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Possibly severe heat wave looming for 25th to 29th June, also some local severe storms


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6 minutes ago, h2005__uk__ said:

In that video, the MetO are forecasting these maxes for London: Tue 29C; Wed 29C; Thu 30C; Fri 31C.

However, their website has these: Tue 25C; Wed 23C; Thu 23C; Fri 23C.

Significantly different - I don't think I've seen such a variation between a video forecast and an online forecast from the same body.

Is this a stark example of the weather apps and models struggling, meaning human input is required? Do the online forecasts have no human input at all then?

I think you are absolutely right. The online forecasts must be automated straight off the models. The Met Office are sticking to these higher values day after day, I note. 

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Can anyone think of a potential hot spell that has been so downgraded ? The Met Office were really taking note of possibilities because they released a youtube video addressing their concerns for this

Not much chance of high temperatures this week now,only Saturday. Extremely wet now seriously wet after this morning, wettest month in living memory at 231mm smashed the previous record of july 2

So for the record, Heathrow and Northolt reported 34.0 C on Saturday 29th. The 576 dm thickness contour passed through parts of East Anglia on its way to its current location in central Europe. In Fra

Posted Images

Today's highest readings of 36 were in the lower Rhone valley but it's 34 as close to Paris as Auxerre about 100 kms southeast. The 576 dm thickness contour continues to show up in southern England by Friday and Saturday on the latest two GFS runs. The model output may be overdoing the North Sea regional cooling effect, it's fairly weak today with the highest readings in England at Southend and Wattisham (25 C). By the core of the heat wave the flow into southern England is more south than east so any North Sea cooling that takes place mid-week should be extinct by then. I like Saturday for extreme heat because the flow turns more westerly at lower levels and this will waft the heat from the Thames valley towards the urbanized southeast. For the contest we have going, 123 Netweather gurus predict a median high of 35.4 C. 90% go higher than 33. 

The models have all but abandoned any localized thunderstorm potential except for Friday to early Saturday in Ireland into north Wales and northern England when the cold front activates there. If the models are right about the heat being mainly dry, that would also argue for less cloud or convective debris to interfere with temperature rises in the early part of the daytime heating cycle. 

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As mentioned in the model output thread I think this is a good time to assess the accuracy of the GFS 2m temps. Here is yesterdays forecast temperatures compared to actual:

image.thumb.png.a8232566b8cfe3b6edde3bd957637de0.png  image.thumb.png.6d3068d0f18f69509112cee0f5a28a22.png

Generally a bit of an underestimate but not much. This forecast is only 1 day in advance however and usually GFS 2m temp forecasts quickly increase towards the actual day itself. 

Edited by Quicksilver1989
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3 hours ago, Man With Beard said:

I think you are absolutely right. The online forecasts must be automated straight off the models. The Met Office are sticking to these higher values day after day, I note. 

correct as far as I know

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Must be terribly difficult in these situations to forecast anything. Wide area to cover and very variable conditions to take into account. 

A nice memorable storm is always good to get the Adrenalin going. Of course the usual caveats. No one hurt. No one scared. No puppies hurt or disturbed.   Nobody flooded. Nobody has their house zapped by lightning and other hazards.  Dare I say it not nothing too exciting otherwise we might have newspaper headlines such as “Shocking”. Well not really but it is the only  word most newspaper rags know. 

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Be lucky if we see a thunderstorm at this rate,nothing showing Saturday either,may see something next 24hours,but the sytems coming from france look like a damp squib so far in the south.

Edited by Snowyowl9
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https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/june-hot-spell-update

Differences to modelling of most note:

More breaking up of cloud Tue & Wed

Much more of a temperature differential when inland of the North Sea coasts, even just 20-odd miles e.g. London shown to hit 30*C on Thu.
Peak temps widely 4-7*C higher than ECM & FV3 are predicting (away from those coasts).

Mid-30s potential mentioned for Saturday (with usual caveats).
 

Also, details not shown on their maps, but text below implies minimums widely mid-teens+ in countryside, high teens to low 20s urban areas, as opposed to the low teens countryside, mid-teens urban areas that the modelling has overnight into each of Thu and Fri.

 

Truly fascinating to watch this play out.

Edited by Singularity
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57 minutes ago, Singularity said:

https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/june-hot-spell-update

Differences to modelling of most note:

More breaking up of cloud Tue & Wed

Much more of a temperature differential when inland of the North Sea coasts, even just 20-odd miles e.g. London shown to hit 30*C on Thu.
Peak temps widely 4-7*C higher than ECM & FV3 are predicting (away from those coasts).

Mid-30s potential mentioned for Saturday (with usual caveats).
 

Also, details not shown on their maps, but text below implies minimums widely mid-teens+ in countryside, high teens to low 20s urban areas, as opposed to the low teens countryside, mid-teens urban areas that the modelling has overnight into each of Thu and Fri.

 

Truly fascinating to watch this play out.

Reading the charts to my eyes, there is a long drawn Northerly then north easterly flow forecast Wednesday and Thursday so I can't see any significant warmth on those days except for sheltered western parts, so not surprised to see forecast maxes of just 22-24 degrees for the like of London.

As we hit Friday still a flow from the N Sea, despite the warm uppers, this will be counteracted by the source of the windflow.

Its Saturday when the chance of appreciable warmth is most likely, certainly low 30s very probable for SE parts, I will be surprised to see anything higher than 34 degrees, given we will be starting from a low base state, a couple more days of embedded warmth would have helped.. will wait and see.

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57 minutes ago, Singularity said:

https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/june-hot-spell-update

Differences to modelling of most note:

More breaking up of cloud Tue & Wed

Much more of a temperature differential when inland of the North Sea coasts, even just 20-odd miles e.g. London shown to hit 30*C on Thu.
Peak temps widely 4-7*C higher than ECM & FV3 are predicting (away from those coasts).

Mid-30s potential mentioned for Saturday (with usual caveats).
 

Also, details not shown on their maps, but text below implies minimums widely mid-teens+ in countryside, high teens to low 20s urban areas, as opposed to the low teens countryside, mid-teens urban areas that the modelling has overnight into each of Thu and Fri.

 

Truly fascinating to watch this play out.

Reading the charts to my eyes, there is a long drawn Northerly then north easterly flow forecast Wednesday and Thursday so I can't see any significant warmth on those days except for sheltered western parts, so not surprised to see forecast maxes of just 22-24 degrees for the like of London. The source of the air is from the cool north atlantic not the continent.

As we hit Friday still a flow from the N Sea, despite the warm uppers, this will be counteracted by the source of the windflow.

Its Saturday when the chance of appreciable warmth is most likely, certainly low 30s very probable for SE parts, I will be surprised to see anything higher than 34 degrees, given we will be starting from a low base state, a couple more days of embedded warmth would have helped.. will wait and see.

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57 minutes ago, Singularity said:

https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/june-hot-spell-update

Differences to modelling of most note:

More breaking up of cloud Tue & Wed

Much more of a temperature differential when inland of the North Sea coasts, even just 20-odd miles e.g. London shown to hit 30*C on Thu.
Peak temps widely 4-7*C higher than ECM & FV3 are predicting (away from those coasts).

Mid-30s potential mentioned for Saturday (with usual caveats).
 

Also, details not shown on their maps, but text below implies minimums widely mid-teens+ in countryside, high teens to low 20s urban areas, as opposed to the low teens countryside, mid-teens urban areas that the modelling has overnight into each of Thu and Fri.

 

Truly fascinating to watch this play out.

Reading the charts to my eyes, there is a long drawn Northerly then north easterly flow forecast Wednesday and Thursday so I can't see any significant warmth on those days except for sheltered western parts, so not surprised to see forecast maxes of just 22-24 degrees for the like of London. The source of the air is from the cool north atlantic not the continent.

As we hit Friday still a flow from the N Sea, despite the warm uppers, this will be counteracted by the source of the windflow.

Its Saturday when the chance of appreciable warmth is most likely, certainly low 30s very probable for SE parts, I will be surprised to see anything higher than 34 degrees, given we will be starting from a low base state, a couple more days of embedded warmth would have helped.. will wait and see.

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57 minutes ago, Singularity said:

https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/june-hot-spell-update

Differences to modelling of most note:

More breaking up of cloud Tue & Wed

Much more of a temperature differential when inland of the North Sea coasts, even just 20-odd miles e.g. London shown to hit 30*C on Thu.
Peak temps widely 4-7*C higher than ECM & FV3 are predicting (away from those coasts).

Mid-30s potential mentioned for Saturday (with usual caveats).
 

Also, details not shown on their maps, but text below implies minimums widely mid-teens+ in countryside, high teens to low 20s urban areas, as opposed to the low teens countryside, mid-teens urban areas that the modelling has overnight into each of Thu and Fri.

 

Truly fascinating to watch this play out.

Reading the charts to my eyes, there is a long drawn Northerly then north easterly flow forecast Wednesday and Thursday so I can't see any significant warmth on those days except for sheltered western parts, so not surprised to see forecast maxes of just 22-24 degrees for the like of London. The source of the air is from the cool north atlantic not the continent.

As we hit Friday still a flow from the N Sea, despite the warm uppers, this will be counteracted by the source of the windflow.

Its Saturday when the chance of appreciable warmth is most likely, certainly low 30s very probable for SE parts, I will be surprised to see anything higher than 34 degrees, given we will be starting from a low base state, a couple more days of embedded warmth would have helped.. will wait and see.

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Not much chance of high temperatures this week now,only Saturday.

Extremely wet now seriously wet after this morning, wettest month in living memory at 231mm smashed the previous record of july 2007.

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Here is a comparison between temperatures predicted on Sunday for 5pm today and the observed temperatures:

image.thumb.png.a1ad74d7fe1d984d85a7fc38a643411f.png  image.thumb.png.411a5c9ed350a5f6bbc7c9b2ef7ff588.png

Overall a pretty good set of estimates. Cirencester got up to 27C, so temperatures were underestimated a fair bit. Temperatures were also underestimated by quite a lot in South Wales (Got upto 22C in Pembrey sands and opposed to the forecast 14C. Crosby and Barrow in Furness also got upto 21C during the day in spite of forecast maxima of 14C.

In London and East Anglia the GFS predictions were spot on. Here in Hull the temperatures were lower then forecast because of the stubborn bands of rain which have proved slow to clear. Pretty poor day.

Intriguing that some parts of western England had temperatures underestimated by quite a large margin. I think the first test will be forecast maxima in Central Southern England tomorrow given the skies are forecast to clear. Elsewhere I expect maxima to be pegged back thanks to North Sea Cloud. GFS still going for a lot of sunny weather on Thursday so if temperatures over Southern England are a lot higher then forecast tomorrow that will be interesting.

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Today's highest readings were 38 in the lower Rhone valley and 36 in eastern Netherlands near the 576 dm wave crest. This wave crest is forecast to translate east into Germany with a second wave of heat moving north from France towards western Britain over the next two days. With that one, dew points are already around 22 C in some parts of central France (sure I posted this earlier but I don't see it, maybe in the wrong thread). 

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3 hours ago, Quicksilver1989 said:

 

In London and East Anglia the GFS predictions were spot on. Here in Hull the temperatures were lower then forecast because of the stubborn bands of rain which have proved slow to clear. Pretty poor day.

Got it wrong for the solent area too. GFS said 20C, but got to 25C at the official Met Office site in Gosport. 

Worth keeping a close eye on Gosport this week as the models consistently get the solent wrong in this set up, and it often ends up the hot spot. (not just being IMBY! ?

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1 minute ago, Man With Beard said:

Got it wrong for the solent area too. GFS said 20C, but got to 25C at the official Met Office site in Gosport. 

Worth keeping a close eye on Gosport this week as the models consistently get the solent wrong in this set up, and it often ends up the hot spot. (not just being IMBY! ?

Indeed if we get high 20s in the South tomorrow then that would make things really interesting. It got up to the mid 20s in many southern areas today and that was after cloud was sluggish to clear. If these southern areas are sheltered from the cool North Sea winds then it won't take much to lift them further in the sun. How much will the minima hold up tonight as well?

Here is the Sunday 18z GFS predictions for tomorrow and Thursday...
image.thumb.png.be3e9bac16563036bdb1124e80c15a52.pngimage.thumb.png.8f71377759cb3d5fd88c0bd1aba2a774.png  
 

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The first 40 C reading has appeared at Clermont-Ferrand (south central France -- latest reading 40.6) and it's 38 C within 100 km of Paris.

The 576 dm thickness contour has reached a line from just north of Paris to about L'Orient on the Atlantic coast. A small bubble of 582 dm thickness shows up in southwest France. The 570 dm thickness was just touching the southeast coast of England at 12z (CMC analysis for all these). The upper high over Europe has a central height of 599 dm, a value quite unusual there, occasionally you see that or 600-602 dm in subtropical highs over the Atlantic, south-central US or Pacific. The 12z height for London is 592 dm. 

On the meteociel hourly temperature map, I would say the extreme heat corresponds to the 576 dm thickness at present and there is a pooling of higher dew points towards that boundary, 22 C near Le Mans with humidex values above 40 C in a number of locations. But I think as the thicknesses advect north, the heat will begin to show up better between 570 and 576 dm as the dynamic front is further north than the weaker surface front causing that pooling effect. I also notice that the 06z GFS halted the recent trend to less robust northward thickness advection and slightly reversed it allowing the 576 dm contour onto land in Britain and surging the 570 past the northern tip of Ireland on Thursday. Those are signs that the heat in France will be partially released into the circulation setting up ahead of the Saturday cold front which is weak enough to suggest that temperatures won't even fall much on Sunday in southern England. I still foresee 34-36 C temperatures in the greater London area (Saturday seems assured, Friday could be 32-34 with perhaps a higher reading further west). Even on Sunday it will be 26-28 C in southeast England and there appears to be some hot weather possible at times in July also. 

This French heat machine will be hard to break down once established, so it's likely to be there most of the summer feeding into any opportunities for northward advection. 

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Tomorrow will be a halfway house between today's North Sea domination and Friday's French heat invasion. The cooler surface flow will be pushed back to about a B'ham to Luton to Ipswich arc, north of that it will likely just warm slightly over today. West and south of that it should reach 27 to 29 C in many areas. Parts of Somerset and Wales could benefit from being under the best upper support and reach 30-31 C. On Friday I think 33 to 36 C readings will prevail in many areas away from sea breeze territory and even there it could be 28 C. Saturday will see the heat more intense in the southeast and could produce a slightly higher reading (ECM gives 23 C 850 mb over London, that should mix down to about 35-36 C with a south-southwest wind ideal for heat generation, even a touch of downsloping into greater London with that). 

I don't think today's North Sea influence will really linger into the hot spell in any meaningful way, it's not going to take long for the warmer air mass to mix down its potential heat and with any sort of sustained sunshine the results may overperform. 

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It's like this thread is on another planet, despite a sunny afternoon it only reached 11.8C here and is now down to 8C it almost feels like a ground frost risk
We may get above 20C on Saturday - one day only.

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6 minutes ago, 4wd said:

It's like this thread is on another planet, despite a sunny afternoon it only reached 11.8C here and is now down to 8C it almost feels like a ground frost risk
We may get above 20C on Saturday - one day only.

Yes its a alternative universe ground frost possible tonight further north.

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