Model Output Discussion - September Onwards

[Aaron]

He uses TWO quite frequently as MVH.

[Summer Sun]

ECM is looking good tonight, with a strong area of high pressure acting as a blocking sytem to our east

http://www.wetterzen...cs/Recm2401.gif

The would bring with it warm sunny conditions, perfect , hopefully ECM is on to some thing tonight.

[Thundery wintry showers]

This coming weekend will have a mixed bag of sun and showers, and tomorrow has modest potential for thunderstorms, particularly in southern and western parts of England. On Sunday, there might be the odd rumble across East Anglia and Lincolnshire, though central and western areas will have a drier day.

A NW-SE split is looking set to arise next week, though it might not be the sort of NW-SE split that we traditionally expect when pressure is high to the S and SE- it all depends on the positionning of a slow moving cold front. There is a significant chance, in my opinion, of the front becoming slow moving across the south-eastern third of England giving cloudy and drizzly conditions while other areas are sunny and mostly dry bar a scattering of showers in the north-west. It is all subject to change though, and another (just as likely) possibility has the front clearing to the south of the mainland leaving a split between sunshine and showers in western and northern Scotland and dry sunny weather elsewhere.

I think the ECMWF operational run is over-egging the high pressure post T+144 and it certainly has limited ensemble support, though in my opinion there is about a 50-50 chance of high pressure ridging into southern and eastern areas for a couple of days which might bring some warm sunshine to those areas. All in all, it's a pretty standard pattern for September.

[Gibby]

Good evening folks. No report tomorrow morning, back in the evening.

GFS tonight shows the pattern very much as before with an unsettled week coming up with Low pressure always close by to the North with wind, rain and showers for all at times, heaviest in the North. Longer term tonight in total contrast to this morning we see high pressure over our shores with things settling down after next weekend with dry, bright days but some chilly nights with mist and fog in places and ground frost locally.

UKMO also shows an improvement on this morning with a very unsettled weekend and start to next week steadily giving way to drier conditions later next week i.e once we have lost a troublesome trailing cold front near Southern Britain midweek.

ECM tonight completes the hat trick in showing better weather for the south and southeast later next week with this mornings deep lows removed from our shores. However, things still look tentative and we have three or four days of very unsettled conditions before drier and warmer conditions start to take over in the South and East late next week with a warm southerly flow for all by the weekend though low pressure out to the west may bring rain to western regions with time.

In Summary tonight the weather remains in changeable mood. From this morning's deep Autumnal charts things have moderated somewhat this evening though there is still considerable scope for rain at times for all though the prospect of some better weather at times chiefly in the south and southeast is a step in the right direction when compared to this morning's output.

[Thundery wintry showers]

A good summary as usual.

I don't think the high pressure in the GFS FI would bring dry bright days and cool misty nights though, except perhaps during the last few frames of the run- judging by the temperature and rainfall outputs there is too much maritime air trapped within its circulation, and a fairly cloudy scenario with temperatures holding up at night is indicated. The high also doesn't make it to our shores until after T+180, following the passage of a rather active low pressure system.

[kold weather]

Matthew Hugo BSc(Hons), FRMetS

Meteorologist

Weather Commerce Ltd

On Twitter @MattHugo81

ha

Mr Hugo, did he not used to do forecasts for, best not give the name on here?

I wonder how he manages to get hold of the T+768 hour once a week ouput. Its normally guarded by both ECMWF and UK Met as closely as Fort Knox!

I have heard some people who are just ordinary mets get hold of the ECM 30 day forecast (might run to 32 days I suppose) as I've heard many mets over on US weather forums mention the 'Euro weeklies', so its clearly data that is out there if your high enough up the food chain. It doesn't give out huge amounts of info usually but you can usually get a decent enough idea. i suspect something similar is aviable here in Europe as well.

[damianslaw]

An unsettled outlook - maintaining the theme of september's weather so far with no day similiar to the next.

A cool showery weekend for many away from the SE. Early next week - a slow moving cold front will move down across the whole country lingering in southern areas on tuesday with a possible wave feature- so potential for some heavy rain here.

Medium term - tentative signs of slightly stronger heights building in from the south, but at this stage too early to say whether these will become robust enough to deflect the attentions of the atlantic. ECM is very keen tonight on strong heights building in from the south eventually and then ridging into the near continent bringing a potentially very settled dry spell - but this is a long way off.

Interesting to see the meto 30 day outlook is suggesting high pressure dominated first half to October - we've not seen a protracted lengthy settled spell since late april/early may - I do feel such a spell is long due and every chance of this happening sometime in October, recent octobers have seen some notable lengthy settled benign conditions.

[TonyH]

Hi Wales, they will probably have more idea by the end of this month, so keep tuned

[TonyH]

Needless to say it has been hot and dry this month, above 30c each day at Larnaca, and looking at ECM out to 240 hours it should stay hot, just with the chance of the odd storm.

It is likely that October will see a change to more unsettled conditions at some stage but it is still a very warm, fairly dry month, the average maxima still in the 80's F at Nicosia and with only an average of 25mm rain falling on 4 days, suggesting the odd storm as opposed to prolonged frontal rainfall (ref: 'The World Weather Guide' Pearce & Smith).

For what its worth GFS for the day you fly:

Edited September 17, 2011 by Tonyh

[johnholmes]

Taking a look at what may happen in about 10 days time using the 500mb anomaly charts, what do we find?

The 3 500mb anomaly charts on their latest issue for 10 days ahead, with NOAA going out to the 30th, and all show variations over the past few days.

The most consistent has been the NOAA issue with a broad westerly flow from the eastern seaboard into a flattish trough about over the UK. This started out west of the UK several days ago (in their forecast charts, and somewhat sharper). GFS has generally tended to follow this line although the trough has been sharper than shown on NOAA at times. ECMWF also fairly similar until this morning when it shows quite a meridional flow and also shows a +ve area over Europe causing the 500mb flow to be southerly over the UK.

Just how reliable this is I have no idea. It needs several more days and with all 3 going for a similar outlook before I would start taking bets on it.

.

.

Edited September 17, 2011 by johnholmes

[Isolated Frost]

Been watching the 12Z, and it doesn't even give anything above 16C in Durham on the whole run. Some cool maxima and mild minima. And gradually I saw southwesterlies with less mild energy than usual, 5-7C uppers reaching Britain with a warmer Southwesterly flow, I saw 0-4C uppers generally, and the beginning of some real cool pooling in Greenland, some -15C uppers later on. Definitely time to watch for cooler weather now - some real signs of October appearing.

[Gibby]

Hi folks. Been some pretty lively showers around these parts today and could be more tomorrow. Anyway here's a look at the 12z synoptics.

GFS shows Low pressure exiting eastwards into the North Sea tomorrow afternoon leaving a legacy of heavy, sometimes thundery showers to clear later. Things clear from the west later as a weak ridge crosses ahead of a warm front on Monday with more rain spreading east for all. For the North the cold front soon follows with a return to blustery showers in a chilly westerly breeze. Further South the cold front slows down with potential wave development meaning more rain and drizzle possible on Tuesday and Wednesday. Later in the week with pressure having risen to the south and winds backing SW or south with warmer air feeding NE over SE areas. A cold front then is shown to cross east through next weekend with a band of rain crossing east through Britain. FI tonight is virtually dominated by high pressure building from the SW with fine settled conditions eventually developing for all areas with the usual Autumn chances of mist and fog problems if skies clear.

UKMO shows a continuing unsettled theme running through to midweek with the current Low pressure over Northern Britain slipping SE into the North Sea tomorrow with showers slowly clearing from the west. As a weak ridge passes east tomorrow night the weather becomes dry for a while before rain moves in from the Atlantic early Monday subsequently spreading east to all areas through the day. Clearer weather will follw to the North and West with blustery showery conditions there while the South sees a slow moving cold front lie close by providing more extensive cloud cover and rain and drizzle at times. This eventually clears midweek to give a reasonable day or two in the south as temperatures recover somewhat. By 144hrs high pressure looks like receding away with Low pressure to the NW threatening troughs from off the Atlantic soon after.

Finally ECM mirrors the UKMO output infinitely up to 144hrs with rain at times for all in the first half of the week . The South then enjoys a couple of 'ok' sort of days Thursday/Friday before low pressure moves closer in from the Atlantic with rain bearing troughs crossing east over the first part of next weekend. Thereafter pressure remains relatively high to the SE with mild SW winds over the UK with further rainfall to the North and West areas from slow moving fronts while the south and east continues to enjoy the best of the weather with bright skies and a warm breeze. The run ends with recovering pressure though with a small cut off Low near SW Britain running the risk of rain there whilst most other areas become dry.

In Summary tonight the weather remains changeable with rain at times for all at some point or another. With pressure always highest just to the south and southeast of the UK some lengthy dry and rather warm periods could develop at times here while conversely deep Low pressure in the Atlantic could steer active troughs into the North and West which could well become slow moving for a while. All in all the weather remains very volatile so expect to see further shifts in the models mid term in the next few days.

[damianslaw]

5 posts in this thread so far today - either people are very uninterested in conditions at present - or probably the time of year itself (this is not a time for any extremes - indeed mid sept through to mid october is on average the most 'temperate' period of the year, too late for heatwaves or significant warmth - yes we can still just about see 80f but chances of such temps dwindle away rapidly from now on, and far too early for proper cold and snow - this is the most testing time of year for those seeking extreme weather).

The actual synoptics seem stuck in a groove with the same record playing over and over again - an unsettled changeable theme thanks to the atlantic being in quality control - troughs, fronts, showers, strong winds, average temps the order of the day - any suggestion of a pattern change always seems to be shown beyond the reliable timeframe. Typical early autumn conditions - fairly predictable fayre on offer.

[snowflakey]

ECM promise of a more settled FI scenario has seemed to have vanished this morning, but as Gibby mentioned HP is never to far away. I suspect the Jet will win the day on this occasion, but interesting times ahead I feel.

[Gibby]

Good morning. Here's a look at the morning output from GFS, UKMO and ECM.

GFS this morning shows today's showery low pressure moving away late today to leave the UK in a broad westerly flow with frontal troughs moving into the UK tomorrow with the cold front staggering SE over the south by midweek. So rain moves east through the UK tomorrow before showery and windy conditions spread back into the North through Tuesday and Wednesday. Later in the week the weather recovers in the south in response to high pressure south of the UK. Over the weekend a cold front crosses east bringing rain east for a while before as we move into FI high pressure develops to the SE. This brings warm air up from continental Europe which brings fine and warm weather with dry conditions for England and Wales with maybe some misty nights. The weather may stay a little breezy and unsettled in the far NW. At the far end of the run pressure slowly leaks away from Britain.

UKMO today also shows an unsettled start to the week with rain at times as Low pressure to the North controls the weather with a cold front slow moving near Southern Britain for a while Tuesday and Wednesday. Later in the week High pressure builds close to the South with fine, settled conditions developing here at least for a while before it begins to move away east by 144hrs.

ECM this morning also follows close to the UKMO route with a more settled look to things in the far SE for a while late in the week. As the ridge recedes east into Europe for a while an Atlantic depression moves NNE to the west of the UK spreading wind and rain over the UK before high pressure reasserts it's influence to the south from the south by the end of the run.

Things haven't changed much overnight model wise with the immediate 7 days looking like beginning unsettled with breezy, rainy conditions at times before the weather dries up from the South later in the week when it may also feel rather warm in the afternoons. Further on a NW/SE split seems likely with some pleasant dry and relatively warm weather likely in the SE while areas further North and West continue to see some rain at times.

[Backtrack]

5 posts in this thread so far today - either people are very uninterested in conditions at present - or probably the time of year itself (this is not a time for any extremes - indeed mid sept through to mid october is on average the most 'temperate' period of the year, too late for heatwaves or significant warmth - yes we can still just about see 80f but chances of such temps dwindle away rapidly from now on, and far too early for proper cold and snow - this is the most testing time of year for those seeking extreme weather).

The actual synoptics seem stuck in a groove with the same record playing over and over again - an unsettled changeable theme thanks to the atlantic being in quality control - troughs, fronts, showers, strong winds, average temps the order of the day - any suggestion of a pattern change always seems to be shown beyond the reliable timeframe. Typical early autumn conditions - fairly predictable fayre on offer.

Actually I don't agree. I find this time of the year quite exciting.

October especially, as that's when the transition from Summer to Autumn can truly be noticed among the trees and wildlife.

The reason I like this time of year is that you can still get a lovely warm day under the right conditions, and by night you can start to come close to your first ground frost. Perhaps a little early yet for an airfrost, but for everyone away from frost hollows and the highlands, they have yet to see a frost, and it will be interesting to see when the first one occurs.

And also yes you can get a heatwave at this time of year. The maximum temperature ever recorded for the UK is 35.6C, and that was in Doncaster, if that isn't a heatwave, then what is?

From what I first typed, and from what people have posted about the ECMWF 32 day charts, it's looking likely that the first half of October is looking settled? Well in my eyes that means cool by day (14-15C max) and cold by night (4 to 0C). Lovely!

[conor123]

The irony that FI on the 06z run would be far sunnier and more summery than most of summer was here.

[Summer Sun]

Just been looking at the 06z and it's looking likely that a rise in pressure should occur around Sunday and last right through FI.

http://www.wetterzen...s/Rtavn1801.png

http://www.wetterzen...s/Rtavn2041.png

This is the perfect set up below

http://www.wetterzen...s/Rtavn2521.png

http://www.wetterzen...s/Rtavn2761.png

http://www.wetterzen...s/Rtavn3001.png

http://www.wetterzen...s/Rtavn3241.png

http://www.wetterzen...s/Rtavn3481.png

http://www.wetterzen...s/Rtavn3721.png

Rain fall amounts will be extremly low, sunshine values should be above normal for many, with cold and maybe frosty nights

[Liam J]

Actually I don't agree. I find this time of the year quite exciting.

October especially, as that's when the transition from Summer to Autumn can truly be noticed among the trees and wildlife.

The reason I like this time of year is that you can still get a lovely warm day under the right conditions, and by night you can start to come close to your first ground frost. Perhaps a little early yet for an airfrost, but for everyone away from frost hollows and the highlands, they have yet to see a frost, and it will be interesting to see when the first one occurs.

And also yes you can get a heatwave at this time of year. The maximum temperature ever recorded for the UK is 35.6C, and that was in Doncaster, if that isn't a heatwave, then what is?

From what I first typed, and from what people have posted about the ECMWF 32 day charts, it's looking likely that the first half of October is looking settled? Well in my eyes that means cool by day (14-15C max) and cold by night (4 to 0C). Lovely!

Look up the definition of 'heatwave' - 'A continuous spell of abnormally hot weather' it may have hit 35.6c but it was not classed as a heatwave just a very hot day. Anyway when did the UK last experience a continuous spell of hot weather?

I do love this time of year as well BT, out and about with my dogs you get to see all the changes occuring all around you as we enter deeper into autumn.

Looking unsettled for the short - meduim term with rain at times and quite strong winds to the north as low pressure moves over or close to Northern Britain.

[Backtrack]

Look up the definition of 'heatwave' - 'A continuous spell of abnormally hot weather' it may have hit 35.6c but it was not classed as a heatwave just a very hot day. Anyway when did the UK last experience a continuous spell of hot weather?

I do love this time of year as well BT, out and about with my dogs you get to see all the changes occuring all around you as we enter deeper into autumn.

Looking unsettled for the short - meduim term with rain at times and quite strong winds to the north as low pressure moves over or close to Northern Britain.

I didn't check the length of time it was that hot, just assumed it wouldn't of been a one off day.

[MP-R]

A pretty quiet run for anything 'weather'. GFS FI continues to tease the high pressure that will undoubtedly be flattened out as we get nearer the time but would be lovely in May-August. Ideally we want the lows to come further south but the worst of the weather looks reserved for the northern half with the south perhaps drier and occasionally brighter.

[TonyH]

Surely its all 'weather' though. Irrespective of how interesting, exciting, etc., some perceive it?

Sure is interesting here today with a succession of downpours, giving one of the wettest days this year. Also the coolest day of the season, there is usually something of interest in our weather I find.

[95 Degrees]

Surely its all 'weather' though. Irrespective of how interesting, exciting, etc., some perceive it?

Sure is interesting here today with a succession of downpours, giving one of the wettest days this year. Also the coolest day of the season, there is usually something of interest in our weather I find.

Hardly, considering that we had 3 months of uninteresting weather recently (June-September) no gale force wind just blustery, no unusual cool/Atlantic rain, no heat, no storms, nothing was above average or way below, everything above/just below average with play it safe weather and it would be predictable if the models are right and we do get a long settled spell just after the ending of summer when it had 3 months where it could've turned up, hopefully winter will be more interesting, it doesn't eve have to be cold, just something remotely interesting because British summers have been very predictable lately.

[Thundery wintry showers]

I think this is one area where we're never going to get cross-agreement- it all depends on what we find "interesting" and where we live. All of us will be able to cite kinds of weather that interest us more than others, but many of the more "hardcore" weather enthusiasts can usually find something of interest even in the most non-descript spells- sunsets, unusual cloud formations for example.

Looking at the model outputs and the teleconnection signals, there is a suggestion that we could have a warm spell during the last five days or so of September with high pressure temporarily building to the east allowing southerly winds in. It's not a certainty, especially not at this range, but there is a fair amount of support for it. The main way in which the warm southerly could fail is if the trough ends up too far east leaving us in a cyclonic south-westerly regime while central Europe gets the southerly, which is what tonight's GFS 12Z is showing. I can see, in contrast, that the ECMWF 12Z out to T+168 is placing the trough well to the west allowing that southerly in.

Before that, the cold front will move erratically SE over the next two days, followed by sunshine and a scattering of showers on Wednesday/Thursday, with the low pressure and its associated front getting further south than was suggested on earlier runs.

[Gibby]

Good evening.

GFS tonight shows a series of fronts crossing the UK in the next 48hrs with rain and drizzle affecting most areas last to clear from the southeast late Tuesday. Wednesday shows a strong westerly flow over the Uk with showers in the North but drier in the South. This dry weather lasts for the south through Thursday and much of Friday before high pressure to the south moves away east allowing a frontal trough to move into Britain over the weekend. Thereafter there would be a few more unsettled and windy days before high pressure establishes itself near the UK before the end of the run.

UKMO also shows unsettled weather up until mdweek when pressure rises from the south later in the week. So after a few more rain affected days the south will enjoy a drier end to the week with a rise in temperatures though whether it lasts throughout the weekend looks debateable.

ECM finally shows the same general pattern with rain around until midweek when for the second week on a row Thursday looks the best day of the week before pressure falls and unsettled weather returns before the weekend though with warm conditions for a while in the south and east.

Tonight looks a little less optimistic again for fine weather fans as High pressure keeps too far south to affect the weather away from the extreme south. There would remain high pressure to the south and its position would serve to steer warm conditions over Southern and Eastern areas at times from later this week. There would be some rain for many on occasion though amounts of rain in the SE would be small for most of the time.

Edited September 18, 2011 by Gibby