Model Output Discussion 18/11/2012 12Z onwards

[ukpaul]

It's funny how some people hang onto every GFS FI as though it's written in stone. Look at trends, look at the high res and see what all the models are saying, ensembles being especially useful. Having looked at that, today is another step towards a blocked and cold spell, getting potentially progressively so as the forecast warming sets up. I have to say that the trends there have firmed up my opinion that December will find us in cold air for a fair time with the chances of snow that that brings.

Anyway, ECM looks like a much cleaner set up, PV duly in pieces by 192h.

Edited November 19, 2012 by ukpaul

[SMU]

I would 'expect' as per some of my diagrams over the last week or so for that high to back build to greenland-

we *MAY* get a snippet of that at 240 ECM-

S

[danm]

http://www.meteociel...H1-216.GIF?19-0

Wintry in the SE-

A LONG LONG draw easterly-

S

I suspect many parts of Lincolnshire, Yorkshire and Humberside would take a pounding from that. Tight isobars with a strong flow off the North Sea.

[Liam J]

http://www.meteociel...H1-216.GIF?19-0

Wintry in the SE-

A LONG LONG draw easterly-

S

It would be if there was some decent cold over Europe to tap into, not a bad run but i'd like to see a Greeny high setting up for a more guaranteed route to deep cold. Things are becoming very interesting now - I wonder what the JMA will have in store for us this evening...

Edited November 19, 2012 by Liam J

[Duane S.]

Oh yes yes yes to the ECM. This is the evolution we need to see. Energy dragged SE and bingo at +216. Waiting for +240 but I think it's going to be rather tasty.

Never mid the usual cold pooling worries, get THIS in place and it will come.

[phil nw.]

http://www.meteociel...H1-216.GIF?19-0

Wintry in the SE-

A LONG LONG draw easterly-

S

Yes back on track Steve.Nice finish at T240hrs.

[Geordiesnow]

I suspect many parts of Lincolnshire, Yorkshire and Humberside would take a pounding from that. Tight isobars with a strong flow off the North Sea.

Erm yeah, patchy uppers of -5hpa will really deliver wont it.

It just looks a cold and wet horrible chart too me, if we had colder uppers to tap into then the set up would be much better but the reality is, because of the long drawn southerlies scandinavia will soon face then theres no cold uppers to tap into.

That said, in terms of potential, I think the ECM has more of that than the GFS does.

[January Snowstorm]

Looks cold enough (JUST) to me.

Dew points will help hugely, amazing ECM

Here we go again guys,

Edited November 19, 2012 by January Snowstorm

[chris55]

Continuation of great trends as we move into winter!!! And as these trends come into the more reliable time-frames we could be looking at some fun and games as we head into December!!!

[nick sussex]

I suspect many parts of Lincolnshire, Yorkshire and Humberside would take a pounding from that. Tight isobars with a strong flow off the North Sea.

Unfortunately Dan the 850's not quite cold enough to develop good convection off the North Sea.

However at this timeframe we don't know exactly how much cold air will be advected into the flow as that trough splits, there is a chance though of some frontal backedge snow as that low drops south, we should still see lowish dew points brought in from the continent but any snow in that situation more likely away from windward coasts.

Overall a very good ECM run but its going to be nailbiting stuff waiting for the trigger shortwave to be ejected off the main troughing to the west.

Edited November 19, 2012 by nick sussex

[danm]

Erm yeah, patchy uppers of -5hpa will really deliver wont it.

It just looks a cold and wet horrible chart too me, if we had colder uppers to tap into then the set up would be much better but the reality is, because of the long drawn southerlies scandinavia will soon face then theres no cold uppers to tap into.

That said, in terms of potential, I think the ECM has more of that than the GFS does.

As many have said, at this stage it's fruitless to get hung up on what the 850's are. They more often than not change. Previous cold spells over the last few years have shown the same thing - cool rather than cold 850's 10 days out but then much colder 850's often showing as we get closer to the time.

[Geordiesnow]

Looks cold enough (JUST) to me.

Dew points will help hugely, amazing ECM

Here we go again guys,

No its not though, its not even cold enough to generate much PPN as one the cold uppers are not cold enough and instability wise is not the best either(thicknesses look too high for the most part), too me that 216 hour chart will have a weather front near East Anglia delivering a cold raw wet day = horrible!

Set up wise, then yes ECM has more potential than the GFS and perhaps more signs leaning towards a more blocked set up.

[cold snap]

Nick regarding the shortwave for once we actually passed this with very little trouble

The 850s however still not quite the finish article

Edited November 19, 2012 by cold snap

[Mr Frost]

No its not though, its not even cold enough to generate much PPN as one the cold uppers are not cold enough and instability wise is not the best either(thicknesses look too high for the most part), too me that 216 hour chart will have a weather front near East Anglia delivering a cold raw wet day = horrible!

Set up wise, then yes ECM has more potential than the GFS and perhaps more signs leaning towards a more blocked set up.

Geordiesnow If we ended up with a raging Notherly, North Easterly then Easterly you still would not be happy.

Cheer up, it is only the weather. :-)

[snow drift]

This is an improved output. There is more potential and it gets to the later stages in a less messy way. Nick will be pleased I think. I am not sure that the cold does keep getting pushed back T240 from now is still not the end of the month. This week will be interesting as we now could see the potential move forward on the different runs. Really looking forward to the ECM tonight.

12 hours on an I am not disapointed. To much talk about lack of cold uppers etc. Look at the blocking. look at the potential as we move forward. Look at what we are looking at on the 19th of Nov. Enjoy were we are and except that it could go wrong but for now be happy that it could look very different and we could be searching just for a bit of hope.

[Gibby]

Good evening. Here is the evening look at the 12zs from GFS, UKMO and ECM for today Monday November 19th 2012.

All models continue to show Low pressure out to the NW dominant over the UK for the rest of the week and over the weekend. While many are looking for cold in the week that follows it's this week which draws more attention to me as successive bands of rain and strong winds amass quite high rainfall totals for many by the end of the week with the risk of flooding high in places. A series of fronts trail over Southern Britain tomorrow with a new band of rain by morning for all areas lasting on through much of tomorrow, heavy at times with very strong winds in the West. After s brief drier spell on Wednesday further fronts move more slowly East late in the week bringing further copious rainfall West to East over the period of Thursday and Friday. Through all this time it remains mild or very mild at times in the South. Over the weekend pressure remains Low with further rain at times. It will steadily become less mild as winds trend more towards the West and NW.

GFS then shows Low pressure sliding South at the end of the weekend to leave Low pressure close to SE England with further rain at times early next week across the UK in rather lower temperatures. This pattern persists for some days with pressure having risen to the North and settling over Scandinavia by the weekend delivering rather cold weather with further rain in the SE in particular. Pressure then falls over the Atlantic deep in FI with a strong SSE wind developing with rain into many Western and Southern areas later in the weekend extending slowly North with time. With colder air in place locations North of the Midlands could begin to see some wintriness in the precipitation with other areas too joining in with sleet or snow possibilities at the end of the run as the Low pressure slides away to the SE sucking in a chilly Northerly flow.

The GFS Ensembles show a continuing decline in uppers as we move towards the second week of the run. With quite a lot of rain shown in the first week it's not hard to achieve less rainfall in week 2 as High pressure becomes more impactive on the weather over the UK. With temperature levels at this level snowfall would be restricted to the higher elevations at this stage.

The Jet Stream flow continues to blow NE over the UK in the coming week before the flow ridges well North to Greenland and North of Iceland before turning South over Ireland and France next weekend and early in the following week.

UKMO for midday on Sunday shows Low pressure NW of Ireland with a strong SW flow with rain bearing troughs crossing NE over all areas through the day. Temperatures will be close to normal.

ECM shows a vigorous Low pressure moving across the UK on Sunday with gales and heavy rain sweeping across all areas followed by colder and clearer conditions with showers. On Monday low pressure lies in the North Sea with a cold NW flow with wintry showers for all, heaviest in the North. Later in the run High pressure builds North and NW of Britain with Low pressure sinking SE to France and the Low Countries bringing cold and wintry feeling weather across all areas with rain and sleet, and snow on higher ground with a strong and very cold feeling NE wind. The 240 hr chart shows Low pressure over Biscay with High pressure anchored to the North with a cold and raw easterly flow over Britain with some further rain at times with hill sleet and snow in the South and wintry showers affecting Eastern coastal counties.

In Summary the weather is looking gradually more like winter as we move into week 2 with this week characterized by very wet and windy conditions mixed with some drier and brighter spells. There could be some flooding problems later in the week to join those already experienced in Scotland. The transition over the weekend sees further rain at times in lowering temperatures with next week looking much colder than currently with Low pressure to the SE and High to the North throwing up some mouthwatering synoptics as unstable air remains in situ with the chance of rain and sleet and eventually snow longer term should the charts verify and stick around for a while. Even though it's only late November one can only wish that temperatures on the continent of Europe were cold enough for a freeze at the moment in time that those charts verify.

[Met4Cast]

What time does the NCEP Height Anomaly model update?

I think people need to relax a little re: 850hPa temperatures, looking at the details this far out is worthless

[Eskimo]

As others have mentioned, I wouldn't be despondent on the smaller details 7-10 days away, there are very encouraging signs that a pattern change will happen, the finer details are yet to be acknowledged and the models will chase upon them soon I'm sure.

[Ian Brown]

it tends to be those who never sat through crap winter after crap winter on the models before 2008 came along. we got preconditioned that gfs fi's never verified into cold because - they never did. recent years have shown stellar runs making it to T0. if i had started model watching post 2008, i might also take op models post day 7 too seriously. any news on the exeter conflab today ???

Indeed. Prior to 2008, the charts could show all manor of things even at something like T192/216 and you could bet your bottom dollar that a spanner would be thrown in the works, usually in the form a shortwave, to pull the jet further North.

[Duane S.]

Borderline snow-wise in places it may be, a lack of true cold uppers (initially at least) there may be. Call me easily pleased but I'll take this year's projected...

over last year's actual (3 days on) ...

any day thanks very much!

Best days charts of the winter so far today. A pattern change and a cold spell is coming, of that there is now little doubt. As per usual though, how cold and for how long we ar egoing to have to wait a little longer for yet.

[nick sussex]

Nick regarding the shortwave for once we actually passed this with very little trouble

The 850s however still not quite the finish article

Theres always trouble with shortwaves! I wouldn't worry about the 850's the main hurdle is the transition from 168 to 192hrs, the trigger shortwave heads se as the ridge builds to the ne, its absolutely crucial that the energy splits from that main trough to the west.

If you don't get enough energy heading under the ridge then I'll be manning the Emergency Trauma Helpline as hysteria breaks out in netweather!

[Ian Brown]

http://www.meteociel...H1-216.GIF?19-0

Wintry in the SE-

A LONG LONG draw easterly-

S

The source of the air suggests not - I would think even if you got some snowfall mixed in, less cold air is behind (like Feb 10) to bring about a quick thaw.

[latitude]

Even from a newbie point of view im looking for -5 850's for snowfall, and I cant see that on the ECM on face value. But i suppose its the pattern change and blocked atlantic that is key. Get the pattern change sorted then the cold should follow.

[SMU]

Too much panic...worry not!!

(NB: as a respected UKMO colleague just said to me about this, to put into perspective: "I just don't get why so many people get so fretful about the longer-range stuff showing in GFS and the like. It's a total waste of energy, as the underpinning science is still so way, way off affording any worthwhile reliability that detailed analysis is pointless and often results in an exhaustive over-analysis from what I see looking on forums..."

With regards to the 850's-

I think peoples comments are correct, yes there can & will be some variation on the 850's however they wont get down to the desired spec to generate snow showers.

Cold & wet would be the order of the day, maybe some wintryness over central / SW areas on the 216 Chart- away from coasts.

What we are looking for is what 1 or 2 of us have been elluding to over the last week or 2.

Retrogression back to greenland-

The long pebble shaped high will sharpen up - this is dictated by the developing jet profile over greenland, once this happens & goes northwards then so very cold air will start to filter south & west through Scandi...

So a summary of the next 10 - 15 days is-

Mild > moving to average in 5 days > changing to chilly conditions out to day 7/8 > moving into the cold catagory out to day 10- probably 4/5 degrees below Nov maxima by then-

10-15 static temps at the start hoping for a top up cold from the NE day 12-15.....

Off course that late period of time is open for significant variance at this stage-

S

PS Ian I said Wintry

Edited November 19, 2012 by Steve Murr

[Ian Brown]

Erm yeah, patchy uppers of -5hpa will really deliver wont it.

It just looks a cold and wet horrible chart too me, if we had colder uppers to tap into then the set up would be much better but the reality is, because of the long drawn southerlies scandinavia will soon face then theres no cold uppers to tap into.

That said, in terms of potential, I think the ECM has more of that than the GFS does.

Agreed, whatever the possible marginality inland it would be no good for coastal areas.

Nice to look at these synoptics nonetheless and I think some sort of major pattern change is guaranteed. However I would prefer to see a true cold feed shown (sub 528 dam and sub -7 uppers) and the only way to get that at this stage is a through North Easterlies or Northerlies and both appear to be off the table at least in the first phase of the blocking change.