Model Output Discussion: 12Z (22/11/12) And On...

[Methuselah]

A nice new thread, in anticipation of a 12Z Snowmageddon!

[crimsonp]

ooooo snowmageddon!!!

got to be honest but this mornings 06Z wasn't as good as last nights pub run but it was still not to shabby in respects of the "cold snap"! although that greenlandish high was not as long as we all hoped for........ gonna be a busy day/weekend on here R.P.

[Frosty.]

The most worrying aspect of the Gfs 06z op run, and no doubt other runs, is how much southern britain gets battered by low pressure with strong winds and heavy rain, we already have lots of flooding and warnings and the 6z shows another battering for the south on saturday, monday and tuesday with spells of persistent and heavy rain, slow moving fronts and squally winds, also, into next week the temps start to drop considerably from current values. On the 6z, the north is worst affected by the cold, which intensifies from the northeast from around the middle of next week onwards so that's only 6 days away, the synoptics are quite stunning for late november, really special, especially for northern britain but it eventually turns much colder everywhere with a wintry spell setting in, also some sharp frosts and high windchill. The Ecm 12z op run last night was truly epic but even the 6z is far better than anyone could hope for on the cusp of winter.

[Methuselah]

ooooo snowmageddon!!!

got to be honest but this mornings 06Z wasn't as good as last nights pub run but it was still not to shabby in respects of the "cold snap"! although that greenlandish high was not as long as we all hoped for........ gonna be a busy day/weekend on here R.P.

lol 'Sleetmageddon' doesn't have the same ring to it...

[phil nw.]

As the influences on the vortex ebb and flow through expected wave breaking so will the orientation of any blocking.

Have to say the forthcoming pattern smacks of reloads -it may not be perfect to start with-if you are a cold lover-but there looks like further trough disruption from the north or north east which gives chances of colder air coming this way perhaps into week 2.

Edited November 22, 2012 by phil n.warks.

[Nick F]

Looks like a win, win situation ahead to me looking at the 06z GFS ensemble mean - which keeps troughing locked over Europe and a ridge over Iceland/S Greenland. It doesn't look like the block to the N and NW will be broken down in too much of a hurry.

Now it's a question of how cold will it get and how much snow will there be! It's all down to the shape of the parent low pressure system over Europe, modelling shortwaves around it and whether we can get a direct feed from the NE to tap into the deep cold air. This will, unfortunately, chop and change with every run this far off.

Edited November 22, 2012 by Nick F

[Weathizard]

The most worrying aspect of the Gfs 06z op run, and no doubt other runs, is how much southern britain gets battered by low pressure with strong winds and heavy rain, we already have lots of flooding and warnings and the 6z shows another battering for the south on saturday, monday and tuesday with spells of persistent and heavy rain, slow moving fronts and squally winds, also, into next week the temps start to drop considerably from current values. On the 6z, the north is worst affected by the cold, which intensifies from the northeast from around the middle of next week onwards so that's only 6 days away, the synoptics are quite stunning for late november, really special, especially for northern britain but it eventually turns much colder everywhere with a wintry spell setting in, also some sharp frosts and high windchill. The Ecm 12z op run last night was truly epic but even the 6z is far better than anyone could hope for on the cusp of winter.

Indeed and if all this happens and then it turns cold, the ice will be unbearable, being on the eastern side of south coast its a lovely day here today but with all the rain being projected I can see seriously flooding problems inland.

Think we are seeing at the moment what always happens in the build up to cold spells here, we NORMALLY have a fantastic evening of tantalising runs and then wake up and its all doom and gloom!(In respect to the evening before) I'm sure the happiness will return tonight, well I hope so anyway. With the sypnotics we have as has already been said, if next week is a let down(which it may well be) we'll probably get a second bite of the cherry.

Edited November 22, 2012 by Weathizard

[Frosty.]

Indeed and if all this happens and then it turns cold, the ice will be unbearable, being on the eastern side of south coast its a lovely day here today but with all the rain being projected I can see seriously flooding problems inland.

Think we are seeing at the moment what always happens in the build up to cold spells here, we NORMALLY have a fantastic evening of tantalising runs and then wake up and its all doom and gloom!(In respect to the evening before) I'm sure the happiness will return tonight, well I hope so anyway. With the sypnotics we have as has already been said, if next week is a let down(which it may well be) we'll probably get a second bite of the cherry.

I think at the very least, next week will turn much colder relative to the mildish weather we have this week, the hills and mountains of the north can reasonably expect the rain to turn to snow and then for even colder air to rush southwest from norway towards the end of next week, I think the 6z is synoptically very special but it just takes a bit longer for the cold air to penetrate the south but I think it's coming, I am much more concerned about the heavy rain and gales that look like continuing on and off until the middle of next week in the southern half of the uk.

[Jason T]

Indeed and if all this happens and then it turns cold, the ice will be unbearable, being on the eastern side of south coast its a lovely day here today but with all the rain being projected I can see seriously flooding problems inland.

Think we are seeing at the moment what always happens in the build up to cold spells here, we NORMALLY have a fantastic evening of tantalising runs and then wake up and its all doom and gloom!(In respect to the evening before) I'm sure the happiness will return tonight, well I hope so anyway. With the sypnotics we have as has already been said, if next week is a let down(which it may well be) we'll probably get a second bite of the cherry.

I don't think we will have to wait or worry about a second bite of the cherry. What ever happens in the output i can only see, Carry on where we left off. I don't believe any run is a big down grade now, Just fine tuning needed to soop up the PV 5000HP Cold train through Europe. Have a feeling this evening there will be server error message (BUSY) please try again later. Enjoy.

[Shunter]

Not the right thread but appropriate given the lowering of wintry expectations by some members on this mornings 06z output ...........

The latest Met Office extended forecast endorses GP & others thoughts of an extended Cold spell for the UK well into December ( they even mention the S word ! ). They must be confident of the forthcoming pattern change to publish this.

"As is usual, there are uncertainties in the forecast for this period. However, there are signs that northerly winds may be quite frequent across the UK. So, on balance, colder than average conditions are favoured, with a risk of frost and fog, and an increased risk of some snow"

[Duane S.]

With all the rain around lately you can guarentee the moment the cold air arrives precipitation will be no where in sight.

It's not looking like a 'dry high' scenario, I think there would be plenty of PPN around. Initially though southern folk, away from hilly areas, may have to endure sleet / rain. But that's neither here nor there, the main thing is that in terms of driving cold to our shores the atmosphere profile is right up with 2010, once set up the cold is going nowhere fast. There will be plenty of white stuff on offer as we head towards the end of the first week of Decemeber I'm sure. As always some areas will do better than others, this far out I wouldn't even attempt to say where they will be!

[LomondSnowstorm]

It's not looking like a 'dry high' scenario, I think there would be plenty of PPN around. Initially though southern folk, away from hilly areas, may have to endure sleet / rain. But that's neither here nor there, the main thing is that in terms of driving cold to our shores the atmosphere profile is right up with 2010, once set up the cold is going nowhere fast. There will be plenty of white stuff on offer as we head towards the end of the first week of Decemeber I'm sure. As always some areas will do better than others, this far out I wouldn't even attempt to say where they will be!

Yes, we have moved quite far from the mid latitude blocking scenario that we could have had and are now looking at blocking in a very favourable area i.e. Greenland-Iceland-Svalbard. Given the source of the cold is likely to be Polar or Arctic rather than continental I'd think that north and east is probably better than south and west in this instance for cold at least, but as you say beyond that is anyone's guess. Even at relatively short range it's hard to pin point the details in these setups where there's a mix of convective showers, more organised troughs and fronts and the odd shortwave feature.

[Duane S.]

AO tanking, no surprise looking at recent outputs

It wouldn't be too far fetched to wonder if -6 will be breached, such could be the pressure anomaly over the Arctic in the coming weeks! And don't forget, that's after a series of strongly neg -AO episdoes in 2009 which resulted in them changing the lower amount from -4 to -6!

[Frosty.]

Gfs 06z and Ecm 12z last night were awesome for wintry FI potential but probably next week will just be turning cooler and remaining very unsettled, probably the 6z op run was too eager to drag colder T850's into the far northeast of the BI later next week, it may take longer than that but latest meto 16-30 dayer is a stonking update with frequent Northerly winds and increased chance of snow, so longer term prospects sound a lot more wintry than anything we will get in the next 10 days or so, but on the other hand, we could still accelarate into a more wintry spell but next week will probably be cooler and wet with more showery conditions further north and NE'ly winds across the far north of the uk which could eventually strengthen because early next week, low pressure looks like being complex and slow moving across southern england, and the eastern north sea and southern scandinavia but it looks like an Atlantic anticyclone will extend a ridge northeast over Faeroe into the Norwegian Sea, as a result, a cool NEly airflow may increase fresh to strong at times later.

Edited November 22, 2012 by Frosty039

[nick sussex]

Looking upstream to see how events there could effect the pattern in Europe.

There is still some uncertainty in terms of amplification off the eastern USA discussed by NOAA:

EASTERN US...

THE DISPARITY AMONG THE GUIDANCE CONTINUES MON-TUE/D4-5 WITH LOW

PRESSURE EXITING THE SOUTHERN PLAINS. FROM THERE THE MODELS SPREAD

OUT TO THE NORTHWEST /UKMET AND CANADIAN/ TOWARD MICHIGAN...

THROUGH THE SOUTHEAST THEN OUT TO SEA /ECMWF/... OR UP THE

APPALACHIANS AND NORTHEAST COAST /00-06Z GFS/. THE TRACK IS

DEPENDENT UPON HOW MUCH NORTHERN STREAM ENERGY CAN INTERACT WITH

THE SOUTHERN PORTION OF MID-LEVEL ENERGY...

As this developing low exits this area it will have a knock on effect on troughing to the west of the UK, you can see the impact of this here:

The GFS 06hrs at 168hrs:

The ECM 00hrs at 168hrs:

The ECM is flatter upstream as compared to the GFS which is much more amplified, the effect here is likely to impact ridging to the north and into Greenland and also effect where any shortwave forms to the west and its track in towards the UK.

The ECM ensemble mean is more amplified upstream so we'll have to see whether the ECM operational output edges back to this tonight.

If the operational is wrong re this low then the rest of the ECM output in terms of that crucial local detail on this side of the pond for the UK can be discounted.

Edited November 22, 2012 by nick sussex

[johnholmes]

Regarding the 850mb temperatures, one of the important must haves for any precipitation to fall as snow.

If someone can find what the average late November values are for the UK then looking at the NAEFS 850mb temperature anomaly will give the first quick idea on how low the models are suggesting the values may get. From about T+144 way out to the realms of fantasy at T+384 on NAEFS it shows values over the UK and areas upwind of the UK to be between zero and -4C below the long term average.

[Tim Bland]

Regarding the 850mb temperatures, one of the important must haves for any precipitation to fall as snow.

If someone can find what the average late November values are for the UK then looking at the NAEFS 850mb temperature anomaly will give the first quick idea on how low the models are suggesting the values may get. From about T+144 way out to the realms of fantasy at T+384 on NAEFS it shows values over the UK and areas upwind of the UK to be between zero and -4C below the long term average.

According to ensembles the 30yr average is around 0c In the south and -2c in the north

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

Edited November 22, 2012 by Tim Bland

[Paul]

Latest look at the upcoming weather with Michael Fish - staying very unsettled to start with more wet and windy weather to come, but turning cooler/colder next week..

[summer blizzard]

Latest look at the upcoming weather with Michael Fish - staying very unsettled to start with more wet and windy weather to come, but turning cooler/colder next week..

Excellent forecast, really illustrating the high rainfall and win potential which has been overlooked.

[Timmytour]

Before Snowdon gets buried in Snow, looks like parts of North Wales will get buried in rain!

[chiffer]

As far as models go it look like were in a very interesting month at least. Glad most weather enthusiasts see this is great potential!

[Matty M]

GFS still not really having that low Sunday.

NAE shows possibly dangerous low approaching from south at 48hrs while GME has a strong depression moving northeastwards through UK.

I wonder is GFS missing this or what are peoples thoughts?

Reasonable run to run consistency from GFS to 120hrs.

Small differences in trough over UK and extent of Arctic High.

[johnholmes]

GFS still not really having that low Sunday.

I wonder is GFS missing this or what are peoples thoughts?

.

I thought I had bad eyesight mate, it is there just 5mb or so les deep than NAE shows it but it is certainly there and about the same place as NAE shows it?

[Matty M]

I thought I had bad eyesight mate, it is there just 5mb or so les deep than NAE shows it but it is certainly there and about the same place as NAE shows it?

Ye it's there but alot more than 5mb in the difference, more like almost 15mb.

So i was just pondering whether the resolution of the NAE was picking up developments the GFS was not.

If you look at 6z GFS Ensembles you will see some runs show a very severe wind event for parts while the majority of GFS Ops have not, so just highlighting this incase people think the risk for Sunday is off.

Edited November 22, 2012 by Matty M

[Timmytour]

I'm running the GFS 12z precipitation chart backwards from +105 imagining it to be the way things are in a couple of weekes with all that blue and green stuff hitting us from an Easterly direction :-)

what's happened to T126? T123 and T129 are there!

Edited November 22, 2012 by Timmytour