Model Output Discussion 18z 28/07/13

[Summer Sun]

High pressure just close enough to drift over the UK at t240 but this time it brings a north westerly flow for a time so bright for many but feeling fresher given the wind direction and once again the Atlantic remains very very quiet

 

Edited September 3, 2013 by Summer Sun

[Summer Sun]

Here is the latest on the models from Gibby

 

Good evening everyone. Here is the report on the 12 noon outputs from GFS, UKMO, GEM, NAVGEM and ECM for tonight Tuesday September 3rd 2013.

 

All models show 24-48 hrs more of the current summer spell of weather currently being enjoyed by Southern and Eastern Britain. The cloudier West and North will see at least some brightness and warmth tomorrow as drier air currently arriving across the South extends further North. With still air and September nights fog is a rank certainty in the current setup and tonight will be no exception, mostly across the South of Britain. Through Friday and the weekend the weather transforms itself quickly as a front strengthens over Eastern England as Low pressure forms across it on Friday. Many areas will become substantially cooler on Friday with spells of thundery rain and a chill North wind. The weekend may see more showery conditions and less cool weather but some of the showers will be heavy slow moving and thundery as Low pressure looks like lying over the top of the British Isles.

 

GFS then shows changeable conditions throughout next week and the end of the run with various areas of Low pressure and fronts never far from the UK. There would no doubt be some dry and bright weather from time to time but it would not to be relied upon as further rain or showers would most certainly arrive within days on the basis of tonight's GFS operational output. Temperatures would be close to average for much of the time but in any prolonged periods of rain it would feel chilly.

 

The GFS Ensembles show some very warm uppers over the coming days before a marked cool down with much spread thereafter. There will be rain accompanying the fall off reducing in quantity the deeper into the run we travel both North and South. The operational was a cool outlier late in the run in the South.

 

The Jet Stream shows a split in the flow over the coming days with the split encircling the UK in association with the UK Low pressure before settling on a West to East flow across the Atlantic and over the British Isles.

 

UKMO tonight shows Low pressure well established over the UK early next week with rain or showers scattered about the entire UK and temperatures well down on recent values.

 

GEM tonight shows Low pressure making Southern Britain it's home next week with spells of rain and showers encircling around the Low pressure over Southern Britain and some areas further North too at times while the far north stays drier and brighter and possible rather warm in the sheltered West and in any brightness.

 

NAVGEM too keeps Low pressure close to the SW with rain at times in the South and SW. Northern and some Eastern areas will be the best places to see the best of the dry and brighter conditions available.

 

ECM tonight shows Low pressure close to SE England at the weekend moving NW then back SE next week maintaining several days of cloudy weather with showers or outbreaks of rain in places with nowhere immune. Later in the run pressure builds again from off the Atlantic with dry and bright weather returning for many to end the run.

 

In Summary tonight the pattern looks like becoming quite complex once the certainty of Low pressure at the weekend arrives. With such a cut off Low center it could drift almost anywhere with the models illustrating different positions between them for the Low center with any resulting longer term predictions of the weather beyond next week foolhardy at this range and given that such complex synoptics that will be in place next week. I think we can expect many ups and downs between the models on the events beyond next week over the coming days before an eventual agreed pattern emerges.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

 

[legritter]

Good  evening gang ,iv not posted for a while but here goes ,a brilliant start to September ,certainly cheerfull weather with most other news not so cheerfull .looking at modells and data after friday we have some action weather which most forecast modells agree on but as usual low pressure centres and tracks all slightly different .there could be some headline news regarding rainfall so certainly an interesting time a coming .Fax charts as usual come into play ,and it was great to see a fax chart with Correction on it ,to me there is a certain work of art looking at these charts .what ever is the outcome past next week its certainly down hill now ,but we all want to go there dont we ,bring on the 528 dam line ,i did see it a few days ago on a chart but not sure where ,cheers gang 

[draztik]

i think this has been the closest we have seen the cold air mass (528)to the UK.

Edited September 3, 2013 by draztik

[mushymanrob]

well the notion of a true cut off low has now all but gone if the latest runs are to be believed (although i post before the 00z ecm comes out). dont forget, it was the ukmo that first dropped the cut off low option so if this becomes reality then thats a big 'well done'.

 

enjoy today and for some tomorrow, its unlikely to get as warm again until next may at the earliest.

[Man With Beard]

It still feels a bit like "pin the tail on the donkey", but the models are getting a little closer to agreeing on the weekend's depression. No-one exempt from the risk of rain it seems:

 

 

ECM's "pick and mix" FI brings back summer next week

Edited September 4, 2013 by rjbw

[Captain Shortwave]

ECM is interesting this morning, it ejects the cut off low quite quickly back into the Atlantic jet meaning

 

High pressure builds in a lot quicker again, this trend needs to be watched.

[draztik]

The gfs ensembles show the likely evolution to be this at t174

so, if the ecm verifies, the gfs is incredibly lacking! I realise the models tend to be struggling atm, as we see cooling in the atmosphere, but that's quite a difference in trend (ecm) from the ensembles of the gfs and ggem.

[The PIT]

The gfs ensembles show the likely evolution to be this at t174

so, if the ecm verifies, the gfs is incredibly lacking! I realise the models tend to be struggling atm, as we see cooling in the atmosphere, but that's quite a difference in trend (ecm) from the ensembles of the gfs and ggem.

That's why it's FI land. Since a big divergence starts much earlier I wouldn't take much notice of the charts and would expect a lot of chopping and changing to in the period from T120 from both models.

Edited September 4, 2013 by The PIT

[Frosty.]

Let's not write off the chances of another very summery spell, this morning's Ecm 00z is looking very nice for next week with a lot more warm and sunny weather to come after the unsettled and cooler blip with the PFJ shunted to the north of the uk, I certainly won't be giving up for a while yet since we can still break 80F in early october if the synoptics are right.

Edited September 4, 2013 by Frosty.

[shedhead]

The gfs ensembles show the likely evolution to be this at t174

so, if the ecm verifies, the gfs is incredibly lacking! I realise the models tend to be struggling atm, as we see cooling in the atmosphere, but that's quite a difference in trend (ecm) from the ensembles of the gfs and ggem.

Indeed...ECM offers a straw to clutch this morning, but it's a tenuous one to say the least. Still think we are looking down the barrel of a protracted unsettled spell here, one that will probably last until at least mid month and maybe even well into week 3, at least across the southern half of the UK. 

[Cecil Hogmanay Melchett]

Indeed...ECM offers a straw to clutch this morning, but it's a tenuous one to say the least. Still think we are looking down the barrel of a protracted unsettled spell here, one that will probably last until at least mid month and maybe even well into week 3, at least across the southern half of the UK. 

I agree!! But then again after a very very dry warm summer i dont think many of us will mind an unsettled spell of weather.In fact with temps around 25degrees here today i actually would welcome a cooler spell of weather,it was uncomfortable last night.

Hopefully GFS/UKMO are nearer the mark although i think its being far to optimistic to be suggesting unsettled into week 3.

[Polar Maritime]

As the BBC keep saying, "drastic changes by the weekend". The models beyond this are really struggling with this up coming pattern change. An interesting few days model watching coming up..

[No Balls Like Snow Balls]

The NW looks really wet this weekend with 36 hours of rain a possibility. Latest ECM prceip charts below:-

 

 

 

 

 

 

 

Edited September 4, 2013 by No balls like Snow Balls

[Biggin]

As the BBC keep saying, "drastic changes by the weekend". The models beyond this are really struggling with this up coming pattern change. An interesting few days model watching coming up..

Yes the models are struggling to get a handle on the weekend and post weekend. Been a lovely summer here.But once a few TS and Hurricanes start coming into the mix, I can see the models (and dare I say Draztic and Shedhead) eventually getting their "long predicted but never quite getting there", Summer breakdown.  I am quite surprised how often these last couple of months the models and others gloomy predictions of end of summery weather amounted to very little. 

Edited September 4, 2013 by Biggin

[Tamara]

As the BBC keep saying, "drastic changes by the weekend". The models beyond this are really struggling with this up coming pattern change. An interesting few days model watching coming up..

It seems the BBC are getting a bit like the Daily Express...but that is for another thread.

 

Its true of course that the weather is in for a change for sure this weekend, but I see no reason at all not to think that the pattern will rinse and re-set back to something quite familiar once more. This is the second dogs breakfast low pressure system in as many weeks, and even without being any kind of expert, there is a certain predictability of the meal that they scramble over these features.

 

The re-set from the west is fairly inevitable later next week and I think further reasonably settled weather should emerge at least for parts of southern UK. Rather more changeable and less settled in NW 'erm most parts perhaps.

 

The EPS members for the midweek period next week show a mix of possibilities but there is no suggestion of any long lasting  general breakdown for the UK. I think that the theme of overplaying the weekend low is evident here and it is unlikely to hang around as much as the models suggest at face value. Another example of being wise not to take operational output at face value

 

.

 

And even if it does phase with the next jet streak from the atlantic its effects are not likely to extensive with the PFJ, much as Frosty suggests, still kept to the north of the UK

[Weather Boy]

The NW looks really wet this weekend with 36 hours of rain a possibility. Latest ECM prceip charts below:-

 

130904_0000_78.png

 

130904_0000_84.png

 

130904_0000_90.png

 

130904_0000_96.png

 

130904_0000_102.png

 

130904_0000_108.png

 

130904_0000_114.png

 

Interesting that the focus of the wet weather has really changed since the start of the week when it looked as if the southern half of the UK would cop it, with the possibility of the Low being either over S England or out to the South or SW of the country.

 

Now, it looks as if East Anglia could be be the place to be if you want to avoid the worst of the rain (although I guess they will get it on Friday) whereas the NW of England, NI and SW Scotland look to be worst affected.  If you had assumed that the models from Monday were correct, you would have thought that they were the favoured spots. 

 

It just shows how difficult it is to nail down the detail even at a reasonably close timeframe.  However, at this range I suspect that there is not likely to be a huge alteration beyond the principle that East and South-east best and NW England worst, but I suppose things could still change.

 

If you look at the graphic for Saturday on last night's BBC forecast, it looked as if those SE of a line from Humber to Severn could get a decent day Saturday, but the words used to illustrate conveyed how uncertain all that is.

 

Edit: and God knows why some people are trying to make predictions for next week and even the rest of the month in some cases when we barely have an idea of this weekend just now!

Edited September 4, 2013 by Weather Boy

[Summer Sun]

Tuesday onwards looks very nice from ECM

 

[Weather Boy]

Tuesday onwards looks very nice from ECM

 

 

Yes, as Frosty would say - BANK

[Summer Sun]

Here is the latest from Gibby on the models

 

Good morning. Here is today's edition of the review of the midnight outputs from GFS, The Fax Charts, UKMO, GEM, NAVGEM and ECM for today Wednesday September 4th 2013.

 

All models show a High pressure area exiting the SE of England today on its way across Europe. Very warm air around this feature is shown to blow North across the UK today with dry and sunny weather away from the NW where a front approaches later in the day with attendant occasional rain. Through tonight and tomorrow this is shown to move slowly SE across Britain reaching Northern and Western parts of England and Wales by evening and areas further East and SE overnight. On Friday a Low pressure forms near the East in association with this front intensifying the rainfall across England and Wales and dragging cool Northerly breezes across all areas. All models then show Low pressure close to the UK over the weekend with rain or showers for all at times.

 

The Fax Charts show the general progression of events listed above as troughs move down from the NW and develop a Low pressure close to SE England within it's core deepening and spiraling rain and showers across the UK over the weekend in much cooler air.

 

GFS begins next week with Low pressure over Southern Britain where it is maintained for most of the week with showers each day across the South whereas the North remains more likely to see less showers and longer drier spells in average temperatures. By the weekend a NW flow develops behind the final exit of the trough over the South renewing the trend towards drier conditions as High pressure from the SW again becomes influential with dry and benign weather. A hint of something a little more changeable again is hinted at by the end of the run.

 

The GFS Ensembles shows temperatures over the South reverting close to the seasonal average from the weekend with rain at times. The North is shown to maintain 850 temperature values more likely above average although this may not always be reflected at the surface given cloud and possible rainfall at times which is shown Nationally from Friday. The spread is slightly less big this morning apart from the customary wide spread at the end of the run.

 

The Jet Stream splits from it's flow north of the UK in the next few days as it cyclonically blows around the UK in the area of the cut off low over Southern Britain at the weekend. It takes a long time for this to simplify into a more direct West to East motion across the UK later in the run.

 

UKMO today shows Low pressure having been over the UK for some days exiting East on Tuesday with High pressure building from the West. Tuesday is still likely to be showery across the UK but these will probably die out from the West through the day.

 

GEM today shows low pressure over the UK sinking away South having spent several days over the UK giving rain and showers for all. By the end of the run with the Low having shifted its axis down to the SW and High pressure over Scandinavia it's the SW who would maintain the risk of showers while Northern and Eastern areas become dry and quite warm in the sheltered west as any sunshine breaks through.

 

NAVGEM shows the Low filling in situ over the UK next week maintaining showery weather for all for some considerable time lessening by midweek as pressure begins to rise from the SW squeezing the remaining life out of the feature with drier and brighter conditions developing.

 

ECM shows High pressure building back NE strongly next week as the Low moves East across the UK in the form of a trough early in the week followed by dry and fine weather with overnight mist and fog likely in the South while the far NW may stay cloudy in a slowly increasing SW wind in 10 days time.

 

In Summary the models are really struggling with the sequence of events from as early as this weekend. As is usual in September as seasonal cooling takes place across the Northern hemisphere synoptics can often become complex and then add the injection of ex tropical storms in the Western Atlantic and you have the ideal cocktail for some wildly fluctuating synoptics shown from run to run and more certainly model to model. That is exactly what we have this morning with everything shown this morning ranging from the return of late Summer from ECM next week to the more unsettled and potentially thundery GEM for the SW with pressure High over Scandinavia. There is a bias slightly towards High pressure building back from the SW later next week but until I see this still being shown at the weekend's output and because of the uncertainties I have noted cautious optimism to this evolution might be the best approach.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[No Balls Like Snow Balls]

Let's not write off the chances of another very summery spell, this morning's Ecm 00z is looking very nice for next week with a lot more warm and sunny weather to come after the unsettled and cooler blip with the PFJ shunted to the north of the uk, I certainly won't be giving up for a while yet since we can still break 80F in early october if the synoptics are right.

 

The latest ECM daytime temps to go with next weeks ECM high pressure 00Z charts are as follows:-

 

London, Tues - Fri, 18c-20c

Manchester, Tues - Fri, 16c-18c

Glasgow, Tues - Fri, 14c - 18c 

 

Feeling pleasent in any sunshine, but certainly no where near the the dizzying heights of this week if the op run and temps were to verify as is.

Edited September 4, 2013 by No balls like Snow Balls

[Frosty.]

Whilst the cool & unsettled weekend is nailed, the GEFS 00z mean does show a recovery next week, the shallow trough fills in situ and dissolves with pressure slowly rising, especially for the east/se where the best of the weather would be, the mean shows a very slack slow moving pattern next week and what winds there are would be sourced from the south or at least south of west so temperatures would bounce back to very respectable levels after the cooler showery blip, there would be a tendancy for the north & west of the BI to slowly become more unsettled over a period of time but changes would be slow, eventually the mean ends up with a north-south split, the north of the uk being cooler and more unsettled with an oceanic flow and the south of the uk where it would be progressively more settled and warmer with less in the way of unsettled weather overall, even by the end of the run, the PFJ is still keeping the really autumnal weather to the north of the BI, we could squeeze a decent amount of summery weather yet before autumn really kicks in.

[No Balls Like Snow Balls]

GFS 06Z keeps it unsettled into early next week.

 

 

 

 

 

Another rain event Monday into Tuesday.

 

LP hangs around welL into deepest darkest FI. Not anything like the ECM 00Z

Edited September 4, 2013 by No balls like Snow Balls

[Frosty.]

The Ecm 00z ensemble mean, as with the GEFS 00z mean, shows a recovery after the weekend's cool shallow trough fills in situ and dissolves although there remains a residue of instability which means the risk of showers, some heavy and thundery would still be present, however, at least the temperatures would bounce back to warmer levels with increasing humidity and sunshine amounts would also increase, the pressure pattern next week looks very sluggish with the PFJ well out of the picture to the northwest, it means the weather pattern next week would be more akin to summer than autumn although with light winds and where skies clear overnight, the risk of mist & fog would increase but soon burning off during the days since the sun still has plenty of power, all in all, next week looks decent once the weekend trough loses it's grip early next week and  the ecm mean shows high pressure encroaching across the south later in the period.

Edited September 4, 2013 by Frosty.

[shedhead]

Even by mid month the 06GFS keeps a fairly noticable 500mb height anom to the S, so whilst it's perhaps tempting to get suckered into ECM's much drier, more settled picture caution is advised. 

 

 

Edited September 4, 2013 by shedhead