Model output discussion - hot spell beckons but then what?

[matty007]

July record (36.7c) is 100% going. Decent chance of beating 38.5c and a slight chance of 40c. If pretty much all the models are forecasting 37-38c then you can easily take that as highly likely. Even if you only add a degree you are at 38-39c

If even the pessimistic beeb is forecasting 37c for London, you sit up and take notice. You can usually add 2-3c to their forecast 

They are forecasting 35c for my location (Haverhill, Suffolk). That is unheard of. Typically we are around 32c even in 2006, 2013,2015

Once the models are three days out, they are pretty damn reliable and this is a stable situation unlike the plume before. No signs of degradation whatsoever. 

Thursday is going to definitely be a record breaker. Perhaps multiple records.

 

 

Edited July 22, 2019 by matty007

[Frosty.]

Thursday's GEFS 6z mean is beyond insanity!!..the magic 100F is within reach i would think!!!!...what a week!!!!

[CheesepuffScott]

NetWX model with that 38C on Thursday in SE corner.. but widely mid 30s W London eastwards and from Kent up to around Lincoln

[matty007]

It's also interesting that the hottest point in the models is typically around the same area. Usually it highly differs due to change of direction etc. But it seems a fairly consistent and stable plume with the hottest point in southern london into Kent. 

So expect the hottest temperature in the Seven Oaks/ Maidstone area, maybe towards Faversham. 

Seems ominous......... 

[nick sussex]

Looking at the forecast temps for the UK by the GFS, it’s already out by several degrees today so far .

Its forecast is currently missing by around 2c on the low side especially towards eastern areas .

With several more hours of warming to go that 2c might be even more .

[Methuselah]

1 hour ago, Alderc said:

Is it like an unwritten rule of model threads that once we start approaching record temperatures we instantly flip to quoting Fahrenheit  

Seriously though (in my best American accent) it appears as though there is an increasing probably our nations Captial will experience triple digit heat on Thursday

Ah Chris, it's just that we 'bilingualists' are a dying breed!

And, on to today's GEFS 06Z ensembles...Do they keep getting better?

   

   

In any other year (though not last year!) I'd have given my eye-teeth, for an extended outlook like that!

[Ben Sainsbury]

13 minutes ago, CheesepuffScott said:

NetWX model with that 38C on Thursday in SE corner.. but widely mid 30s W London eastwards and from Kent up to around Lincoln

Thanks for showing the snapshots of the Netwx, my apologies for not showing them earlier. Latest run shows a slightly better flow off the continent.

[Guest]

6 minutes ago, nick sussex said:

Looking at the forecast temps for the UK by the GFS, it’s already out by several degrees today so far .

Its forecast is currently missing by around 2c on the low side especially towards eastern areas .

With several more hours of warming to go that 2c might be even more .

Correct, it’s out by 3c here but completely the wrong way due to the complete lack of a clearance......

[Djdazzle]

3 minutes ago, Alderc said:

Correct, it’s out by 3c here but completely the wrong way due to the complete lack of a clearance......

Temps starting to increase more quickly now as the cloud melts away. Also beginning to import more of a continental influence as the day goes on.

[nick sussex]

3 minutes ago, Alderc said:

Correct, it’s out by 3c here but completely the wrong way due to the complete lack of a clearance......

I think it forecast 19 to 21 for the coast there.  Down here it’s doing okay currently 31c , although the humidex value is already at 39 . 

I tend to find the worst time of the day here for heat around 5 pm, almost as if the ground says right I’ve absorbed lots of heat now I’m going to release it !

[Frosty.]

The GEFS 6z is sniffing around for another plume in early August!!!

[Mapantz]

19 minutes ago, nick sussex said:

Looking at the forecast temps for the UK by the GFS, it’s already out by several degrees today so far .

Looking at current max temps tables, the GFS is spot on at 13:00

It shows 26's and 27's

[nick sussex]

3 minutes ago, Mapantz said:

Looking at current max temps tables, the GFS is spot on at 13:00

It shows 26's and 27's

Have you factored in it uses UTC time not summer time in its forecasts .

[Mapantz]

3 minutes ago, nick sussex said:

Have you factored in it uses UTC time not summer time in its forecasts .

I'm viewing it on Netweather's GFS hourly viewer. It shows the correct time.

[knocker]

Sat at 1130 UTC and midday chart

[Updated_Weather]

1 minute ago, Mapantz said:

I'm viewing it on Netweather's GFS hourly viewer. It shows the correct time.

XC weather has 28c reported at Royal Air Force base in Mildenhall

[Derecho]

2 hours ago, shaky said:

Gfs also pushes heat further west and struggles to clear as quickly!!

Any more upgrades and you'll run out of exclamation marks shaky 

There is an emerging trend for the heat to sluggishly clear the east I think. The GFS still has temperatures in the upper 20s here on Friday. I'd say 11 of the 20 ensemble members still have Hull hanging onto +15C 850s by Friday evening and a small number still have the +20C isotherm over the far SE. 

Only 5 ensemble members had the +15C isotherm over me by Friday evening during yesterdays 12z.

For Thursday the OP shows to be that the really hot air will be east of Southampton, I don't think any of the ensembles go much further east then that but quite a few ensemble members have that line a bit further west.

 

[nick sussex]

7 minutes ago, Mapantz said:

I'm viewing it on Netweather's GFS hourly viewer. It shows the correct time.

Ah ok . Didn’t realize there was an hourly viewer . I think it really depends where you are. 

[Ross Andrew Hemphill]

16 hours ago, Mr Frost said:

Well I type this as torrential rain pours down outside with winds gusting to 35mph - feels like a late September night! 

Temperatures here are forecast to go no higher than mid 20’s (I am near the West coast of Scotland ) but there is a chance of thunderstorms also so I can’t really complain! (Latest GFS for Tuesday, Wednesday and Thursday)

On a side note being a big lover of weather extremes I am really looking forward to seeing how high the temperatures go down South - extremely jealous of you all! 

Once again it has been a fascinating read in here today - these plumes always deliver great discussion from all members. (Those who prefer hot or cool Summers) 

Have a good night all!!

Didn’t realise we lived so close Mr Frost, that rain was horrendous last night but quite nice at the same time!  

Anyway, the models give Western Scotland a high of 26C on Tuesday and Thursday which is really good for this area, along with some big thunderstorms in between!! If we do break the record(s) in the South it would be incredible, but at the same time I worry about a lot of people who really can’t deal with the heat and especially the humidity, so please stay safe everyone and enjoy the crazy ride! ️

 

Crazy that the models usually backtrack or push the heat West, not this time...

[nick sussex]

Meteo France have upgraded temps for Paris on Thursday , now expected to hit 42c in parts of the capital .

That area of France and n and ne of there will be where the source of air for the UK will be .

As long as the models don’t do any eastwards corrections it will be down to sunshine amounts and if favoured areas of the UK can avoid any heavy showers .

Without that variable a good chance I would have thought to break the record .

[snowblizzard]

57 minutes ago, knocker said:

Sat at 1130 UTC and midday chart

Cloud very reluctant to break-up across Southern Counties at the moment!

Hopefully, we'll see some clearer skies when the wind direction changes to more Southerly? 

[Stonethecrows]

1 hour ago, matty007 said:

It's also interesting that the hottest point in the models is typically around the same area. Usually it highly differs due to change of direction etc. But it seems a fairly consistent and stable plume with the hottest point in southern london into Kent. 

So expect the hottest temperature in the Seven Oaks/ Maidstone area, maybe towards Faversham. 

Seems ominous......... 

Ominous? Strange word for a one off day of record temps, sounds like you're predicting the end of days!. It's Interesting, noteworthy and i'll agree it's not a record we want to be seeing broken but hardly ominous lol

[shaky]

Apparently according to one of the posters on theweatheroutlook forum the 06z ukv still showing 38 39 degrees across the east/south east!!

[Man With Beard]

With regards the modelling, my next milestone would be what the ARPEGE comes up with on its 12Z run, as Thursday will be within D3 by then. 

My rule of thumb for predicting temperatures in a heatwave is usually:

Before D5: don't bother

D4/D5: ECM (add 2C to 4C to raw)

D3: ECM (add 2C to 4C) and ARPEGE

D2: ECM (add 2C to 4C), ARPEGE, AROME in that order

D1: AROME, ARPEGE, ECM (add 2C to 4C), EURO4 (add 2C to 3C) in that order

This blend normally works. GFS is discounted - it can't work out local differences. ARPEGE is pretty good inside D3 and even better at D2 but I find unreliable at D4/D5. UKV - I haven't enough experience of this yet.

If the ARPEGE goes with the ECM, I'd expect it to show between 37C and 40C for Thursday this afternoon. 

Interesting reading weather media reports - I sense the nervousness - some talk of breaking the July record but almost nothing on the all-time record and none on 40C - I guess they are aware how a small shift could change everything. Yet, an objective forecast based upon the ECM, the best model at this range, would lead to a forecast of 39C or 40C for Thursday.

[mb018538]

23 minutes ago, Man With Beard said:

With regards the modelling, my next milestone would be what the ARPEGE comes up with on its 12Z run, as Thursday will be within D3 by then. 

My rule of thumb for predicting temperatures in a heatwave is usually:

Before D5: don't bother

D4/D5: ECM (add 2C to 4C to raw)

D3: ECM (add 2C to 4C) and ARPEGE

D2: ECM (add 2C to 4C), ARPEGE, AROME in that order

D1: AROME, ARPEGE, ECM (add 2C to 4C), EURO4 (add 2C to 3C) in that order

This blend normally works. GFS is discounted - it can't work out local differences. ARPEGE is pretty good inside D3 and even better at D2 but I find unreliable at D4/D5. UKV - I haven't enough experience of this yet.

If the ARPEGE goes with the ECM, I'd expect it to show between 37C and 40C for Thursday this afternoon. 

Interesting reading weather media reports - I sense the nervousness - some talk of breaking the July record but almost nothing on the all-time record and none on 40C - I guess they are aware how a small shift could change everything. Yet, an objective forecast based upon the ECM, the best model at this range, would lead to a forecast of 39C or 40C for Thursday.

I think when we’re talking in terms of all time UK maxima and temperatures In the mid to upper thirties it would be a massive error for the models to be 2-4c out. Personally I think we will probably just edge the 36.7c July all time record...maybe just shy of 100f. My guesstimate is 36.8-37.6c