UK but they all show it differently but agree on more unsettled weather. Out in the Atlantic we have 2 other lows every model has it's own idea but the ECM and UKMO show something very similar here where two lows are expected to meet like shown in the image,

Are the models finding the zonal weather easy to model? I don't think so still big differences seen at 96 hours.

120 hours Friday - ECM, UKMO and JMA show a strong low in the Atlantic around 970mb moving NE like this,

This would bring more unsettled weather to the UK.

However the GFS, GEM and NOGAPS place this low a lot further West in the Atlantic,

144 hours Saturday - GEM and GFS make things a bit messy lows and shortwaves,

The rest of the models disagree and go for something more simple and place one large low near or over Iceland,

All in all they still agree on a unsettled set up.

168 hours and beyond the changeable outlook - GFS keeps the Atlantic weather rolling in all the time. JMA brings some stormy weather over the far North of Scotland then builds up pressure in the Northern Atlantic and sends the Atlantic lows more South, NOGAPS similar to the GFS keeps Atlantic in charge and the ECM at first unsettled in the North but calms the Atlantic down then builds pressure up from the South into the new year.

Overall - Christmas should be calm although for some it will be wet at times. After Christmas the models show a unsettled period of weather to finish off the month and year. Into early January the models show either a unsettled theme continue or high pressure building in.