Model Output Discussion 18z 28/07/13

[Milhouse]

Summer on its way back after the recent cooler spell.

 

[Gaz1985]

Summer on its way back after the recent cooler spell.

 

 

Good, been a definite chill in the air today here but hopefully proper Autumnal changes will hold off for a while. 

[Summer Sun]

As you were from UKMO with high pressure building in again later in the week

 

[Summer Sun]

8 days away but a week Monday would start with a frost in some sheltered parts across the north with these temps

 

[Summer Sun]

And summer warmth continues once again from ECM

 

 

[draztik]

September looks to be an extension of what we have seen since July.., in some fashion or another! Looks like it will be October before the Atlantic gets going, and even that is no sure thing!

as long as we don't see temps nearing 28, im happy! 20-25, would be very pleasant indeed.

[Summer Sun]

ECM ends with high pressure remaining in charge with it the extended summer continues

 

 

[Milhouse]

Confidence is building for a second spell of warmth to affect most parts beginning at the weekend and lasting into the following week. The Azores high builds northeast and joins forces with high pressure to the east of the UK. After departing briefly at the end of the week, the very warm upper temperatures push back westwards

 

Rather impressive to see 10c upper temps so far north so late in the year.

 

[No Balls Like Snow Balls]

ECM 12z still showing a wet Friday for many in the south / south east. Moving up the East of the country during the course of the day. Many many posts about continuing warmth but nothing about the rain. Maybe its denial lol.

[Summer Sun]

Confidence is building for a second spell of warmth to affect most parts beginning at the weekend and lasting into the following week. The Azores high builds northeast and joins forces with high pressure to the east of the UK. After departing briefly at the end of the week, the very warm upper temperatures push back westwards

 

Rather impressive to see 10c upper temps so far north so late in the year.

 

 

Looks like a lovely spell of weather is coming up with Autumn remaining on hold for a while yet long may this continue

 

[Summer Sun]

ECM 12z still showing a wet Friday for many in the south / south east. Moving up the East of the country during the course of the day. Many many posts about continuing warmth but nothing about the rain. Maybe its denial lol.

 

Or it maybe because the rain isn't certain yet and GFS 12z illustrates this by how patchy it is

 

 

[Captain Shortwave]

ECM 12z still showing a wet Friday for many in the south / south east. Moving up the East of the country during the course of the day. Many many posts about continuing warmth but nothing about the rain. Maybe its denial lol.

or its 12 hours of potential rainfall in amongst 10 days of dry weather. 

Sorry apart from a potential chilly night or two, the weather doesn't look particularly Autumnal. Also the 17C maximum you touted for Friday earlier seems to disagree with the bbc week ahead forecast this afternoon which had a high of 25C in the South east

 

Excellent ECM with temperatures remaining very warm until next week where they might dip a little as a new area of high pressure builds in, with uppers of 10-12C it would still be warm by day but the nights might feel a little fresh.

Edited September 1, 2013 by Captain shortwave

[William of Walworth]

We love you, recent models.

 

Will investigate details properly tomorrow, but HP influenced (even dominated!) conditions, suggests pleasantness without any hint of 'heatwave'.

 

That suits us summer lovers fine, going into September ....

 

Maybe tomorrow's detail,when I get time to look into it, will contradict me .... hoping not!

Edited September 1, 2013 by William of Walworth

[Joe8987]

So another heatwave then, can't remember a summer so consistently warm as this one. No real cool weather at all and above 20c nearly every day.

Although I do have my doubts about those charts coming off, especially in September.

[Milhouse]

ECM 12z still showing a wet Friday for many in the south / south east. Moving up the East of the country during the course of the day. Many many posts about continuing warmth but nothing about the rain. Maybe its denial lol.

 

Maybe is because of the last time we were forecast heavy rain moving north, last Saturday i believe, and it stayed mostly dry during daylight hours for many parts. It was only the SE that saw any meaningful rain.

 

 

Nothing really showing up here

 

[AWD]

I think there is a misconception in here that just because it's the first day of meteorological Autumn today, it means that there must be obvious autumnal weather to go with it. There isn't, to the naked eye it's looking decidedly summer-esq for the next week or so.

However, autumn is more than just a "big storm" or cooler temperatures etc, it's an undergoing seasonal change across the northern hemisphere, not just the UK.

If we look at the 500mb anomaly charts;

The EC Op in FI;

And the NAEFS suite for the same time period;

You can see the first signs of an autumnal presence there. A strengthening polar vortex. Some cold air developing over Greenland for example.

Incidentally, the NAEFS suite do show the presence of warmer than average 850hpa temperatures over the UK even by day 10, so we can see the mix of late summer and early autumn there in one chart.

Currently it's a cool autumnal feel here now. No question many of us have seen the first sniffle of autumn, especially temperature wise, this weekend.

A look at the GFS Op with reference to night time temps, here are the MAX projected temperatures for the weekend period;

Again, some cool temperatures there, especially in the north, where some ground frosts are a possibility. Another sign of some early autumnal presence being felt.

So IMO, there are plenty of signs, on a wider picture, of the transition between summer and autumn starting to make itself known. The keyword being transition. Seasons often overlap each other, as March proved this year. A big autumn storm doesn't just arrive on September 1st and say "autumns here". It's a transition period which is what current modelling is showing.

We have some warm daytime temperatures being shown, something more akin to summer along with the migration of high pressure cells. We also have some wet conditons possible in the south early next week.

We also have some cool night time temperatures being modelled and a strengthening polar vortex, something more akin to autumn. So IMO, we are seeing a transitional period of weather between late summer and early autumn.

The noticeably quiet thing at the moment is the Jet Stream. That's probably what's causing the misconception in here of "no autumn". Yet, especially with recent years, that side of things doesn't often get going until October really, so nothing really abnormal there.

To add, another "autumnal" presence is the ever reducing daylight hours and the ever increasing darkness.

Edited September 1, 2013 by AWD

[Summer Sun]

Here is the latest on the models from Gibby

 

Good evening. Here is tonight's look at the midday outputs of the big 5 computer models for September 1st 2013.

 

All models show the week to come split into two with the first half seeing a North/South split with the North staying mostly cloudy with a little rain while the South stays dry and becomes very warm with some sunny spells. Late in the week a trough of Low pressure moves over from the West with sunny spells becoming harder to find with an increased risk of showers and outbreaks of rain.

 

GFS then shows NE winds developing over the South at the weekend with a few showers possible and still very respectable temperatures while the North lies under a ridge from an Atlantic Anticyclone. Here dry weather would develop with some sunshine but chilly conditions could develop by night. Longer term and slack pressure seems to be projected across the UK with some showers in places but a lot of dry and benign early Autumn weather too with no overall pressure system having overall control over the UK.

 

The GFS Ensembles show a warm couple of weeks to come with uppers remaining above average over the South throughout. The operational was slightly on the warmer side of the set and rainfall is shown to fall over the South at times from the end of the week on but all in all not a bad set of ensembles tonight.

 

The Jet Stream shows complete confusion in the second half of the output with no set pattern shown from the varied options on offer from the members of the set. In the short term though the flow is shown flowing East North of Scotland then it does turn South to the West of Britain later this week to accommodate the Low pressure trough over the UK at the end of this coming week.

 

UKMO tonight has watered down considerably the extent of the unsettled weather at the weekend with any rain form the Low to the South restricted to the extreme South with the vast majority of the UK under dry and bright conditions with some sunny spells, especially in the West.

 

GEM tonight does keep things closer to this morning's formula with Low pressure to the South at the weekend keeping things rather unsettled with rain at times with the North staying drier and brighter closest to a High pressure ridge.

 

NAVGEM too keeps things unsettled from the weekend with Low pressure dominant close to the South or SW with outbreaks of rain or showers in the South while the North stays dry and largely fine.

 

ECM too shows a cut off Low to the South of the UK but further South than this morning meaning less of the UK would fall under it's influence with just the far South and SW at risk of thunder showers at times while the rest of the UK lies under High pressure with fine and dry conditions if less warm than this week.

 

In Summary the main difference tonight is that the operational runs of GFS, UKMO and ECM show the Low next weekend further South than on this morning's output with less of the South of Britain affected by it's circulation, hence the fine weather shown for the North on this morning's output is extended to affect more of Southern Britain too on tonight's offerings. With so much uncertainty still being shown on this mid range charts there is no point in speculating on the thereafter tonight.

 

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

[No Balls Like Snow Balls]

or its 12 hours of potential rainfall in amongst 10 days of dry weather.

Sorry apart from a potential chilly night or two, the weather doesn't look particularly Autumnal. Also the 17C maximum you touted for Friday earlier seems to disagree with the bbc week ahead forecast this afternoon which had a high of 25C in the South east

Excellent ECM with temperatures remaining very warm until next week where they might dip a little as a new area of high pressure builds in, with uppers of 10-12C it would still be warm by day but the nights might feel a little fresh.

I quote the info that is available. Latest max temp for London on Friday based on ECM 12z is 18c. If that is wrong then so be it but if that what it says then that's what it says. No prizes for being right or wrong. Edited September 1, 2013 by No balls like Snow Balls

[No Balls Like Snow Balls]

Maybe is because of the last time we were forecast heavy rain moving north, last Saturday i believe, and it stayed mostly dry during daylight hours for many parts. It was only the SE that saw any meaningful rain.

 

 

Nothing really showing up here

 

Im talking about the ECM precip chart. You've posted the GFS, can't really discuss when your posting the wrong model chart.

 

 

 

 

 

 

 

Edited September 1, 2013 by No balls like Snow Balls

[Captain Shortwave]

I quote the info that is available. Latest max temp for London on Friday based on ECM 12z is 18c. If that is wrong then so be it but if that what it says then that's what it says. No prizes for being right or wrong.

It's worth noting that the ECM op was a cold outlier for surface temperature on Friday in this mornings output, pretty much the bottom member out of both ECM and NCEP suites, ensembles place the temperature around or a little above average 

For rainfall I really don't see the point of arguing either way, at 5 days out any precipitation chart will probably be wrong especially in this split energy situation. 

Edited September 1, 2013 by Captain shortwave

[No Balls Like Snow Balls]

It's worth noting that the ECM op was a cold outlier for surface temperature on Friday in this mornings output, pretty much the bottom member out of both ECM and NCEP suites, ensembles place the temperature around or a little above average 

For rainfall I really don't see the point of arguing either way, at 5 days out any precipitation chart will probably be wrong especially in this split energy situation. 

 

 

Yeah man not gonna argue. BBC mentioned chance of heavy rain at end of countryfile, with the normal un-certainty statement.

No less valid then posts mentioning potential for warmth to carry on into next week. If the 12z op ECM were to verify then the South would also see rain on Monday and Tuesday. There is always 2 sides to a story, otherwise people might start to think that there is nothing else going on other than sun and warmth. 

[damianslaw]

Immediate timeframe very much summer hangover conditions - very often the start of each meteorological season sees the weather in a 'hangover' state from the season just gone - i.e. a sluggish hard to shake off state, none more so than in early September which in average is often a very benign pleasant period with high pressure always lurking close to our shores and an ineffective atlantic, combined with SST's being at their yearly maxim and europe coated in its residual summer warmth, we shouldn't really expect a major switch at this stage to cool autmnal conditions, such weather often doesn't show its hand until around the equinox.

 

As we head towards the end of the week, we see some trough disruption heading our way and a cut off low scenario with a robust ridge developing out to the west - its a bit of a messy picture.

 

As temps cool rapidly to our NW in the next 2 weeks, if we maintain the propensity for energy to advect SE, then we could quite quickly tap into some very cool uppers by the middle of the month, thanks to what should be a more invigorated polar vortex by then. For the time being its very much early september weather we've often become used too - very pleasant useable weather, but very dull if you like 'interesting weather' - this can be a very trying tedious period of the year for those wanting the weather to have some 'oopmh' about it... I often switch off from model watching until the autumn equinox when autumn in my book begin proper.

[draztik]

Interesting output from the GFS 18z this evening.

 

Here is the model at 138, keeping low pressure over the UK

 

this is from the GFS 12z at the exact same time frame, with HP over the UK, and low to the south embedded over Portugal

 

We will have to see how this develops, and see if there are any subtle moves in the ensembles... but a big change this evening, with the 18z dropping the low to the South pattern.

Edited September 1, 2013 by draztik

[Isolated Frost]

Tuesday and Wednesday look relatively warm, got to be looking at 22c+ for most of southern Britain.

Friday, on the other hand sees a cool north-east flow, a peculiar interruption in the upper flow and the subtropical HP cell ridges north- this highlighted well below

[mushymanrob]

So another heatwave then, can't remember a summer so consistently warm as this one. No real cool weather at all and above 20c nearly every day.Although I do have my doubts about those charts coming off, especially in September.

 

you must be young then! 03 was...ok i guess thats ten years ago now...