Thread by @RoostWeather

GFS 06Z run producing 42-43ºC as a maximum #temperature for the 17th July... here's some points of interest from a meteorological, and climatological point of view...

Plenty of discussion of whether this is realistic, or if there is some warm bias, problem with soil dryness/ feedback loops etc.

But, f/c 850mb temperatures are around 27-28ºC - assuming this is at 5000 ft (actually around 5150 ft) supports 42-43ºC in a well mixed atmosphere.

Looking at Herstmonceux #climate though, indicates that this air mass would be an extraordinary 5-6ºC higher than anything recorded since 2000 (and likely ever).

The highest since 12Z 28th June 2019 (22.6ºC)

We can also calculate the 1000-850mb thickness, which is often used in a similar way to the 850hPa #temperature as a cross check to model forecast temperatures.

At sea level, you need a thickness of 1450dam, assuming 1012mb sfc pressure and 2C super adiabat, to realise 42ºC

Again appealing to Herstmonceux climate, this is an incredible 28m above anything previously recorded.

The highest currently is 1422dam, recorded on 10th Aug 2003, which is when the old UK temperature record of 38.5ºC at Faversham was set.

In summary, it seems like achieving these temperatures is realistic in terms of the modelling, but requires conditions so far outside the recent climate that it seems hard to believe.

However, our warming climate means that we probably underestimate the chance of it happening.