General Model Output Discussion

[bluearmy]

That's a good point, the gfs did something even more bizarre than usual! what do you think of those ECM ensembles, could the control run be doing what Dave mentioned regarding the PV dropping down to our east and much colder air being advected westwards, if the PV splits this must be a possibility.

NOAA cpc have very high confidence in this output - little sign of the higher heights sinking anywhere over the period. as yesterday, the jet getting ever closer in the second week. channel low must be a cert if that verified.

http://www.cpc.ncep.noaa.gov/products/predictions/610day/610day.03.gif

http://www.cpc.ncep.noaa.gov/products/predictions/814day/814day.03.gif

i see that GP has posted his thoughts in a similar fashion to these charts in the in depth thread.

next winter is going to be such an anti climax !!

Edited January 7, 2010 by bluearmy

[Tim Bland]

You can see from the GEFS ensembles that the 12z was an outlier in relation to the Low next week

http://www.netweather.tv/index.cgi?action=ensviewer;sess=

FWIW my opinion of the GFS at the moment is that it is good for short term precipitation (excluding convective) and the Ensembles give a fair indication of trends. The trend from the ensembles today is for a slight warming but still cold enough for snow for the forseable future with little in the way of thaw away from the south / south west.

[Altostratus]

The ECM ensembles are excellent. I’m a little surprised there hasn’t been more mention of them. Maybe it is because everyone is focusing their attention on tonight’s exceptionally low temperatures.

The operational run is clearly warmer than average towards the end of the run. Bearing in mind that the operational run was cold throughout, the ensembles are painting an even colder outlook. The ECM has been outperforming the other models consistently this winter and I have found the ECM ensembles to be a particularly useful guide as to the general temperature trend. I have been watching them closely and they haven’t yet got the trend wrong. If this is to be believed, it looks like remaining very cold throughout the period – definitely no mild weather on the horizon yet. If anything, the average looks to dip again at the end of the period. Some very cold runs are starting to show up as well. This is usually an indication that something is afoot.

[Cloud 10]

The extended ecm ensembles continue to show the average temp below freezing.

ecm ensembles

The control run is bitterly cold and probably shows what would happen if we tapped into a chunk of the polar vortex.

[BLAST FROM THE PAST]

This is a chart I used to pray for as a kid.

Now how I see the month panning out. Snow upgrades for this weekend with big event Sat night, Sun and Mon...the 7th-10th snow/blizzard warning i isssued in Dec [likely to extend to 12th] and is MAINLY a SE event. Next is that the Block remains similar to ECM and undercutting LPs 14-20 with big snow for SW and South UK and Southern Ireland [bitter E/ENE winds]. Cold to remain to at least 22nd poss 24th. Breakdown of sorts before its looking like reload from NE at end of month. Solar indicators are that the jet WILL REMAIN ON SOUTHERLY TRACK and even when it shifts north nowhere near the dreaded corridor.

Huge bonus on BBC SE News this eve...Michael Fish did the forecast...superb.

BFTP

Edited January 7, 2010 by BLAST FROM THE PAST

[Altostratus]

Manchester airport today is recording a max of -6c

It just goes to show how important it is to have a blanket of snow across the country. The cold uppers certainly help, but without the snow blanket, these temperatures would not be possible. Across a standard day, the snow cover makes it easier for a net removal of heat across the boundary layer. This makes it possible for successive days to become colder and colder. Dec 81 is a good example of this. The uppers were never exceptionally cold like in Jan 87, but the good snow cover allowed heat to be removed and for temperatures to fall from day to day. That is not to say the uppers aren’t important, as they are; they will limit the extent of heat removal from the system.

While we are discussing temperatures, tonight is a very good example of the GFS not predicting night time temperatures very well. Many people have commented on how the GFS has a tendency to calculate too high temperatures. Shown below is the forecast from the 18Z for first thing tomorrow morning:

http://www.wetterzentrale.de/pics/Rtavn1217.png

Certainly for southern areas, this looks to be very inaccurate. I guess the GFS isn't aware of the extensive snowcover.

[Nath]

Looking at the models for 144+ its a case of GFS warm up V rest cold or V cold. I would say 60/40 to the cold continuing with 10% severe continuation of the cold.

As to enjoyment of severe cold I love it and I do want to see a exceptional 2010 winter, but at the same time I hope people look out for the elderly or other vulnerable people who could be at risk.

At the end of the day the weather will do what it does and we can only react to it when it does it, if you know what I mean.

[Nick F]

PLEASE CAN WE STICK TO MODEL DISCUSSION! Not talk of preferences or how the UK is handling the cold spell!

(You may find your o/t post in cold spell discussion)

Rant over

18z GFS has backed off a mild breakdown in line with the Euros, with lows being forced under the block maintaining the cold over the UK.

[Luke Best]

Hi Luke Id say its not so much a dry line as an upper level warm front. meaning that the upper section of the warm front is well..warm but surface temps are unaffected to a greater

extent. So if the ground level is 0oC or better -1oC or lower snow or possible freezing rain will fall, if the surface levels are at 1oC or more then mixing of the air occurs and

temps rise a little through the heights to you would see rain or wet snow. You will only be able to tell on the day. If you are at -1oC ( quite possible considering current temps) you are like to see snow especially if the wind direction there is ENE, ESE would be off the solent, and that could spell disaster with the temps a degree up. An easterly would be..well nail biting. Good luck

Hi PubliusEnigma - thanks so much for your response.

Luke

[Mark Bayley]

18z brings the risk of snow showers spreading well inland across parts of the Midlands and reaching Wales! The further South you are the more frequent and heavy the showers will be. Scotland will remain mostly dry however the risk of precipitation increases as we head into the week. Overall just about everywhere at risk of seeing some snow over the coming days and into next week. The further South faring better. Medium term and the GFS is far better than the 12z keeping the 850hpas colder and the risk of snow just about anywhere.

With regards to Ians Comments. I agree that the cold spell is dangerous to the vulnerable, and is costing businesses a lot of money. Most of us on here enjoy snow and cold. This something we have not seen for years, and is unlikely to repeat its self soon! I think we should be able to enjoy this spell of weather. That's why were all on here! I shall be hoping for an average Feb. I still want some snow in it, but northerly topplers will do me fine with milder weather in between!

[Spurry]

While we are discussing temperatures, tonight is a very good example of the GFS not predicting night time temperatures very well. Many people have commented on how the GFS has a tendency to calculate too high temperatures. Shown below is the forecast from the 18Z for first thing tomorrow morning:

http://www.wetterzen...s/Rtavn1217.png

Certainly for southern areas, this looks to be very inaccurate. I guess the GFS isn't aware of the extensive snowcover.

Northern areas are being vastly underestimated as well , it is -9c here in wigan at the moment , and we are no means the coldest place in this area , far from it in fact :lol:

[Supercell]

Anyway, back to the GFS 18z output. Short term ppn distribution is looking promising (particularly considering when this model consistently has a poor grasp of the spread). The longer term is a more likely evolution, the low struggling to penetrate such established blocking.

Edited January 7, 2010 by Ross B
Removed Off-Topic Part of post.

[Jason M]

The 18Z looks interesting. I've been watching the models for years and cannot decide whether we will get a blizzard or rain fest next week with the undercutting low. Would be interested in Ian's views on this.

Experience tends to make me lean towards a classic North of M4 event (with Essex getting rain as usual )

Edited January 7, 2010 by Ross B
Removed Off-Topic Part of post.

[rich1]

looks as though GFS has gone off the idea of breaking the whole lot down on wednesday

good enough for me, wouldnt be worrying too much about marginality unless you live near the coast, sometimes I feel it can be a case of people feeling insecure about the prospects unless every single factor is in favour, as I see it many areas have existing deep snowcover and feel that the progged maxes may be a little colder in reality. is not a particularly 'wet' run but these things can be tricky to be definite in terms of precipitation

so in synoptic terms, better than the last run and maybe following [again] the euro models in the mid term. Looks as though I will keep my snow for some time yet

[andymusic]

18z brings the risk of snow showers spreading well inland across parts of the Midlands and reaching Wales! The further South you are the more frequent and heavy the showers will be. Scotland will remain mostly dry however the risk of precipitation increases as we head into the week. Overall just about everywhere at risk of seeing some snow over the coming days and into next week. The further South faring better. Medium term and the GFS is far better than the 12z keeping the 850hpas colder and the risk of snow just about anywhere.

With regards to Ians Comments. I agree that the cold spell is dangerous to the vulnerable, and is costing businesses a lot of money. Most of us on here enjoy snow and cold. This something we have not seen for years, and is unlikely to repeat its self soon! I think we should be able to enjoy this spell of weather. That's why were all on here! I shall be hoping for an average Feb. I still want some snow in it, but northerly topplers will do me fine with milder weather in between!

I wouldn't say "unlikely to repeat itself soon" get used to this Joe B thinks we are entering an extended cycle of winters for the next couple of decades which will be just like this one or worse due to solar minima!

[chionomaniac]

I am really liking the big difference in the GFS 18Z at T+168. We have another split vortex and Arctic High as a result. A good trend for continued long term cold.

Will a cold FI follow.

[igloo]

I wouldn't say "unlikely to repeat itself soon" get used to this Joe B thinks we are entering an extended cycle of winters for the next couple of decades which will be just like this one or worse due to solar minima!

more like the shifting of the jet stream further south dew to melting of fresh water in to the northern altantic i think anyway

[Downpour]

This is a chart I used to pray for as a kid.

Has the El Fish been brought of retirement?! I don't blame them, I'm sick of the likes of Dan Corbett and his mild loving mates. Rob McElwee was in danger of being the only decent forecaster on there!

[bluearmy]

I am really liking the big difference in the GFS 18Z at T+168. We have another split vortex and Arctic High as a result. A good trend for continued long term cold.

Will a cold FI follow.

until it hits low res !!

if the cold is to continue, GFS will at some point realise this and the signal will be strong enough for fi to be cold. until this point is reached, dont expect GFS to show cold fi's. of course the cold has to end at some point and around T240 looks to be favourite at the moment though this is purely a statistical stab. the nwp doesnt support any real breakdown with likely wind direction between s and e for most of next week and beyond.

[Downpour]

more like the shifting of the jet stream further south dew to melting of fresh water in to the northern altantic i think anyway

A much more likely reason although Joe B won't admit that as he doesn't seem to believe in AGW.

It just goes to show how important it is to have a blanket of snow across the country. The cold uppers certainly help, but without the snow blanket, these temperatures would not be possible. Across a standard day, the snow cover makes it easier for a net removal of heat across the boundary layer. This makes it possible for successive days to become colder and colder. Dec 81 is a good example of this. The uppers were never exceptionally cold like in Jan 87, but the good snow cover allowed heat to be removed and for temperatures to fall from day to day. That is not to say the uppers aren't important, as they are; they will limit the extent of heat removal from the system.

While we are discussing temperatures, tonight is a very good example of the GFS not predicting night time temperatures very well. Many people have commented on how the GFS has a tendency to calculate too high temperatures. Shown below is the forecast from the 18Z for first thing tomorrow morning:

http://www.wetterzen...s/Rtavn1217.png

Certainly for southern areas, this looks to be very inaccurate. I guess the GFS isn't aware of the extensive snowcover.

Oh dear, I can confirm that was way off as it was -5 when I left at 0900 this morning - in Ealing, west London.

[chionomaniac]

until it hits low res !!

if the cold is to continue, GFS will at some point realise this and the signal will be strong enough for fi to be cold. until this point is reached, dont expect GFS to show cold fi's. of course the cold has to end at some point and around T240 looks to be favourite at the moment though this is purely a statistical stab. the nwp doesnt support any real breakdown with likely wind direction between s and e for most of next week and beyond.

Yes, but another GFS demonstration of the results of a split vortex with shocking cold shifted south from the Siberian vortex segment. That could be very damaging to whatever country it hits!

[john w]

Who is this Joe B...Keep hearing about him.

Anyway and WRT Sunday...I do wonder how much the models are downplaying the precipitation considering the potential that came from the event this Tuesday and Wednesday. I really do think it will be all eyes to the NAE.

Our area never does too well out of Easterlys ironicaly (home counties)I do think the modification of the airmass over London does affect this though I have no doubt that we will see a shower or two.

Models not showing any sign of a breakdown until i go skiing now....imagine that off on the 16th and if BFTP is correct about lows from the 14th i may head to Gatwick early, in fact I might just get a placement at EGKK for a week

Edited January 7, 2010 by john w

[PubliusEnigma]

I am really liking the big difference in the GFS 18Z at T+168. We have another split vortex and Arctic High as a result. A good trend for continued long term cold.

Will a cold FI follow.

chuckle Wasn't a whole bunch of people slating the GFS only 6 hours ago ?? Now its backed down from the mild invasion next week, suddenly its a reliable model again..

Personally I think its staying cold, and I also think and its only a hunch that We could see a very extended cold spell with the whole of february and early march seeing

a snow fest, with only a brief respite at the end of January. This winter could exceed those of 62/63 76/77 ! We've had a trend in the last three summers especially in June and July

of a set up very similar to the one progged for next week, with LP to our SW and an Arctic HP or West Scandi HP, and if you recall that pattern lasted up to 8 weeks at times.

causing wash out summers and dull summers. the point here being, pattern matching alone, affiated to the output to 240+ and beyond, the longetivity of a set up like this seems

to be of a minimum 4 week duration, possibly as much as 8. That based on the last three instances of this pattern occuring in Summer 07/08 and 09.

[Jason M]

Hi All

Looking through the 18Z it wouln't take much change to leave us in an even colder spell than we currently have.

Be interesting to see the ensembles tonight.

Next week will be fun for the Met Office!!!!

Jason

Edited January 7, 2010 by Jason M

[stewfox]

While we are discussing temperatures, tonight is a very good example of the GFS not predicting night time temperatures very well. Many people have commented on how the GFS has a tendency to calculate too high temperatures. Shown below is the forecast from the 18Z for first thing tomorrow morning:

http://www.wetterzen...s/Rtavn1217.png

Certainly for southern areas, this looks to be very inaccurate. I guess the GFS isn't aware of the extensive snowcover.

The GFS will model in the wind as well.

The wind is picking up in the South (from NE), it wont be as cold as last night. I think the 18Z for min temps is fairly accurate (-3c here now) was -15 this morning