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phil nw.

Model Output Discussion 26/08/2012

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A brand new thread seems overdue, as others have said, so here we are then ready for the 12Z outputs.

As ever please keep on topic by keeping to what the outputs actually show.

Thanks all.

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The combined 00z ens graph for London indicating a dry and somewhat warmer period from next weekend.

post-2026-0-71403900-1345994130_thumb.gipost-2026-0-40805300-1345994172_thumb.gi

underlining the modelling of the building Azores High as we enter September.

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I thought the GFS 06z was an excellent run for at least the southern half of the uk beyond thursday but the north would have to wait until after next weekend before seeing much improvement but with good agreement now between the gfs 00z-06z and ecm 00z, the chance of a fine and warm early september now appears to be pretty good but as ever, a bit of caution is required as no professional forecaster would stick their neck out yet and say an anticyclonic spell was nailed on but from a very amateur point of view, the model trends are promising a golden start to autumn for many.

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In the previous thread there were a couple of comments about warm Septembers being followed by cold winters.

As always the answer is there is no correlation between September weather types and the following winter. This is true of any month and any attempt to correlate weather further down the line.

As Pete has posted the forecasts which GP does are not based on any such link.

The overall pattern from 500mb charts suggests that a settled spell for much if not for almost all the UK looks about a 75% probability from 31/08 into 7-8 September on current outputs.

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Hi Folks. I've had several emails recently from posters in the other forum asking why I no longer include my Model Output reports here on Netweather anymore. Other than time restraints and general oversights I can offer no real answers to this but am pleased to say that as from tonight I will post them here once more and try to continue them through the exciting winter months. The first one will be shortly after 8pm.

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12z maintains a build of high pressure but it is more similar to yesterdays output in that it is further north, and ridges in later than some previous runs. This could either mean the window for warmth and sunny weather will be shortened come the time, and perhaps northern Engand North Wales will not benefit in terms of sunshine.

However it is still not close enough be immune from any major changes to the developing pattern.

12z GFS seems more in line with the 0z ECM.

UKMO 12z similar.

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High pressue still on track to arrive on Friday but i think this will be a transitional sort of day with the cool air still hanging on in the east and the warmer uppers making their way across the UK. By Saturday the transition is complete.

Recm1201.gif

Recm1441.gif

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High pressure dominates from Friday

Recm1681.gif

Recm1921.gif

Recm2161.gif

Should be warm as well

Recm2162.gif

Recm2401.gif

Recm2402.gif

Lovely start to September

good.gif

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Hi Guys. Here's the first of my reports on the models after a long break.

All models are in agreement in the sequence of weather over the coming 5 working days. A ridge of High pressure is moving away East from Eastern Britain with freshening Southerly winds developing in the West in association of a deep Low pressure moving NE close to the NW. Fronts moving slowly East will bring rain to the West late tonight marching Eastwards tomorrow to all but the far SE by late afternoon. Some of the rain will be heavy. The front will clear East overnight tomorrow. All models show Tuesday with a somewhat showery SW flow with few if any showers in the South. Wednesday may start dry but a further Low and active fronts cross East through the latter half of the day bringing rain and squally winds Eastwards with it. Thursday sees the beginning of a marked improvement in the weather in the South with initial showers in Eastern Britain clearing away through the day. Further North a ridge passes too giving a dry interlude before a warm front crosses East on Friday with rain and drizzle here. Further South the working week ends with light Westerly winds, some sunny breaks and a lot of cloud too in a light West wind.

GFS then shows 4-5 days of High pressure close to Southern Britain dominating the weather with some fine and bright weather in variable amounts of cloud. The North sees cloud and a little rain early in the weekend die away with a chance for Northern regions too to enjoy in the fine weather in the South by midweek of week 2. As we move through FI the operational run shows High pressure moving slowly away East leaving much of the UK in nomansland with fairly slack pressure, something of a weakness coming up from the South and warm conditions at the surface. A lot of dry weather would prevail though the chance of a shower towards the South at times increases. In far FI Low pressure takes control off the Atlantic with rain and showers developing for all in cooler, breezier air.

The GFS Ensembles show a sharp warm up at the turn of the month with 850’s above the long term mean for the rest of the run aided by a warm outlier from the operational. There is a lot of spread in the ensembles from mid run though with little precipitation shown for the South at least it looks like models cannot decide the position of the High and what temperature of air that gets entrained within it rather than any return to disturbed weather. A few members including the control for a while show some quite chilly uppers as we move further into the month.

The Jet Stream Forecast shows the current track running East over Northern France and Southern Britain continuing for a while longer before it ridges North over the Atlantic by next weekend and sets up blowing East over or to the North of Scotland by the start of the new week.

UKMO tonight shows High pressure centred just off SW England by noon next Saturday with fine and settled conditions having developed over the South with some warm sunshine. The North still lies under the influence of moist Westerly winds with hill and coastal fog and some drizzly rain towards Western Scotland.

ECM shows High pressure as well down near Brest on Saturday with Westerly winds over all of Britain. With the air being rather moist cloud amounts would be large for most and thick enough in the NW for some hill coastal fog and drizzle. From Sunday onwards though ECM looks much better than this morning with High pressure holding firm as it transfers gently eastwards with the fine, warm and bright conditions in the South extending further North early next week. The run ends at midweek with High pressure slowly declining to the East with falling pressure to the West offering the possibility only of a breakdown late in the week.

In Summary the change in the weather is still very much on the cards though Northern areas will have to be patient. High pressure developing near to the South at the weekend looks like hanging about for a while delivering fine and warm early Autumn conditions to the South from Saturday and areas further North too as we enter the English return to school week. Easy to forget but we still have four or five more days of comparatively poor weather to get through first.

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High pressure dominates from Friday

Recm2402.gif

Lovely start to September

good.gif

The last chart, thunderstorm potential?

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Gibby -- "Hi Guys. Here's the first of my reports on the models after a long break."

Thanks Gibby for your useful reports once again. Glad they are back. . . Like other Northerners -- "will try to be patient". -- as you suggest!

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A very promising ECM 12z run from next weekend onwards for most of the uk, only the far nw and n of scotland would miss out on the warm anticyclonic spell further south but we still have a few unsettled days to come first with tomorrow bringing wet and windy weather to most areas by the end of the day but then tuesday brings a window of fine weather before a showery trough spreads east on wednesday, thursday brings the first signs of the big change with showers clearing away to the far northeast and pressure rising from the southwest, and that trend gathers pace from friday onwards but the north of the uk will probably have a slower transition to the anticyclonic spell but then next week looks warm and sunny with light winds for many.

post-4783-0-58845200-1346010745_thumb.pn

post-4783-0-52108700-1346010781_thumb.pn

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I like tonight's GFS. Not as wet this week as first thought, high pressure establishing by Friday and lasting into the first week of September. FI presents the possibility of some thundery activity (emphasis on possibility) before very unsettled conditions arrive by about the 10th from the Atlantic. That would be a pretty standard start to September and would deliver something for everyone if it came off.

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A very settled Gfs 00z from the weekend onwards in southern areas, a few unsettled blips in northern britain but really it's a glorious early autumn outlook with plenty of warm sunshine and light winds. The gfs 00z shows about a week of unbroken fine weather in the south with yet more azores high pressure ridging northeast once the main high pressure cell pulls away east but low pressure near iceland does disrupt the fine spell in scotland by the end of next week. As for this week, after today's rain, tomorrow has a window of fine weather but then a showery trough by midweek, then pressure will rise but scotland will have to wait for the low near iceland to clear off northeast and then they will join the south in the warm and sunny outlook but with high pressure, there will be some mist and fog overnight with minima in single digit celsius but then the airflow warms up during next week so the nights will also become warmer and more humid.

post-4783-0-62331900-1346050675_thumb.pn

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Good morning. Here’s my interpretation of the 00zs today.

All models support another unsettled week to come with cloud and rain in association with a cold front moving slowly East today and tonight. The rain may be heavy in places clearing to drier weather in the West overnight. Tuesday shows a SW flow with sunny periods and a lot of dry and bright weather over England and Wales while showers occur towards Western and Northern parts. Wednesday sees winds backing off towards the South again as another very active trough swings East through the day with rain and squally winds moving West to East late in the day and overnight Wednesday. Thursday sees this feature only slowly moving away East with another unsettled day likely in a developing cool NW breeze. By Friday pressure has risen strongly everywhere with High pressure developing down to the SW. A much drier and brighter day is likely for the South while Northern areas North of the Midlands cloud over later as a warm front moves in from the West with rain for many.

GFS then shows a rather cloudy Saturday with a front slow to clear the East. Some residual rain and drizzle will leave the East early in the day with drier and brighter weather following especially in the lee of high ground. It would become more humid, a trend which continues over the following days as High pressure takes control centring over the UK by Monday. A lot of cloud looks likely to be trapped within it but with time this should break up with some warm sunshine as we enter next week. Through FI today a slow passage of High pressure away eastwards is shown with a slow but gradual return to an Atlantic influence as Low pressure moves over Britain by the end of the run with rain at times.

The GFS Ensembles show a substantial warm up as we enter the new month with average 850’s staying above normal for the rest of the run. The operational and control runs were a warm outliers for a time later on. Even Scotland shows warmer than average uppers too once the new month begins and what’s more noticeable is there is programmed to be much less rainfall than has been witnessed for some time in all locations from the start of he warmer period.

The Jet Stream Forecast shows the current West to East flow across Sputhern Britain and France continuing for a few more days before ridging strongly North in the Atlantic late this week setting up a position North of Scotland thereafter.

UKMO closes its run on Sunday with High pressure centred over NW France with a light Westerly flow in the South and a breezier Westerly further North. Still a lot of cloud up here with maybe some rain in the far North while Southern areas see brighter and dry conditions where it will begin to feel quite warm.

ECM too shows High pressure down to the SW for Sunday with a Westerly flow over the UK with a mixture of cloud (sometimes rather a lot) and sunny intervals. Early in the week the weather brightens with more sunshine and conditions by day becoming rather warm though some cooler nights look likely with the risk of mist and fog in the early mornings. Later in the week the weather remains dry and warm though with High pressure moving away East things begin to look more unsettled by Thursday as Atlantic fronts approach from the West.

In Summary the weather looks like becoming settled and dry as we move out of August and into September. High pressure should dominate with just cloud cover being a pest as long as we keep an Atlantic drift over Britain. Innitially this cloud would remain thick enough to promote rain and drizzle in the North next weekend. As the High drifts East of Britain through next week things should become warmer and sunnier as a drier continental feed assists in the break up of cloud though of course once this happens the door is open to the atlantic as ECM shows towards the end of its run and GFS too late on. Nevertheless, still a period of very useable weather to look forward to with a break from all the recent rainfall for most.

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Following on from the usual first class summary of the models by Gibby (welcome back) and taking a look further ahead using the inevitable 500mb anomaly charts, ec-gfs link below from this morning

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

This is a similar prediction to what all 3 have been showing for the past 4-5 days. This does give a reasonable confidence in this pattern being there. By the weekend it should be in place, albeit as Gibby suggests more for southern areas at first but extending through next week into most of the UK. Essentially a dry spell with a good deal of sunshine for many and probably lasting for the first 10 days of September possibly longer. Just how warm and how much sunshine is for the synoptic models as we get closer to the time-details on weak fronts in the NW and low level inshore flows and possibe early mist/fog etc.

A promising look for the farmers anyway who in a number of places are behind their summer schedule.

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Following on from the usual first class summary of the models by Gibby (welcome back) and taking a look further ahead using the inevitable 500mb anomaly charts, ec-gfs link below from this morning

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

This is a similar prediction to what all 3 have been showing for the past 4-5 days. This does give a reasonable confidence in this pattern being there. By the weekend it should be in place, albeit as Gibby suggests more for southern areas at first but extending through next week into most of the UK. Essentially a dry spell with a good deal of sunshine for many and probably lasting for the first 10 days of September possibly longer. Just how warm and how much sunshine is for the synoptic models as we get closer to the time-details on weak fronts in the NW and low level inshore flows and possibe early mist/fog etc.

A promising look for the farmers anyway who in a number of places are behind their summer schedule.

John I think I speak for every farmer in the UK who will thank you for your last sentence after such challenging weather in spring and early summer.

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best you wait to see if I am right but I do hope I am; the 500mb charts are generally pretty good when consistent over several days, so good luck

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High pressure dominates through the first week of september on the 06z this morning, in FI it turns more unsettled during the 2nd week, but before that we have a settled week coming up just in time for the schools going back

good.gif

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High pressure dominates through the first week of september on the 06z this morning, in FI it turns more unsettled during the 2nd week, but before that we have a settled week coming up just in time for the schools going back

good.gif

Indeed, much in line with my own thoughts really. A settled first half of the month before heights to the NW and a Southerly tracking jet take hold again. Just a pity this week isn't nice since it's the last week of the school holidays

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Interesting times ahead, as we head into September we are likely to see a settled pattern emerging. It's pretty likely that the first 7-10 days will be dominanted by a UK/Scandi ridge with the trough well out into the atlantic however where do we go thereafter?

Currently we have quite an amplified phase 3-4 MJO pattern, this generally indicates a trough pattern to our west and a ridge to our east for the end of august/beginning of september.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml

http://raleighwx.americanwx.com/MJO/AugustPhase3500mb.gif

As we head into September, the MJO is likely to become less amplified, however El nino is starting to show its hand and the early September pattern predicted is very typical of this.

The wildcard here is angular momentum, as el nino develops expect some sharp rises during the autumn, I just wonder whether a return to unsettled conditions shown in the FI realms of the models is a bit too optimistic.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltotaam.sig.90day.gif

You can see from the link above that if we rewind a year, angular momentum rapidly increases during September, could sun/warm lovers be in for a treat this September? Its a distinct possibility!

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Interesting times ahead, as we head into September we are likely to see a settled pattern emerging. It's pretty likely that the first 7-10 days will be dominanted by a UK/Scandi ridge with the trough well out into the atlantic however where do we go thereafter?

Currently we have quite an amplified phase 3-4 MJO pattern, this generally indicates a trough pattern to our west and a ridge to our east for the end of august/beginning of september.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml

http://raleighwx.americanwx.com/MJO/AugustPhase3500mb.gif

As we head into September, the MJO is likely to become less amplified, however El nino is starting to show its hand and the early September pattern predicted is very typical of this.

The wildcard here is angular momentum, as el nino develops expect some sharp rises during the autumn, I just wonder whether a return to unsettled conditions shown in the FI realms of the models is a bit too optimistic.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltotaam.sig.90day.gif

You can see from the link above that if we rewind a year, angular momentum rapidly increases during September, could sun/warm lovers be in for a treat this September? Its a distinct possibility!

A mainly settled, warm September has been the theme for the past several years now....infact, this year is seemingly closely following the pattern of the past few years in general; an early season very warm and settled spell, a wet June and July, an improving August and a warm, settled September. There has been very little deviation away from this repeating pattern in recent years.

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The GFS 6z is quite a remarkable run. The whole of next week would be very warm and settled almost nationwide with 10c upper temperatures sat over the whole country. Gradually throughout the week the high edges east which would drag up some very high temperatures from the continent. I would say that 30c isnt out of the question with continental Europe looking likely to turn very warm too. The fine spell breaks down on Sunday 9th so the 6z brings 7/8 days of very warm conditions.

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Fully agree,

The GFS 6Z is an epic run from the weekend onwards, only the very far north maybe missing out on the very warm and sunny anticyclonic spell, more or less sunshine all the way with a continental flow eventually, a brilliant first 10 days or so of September which will put the pathetic first 6 weeks of this summer to shame, it's just a bit of a pity it's so late with the nights now beginning to draw in.

post-4783-0-92155700-1346081957_thumb.pn

post-4783-0-54324600-1346081986_thumb.pn

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Fully agree,

The GFS 6Z is an epic run from the weekend onwards, only the very far north maybe missing out on the very warm and sunny anticyclonic spell, more or less sunshine all the way with a continental flow eventually, a brilliant first 10 days or so of September which will put the pathetic first 6 weeks of this summer to shame, it's just a bit of a pity it's so late with the nights now beginning to draw in.

Thankfully the days are still long enough to bring some decent heat as the chart you posted shows

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