Model Output Discussion

[PubliusEnigma]

I'd be VERY surprised if the temperatures were that low. GFS is criminally offensive when it comes to poor temperature predictions, and many times this summer it has prediction some bizarre temperatures both day and night, which have not materialised.. likewish I don't expect these to materialise either. I've known them to be as much as 5C too low in latter parts of June.

By the same token then are you saying they are underestimating the temps on the Bulgarian/Romamian Border, and that they could perhaps

reach +41 to +42oC ! ?

[Derp Patrol]

By the same token then are you saying they are underestimating the temps on the Bulgarian/Romamian Border, and that they could perhaps

reach +41 to +42oC ! ?

I find that the GFS often overdoes the continent temperatures and underestimates our ones a lot.. The temperatures for the vast majority of the UK on that chart are complete tosh.. 14C in London in July? that's borderline impossible, 18C is the lowest temperature I think i've ever seen in July for London

[Paul]

Sometimes all is not as it seems, PE has posted the chart from midday which isn't going to be the max for the day - the charts at 1500 and 1800 show a different story:

[Summer Sun]

Sometimes all is not as it seems, PE has posted the chart from midday which isn't going to be the max for the day - the charts at 1500 and 1800 show a different story:

Hi Paul, i have just looked at the Wteerzentrale temp charts and there temps are slightly lower than Netweather's is this because your's focus more on the UK and Ireland where as there's don't?

Edited July 14, 2011 by Gavin D

[Paul]

They're not plotting as many data points on their maps Gavin so you're effectively getting to see more detail on the netweather ones.

[Summer Sun]

Yeah thought the Netweather one's showed more detail, keep up the good work guy's.

[gottolovethisweather]

Hello all.

I don't often post in here as I'm more scientifically challenged than a lot of knowledgeable folk but I have a question with regards to this immediate weekend.

Just how much rainfall is anticipated to fall? I ask as the attached indicate there are a succession of fronts over us in the upcoming few days.

The above charts only cover part of the timescale involved, but it seems inevitable, some localised flooding will occur over vast parts of the country.

I'll leave the proper analysis to those folk more informed on these matters but this situation does seem to have shades of 19th/20th July 2007 about it, does it not? see http://en.wikipedia...._Kingdom_floods and note the following.

On 20 July, another active frontal system moved across Southern England. Many places recorded a month's rainfall or more in one day. The Met Office at RAF Brize Norton in Oxfordshire reported 126.6 mm (5 in): a sixth of its annual rainfall. The college at Pershore in Worcestershire reported 142.2 mm (5.6 in),^[13] causing the Environment Agency to issue 16 further severe flood warnings.^[14] By 21 July, many towns and villages were flooded, with Gloucestershire, Worcestershire, Warwickshire, Wiltshire, Oxfordshire, Berkshire, London and South Wales facing the brunt of the heavy rainfall.

Kind Regards

gottolovethisweather

Edit: according to other resources on the internet I may be way out and I stand corrected!

Edited July 14, 2011 by gottolovethisweather

[Harve]

I find that the GFS often overdoes the continent temperatures and underestimates our ones a lot.. The temperatures for the vast majority of the UK on that chart are complete tosh.. 14C in London in July? that's borderline impossible, 18C is the lowest temperature I think i've ever seen in July for London

Yes, I think the real issue is that it overdoes the cooling effects of the coast far too much! I wouldn't be able to explain why it also underestimates our winter temperatures, though.

[Downpour]

Correct analysis IMHO from Gavin and others - GFS has been, and will continue to be, a joke model if you are looking only at air temps. This is particularly true in the SE where ludicrous outlooks of 14c are routinely cooked up by GFS only for the reality of 18 or even 20 to materialise. You can also apply this critique to rainfall - barring storms that track right into the M25 region you might as well slice forecast totals in half - and I speak as a member who is trying to establish a new lawn and actively WANTS good rain. Amazing how actually wanting the wet stuff at times makes you more realistic when it comes to GFS. My forecast, for what it's worth, is a decently rainy weekend followed by an improvement into next weekend and a possible warm up for the classic English high summer period of late July and early August.

[Derp Patrol]

Yes, I think the real issue is that it overdoes the cooling effects of the coast far too much! I wouldn't be able to explain why it also underestimates our winter temperatures, though.

yes definitely agreed. You just need to look in the south east of France north of Nice it's predicting 10C haha, total tosh!

[bluearmy]

yes definitely agreed. You just need to look in the south east of France north of Nice it's predicting 10C haha, total tosh!

quite mountainous just north of nice ???

naefs fi continues to offer the possibility of a decent end to july.

can kevin enlighten us as to years which have seen no periods of anticyclonic dominance > 3 days through june, july and august. i'm pretty sure we will see one settled period before august is out. would surely be a statistical oddity for us not to ???

Edited July 14, 2011 by bluearmy

[Geordiesnow]

I'd be VERY surprised if the temperatures were that low. GFS is criminally offensive when it comes to poor temperature predictions, and many times this summer it has prediction some bizarre temperatures both day and night, which have not materialised.. likewish I don't expect these to materialise either. I've known them to be as much as 5C too low in latter parts of June.

You say that but at times the GFS model does tend to be accurate with the temps if we have heavy rain under a cool airmass which is what that particular chart was showing, Actually I would be surprised if temps get above 15C if we had heavy rain and uppers of around 5C if not slightly below.

Sometimes the UKMO overcooks the temperatures and this is reflected in the BBC forecasts of at times vary temperature predictions. Be interesting how low the temps will be for the weekend and next week in any heavy persistant rain and a fairly modest airmass.

[William of Walworth]

Correct analysis IMHO from Gavin and others - GFS has been, and will continue to be, a joke model if you are looking only at air temps. This is particularly true in the SE where ludicrous outlooks of 14c are routinely cooked up by GFS only for the reality of 18 or even 20 to materialise. You can also apply this critique to rainfall - barring storms that track right into the M25 region you might as well slice forecast totals in half - and I speak as a member who is trying to establish a new lawn and actively WANTS good rain. Amazing how actually wanting the wet stuff at times makes you more realistic when it comes to GFS.

My forecast, for what it's worth, is a decently rainy weekend followed by an improvement into next weekend and a POSSIBLE warm up for the classic English high summer period of late July and early August.

Absolutely correct on GFS's erm ahem eccentricity re temps.

Just been quickly scanning the last two sets of output. From those, I think there's at least something to be said in favour of that bolded prediction (my caps added!). With suitable caution re FI obviously!

Lets hope future runs confirm this slow move towards more HP influenced conditions for later next week/next weekend. Such ideas seem also plausible from Gibby's excellently objective/balanced summaries. For now!

Edited July 14, 2011 by William of Walworth

[johnholmes]

I14C in London in July? that's borderline impossible, 18C is the lowest temperature I think i've ever seen in July for London

I doubt the figure of 18C is correct but cannot find the absolute lowest afternoon value for London anywhere?

anyone able to help please?

[Upgrade]

in 2007 we had a few days in july and august in london where the temps were no higher than 16 degrees. But this is unusual.

This coming Saturday temperatures are not forecast to get above 18 degrees. I expect if the rain is as heavy as expected and the winds strong, we may well have a 16 degree day.

[paul tall]

I doubt the figure of 18C is correct but cannot find the absolute lowest afternoon value for London anywhere?

anyone able to help please?

Well as the average July max is 22º in London, it is hard to imagine there won't have been days with a max of less than 18º

Certainly in the North East we can have July days maxing at 14º!

[SP1986]

In heavy rain it's not inconceivable that such temperatures could be achieved, but under the conditions the GFS was showing, light rain/showers, it's highly unlikely, under the setup conditions.

18z looks more realistic in this sense.

Plus of course to achieve 13C in central England in July, it has to be pretty much be raining heavily all day, or achieve a fairly deep Arctic airmass with showers.

[TonyH]

I doubt the figure of 18C is correct but cannot find the absolute lowest afternoon value for London anywhere?

anyone able to help please?

There have been cool July maxima of just 12-13c in Coventry, so London's probably 14-15c.

There have been cool July maxima of just 12-13c in Coventry, so London's probably 14-15c.

From our friends over at UKWW, 12c 54f in July 1888 would take some beating, also the possibility of snow (scroll down the page to find):

12c in London UKWW

Edited July 15, 2011 by Tonyh

[johnholmes]

thanks folks, so a maximum in London below 18C has occurred before even if a long time ago

[mushymanrob]

hmmm.... its looking like after an unsettled period some sort of northerly will occur as pressure rises to our west courtesy of the azh ridging northwards, the gfs still suggests it linking with the scandinavian high which the 00z and with low pressure over nw europe this is expected to advect some high uppers. now this is fi of course, but i think it would be interesting to see this unusual scenario IF it ever happened.

[ribster]

in 2007 we had a few days in july and august in london where the temps were no higher than 16 degrees. But this is unusual.

This coming Saturday temperatures are not forecast to get above 18 degrees. I expect if the rain is as heavy as expected and the winds strong, we may well have a 16 degree day.

Well, was just 15c here yesterday, and not particularly wet, and while breezy it wasn't blowing a gale. I can see temps at the weekend being lower than those predicted.

[johnholmes]

latest 500mb anomaly charts-or rather the ECMWF-GFS version

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

valid out to 25 July and they continue the type of chart that they and NOAA have been consistently showing for some time. Little sign of dryness and heat for many areas?

[picog]

Looking wet for us all by midnight on Saturday — courtesy of weatheronline.co.uk

Edited July 15, 2011 by picog

[Gibby]

GFS this morning is awful for summer with low pressure moving in late today and tomorrow and never leaving our shores throughout the rest of the hi-res part of its run. put simply after rain moves in tonight and tomorrow there is likely to be rain in most places on all days at some point or another out to next Saturday. Some of the rain will be heavy and in the form of showers but it will be cool and breezy with just short bright spells. In the low res end of the run pressure does slowly build toards the NW but for much of the time it is too far North and West for us to tap into anything decent on this run meaning winds remain with a Northerly component with further showers at times especially towards the east.

UKMO is also poor with the same Low pressure crossing the UK slowly over the next three days to then prove reluctant in moving away leaving a legacy of rain and showers well into next week in rather cool conditions.

ECM has also backtracked from last night's operational in as much as keeping Low pressure influential to our weather throughout this morning. It brings the main centre over the UK from tomorrow untll Tuesday before a gentle filling process takes place before the whole setup is rejuvenated late in the run from Scandinavian Low pressure which moves back SW towards us maintaining the cool and very changeable weather going.

In Summary after last night's hope, things have backtracked somewhat this morning with all chance of the Azores high taking command all but vanished from ECM while GFS has it building too far North and West of the UK to bring us any meaningful effect. Instead it looks a changeable couple of weeks ahead with rain at times for all and just brief dry spells when temperatures may crawl up to comfortable levels.

[VillagePlank]

London 850hPa GEFS ensemble min,max,mean output:

A new feature, this morning. Instead of steadily getting better after the 18th it looks like a slight improvement after Sunday degrading into the middle of the week, and then warming up quite nicely, thank you, at the end of the next week. FI difficult to call this morning as all three parameters show more or less the same trends with the difference being one of magnitude rather than pattern.

Edited July 15, 2011 by Sparticle