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Model output discussion - August hot spell - how hot, how long?


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9 minutes ago, kold weather said:

Yes the AROME shows a line of convection slowly drifting NE, it looks a litlte more active on the fronts southern tail than was advertised yesterday which leads to a stronger chance of some convective action making it towards the SE by the close of plsy today, and indeed several models are kicking off showers even over the SE overnight.

How high Saturday goes probably largely depends on how much convective overhang there is and whether any more cells break out.

Mon-Weds now looking increasingly stormy and basically tropical in nature, with 30-33c and high chance of daily thunderstorms. Very impressive to see and going to be an amazing, if maybe unbearable at times and for some, period of time coming up.

Well AROM has cloudcover and showery activity all day across the entire south east tomorrow and has pulled back it max temps significantly. Arpege still goes for mid 30's tomorrow however I'm not sure how given the cloud shower it also has. I strongly suspect there could be some big shifts in forecasts at times over the weekend. 

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5 minutes ago, Alderc said:

Well AROM has cloudcover and showery activity all day across the entire south east tomorrow and has pulled back it max temps significantly. Arpege still goes for mid 30's tomorrow however I'm not sure how given the cloud shower it also has. I strongly suspect there could be some big shifts in forecasts at times over the weekend. 

Much is going to depend on how discrete any thunderstorm activity tomorrow becomes.

Arome certainly going for a very active outlook tomorrow compared to other models over the SE, looking at the met office website they also show some shower activity although not as much. My guess is somewhere in the middle. The flow is fairly unstable so I do expect some to kick off, but I feel the AROME is rather overdoing it for tomorrow (it can be overagressive in these set-ups) and anywhere that stays away from convection is probably going to have a fair shout at 35c tomorrow, if a hotspot stays clear, then those 36-37c ranges very much are do able again.

 

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12 hours ago, cheese said:

It didn’t, but we still exceeded 30C five times that month in Leeds. Including 5 consecutive days above 30C starting in late July. Chances are we won’t exceed 30C at all this month, let alone 5 days on the trot.

So yeah, Damien is right - this isn’t looking like a classic national heatwave. I’m sure records will fall somewhere but I think August 1995 is more than safe for now. I’d be surprised if even 1997 was threatened.

Stonyhurst had a min of 16.1C overnight- shouldn't be hard to average over 20C for the 24 hour period with minima like that. You don't need a lot of 30C days in the north to get a high CET. Also we are still early in the month- still time for a more widespread hot spell with the continent being so hot.

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Why do people get so hung up on cloud cover predictions? They ate often very inaccurate at even close range. @Alderc you should know that as you were not expecting much sun yesterday and did quite well.

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3 minutes ago, Djdazzle said:

Why do people get so hung up on cloud cover predictions? They ate often very inaccurate at even close range. @Alderc you should know that as you were not expecting much sun yesterday and did quite well.

Agreed, it already looks like the cloud cover is breaking up more in the north and west than was forecast yesterday.

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1 minute ago, Scorcher said:

Agreed, it already looks like the cloud cover is breaking up more in the north and west than was forecast yesterday.

If your just looking at the chance of record breaking temperatures, the cells to the SW make that much more difficult. Not impossible by any means, but harder for sure. Its not much, but when going for the truly exceptional in somewhere like Heathrow, that does make a difference to the odds. 

 

 

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1 hour ago, kold weather said:
1 hour ago, Paul said:

A more zoomed in view of the UKV temperatures this pm, across the southern half of Britain. 

frizoom.png

The BBC forecasts are really annoying now because they base the entire temperature of the north west on Liverpool, so they show 24C for the whole region. You now have to look at Birmingham (28C) and assume Manchester will be about 26C.

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10 minutes ago, Djdazzle said:

Why do people get so hung up on cloud cover predictions? They ate often very inaccurate at even close range. @Alderc you should know that as you were not expecting much sun yesterday and did quite well.

Not looking at the predictions from the models for today looking at Satellite imagery which shows a lot of cloud to south west. However tomorrow is now in range of the mighty Arome and while yes a pinch of salt is required its a possible solution. Yesterday was as forecast really with the sun out by 1-2pm so no reason not to put some faith in Arome/Arpege

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1 hour ago, Paul said:

A more zoomed in view of the UKV temperatures this pm, across the southern half of Britain. 

frizoom.png

Interesting, some big old differences down this way, Arpege has max of 32C, although I it always overshoots temps here.

Temps are off to a sluggish start, normally by 9am on a day when you are shooting for 37C in London I'd expect to see 27/28C widely now across the south east and southern coastal sites, only 23C at Heathrow for instance and only 21.4C here. 

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5 minutes ago, Alderc said:

Interesting, some big old differences down this way, Arpege has max of 32C, although I it always overshoots temps here.

Temps are off to a sluggish start, normally by 9am on a day when you are shooting for 37C in London I'd expect to see 27/28C widely now across the south east and southern coastal sites, only 23C at Heathrow for instance and only 21.4C here. 

Heathrow nearly at 25c, but it was 30c by 10am last Friday. Looks to me as if it’ll be 1-2c below last Friday?

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I know the met office app is not meant to be taken at face value but it does show and E/NE wind from tomorrow into next week , just wondering if that'll be the case and what affect it'll have if any of temps or weather type if any

Edited by Gordon Webb
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10 minutes ago, Alderc said:

Interesting, some big old differences down this way, Arpege has max of 32C, although I it always overshoots temps here.

Temps are off to a sluggish start, normally by 9am on a day when you are shooting for 37C in London I'd expect to see 27/28C widely now across the south east and southern coastal sites, only 23C at Heathrow for instance and only 21.4C here. 

Just hit 25c in Cambridge. I remember last July 25th it was 30c at 10am. Sky Cloud free at the moment. Very little if any breeze and looking like it’s going to bake. 

Image from University of Cambridge 

 

54441495-337C-4258-9CBB-66F618897CA3.png

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4 minutes ago, tesaro said:

Just hit 25c in Cambridge. I remember last July 25th it was 30c at 10am. Sky Cloud free at the moment. Very little if any breeze and looking like it’s going to bake. 

Image from University of Cambridge 

 

54441495-337C-4258-9CBB-66F618897CA3.png

That uni site is on a roof and is often a little under other temps like the botanical gardens/NIAB. Last year on the 38.7c day it only recorded a max of 36.1c. 

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30 minutes ago, mb018538 said:

Heathrow nearly at 25c, but it was 30c by 10am last Friday. Looks to me as if it’ll be 1-2c below last Friday?

But it clouded over last week around 4pm if it carries on with no cloud today then it would keep climbing 

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42 minutes ago, Alderc said:

Interesting, some big old differences down this way, Arpege has max of 32C, although I it always overshoots temps here.

Temps are off to a sluggish start, normally by 9am on a day when you are shooting for 37C in London I'd expect to see 27/28C widely now across the south east and southern coastal sites, only 23C at Heathrow for instance and only 21.4C here. 

 

35 minutes ago, mb018538 said:

Heathrow nearly at 25c, but it was 30c by 10am last Friday. Looks to me as if it’ll be 1-2c below last Friday?

Yep I headed out to a couple of shops about 20mins ago and I have to say in the shade it doesn't yet feel THAT hot. I'm in north London. Last Friday temperatures were rocketing in the morning. So the latest model runs could be right in pegging back the temperatures today from 37c to about 34c/35c. 

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8 minutes ago, Swave Snow said:

But it clouded over last week around 4pm if it carries on with no cloud today then it would keep climbing 

Slight high cloud actually has an insulation effect although ideally you'd want it after 3pm. If you stay in clear skies then you'll start to see the temperature begin to drop earlier. 

At any rate as suspected the models appear to have moved into the 33-35C range moreso than some of the OTT estimates (though we shall see if those people were correct today). 

..

GFS and Euro seem to more or less agree that the heat more or less goes on Wednesday/Thursday albeit pressure stays fairly high as do uppers so dry and still quite warm. 

 

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14 minutes ago, Swave Snow said:

But it clouded over last week around 4pm if it carries on with no cloud today then it would keep climbing 

Unlikely to see much heating beyond 4pm anyway....we are some way below last Friday at the moment, so it’s looking like 37/38c is off the table. Perhaps!

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11 minutes ago, mb018538 said:

Unlikely to see much heating beyond 4pm anyway....we are some way below last Friday at the moment, so it’s looking like 37/38c is off the table. Perhaps!

I think that there will be a slower but more sustained rise today as the lighter wind takes a bit longer to advect the heat from France.

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1 hour ago, Alderc said:

Interesting, some big old differences down this way, Arpege has max of 32C, although I it always overshoots temps here.

Temps are off to a sluggish start, normally by 9am on a day when you are shooting for 37C in London I'd expect to see 27/28C widely now across the south east and southern coastal sites, only 23C at Heathrow for instance and only 21.4C here. 

I said elsewhere, we are 3c lower here in SE London than at this time last Friday.

26c today vs 29c last Friday.

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There is jo need to panic re high temps.

The hourly increase between 10-2 is about 2/2.5c

For example we were 23.2 at 10 its already 24.9 here +1.7 in 35 mins..

Top outs for 10am were ~ 25c.

That gives us a projected temp for somewhere like heathrow as 33-34c at 2pm.

4 hours post that to get 3-4 degrees is entirely realistic.

First target is 30c at 12pm.....

Thanks

Edited by Steve Murr
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9 minutes ago, Alderc said:

That seems to have been toned down a fair bit from last night? 

Broadly 1-2c lower.

Today will give a good indication of the models grasp of the actual heat and will show whether the models backed off too much.

Still very hot to be fair as well.

Steve, given we are still accepting warm air in its entirely possible we carry on at near 2c an hour through to 3.30-4pm before things level off.

Edited by kold weather
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5 minutes ago, sunnijim said:

I said elsewhere, we are 3c lower here in SE London than at this time last Friday.

26c today vs 29c last Friday.

Doesn’t equate that today’s max will be 3C short though.

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