Model Output Discussion - 21st - 28th November

[johnholmes]

The overnight runs really emphasise the Zonal pattern that we are now entering-- with less amplitude it looks a milder scenario than the 12z`s of yesterday.

Still some brief skirmishes with Polar air into the North at times but mainly a mild outlook for many.

Towards the end of next week it does looks a little colder for a short time

http://www.meteociel.../fax/fax84s.gif

but the Azores High moves in and the flow turns to a milder South West again.

The mean Hts comparisons days 8-10 tells it`s own story

http://www.meteo.psu...0z/hgtcomp.html

A pretty rock solid old fashioned mainly mild zonal pattern.

The main hope for any cold is for some ridging further north in the Mid-Atlantic to turn the winds towards North of West but with such a strong Vortex any cold incursions would be shortlived.

I'm not sure how, using the ECMWF and GFS charts you can say 'rock solid mainly mild...'?

Take a look at the heights to give some idea of what the type of atmospheric structure its predicting. A difference between the two for sure with ECMWF some 6 perhaps 10DM colder than GFS. Both though would suggest to me, more Pm air than Tm air. Sure there will be a mix and it will be unsettled with the prospect of further gales near lows as they track quite close to the far north or NW, but fairly frequent incursions of Pm air very well south. About normal as an average for the south regarding temperatures, the far south, a touch below for central areas and below average further north is how I would summarise the temperature structure?

That for the next 5-10 days anyway.

[Thundery wintry showers]

Nothing like the snowy outlook of this time last year, but certainly a lot going on in today's model outputs, unlike earlier in the month when there was often very little to discuss other than "when will that Euro high finally retreat?". The models are not disagreeing on the general pattern this time around, and on this occasion it seems that the GFS has been nearest the mark, perhaps a little over-progressive initially at bringing the Atlantic in but the UKMO/ECMWF grossly underestimated the Atlantic's arrival in earlier runs.

The main thing to watch in my opinion is Sunday's low, which looks set to produce damaging winds in Scotland, perhaps extending into parts of northern England for a time. After that, a rather warm start to the week with a south-westerly flow, some dry sunny weather in the east to begin with but cloudy wet weather extending eastwards during the course of Monday and Tuesday. From Wednesday onwards the models agree that we will see some polar maritime incursions with sunshine and blustery showers, and some of the heavier showers may well end up wintry to low levels across Scotland, Northern Ireland and parts of northern England, and on high ground further south too.

All three models are pointing towards a lot of cold air flooding the eastern Atlantic around T+168, which depending on how the synoptics play out, might give us a window of opportunity for some cold zonality- though in my experience the models often overdo the NW-SE tilt to the jet, with the reality being that secondary lows/shortwaves form and the polar air has to return a longer distance over the Atlantic than originally modelled at this range.

[rich1]

http://www.wetterzentrale.de/pics/MT8_London_ens.png

unsettled, alternating between average, above average and chilly. Mean shows standard zonality/cool zonality

wouldnt mind the yellow run but looks mobile for the next few weeks. Not brilliant but as I have to fly in to Europe on the 15th, I dont really fancy another 4 days of my holiday stuck in a freezing airport in Germany again. It can all wait till after that for me. Would like to see some better upstream signals though, have to say, but they can change

[bluearmy]

I'm not sure how, using the ECMWF and GFS charts you can say 'rock solid mainly mild...'?

Take a look at the heights to give some idea of what the type of atmospheric structure its predicting. A difference between the two for sure with ECMWF some 6 perhaps 10DM colder than GFS. Both though would suggest to me, more Pm air than Tm air. Sure there will be a mix and it will be unsettled with the prospect of further gales near lows as they track quite close to the far north or NW, but fairly frequent incursions of Pm air very well south. About normal as an average for the south regarding temperatures, the far south, a touch below for central areas and below average further north is how I would summarise the temperature structure?

That for the next 5-10 days anyway.

i think phil was commenting on the 8/10 day mean charts john which, by definition, will not show the colder incursions. one reason i so dislike these charts is that they only reflect the ops at a timescale which most of us would agree is fi. would be much better if the producer of this output was to do the same from the ens mean rather than the ops.

[shedhead]

I'm not sure how, using the ECMWF and GFS charts you can say 'rock solid mainly mild...'?

Take a look at the heights to give some idea of what the type of atmospheric structure its predicting. A difference between the two for sure with ECMWF some 6 perhaps 10DM colder than GFS. Both though would suggest to me, more Pm air than Tm air. Sure there will be a mix and it will be unsettled with the prospect of further gales near lows as they track quite close to the far north or NW, but fairly frequent incursions of Pm air very well south. About normal as an average for the south regarding temperatures, the far south, a touch below for central areas and below average further north is how I would summarise the temperature structure?

That for the next 5-10 days anyway.

At that range though John the models rarely factor in shortwave developments, that time and time again we've seen pull milder air across the country when the time comes. Perhaps we should bank the 180hr chart now for 18z next Saturday, when Pm air is progged to flood well south and then take a look at the actuality this time next week.

[johnholmes]

i think phil was commenting on the 8/10 day mean charts john which, by definition, will not show the colder incursions. one reason i so dislike these charts is that they only reflect the ops at a timescale which most of us would agree is fi. would be much better if the producer of this output was to do the same from the ens mean rather than the ops.

hi ba

yes my comment did mean the 8-10 day upper air charts he showed.

I find them pretty good guidance although, over the past 5-7 days, they are somewhat at odds with one another over the position and strength of the main troughs and ridges which makes giving a forecast using them not easy but I believe my comment about the overall temperatures is about right.

Not as mild as phil commented hence my post in reply.

At that range though John the models rarely factor in shortwave developments, that time and time again we've seen pull milder air across the country when the time comes. Perhaps we should bank the 180hr chart now for 18z next Saturday, when Pm air is progged to flood well south and then take a look at the actuality this time next week.

oh I'm sure shed that I fairly frequently comment that forecasting upper air patterns is considerably easier than doing it for the surface. Quite often the interaction between Pm and Tm air will give differences but that must be expected. Anyone expecting detail at times scales beyond T+120 toT+144 is going to have fairly frequent shocks at what actually transpires. There is a reason that professional forecasters use the term, unsettled, continuing unsettled; some see it as a cop out. Its not, its an accurate reflection of what is going to happen.

Edited November 26, 2011 by johnholmes

[phil nw.]

i think phil was commenting on the 8/10 day mean charts john which, by definition, will not show the colder incursions. one reason i so dislike these charts is that they only reflect the ops at a timescale which most of us would agree is fi. would be much better if the producer of this output was to do the same from the ens mean rather than the ops.

Yes quite correct B.A. i was referring to the Mean Hts. when i suggested the rock solid mainly mild zonal pattern.

I agree those charts are not perfect but is any output even withinT144--as yesterdays GFS12z proved.

We can only work with what we have access to and they are usefull to compare the general pattern between the 2 main models.

I'm not sure how, using the ECMWF and GFS charts you can say 'rock solid mainly mild...'?

Take a look at the heights to give some idea of what the type of atmospheric structure its predicting. A difference between the two for sure with ECMWF some 6 perhaps 10DM colder than GFS. Both though would suggest to me, more Pm air than Tm air. Sure there will be a mix and it will be unsettled with the prospect of further gales near lows as they track quite close to the far north or NW, but fairly frequent incursions of Pm air very well south. About normal as an average for the south regarding temperatures, the far south, a touch below for central areas and below average further north is how I would summarise the temperature structure?

That for the next 5-10 days anyway.

John,I did also mention the colder interlude next week and linked the T84hrs. Fax showing the advancing cold front.

I also did mention in my post about the brief skirmishes of cold air for the North but apart from that to me it looks like that with the Azores high so close by days8-10 that there would be quite a bit of Pm air around away from the far North.

The problem is i think that although the general pattern is pretty well set ----Strong vortex,lows to the North and High pressure to the South-- subtle differences in the amplitude will show different amounts of Pm air getting south from various outputs.

The bottom line though is-- away from the Scottish highlands-- it`s far from a Wintry setup.

[Thundery wintry showers]

I think a fairly mild zonal pattern is quite likely to be the theme over the next 15 days, with a colder blip around the end of November/beginning of December, but I am mainly basing this on the models' tendency to underdo secondary low development and send too much Arctic air south. Taken at face value, the current model outputs are suggesting an average to fairly cold zonal pattern as we head into December. not dissimilar to what we got during the Decembers of 1993 and 1999.

[nick sussex]

Not much change in the GFS 06hrs run in terms of the overall pattern, however the troughing in the eastern USA is more amplified than the previous 00hrs output.

http://www.meteociel...npara=0&carte=1

That deepish low crossing Canada at 168hrs is very important for the downstream pattern in Europe.

I should elaborate on that a bit more, because we're likely to have high pressure in the Atlantic we need something to help pull this west and not drive it east into central Europe, the way to do this is to have a more amplified upstream pattern.

If the pattern flattens out the Azores high will likely get pushed in towards Europe, so its down to what level of amplification we have upstream to guard against that happening.

Look out for that low across the outputs this evening, it is likely to verify but its level of amplitude is uncertain. Also how much it develops, because of the pattern low pressure is likely to keep crossing the USA and Canada forced around that east Pacific ridge.

Edited November 26, 2011 by nick sussex

[Cecil Hogmanay Melchett]

Not much change in the GFS 06hrs run in terms of the overall pattern, however the troughing in the eastern USA is more amplified than the previous 00hrs output.

http://www.meteociel...npara=0&carte=1

That deepish low crossing Canada at 168hrs is very important for the downstream pattern in Europe.

I should elaborate on that a bit more, because we're likely to have high pressure in the Atlantic we need something to help pull this west and not drive it east into central Europe, the way to do this is have a more amplified upstream pattern.

If the pattern flattens out the Azores high will likely get pushed in towards Europe, so its down to what level of amplification we have upstream to guard against that happening.

Look out for that low across the outputs this evening, it is likely to verify but its level of amplitude is uncertain.

Yes nick thats a very important aspect of the current models,we most certainly DO NOT want the azores high getting shunted into Europe.

[nick sussex]

Yes nick thats a very important aspect of the current models,we most certainly DO NOT want the azores high getting shunted into Europe.

In a nutshell once the Azores high is pushed into Europe its game over for even PM incursions.

The overall NH pattern is quite set however the degree of amplification upstream is open to debate, the best thing I've seen all day in terms of output is the GFS 06hrs run in the higher resolution.

The fact that w'ere not talking about the wayward lower resolution output is a positive. Show me an amplified eastern US trough and I can make a case for something more interesting!

Of course the odds currently favour the pattern flattening out but lets wait and see what the models do this evening.

[Frosty.]

The further north you are, the more chance of colder polar maritime incursions but southern britain never really gets into sub 528dam air but scotland does on several occasions on the latest gfs and ecm, snow will affect northern hills and perhaps low ground at times in the far north of the uk as there is also a risk of brief arctic blast at the end of next week but not reaching the south. It's very frustrating watching the 528dam line not penetrating into southern areas but until the jet starts pushing further south it won't change, for scotland and in particular the north of scotland, there is some snow to look forward to but hardly anything further south. At least the south should get some heavier spells of rain next week.

[Frosty.]

I think a fairly mild zonal pattern is quite likely to be the theme over the next 15 days,

The gfs 06z and ecm 00z show cold zoneality dominating northern britain for the next 7-10 days with shortlived milder blips, for southern britain it's generally average temps but occasionally milder but also a little below average on a few occasions.

[Bobby]

In a nutshell once the Azores high is pushed into Europe its game over for even PM incursions.

wait and see what the models do this evening.

The ensemble mean (+384) worryingly shows this.

Wost winter setup of all IMO.

[Frosty.]

Latest meto has not altered much in tone and still indicates a colder zonal pattern for more northern parts of the uk with regular incursions of sub 528 dam line and snow for hilly northern regions, this is all in line with the 00z and 6z models so far today, rather more average pattern for the southern half of the uk but perhaps a window of opportunity later next week for colder air to penetrate southern england very briefly. The pattern will edge further south next week allowing heavier rain into the south but also allowing more in the way of hill and mountain snow for the north albeit with less cold or slightly milder sectors for the north at times which will melt the snow from the hills between colder snaps.

[TonyH]

Guide to the weeks weather for west Wales and the central Midlands for Sunday 27th November to Saturday 3rd December

Headline: Very unsettled, often windy, mild to average temperatures.

Tonight's strong winds and rain should have cleared away by Sunday morning. A week transient ridge gives a mostly dry if breezy day, just the outside chance of a shower. Reasonably mild, although clearing skies will lead to a slight frost overnight.

After a chilly start to Monday with frost in places, cloud and wind spreads over by afternoon. Rain at times during the afternoon and evening for west Wales,some heavy, while only light rain for the Midlands. Windy with further rain at times during Monday night for Wales, a very mild night. Another spell of heavy rain moves into west Wales early on Tuesday, this cold front crossing the Midlands late in the day too. A mild day again, but turning cooler during the afternoon for Wales.

Chance of a touch of frost first thing Wednesday but most likely too breezy, and with some showers still going over west Wales. Then, a secondary low feature is modelled to cross the UK either late Wednesday or early Thursday, so that we are set for another period of wet and windy weather, and depending on the exact track of this low there is likely to be gales in places Wednesday night, provided that it winds itself up enough, as it looks like doing.

Further showers or longer spells of rain for all of us to end the week and over next weekend, but more especially for west Wales. Often windy and cooler too, with a sprinkling of snow for the Snowdonia summits.

Supportive charts here:

http://forum.netweather.tv/topic/69041-wales-regional-weather-discussion/page__st__140__gopid__2165750#entry2165750

[syed2878]

I'm sorry adminds i know this is the mod thread. I c 1-2 posters mensioning globle warming take a look at the leacked emails then talk about globle warming. If any1 want thos emails pm me. Again sorry admins and posters.

[Cheese Rice]

A cool spell seems the most likely outcome. the majority of the UK will see sub 0.c 850's with Scotland seeing -5 850's at times. Usually this would result in average to slightly below in the south with below average temperatures in the north.

A quick look at the meto 6-15 day shows a cool zonal pattern.

Showers will turn to snow at times over high ground in the north, perhaps falling to lower levels on occasions, with a low chance of this also threatening central parts of the UK early on. There will, however, be some drier and more settled interludes too, especially towards the south of the country later in the period. Temperatures are likely to be around or a little below the seasonal average, bringing an increased risk of frost overnight almost anywhere during any more settled spells.

With an ever increasing risk of frosts between each low, we could see quite a cool first half to December. It all really depends on whether precipitation/cloud cover clears at night.

[vortex_liam]

Bad winter setups atm :L

[Harsh Climate]

Bad winter setups atm :L

What we are seeing is a pretty average start to winter, nearly all the good to great winters over the last century didn't even start untill after christmas so there is nothing to be worried about just yet! If the charts look like they do now around a week before christmas then we might have something to be concerned about. So that's a good 3 weeks, plenty of time for a change! And we all know how the gfs can just throw some beauties in out of nowhere, then build towards that! so stay positive people

Edited November 26, 2011 by Harsh Climate

[summer blizzard]

Some of you are far too depressed.

While there is no sustained cold on the horizon the fact is that the average winter pattern is for WSW winds. The models are in pretty unanimous agreement that the winds will have a northerly element in the opening days of December giving what is generally referred to as 'cool' zonality.

While this pattern is unlikely to produce snow away from the north and western high ground, it will feel cold and there is a good chance of frost.

[Bottesford]

Can we please stick to talking about the models and not about winter in general - plenty of threads for that. Meanwhile plenty of weather going on this week ripe for discussion.

[lorenzo]

12z beginning its roll now.

Down both barrels here at 84 http://176.31.229.228/modeles/gfs/run/gfsnh-5-84.png?12

JS really powering up over the Greenland http://176.31.229.228/modeles/gfs/run/gfsnh-5-90.png?12 then enough to force it way south west of the UK allowing more PM incursions

More storms in the post then...

[Frosty.]

Can we please stick to talking about the models and not about winter in general - plenty of threads for that. Meanwhile plenty of weather going on this week ripe for discussion.

Indeed, whether you like this weather or whether you don't, it's looking unsettled and average in the south and unsettled and colder in the north but with milder sectors for all areas from time to time, very limited risk of frost due to wind strength and cloud cover but snow for the hills of northern britain is set in stone from middle of next week as Pm air floods into the north of the BI.

[Grimsby Snow Lover]

Well, upto next Saturday we has a little consistency from the 12z GFS run. Things do seem to remain windy pretty much all next week with temperature ranging from average to slightly below if you ask me. Finally a more traditional feel to the weather. With any luck next weeks will slow my daffs down as some are poking through the soil!!

http://hw.nwstatic.c...1/ukmaxtemp.png

Followed by a nice bit of GFS eye candy

http://hw.nwstatic.c...hgt500-1000.png

Edited November 26, 2011 by Grimsby Snow Lover