Model Output Discussion 13/11/13 >

[MR EXTREMES]

anyone seen the gem this morning might be worth having a look its what ive been harping on about for the last few days it starts amazing but ends where I expect the other models will.

 

high pressure slips over us then moves east but not only moves east it vanishes east and also notice low pressure slowly being replaced but higher pressure.

 

now this was the model lastnight that was a thing of beauty slowly but surely one by one there all slowly backing of from the ideas of adecent prolonged wintry spell.

 

but as frosty suggested its going to be cold next week and it will feel wintry but my concern is the longer term prospects and stubbon vortex and strong jet futher north not good.

 

nav gem is nice though and the ecm is ok but be heading the right way sorry but leaves us open to attack from lows from the northwest.

Edited November 17, 2013 by model rollercoaster

[nick sussex]

I think at this stage the best we can hope for is a continuing mid Atlantic block or the high pressureto sit over the Uk. The last thing we need is a scandi high that would keep that area above averageand pump mild air exactly where we don't want it this early in the season. Unfortunately I think aScandi high could be where we are heading. Shotski

IMO a Scandi high is always welcome and you can get an injection of cold uppers on its eastern flank, which can get advected back to the UK.

[johnholmes]

Ahead of the next 5-6 days the upper air is far from clear looking at the 500mb anomaly charts. Theh main 3 do not show an Atlantic dominated pattern but have differences so the weather looks to remain on the coldish side but as to the positions of the main upper trough and ridge then that is not clear.

I made these notes this morning based on the NOAA outputs last night and the ECMWF-GFS this morning.

 

Ec-gfs

Differences in how they treat around uk with ridge/trough, and both show changes from sat output

Ec=more meridional with gfs showing ridge/+ve as a rather flatter idea and over uk east/ene; neither is very much like the 8-14 noaa last evening with its 6-10 a sort of half way house between these two this morning?

So no sign of the atlantic returning but differences leaving doubts about just what the upper pattern may be around 10 days time

 

The detail of the depression (short wave if you like the mis used expression) on Wednesday will alter its detail over the next 24 hours so the forecast detail will also change. Fact of life folks forecasters often spend some of their time playing catch up as some of you call it. Its the weather and we are still kids in terms of understanding all its nuances. Very sadly what happened with the major storm in the Philipines a week ago bears testimony to that.

Edited November 17, 2013 by johnholmes

[nick sussex]

The ECM ensemble mean is solidly behind a below average spell of weather , it splits the PV and keeps low heights to the south.

The GFS ensemble mean is totally different to its operational output, this stretches the PV to the north and brings in a Scandi high before too much energy spills over the top towards day 10.

Overall its a very confused picture because of these differences, in terms of upstream NOAA didn't think much of this mornings GFS run and view it as an outlier solution but that update was done before they viewed the ECM. So we won't know what they think of that till this evening.

[Frosty.]

It's a very fluid situation in the week ahead, yes there will be some occasional mixing out of the cold uppers but soon followed by a deeper cold surge and the mixing out process ends later in the week with cold air digging in fully, according to the Ecm 00z op run. The Gfs 00z shows the midweek reload but then goes down the anticyclonic route for a time although the high eventually drifts away to the southwest which opens up a spell of cold zonality with a risk of rather colder intervals embedded in the flow with wintry showers at times.

[carinthian]

Who knows what will happen in 7 days. However, this week looks an interesting period of wintery weather in your part of the world. The UKMO will now be firming up on the developing low circulation to form between Iceland and Scotland. I am fairly sure it will sink across the heart of the country in the flow. Always difficult to predict the snow zone and warm air sector in this type of situation. The Exeter experts and will be analysing all the information made available to them now and will i am sure come up with a more exact prediction later this morning.

c

[SLEETY]

Whats up with the models at the moment,they are all over the place,even in the earlier time-frame their is hardly any consistency between them and the later output is just a complete mess no  consistency at all.

[West is Best]

West, he was referring to a warm sector in a shortwave. Nothing else.

 

And that's the language I'm inviting people to be careful about. People come on here for guidance and if they see terms like 'warm sector' they may get thoroughly confused. It's a very non-empirical term so if you want to be scientific post the actual T850 upper air temp variations. However, just so we're crystal clear: there is no warm sector. It is just less bitterly cold. Allied to this, as John Holmes points out, the track of that low is nowhere near nailed down. 72 hours ago it didn't even exist on the models. Even if it did track to the extent that precipitation fell as rain not snow for some on Wednesday, what is expected of mid November? The devil will be in the detail but in the meantime, we're in for a very cold spell for  the time of year, both qualitatively and empirically. The CET will certainly take a hammering.

 

Sleety: this often happens during a significant pattern change. I wouldn't be at all surprised to see us heading for major blocking from the north-east as the runs develop over the next week. Either way, we're coming out of zonality and the models are attempting to adjust.

Edited November 17, 2013 by West is Best

[cyclonic happiness]

this  should  make the snow lovers happy for  Tue/Wednesday

Oh look, all the arctic ice has shrunk and slipped down over the British Isles :-D I hope this is a joke, otherwise it's an omen! :-p

[Captain Shortwave]

Shame about the UKMO here, frankly if last nights run was correct then we would be a few runs away from being home and dry with a prolonged spell of cold. As of now we really don't have much of a clue to where things are going. But it does seem like the polar vortex seems to be doing just enough to prevent heights our side of the pole from building far enough north to really get us into a wintry seen besides one which is calm with frost and fog. GFS was pretty bad this morning but there is better output within the suite. I'd take the control run for example

Note the split flow in the Atlantic so there should be an undercut starting to develop, and the cold pool moving south west across the Baltic states. Good chart.

The cynic in me feels we might just end up with a UK high here but enough ridging to at least drag cold air down into Europe (aka ECM op). A set up like that would deliver ice days to more sheltered areas, though it might be more due to mist and freezing fog sticking around all day.

Edited November 17, 2013 by Captain shortwave

[bluearmy]

west, its the area between a warm front and a cold front - its a warm sector. if you want to know how warm, go look at the charts ! if we take all the technical terms out of here we may as well be on cbeebies.

 

and tim, the fax at day 4 last night WAS modified away from snowfall with the triple point moved east from the ukmo gm. whoever drew that seemed to have taken input from other data such that there was very little snow risk for the uk. that hasnt changed this morning - the triple point a further 100 miles east.

[cyclonic happiness]

Well, in regards to the warm sector, when was the lat time we had a 'safe' area of snow with no warm sector, I can't remember.

 

Even in 2010 the Midlands missed out on at least 4 snow events because of Warm sectors, it's always going to be a worry.

 

But in recent years we do see to be 'just' on the right side of cold to get snow even with the warm sectors, so all is not lost! ;-)

[shedhead]

And that's the language I'm inviting people to be careful about. People come on here for guidance and if they see terms like 'warm sector' they may get thoroughly confused. It's a very non-empirical term so if you want to be scientific post the actual T850 upper air temp variations. However, just so we're crystal clear: there is no warm sector. It is just less bitterly cold. Allied to this, as John Holmes points out, the track of that low is nowhere near nailed down. 72 hours ago it didn't even exist on the models. Even if it did track to the extent that precipitation fell as rain not snow for some on Wednesday, what is expected of mid November? The devil will be in the detail but in the meantime, we're in for a very cold spell for  the time of year, both qualitatively and empirically. The CET will certainly take a hammering.

 

Sleety: this often happens during a significant pattern change. I wouldn't be at all surprised to see us heading for major blocking from the north-east as the runs develop over the next week. Either way, we're coming out of zonality and the models are attempting to adjust.

Whilst you are of course correct that the exact track of the shortwave hasn't been nailed WiB, you are incorrect to suggest it is not a 'warm sector' moving south on Weds. The area between the warm and the cold fronts shown on this fax chart is called a warm sector....you can call it a teapot if you want to, but a warm sector is what it is.

 

[nick sussex]

And that's the language I'm inviting people to be careful about. People come on here for guidance and if they see terms like 'warm sector' they may get thoroughly confused. It's a very non-empirical term so if you want to be scientific post the actual T850 upper air temp variations. However, just so we're crystal clear: there is no warm sector. It is just less bitterly cold. Allied to this, as John Holmes points out, the track of that low is nowhere near nailed down. 72 hours ago it didn't even exist on the models. Even if it did track to the extent that precipitation fell as rain not snow for some on Wednesday, what is expected of mid November? The devil will be in the detail but in the meantime, we're in for a very cold spell for  the time of year, both qualitatively and empirically. The CET will certainly take a hammering. Sleety: this often happens during a significant pattern change. I wouldn't be at all surprised to see us heading for major blocking from the north-east as the runs develop over the next week. Either way, we're coming out of zonality and the models are attempting to adjust.

Bitterly cold! have you just come back from Dubai? I have to disagree re the term warm sector, this is widely used by meteorologists. In terms of this shortwave now that the models generally agree on the track it would need a huge correction westwards to give an all snow event and this would still be largely confined to higher ground anyway. Yes it will turn colder and maybe much colder if blocking takes hold further north or east but in terms of the next week I really don't think its anything that unusual for November.

[bluearmy]

that ecm op is the least surface cold run for the south of the uk for a long time. also, the 20th always looked to be the coldest day of the upcoming spell via the ens but the introduction of this little depression means it will likely be the least chilly. 

[IDO]

And that's the language I'm inviting people to be careful about. People come on here for guidance and if they see terms like 'warm sector' they may get thoroughly confused. It's a very non-empirical term so if you want to be scientific post the actual T850 upper air temp variations. However, just so we're crystal clear: there is no warm sector. It is just less bitterly cold. Allied to this, as John Holmes points out, the track of that low is nowhere near nailed down. 72 hours ago it didn't even exist on the models. Even if it did track to the extent that precipitation fell as rain not snow for some on Wednesday, what is expected of mid November? The devil will be in the detail but in the meantime, we're in for a very cold spell for  the time of year, both qualitatively and empirically. The CET will certainly take a hammering.

HiSorry about that; the Dewpoints should highlight the lack of snow as the low tracks south: I was just highlighting this, as the UKMO Fax last night indicated snow to eastern Britain, as it track south was further west.As for the Arctic blast, the formation of the low has tempered much of the flow, and it is less Arctic sourced. The uppers and the cloud/rain will certainly make it feel cold, though it is a brief shot, as a ridge quickly edges in:The good part of this low going more to our east (in my opinion) is that it will prop up the Med lower heights: A strong line of LP systems.With NOAA indicating strong ridging in the Pacific/W.America: This long wave pattern should remain amplified, and along with the Med lower heights, HP should be close to the UK. Even if it is pressed by the active PV recent runs have suggested pressure is reinforced from the SW.What I was saying is that where the heights build to, will effect the medium term cold and this remains unresolved.

[Purga]

So a big downgrade of the cold from GFS this morning with a quick return to solid zonality in FI

 

ECM is much better but even so the ECM ensembles downgrade the cold from previously

 

http://oi42.tinypic.com/2cco00z.jpg

 

not bad but not spectacular.

[Ian Brown]

Whilst you are of course correct that the exact track of the shortwave hasn't been nailed WiB, you are incorrect to suggest it is not a 'warm sector' moving south on Weds. The area between the warm and the cold fronts shown on this fax chart is called a warm sector....you can call it a teapot if you want to, but a warm sector is what it is.

 

Yes, even in the middle of the winter the outcome would be the same from his sort of feature, principally your chances of seeing snow on low ground from it at the beginning and end of the event as the bulk of the PPN is contained within the warmer segment of the feature.

So a big downgrade of the cold from GFS this morning with a quick return to solid zonality in FI

 

ECM is much better but even so the ECM ensembles downgrade the cold from previously

 

http://oi42.tinypic.com/2cco00z.jpg

 

not bad but not spectacular.

I think what we are seeing is a trend for lower heights at Northern latitudes in FI as the models reflect the Strat cooling. Time for changes of course but our mid-latitude High looks like coming under pressure from the jet.

[Frosty.]

Why worry about the ukmo, its flip flopping with the rest of them, at least the ecm 0z op is more wintry and synoptically superior to the 12z last night..it's crucial what mogreps is showing..over to you ian :- )

[shedhead]

that ecm op is the least surface cold run for the south of the uk for a long time. also, the 20th always looked to be the coldest day of the upcoming spell via the ens but the introduction of this little depression means it will likely be the least chilly. 

Indeed, when you now look back over the hype of the last 3 or 4 days some of the things said regarding the early to middle part of next week frankly now look way off the mark.  The main trouble again stemmed from many folks refusal to accept that models really do struggle to nail the detail in the 144-168hr range when the weather is not coming from the west, along with the fact they rarely pick up any shortwave spoilers until within T+120hrs.  Taking the often very clean looking charts at 144hrs and beyond and expecting them to verify as shown when weather is coming from the north or east always has been foolhardy...and frankly still is. WiB mentioned the potential confusion for new members when terms like 'warm sector' are use when the weather is cold, but imo they are likely to become far more confused by all the calls for cold/very cold charts to verify when often a week or more away. 

[phil nw.]

The way the ECM mean shows the shape and location of the stretched vortex leaves the Atlantic sector prone to continued blocking.

http://www.meteociel.fr/modeles/ecmwf/runs/2013111700/EDH1-192.GIF?17-12

 

Ok not an excitingly cold setup yet but that area to our nw will continue to see +ve height anomalies.

http://www.meteociel.fr/modeles/ecmwf/runs/2013111700/EDM101-216.GIF?17-12

 

No sign of any Atlantic jet overpowering  the pattern in the medium term.

[Ian Brown]

Indeed, when you now look back over the hype of the last 3 or 4 days some of the things said regarding the early to middle part of next week frankly now look way off the mark.  The main trouble again stemmed from many folks refusal to accept that models really do struggle to nail the detail in the 144-168hr range when the weather is not coming from the west, along with the fact they rarely pick up any shortwave spoilers until within T+120hrs.  Taking the often very clean looking charts at 144hrs and beyond and expecting them to verify as shown when weather is coming from the north or east always has been foolhardy...and frankly still is. WiB mentioned the potential confusion for new members when terms like 'warm sector' are use when the weather is cold, but imo they are likely to become far more confused by all the calls for cold/very cold charts to verify when often a week or more away. 

 

Yes the 'northerly' now looks completely different to what looked on the cards a few days ago - and with norherlies you normally have a greater leeway than with easterlies, where your timeframes for accuracy are T72, maximum T96.

The way the ECM mean shows the shape and location of the stretched vortex leaves the Atlantic sector prone to continued blocking.

http://www.meteociel.fr/modeles/ecmwf/runs/2013111700/EDH1-192.GIF?17-12

 

Ok not an excitingly cold setup yet but that area to our nw will continue to see +ve height anomalies.

http://www.meteociel.fr/modeles/ecmwf/runs/2013111700/EDM101-216.GIF?17-12

 

No sign of any Atlantic jet overpowering  the pattern in the medium term.

 

I disagree Phil and the trend is there in the NWP for the erosion to come from the North from day 12 onwards, but of course that is a long way off.

[radiohead]

The ECM ENS anomaly on day 10 looks good to me.

 

 

And the operational at T168 is loaded with potential. It wouldn't take a huge amount of adjustment for this to end up being a very good chart indeed, and changes will happen by T168 - we just don't know which way yet.

 

Edited November 17, 2013 by radiohead

[Joe Levy]

Indeed, when you now look back over the hype of the last 3 or 4 days some of the things said regarding the early to middle part of next week frankly now look way off the mark.  The main trouble again stemmed from many folks refusal to accept that models really do struggle to nail the detail in the 144-168hr range when the weather is not coming from the west, along with the fact they rarely pick up any shortwave spoilers until within T+120hrs.  Taking the often very clean looking charts at 144hrs and beyond and expecting them to verify as shown when weather is coming from the north or east always has been foolhardy...and frankly still is. WiB mentioned the potential confusion for new members when terms like 'warm sector' are use when the weather is cold, but imo they are likely to become far more confused by all the calls for cold/very cold charts to verify when often a week or more away. 

I definitely agree with this, but also, now that the charts are not so good at t144, it's important that we don't start assuming that means that they will verify either! I general, we can be quite confident about what will happen in the next 72 hours, sometimes have a good idea of the general idea for a couple of days after that but anything beyond and it is very uncertain! A slight change one way on the 168 chart for ECM (posted above by radiohead) could produce a very cold chart, but equally that could not happen either!

[Summer Sun]

I don't think its too much of a surprise to see UKMO backtracking this morning GFS and ECM were not supporting it.

 

The general pattern now appears to be a steady rise in pressure from the west later in the week, so becoming drier and remaining chilly with a risk of frost and fog

 

ECM

 

 

GFS