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


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2 minutes ago, DAVID SNOW said:

Paris?

No England / Wales. Will only take a slight shift on the flow to more of a SE.

Edited by Djdazzle
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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

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1 minute ago, Stabilo19 said:

GFS 06Z raw data for Saturday has 29 degrees for London. I don't think the record (35.6) will be broken at this rate. 

Depends how things evolve this week. With all the extreme heat in France, a SE wind will see the record here challenged.

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Just now, Djdazzle said:

Depends how things evolve this week. With all the extreme heat in France, a SE wind will see the record here challenged.

 

True, I don't think we can trust much beyond Tues - Wed! 

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In August 2003, the record breaking weekend was only forecast to be around 30C on Wednesday’s forecast. However, the flow was modified to be more SE as the weekend approached, which led to the record being broken.

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3 minutes ago, Djdazzle said:

Depends how things evolve this week. With all the extreme heat in France, a SE wind will see the record here challenged.

True but that isn't wants being shown with a eventually shift to the north west.

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Why are so many still expecting to see very hot weather in the coming week?

The models have delayed it and watered it down, the BBC/MetO don't seem sure, the weather apps don't support it now (I know they're not 100% reliable, but still), there's a risk of an easterly flow/cloud cover and we've had a cool, wet period so the ground's not already warm.

The only thing seems to be these weirdly high uppers?

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2 minutes ago, Djdazzle said:

In August 2003, the record breaking weekend was only forecast to be around 30C on Wednesday’s forecast. However, the flow was modified to be more SE as the weekend approached, which led to the record being broken.

Two things, its June not August and that forecast is 16 years ago, don't you think they have improved over that time?

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4 minutes ago, The PIT said:

True but that isn't wants being shown with a eventually shift to the north west.

At the end of the weekend, maybe. But from Thu / Sat, it’s a distinct possibility,

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1 minute ago, DAVID SNOW said:

Two things, its June not August and that forecast is 16 years ago, don't you think they have improved over that time?

I am talking about the June record going, not the all time one. Forecasts have improved, but we are talking very subtle shifts in direction here.

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3 minutes ago, Djdazzle said:

I am talking about the June record going, not the all time one. Forecasts have improved, but we are talking very subtle shifts in direction here.

Interesting week ahead weather wise, and the forecasting of it(whichever way it goes).

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1 hour ago, Froze were the Days said:

'poor summer' !?!...well might have been further north but here in the south, south/east there hasn't been a 'poor' summer since the Olympic summer of 2012, just the more unsettled month...

Unremarkable is perhaps more apt. Not much happened that summer.

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1 hour ago, summer blizzard said:

Unremarkable is perhaps more apt. Not much happened that summer.

It did on the canals and rivers, flooding happened throughout the summer and autumn months shutting navigation for long periods on some rivers, the Nene was only navigable for about 4 weeks of 2012.

I was trapped in a lock for a week on the Soar when  everything around disappeared underwater!

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Latest BBC forecast suggest warmest temperatures around South Wales for Thursday and Friday (27c/28c for Cardiff & 24/25c for London), then the hottest weather shifts to the SE for the weekend (up to 30c in London and 25c in Cardiff). 

Ofcourse actual temperatures still up for debate. Still suspect temperatures will be higher than forecast as we go through the week, particularly if we manage to get more of a SE’rly surface wind flow. 

Edited by danm
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19 minutes ago, matty40s said:

It did on the canals and rivers, flooding happened throughout the summer and autumn months shutting navigation for long periods on some rivers, the Nene was only navigable for about 4 weeks of 2012.

I was trapped in a lock for a week on the Soar when  everything around disappeared underwater!

Ah, i was talking of 2016.

2012 was of course an exceptional summer for the wrong reasons.

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If only it wasn't a game of probabilities, I'd gladly take the met office's forecast for Thurs to Sat at its word. High 20s, dry and sunny? Yes please.

I'm a pale skinned, freckled celt. Once it goes above 30, I need to hibernate ?

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I have the hunch that models will begin to show a more southerly component for the core of the heat Friday-Saturday and this will allow the higher readings to occur in southern England as in France. 

Meanwhile, the heat is on the move north. Today's hot spot in Spain is Zaragoza in the northeast at 37 C. Readings in southern France have come up a bit today also, 32 fairly common between Bordeaux and Marseilles. High 20s into Paris region now. The 576 dm thickness was shown a bit further north also, across west-central Spain. Its further progress appears to be a gradual push north into central and eastern France. 

(would agree a lot of things need to fall into line to get to my high reading of 38.7, the real over-under from all guidance appears to be 33 or 34). 

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Caught the 8 pm BBC forecast this evening and watched the wind flow carefully to see how it compared with the modelling of late. It's not an easy comparison but from experience of how their displays look during windy conditions, the flow off the North Sea didn't look as strong Wed-Fri across southern parts especially, once more than maybe 20 miles inland from the eastern coasts.

The more I read around, the more convinced I become that the models aren't predicting enough uplift in response to the strong surface heating (a lot of clear skies are expected). A common boundary layer modification shortfall that's plagued NWP models since their conception, due to not having sufficient resolution to model that process explicitly; they have to estimate the heating using equations that underestimate the true amount of vertical convection when surface heating is particularly high. The impact of this is most notable when there's a strong broad-scale flow that the convection modifies by an amount proportional to the strength of vertical motion.

This explains why, in the past few years of tracking model errors closely, the largest underestimations I've recorded have all been during sunny easterlies in May or June. The sun's strongest, and the North Sea typically still has a fair bit of warming up to do after its early spring minimum.

Last summer,  there was an unusually large number of days with such weather conditions, and I logged underestimations of 2-5*C for the maximums. Meanwhile, the overnight lows were only slightly higher, which makes sense as the higher the temp, the faster heat can be lost, so you'd not routinely expect a 3*C higher maximum to lead to a 3*C higher minimum.

 

So there you have it - I believe that vertical convection in response to surface heating by the sun is the most significant factor between, for example, a Thursday ECM 12z max of 24*C here and a BBC graphics max of 30*C (albeit using Southampton as a proxy).

The sheer size of that difference suggests that they may also be expecting a slightly weaker broad-scale flow for whatever reason, making for perhaps 1-2*C of the difference.

Yes, there's some speculation here, but I've yet to come across anything contradictory (famous last words! ?).

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I see the supressed modelled temperature charts have dampened enthusiasm for the upcoming hour spell - understandable, some of us have waited for years and years for upper air charts like these, only to have it put to us that they will produce averagely warm temperatures. 

I think it is far too early to "throw in the towel". First, I keep on comparing and comparing the upcoming charts to historical charts with similar features. None of them ever produced temperature outcomes like the ones being modelled for my area.

Second, the models tend to be horrible at localized differences. I live in one such place. The models constantly underestimate the heat from this pattern in the spot where I am - as I mentioned a few days ago, the GFS was 10C too low here not 24 hours before an event with similarities last year. 

Third, strange things happen in extreme situations at very short notice. We have this incredible heat over France this week. This will lead to a heat low, and probably storms. It won't take make encouragement for this heat low to try to travel north (that's what they tend to do). You can easily see on historic charts that a 5mb pressure error is quite possible even at T48/T72. A small pattern shift is all it will take to get a wide area into the 90s on Friday. 

I see the Met Office are still sticking 32C on charts for Thursday /Friday. I suspect this is actually a half way house between the lower temps on the models, and the actual potential in the situation ?

Edited by Man With Beard
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Not UK related, but just watched the German national weather forecast on ARD. They are expecting the June record to go on Wednesday, temps of 39 degrees forecast that day, most likely in the west/south west of the country.

The heat is most definitely going to be there, just a question of waiting to see exactly who gets it!?

 

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Met Office seem to think it’ll hit 29c/30c tomorrow in London, with 30c in the capital even on Wednesday and Thursday. Highest temperatures on Thursday will be further west in S Wales, W Country, SW England. Hotter again in the SE on Saturday before it turns cooler on Sunday. 

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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?

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