Model Output Discussions 12z 01/09/2016

[Gordon Webb]

3 minutes ago, Singularity said:

Thanks for the question Gordon -

Essentially there is a low looking to develop south of the U.K., which most models then move east while keeping much of the U.K. clear of the associated cloud and rain - though a few showers could develop in the far south while the far southwest looks prone to a lot of cloud and perhaps a bit of rain. GFS differs in that the low drifts north and across the UK Tue night through Wed, allowing cooler, cloudier weather to move up from the southwest, though perhaps not without some storms firing off just ahead of that.

By Thu, GFS has it fresh and blustery with showers and some longer spells of rain, yet ECM and UKMO keep the very warm air in place and might be right for some homegrown thunderstorms.

I've conducted this whole analysis from my phone though, so it may not be as precise as usual.

thanks very easy to understand so GFS v Most of the others wonder which one will be correct though

[Nouska]

On the subject of that low...       

.....quite an unusual occurrence for mid September I would have thought.

On wednesday we were due to meet up with family for a few days in Bordeaux - that's been cancelled due to illness (not severe) - I'm very glad of that seeing those charts. Perhaps the high-res ARPEGE is being a bit aggressive in the modelling but still quite noteworthy even if less deep.

It's a win win situation - you guys get some late season heat, maybe followed by storms and I'll hopefully get the rain we desperately need.

 

Edited September 11, 2016 by Nouska

[Neilsouth]

On 09/09/2016 at 16:54, Frosty. said:

According to the Gfs 12z it will be overcast tomorrow afternoon across the south / east of England with outbreaks of rain (some heavy) along a slow moving cold front making erratic progress eastwards but warm ahead of it with temps around 22c in any brightness and Kent looks last to see the rain..., it's touch and go but I think you could need a brolly.

 

 

 

Surprisingly it didn't rain all day  

[Frosty.]

1 hour ago, Neilsouth said:

Surprisingly it didn't rain all day  

That's good to hear Neil

The Gfs 12z shows our weather warming up nicely tomorrow, as high as 25c in the s / se and mainly dry with sunny spells across most areas. Tuesday is the hottest day of the week with 31c expected in parts of the SE along with sunny skies across most of England and wales..maybe somewhere like Heathrow will squeeze 32c 90f but then there is an increasing risk of scattered thundery showers breaking out although still with some very warm sunshine on wednesday with temps still very good for the time of year at 25/26c.

[Singularity]

http://www.theweatheroutlook.com/twodata/chart.aspx?chart=/charts/ecm/72_mslp850.png?cb=988

ECM continues to side with ARPEGE and ICON in developing a well defined low to the south of the U.K. by Wednesday, with the hot air languishing across us without much rain to speak of (seems a lot of capping is expected to counter the high potential instability). 

The GFS 12z does now feature a disturbance over the near continent, but also persists with developing one across England with cooler air and a lot of cloud cutting in along the southern flank to wipe out the hot weather across the southwest by Wednesday afternoon. 

Such stark disagreement with ECM at just 72 hours, with neither side backing down, seems most unusual.

[Frosty.]

Some like it hot..and that includes me..and the Ecm 12z isn't backing down, it's showing a change to very warm and then hot summery conditions for much of the week ahead..at least for most of England and wales with scorching sunshine and the increasing heat and humidity could trigger isolated T-Storms AND records would be smashed for the highest September temperature if this run proves correct!..BBQ time...Spock certainly raised an eyebrow at the differences between this run compared to the Gfs

Edited September 11, 2016 by Frosty.

[cheese]

Wow, ECM is sticking to its guns for a hot Thursday, GFS not so keen at all.

[Man With Beard]

Well this is awkward. Fine lines between hot/sunny and wet/cooler from midweek, and those lines are largely close to the south and west (north-eastern areas can probably look away now, you look good for fine weather with a regular cooler coast-line).

GFS the most progressive - rain approaching quickly from the south and west

GEM / UKMO will leave me looking nervously into the channel, possibly hot for most but dodgy

  

Which leaves ECM and the ARGEPE, which keep the rain well away and heat keeps rolling on into Thursday at the very least

  

The consequences are pronounced - the ARGEPE has 32C for Tuesday, 32C for Wednesday and 31C for Thursday. The GFS is over 30C on Tuesday, high 20s in the north on Wednesday, but not hot anywhere on Thursday. Fascinatingly, it shows just mid-teens for parts of the south on Thursday - a 15/16C swing from the ARGEPE! as well as no heat at any time for the SW.

 

 

Edited September 11, 2016 by Man With Beard

[carled]

Even a rank amateur like me can see the massive difference for Wed/Thu (mainly) between GFS and ECM. The GFS is determined to bring in that low across the UK but the ECM is having none of it, instead modelling a system in the Bay of Biscay that prolongs the warmth in the UK.

I presume that the British Forecasting Systems (Metoffice/BBC) aren't using the ECM based on their current forecast for the week ahead... Who's the form horse to back?

Edit - looking at the ECM that would still have VERY high temps in London/SE even on Thursday - high 20s.

 

Edited September 11, 2016 by carled
added a bit of text

[Frosty.]

Ecm is the form horse as its been rock solid for the last few days in showing several hot days in the week ahead whilst the other models have flip flopped..Even the Gfs shows a chance of 32c on tuesday but the ecm raises the bar and extends the heat by a few more days, indeed it's still very warm on Friday before the delayed change next weekend..I'm cheering on the Ecm to prolong the summery spell!

[East_England_Stormchaser91]

A very interesting and unusual setup on the cards for mid September indeed! As a result, the models are struggling to get a grip of the exact outcome, because of such a perplexed scenario. 

Some runs really are ramping up the potential for a biscay storm to develop, bringing some exceptional winds to areas such as Bordeaux. if this is the case, I expect a more prolonged displacement of the heat stalling over us for a bit longer. GFS is keen to move the possible storm low more to the north over us though, and so therefore, sweeping the warmest uppers further north and away from us, with a dig of more polar maritime air tucking in behind from the NW. 

We shall have to wait another 24 hours at least I would say before there is sufficient agreement as to what exactly will be the case. 

In general, if you are a fan of heat and storms, it is looking quite marvellous! 

[ANYWEATHER]

Hello Folks! The much heralded hot spell is now just about to start! The questions are, how hot will it get?  Will it be a record breaker for this time of year? And how much rain will fall...ie Thunderstorms?  From tonights output it really seems to tame the heat down. A record breaker not ,but some really noteworthy heat especially for eastern Uk. Ironically, both ecm and gfs show an Autuminal  Atlantic influence coming on Friday

[Gordon Webb]

1 hour ago, Frosty. said:

Ecm is the form horse as its been rock solid for the last few days in showing several hot days in the week ahead whilst the other models have flip flopped..Even the Gfs shows a chance of 32c on tuesday but the ecm raises the bar and extends the heat by a few more days, indeed it's still very warm on Friday before the delayed change next weekend..I'm cheering on the Ecm to prolong the summery spell!

The form horse doesn't always win

[Frosty.]

13 minutes ago, Gordon Webb said:

The form horse doesn't always win

I know, I just meant the Ecm has been rock solid with its idea of prolonging the autumn hot spell..and I hope its right!

[Man With Beard]

12 minutes ago, Gordon Webb said:

The form horse doesn't always win

What's bizarre for me was that in a recent similar situation, it was the GFS which was further south than the other models (it was bizarrely wrong that time at just T6) - another time, the GFS was less progressive and right! So I have no idea what the form is, really. I always think the ECM or the UKMO are the ones to back in a split trough situation when it's T72-T120, but inside T72, I must admit I'm a bit clueless. I don't think the ARGEPE has done too badly in these short timescales this summer??

[Summer Sun]

This was ECM back on the 5th for Tuesday

And this is it 48 hrs away

Nice to see the hot air picked up in FI come to promise for once

Edited September 11, 2016 by Summer Sun

[Frosty.]

The Ecm 12z ensemble mean will please heat fans for most of the week ahead, it mirrors the operational and its only by Friday the weather starts to freshen up from the west but in the next 4 days we are on course for a late taste of summer with plenty of hot sunshine and a few T-Storms by midweek, at least for the southern half of the uk where records could be broken with temps in excess of 31c 88f...I think 90F or a little higher is achievable between tues / thurs in parts of the s / se if the Ecm is right.

[Summer Sun]

At last! GFS has finally woken up and keeps the heat into Thursday as per the beebs forecast yesterday

[Man With Beard]

37 minutes ago, Summer Sun said:

At last! GFS has finally woken up and keeps the heat into Thursday as per the beebs forecast yesterday

Yes, full house this morning from the models - they've all moved to ARGEPE and ECM. Prepare for a heatwave (unless you're in the far west, or stuck in an office...)

[Frosty.]

More very good news, the Ecm is sticking to its guns, no back down, this week looks very summery with plenty of sunshine and 90F would be broken in the south / southeast if this verifies!

Today is going to become warm, especially in the southeast with 26c and tonight looks warm and humid with temps no lower than 18-20c across southern uk..then tomorrow could bring 31-32c to the south / southeast and if this run is right, wed / thurs will also be hot and friday still very warm...Bank!..scorchio

[northwestsnow]

Very nice ECM op run this morning- for the heat lovers it doesn't get any better in mid September!

http://old.wetterzentrale.de/pics/Recm241.html

http://old.wetterzentrale.de/pics/Recm481.html

http://old.wetterzentrale.de/pics/Recm721.html

Drop off in temps thereafter but it looks reasonably dry for most as we go through the weekend.:)

And a nice cool down over NW Russia at day 10

Edited September 12, 2016 by northwestsnow

[MP-R]

On 9/11/2016 at 06:25, 4wd said:

September often has a very warm spell and can sometimes have the hottest day of the year.

You only need go back to 2011 and some places were close to 30C in the closing days.
It was 25C here on the 30th.
Also I recall an exceptional hot spell in September 1982

Very very rarely does September feature the hottest day of the year, and even rarer does it supersede 30C. 25C is still a good bet but 30C is quite exceptional, especially the later in the month you go.

Looks like a week of two halves to me. Heat such as this, widespread until Wednesday, edging east on Thurscay:

Then much more seasonal by the weekend when fronts have traversed the UK ushering in cooler Atlantic air with sub 5C uppers:

For those who don't like heat, a few much cooler nights from the weekend too (nothing outstanding, but noticeably different to the anomalously warm nights earlier this week):

Before then, some decent CAPE around on Tuesday-Thursday too, favouring the north once again but I'm sure most parts of the country would be in with a chance. From an IMBY point of view, Thursday might be the day for my neck of the woods:

  

 

All in all, quite an interesting outlook in my opinion, and certainly not the dull mundane-ness that so many make out September to be.

[Frosty.]

The Ecm 00z ensemble mean has not downgraded from yesterday, it's a peach throughout this working week with high summer conditions across England and Wales with temps into the mid to upper 20's c and low 30's celsius for the s / se.. this run mirrors the stonking operational  and the highest september temperature record is under threat IF the ecm is right and I think there is a good chance it will be since the other 00z models are now more in line..it's an exceptional 4 days coming up for at least the southern half and especially the southern third of the uk with very warm humid nights, very warm / hot days and plenty of sun with even a risk of a storm or two being triggered by the high temps..enjoy.it if you can. I know some don't like the heat but many of us do and this could be the last time this season.

[Paul]

Just thought I'd share the first in a regular Monday morning series we're hoping to produce, looking at the various forecasting models and what they're suggesting for the week ahead:

Synoptic Guidance - The Week Ahead - 12th September

[Sky Full]

2 hours ago, Paul said:

Just thought I'd share the first in a regular Monday morning series we're hoping to produce, looking at the various forecasting models and what they're suggesting for the week ahead:

Synoptic Guidance - The Week Ahead - 12th September

Thanks for this.  An extremely interesting, comprehensive and informative analysis which is perfect for this thread.  I for one found it very helpful and I am looking forward to more in future.