Model Output Discussion - 28th November

[bluearmy]

Been said a few times over the last few days but still a big difference between the GFS and higher resolution NAM at +84 regarding the low south of Greenland. http://www.weatheron...S=0&WMO== NAM http://www.weatheron...0&ZOOM=1= GFS

http://www.knmi.nl/e...agse/index.html ECM Ensembles, not bad, look at the control run!

we're past the point where events at T84 will make a difference. the energy distrubution is changed by then.

martin's summary is good - the diving energy within cold zonal mean flow and a euro trough means we should be looking to find a mean point for the 'snow line' and then adjust north or south as each day passes. the ex tropical shorteave could still make a much bigger difference for a few days in either direction.

[xioni]

Many keep saying that there is still time for changes and it's true, but most of the model changes so far this week are poor for cold weather.

We seem to have confirmation of a cold variable pattern, a fair amount of high latitude blocking but not of the right intensity and location, which leaves us with plenty of potential.

Could most of Dec go on like this with some great FI setups which never materialise?

[Weathizard]

At 162 the aleutian ridge looks like its sticking its finger up at the polar vortex(that is no more)

Edit: The atlantic looks very flat, and G lots of lows everywhere, worrying + Greenie pressure a lot lower, we still have the arctic high though

Edited November 28, 2012 by Weathizard

[weather eater]

Big change coming up between the 06z and the 00z the Azores high fails to ridge and another LPs at the tip of Greenland; this is going too slid down in a similar manner to the earlier system. Fortunately there is plenty of time for this to switch back.

[bradymk]

we're past the point where events at T84 will make a difference. the energy distrubution is changed by then.

martin's summary is good - the diving energy within cold zonal mean flow and a euro trough means we should be looking to find a mean point for the 'snow line' and then adjust north or south as each day passes. the ex tropical shorteave could still make a much bigger difference for a few days in either direction.

Thanks for the explaining that Ok will keep an eye on that.

Matthew

[bluearmy]

for the first time i see a spread of colder uppers heading west into eastern europe re any developing scandi block at day 10. the extended ecm ens reflect that with the control but only a handful of members bring the cold as far west as holland. it looks feasible on the op but the ens members are clearly not keen. there is something similar of naefs. 'from little acorns' as they say although it looks like we may have quite a few different variables over the next couple weeks trying to be the main influence on the east atlantic. lets hope this is the last time the redidual vortex energy will be the winner ( though i fear it wont be)

[phil nw.]

The cold Arctic air has now dug in over the UK and this will be around until the weekend.

Here`s a snapshot of the pattern for Friday.

Night frosts and possibily a few fog patches around early mornings as well as a few wintry showers near the north and east coasts.Maximum temps likely to be in low single figures over the next few days.

Something of a change to more unsettled conditions look likely as we start next week,indeed we can see from the first image already fronts associated with Atlantic low pressure approaching off the Atlantic and by T120hrs we can see them crossing the country.

spreading in rain with snow over the high ground further north followed by a cold north westerly bringing in a polar maritime feed of showers -wintry again over hills in the north.

Looking out to day10-next weekend- still looks rather cold and cyclonic for the UK.

We can see the NAEF`s height anomalies and the ECM mean hts both suggesting this.

Euro/UK mean trough and heights to our north west.

Any height rises do look more likely out in the Atlantic where some ridging of the flow keeps us in this rather cold north westerly pattern but imo no sign of any deeper cold being available within this period.

Edited November 28, 2012 by phil n.warks.

[Weathizard]

Dreadful run here, powerful high sets up over us and polar vortex over canada fires up at 200hrs(FI I know but still looking for signals), still its the GFS and its been changing a lot so I'll take it with a pinch of salt.

Edit: in hindsight, its not dreadful but not great either, as has been said, lots of lows being spawned around Greenland which is of some concern

Edited November 28, 2012 by Weathizard

[weather eater]

for the first time i see a spread of colder uppers heading west into eastern europe re any developing scandi block at day 10. the extended ecm ens reflect that with the control but only a handful of members bring the cold as far west as holland. it looks feasible on the op but the ens members are clearly not keen. there is something similar of naefs. 'from little acorns' as they say although it looks like we may have quite a few different variables over the next couple weeks trying to be the main influence on the east atlantic. lets hope this is the last time the redidual vortex energy will be the winner ( though i fear it wont be)

Yep every time we get towards the Hi res part of the run that residual vortex sets up another LPs system off Newfoundland/the tip of Greenland and across the Atlantic towards us.

Edited November 28, 2012 by weather eater

[Frosty.]

Any height rises do look more likely out in the Atlantic where some ridging of the flow keeps us in this rather cold north westerly pattern but imo no sign of any deeper cold being available within this period.

Yes phil but the GEFS mean does suggest we could tap into even colder air at times with winds occasionally N'ly and NE'ly and not just polar maritime, at least there is no sign of proper mild weather, just a few less cold days.

[weather eater]

Yes phil but the GEFS mean does suggest we could tap into even colder air at times with winds occasionally N'ly and NE'ly and not just polar maritime, at least there is no sign of proper mild weather, just a few less cold days.

Certainly NWlys veering Northerly at times look likely and possible in that order, I have to say I’m starting to doubt that we will see anything significant in the way of nationwide cold and snow for the foreseeable future, at least that my gut feeling, I hope I’m wrong.

[Glacier Point]

Not sure any model has a grip on the situation past day 5 at the moment.

The commentary on the upper air modelling for the polar vortex from 06z GFS reads something like this...

pulled apart, squeezed, attempted to reform, split, split into three parts.

The broad gist from ensemble means holds sway though.. anomalous ridge in the North Atlantic, deep troughing over much of Europe, below average temperatures over a sustained period with the potential for attacks of more colder air coming from the north, north-east and east.

The upper air volatility is interesting to watch though - signal that the pv is coming under more pressure from below and registering all the way up to 30 hPa.

[phil nw.]

Yes phil but the GEFS mean does suggest we could tap into even colder air at times with winds occasionally N'ly and NE'ly and not just polar maritime, at least there is no sign of proper mild weather, just a few less cold days.

Next week to day 10 is the period i am looking Frosty and it looks pretty Atlantic driven to me.

I can see that as the trough disrupts further south a little later we could get a cyclonic type of north easterly-but further into week 2.

[Adam lufc]

I find it so frustrating that the models have taken us from massive potential to flat boring Synoptics again. With all our potential signals, it still fails us. I will never understand why it's so hard toga e anything half decent here but most others places in the northern hemisphere just gave to click there fingers for snow and cold. The Synoptics on offer this morning continue to produce common winter charts. All theses lows developing in Atlantic and the Azores H never too far away. Here's to hoping last nights ecm pulls the strings and comes true ...... Hmmm

[Buzz]

I find it so frustrating that the models have taken us from massive potential to flat boring Synoptics again. With all our potential signals, it still fails us. I will never understand why it's so hard toga e anything half decent here but most others places in the northern hemisphere just gave to click there fingers for snow and cold. The Synoptics on offer this morning continue to produce common winter charts. All theses lows developing in Atlantic and the Azores H never too far away. Here's to hoping last nights ecm pulls the strings and comes true ...... Hmmm

In short - the Gulf Stream.

Remember that we're a relatively small island surrounded by a mass of water.

[nick sussex]

I'm not sure if this has been posted in a previous thread but I wonder what impact this could have on the outputs, given the timing of the maintenance I would have thought this may be an issue for the 18hrs runs.

Of course we don't know how much data will be missing:

http://weather.noaa.gov/tgstatus/

[Gibby]

I think any lessons to be learnt for those disappointed is not to hang hopes on what the operationals show but to draw a much nearer reality outcome by looking at the ensembles and to date despite some mouthwatering operational charts at no point have the ensembles shown any deep shift downwards into serious cold territory in their mean for any run which I have regularly reported in my summaries and that to me is indication enough to suggest at no point soon would their be any significant cold

Edited November 28, 2012 by Gibby

[samadamsuk]

I find it so frustrating that the models have taken us from massive potential to flat boring Synoptics again. With all our potential signals, it still fails us. I will never understand why it's so hard toga e anything half decent here but most others places in the northern hemisphere just gave to click there fingers for snow and cold. The Synoptics on offer this morning continue to produce common winter charts. All theses lows developing in Atlantic and the Azores H never too far away. Here's to hoping last nights ecm pulls the strings and comes true ...... Hmmm

Hi Adam.

There are lessons we can take each time a modeled severe cold spell doesnt make it to reality - firstly the longer away the chart, the more we have to look at the broad synoptics, but need to factor in that short waves can apear down the line and cut off the delivery of any cold, and secondly - model watching mirrors life in my opinion! - it's the interesting discussions and delving into the technicalitys that I enjoy, as much as the output becoming reality - to enjoy the ride and not to be dissapointed if it doesnt go anywhere - if thats not an option for some people, then cut down your favorits to t96 or whereever you feel you want to jump on board, and only build up excitement at that point.

Looks to me like theres some good cross mopel agreement in 9-10 days time for the atlantic ridge/european LP to have another go once the heights have transferred across the atlantic to our SE - may be scuppered by shortwaves again, but my favourites go up to 10 days, and we all know GP's got 2 brains, so the stable atlantic ridge is something to expect -

Sam

[Frosty.]

Can't understand some posts in the older thread this morning? For me, another good run from the ECM, with a low diving SE through 216 and the cold pool still to our NE, just. But overall, not a bad run.

Agreed, we are now entering a colder and more settled phase, then a rather cold and unsettled spell next week which could easily turn into something even more wintry.

[nick sussex]

How low does the pressure need to go in the med, ECM at +240 seems to take the LP there or is the positioning wrong?

As long as you have low pressure around northern Italy its nigh on impossible to get mild conditions into the UK in winter, low pressure there supports higher pressure to the north or ne.

If you maintain those lower heights over the Med then thats generally a very good sign.

[legritter]

Perhaps if we finish up with a deep complex low to our south we will start to see higher pressure to our north .this is what possibly long range forecast was hinting at a couple of weeks ago . but lets all be patient and enjoy the modells, still 13 weeks of winter to go .if you like the weather interesting the modells are on our side .will the ECM bring it on tonight ,

[Shunter]

Perhaps if we finish up with a deep complex low to our south we will start to see higher pressure to our north .this is what possibly long range forecast was hinting at a couple of weeks ago . but lets all be patient and enjoy the modells, still 13 weeks of winter to go .if you like the weather interesting the modells are on our side .will the ECM bring it on tonight ,

Seems the Meto 15 dayer has now updated to a more unsettled but rather cold forecast reflecting the synoptical changes across all models in the past 24-35 hours.

Having laboured through the various model updates during the past 10 days though you have to ask the question whether meduim range forecasting has improved over the past 20-30 years. We have ENSO's ,Rossby Waves, Stratosphere observations, mountain torques and EL NINA & NINOS all consuming Technical and human resources round the clock which has seen gerat improvements in long range global weather patterns, but they still cannot forecast shortwave developments and their implications within 120 hours around the UK shores. You have to laugh dont you

[Severe Siberian icy blast]

Well said Shaun i am very impressed i have been model watching for many years indeed Shaun i use to give you good forcasts for snow when you were a pupil in St Stephens ( MR MORGAN ) :-] . But back on topic the potential showing up this year is quite exceptional, i have not seen such cold pooling!! it wont take much for the flood gates from the east to open and we will be in the deep freeze.!!

Trust me i am Mr Morgan

Hi sir !! I remember , how bizarre to hear from you on hear , but in hindsight to have been expected given the chats we use to have , good hearing from you. Hears to a very interesting year of weather watching. !!

[Man With Beard]

I think any lessons to be learnt for those disappointed is not to hang hopes on what the operationals show but to draw a much nearer reality outcome by looking at the ensembles and to date despite some mouthwatering operational charts at no point have the ensembles shown any deep shift downwards into serious cold territory in their mean for any run which I have regularly reported in my summaries and that to me is indication enough to suggest at no point soon would their be any significant cold

That is true, although sometimes the Op run can act as a 'leader' of the pack and a few cold/mild solutions end up being right with the rest being wrong. I think the lack of agreement in the ensembles merely indicates the volatility of the situation, as indeed it still does - a few 06Z ensembles still going for something colder late next week, a sign that the Atlantic isn't going to win this one without a fight.

[Gibby]

That is true, although sometimes the Op run can act as a 'leader' of the pack and a few cold/mild solutions end up being right with the rest being wrong. I think the lack of agreement in the ensembles merely indicates the volatility of the situation, as indeed it still does - a few 06Z ensembles still going for something colder late next week, a sign that the Atlantic isn't going to win this one without a fight.

That is true but it quite rarely that happens. In recent weeks the ensembles have often shown a couple of members st times going into the freezer in the same way as a couple have gone into milder territory but until more than a third or half follow a similar track then not much faith can be put in them either way with regards to trending which is what the FI data and Ensembles are useful for. I agree with the fact that a large spread does mean uncertainty which can fudge the mean. With regard to the here and now the trend is for rather cold conditions likely to stay with cool zonality likely. The 06z as an example shows a slow warming trend at the end rather than cooling.

Probably the most important portion of my summaries are the GFS Ensembles as they snapshot the likely course of events rather than what the operational outputs show.

Edited November 28, 2012 by Gibby