Predict the hottest day of 2024 (UK) Competition

[Metwatch]

On 07/05/2024 at 13:21, Metwatch said:

35.3C July 28th, somewhere in London.

Should the 34.8C remain as it is, this would be a pretty decent guess, a bit off with exact date and location, but the previous hottest day was on the 30th July in London, which in a way makes that closer although that was 3 degrees lower!

Edited August 13 by Metwatch

[Summerlover2006]

At this current time who is the closest winner ?? 

[WYorksWeather]

18 hours ago, CryoraptorA303 said:

If I had to guess I'd say losing the dynamical advantage of day being longer than night is what really kills the prospects in the end and starts to seriously disadvantage hot air from a thermodynamical point of view as now night is longer than day and the overall constant direction is loss no matter what the airmass does, while before it could reliably gain or maintain as day was longer.

Another key reason is that in August and early September the SSTs are still slowly rising, which balances out the declining solar input. From mid-September onwards both of those things point towards cooling - they add up rather than cancelling out.

In spring, the equivalent is why for example late February doesn't have that much higher of a temperature ceiling than early February, because solar input is increasing relatively slowly and SSTs are still decreasing. As you flip the page into March though, suddenly both point in the same direction, and you end up with very rapid warming.

[BlueSkies_do_I_see]

 Metwatch I have not had chance to collate every guess and will by mid Sept when I personally consider it neigh on impossible for the UK to exceed 34.8C. 

But from what I can tell you are the closest est guess with 35.2C.  Most went below 33C or above 36C. So well done. 

[WYorksWeather]

 BlueSkies_do_I_see Some of the top end on the GFS ensembles might just about challenge it in the next 10 days or so - a few members going for 34C or 35C at some point late August into the opening days of September. Perhaps just about feasible that 34.8C could be overturned, but I think the likelihood at the moment is very low, less than 10%. No GFS OP run has yet gone that high, nor any other main model as far as I'm aware.

[Metwatch]

 BlueSkies_do_I_see

In terms of date / location though, It does look like @cheese would be the closest!

On 18/05/2024 at 21:09, cheese said:

36.8C on the 10th of August at Cambridge

 

[BlueSkies_do_I_see]

 WYorksWeather I think 35C is around the upper limit of what is possible late August and early September in the UK, so you could end up closer. But having said that, weather records such as this January's 19.9C, February 2019's, Nov 2015's 22.4C,  21.2C and the 40.3C a couple of years ago, keep pushing the envelope of what I perceive possible.

[cheese]

 Metwatch let's split the prize money 

[damianslaw]

 BlueSkies_do_I_see I guessed 34.5 degrees Heathrow first half August, not bad eh!

[WYorksWeather]

 BlueSkies_do_I_see It's an interesting one that - the upper limit debate always is.

Clearly the lowest level the upper limit can be is the 35.6C from 2nd September 1906. That record is pretty well supported by other stations with a large number exceeding 34C, and so there's no real reason to doubt its validity, unlike some other very old records.

I think that you can then make the following adjustments if we're talking about a limit - at a minimum add half a degree to a degree or so by moving the heatwave from the early September period to late August. This would give you about another half an hour or so of daylight, possibly a little more, and hence you'd expect the outcome to have been warmer. Then, you add a degree or so perhaps to account for modern warming, so that probably pushes the envelope to around 38C for late August, probably 37C for early September.

However, you then have to ask how realistic that is a scenario. You could quite well argue that the combination of an extreme late-season plume and a very dry summer to precede it was such a rare event that it might have been a 1 in 1000 year event at the time. That could well mean that even now it would require a 1 in 100 year event to match it. Numbers are hypothetical, but you take the point.

I do think that given we've seen a few attempts to challenge the 1906 record in recent years (2016 and 2023 only 2-3C below it) that we might break it within the next 10-20 years. But I think the odds of breaking it by a very substantial margin, like the upper limit I suggested of pushing the record all the way to 37C for early September, seem much lower.

In terms of this year specifically - I don't expect it to be challenged. Only one or two rogue ensemble members have even showed a raw 35C, let alone anything above that, so the probability is very low. The most recent GFS 12z has also dropped the very hot outliers - for the moment at least we look to be coalescing around an outcome in the high 20s or low 30s. Mid 30s was never looking likely and now looks even more unlikely.

 

 

 

[BlueSkies_do_I_see]

 damianslaw excellent prediction for both temp and August too. You are the closest temperature prediction by 0.1C.