The temperatures are already high this Wednesday, August 16 in the Southwest, but we are moving for the next few days towards a heat wave, undoubtedly remarkable, beyond 40°, in any case, late.
We are not yet at “a heat wave phenomenon”, even if the last days have been particularly hot in the South-West as on the whole territory. But the 15-day forecasts point to a heat wave which could lead to a remarkable heat wave, due to temperatures above 40° that it could reach, but also because it occurs after August 15.
Although it has been hot in recent days, the minimum temperatures – for example that of the night of Tuesday August 15 – were sufficiently cool and did not yet justify heat wave vigilance. For this Wednesday August 16, 2023, we remain in a fairly temperate situation, with thunderstorms forecast for the evening from the Pyrenees to Toulouse.
From Thursday August 17, the situation changes. Very hot air masses will be propelled over Spain and in the South-West with a southerly wind which will rise on the Pyrenean ridges. This warm air mass, from this Thursday and especially Friday, has several characteristics: it will be very hot at altitude, up to 26° in the Pyrenees, at 1500m. In the plain, the forecasts show, over several days, heat that can exceed 35°, or even go up to 40°.
The models indicate maximum temperatures which could rise to 40° in Toulouse, Montauban, Cahors, Auch and Saint-Gaudens. Some days, the heat may be tempered by the autan wind, in Toulouse in particular. This one will contain it despite its intensity. Overnight temperatures will be high everywhere.
As indicated Meteo France “These high temperatures promise to be lasting with peaks close to 40°C in the Mediterranean South and in the Rhône Valley from this weekend.“In this case a heatwave episode (To characterize a heat wave, the phenomenon must last at least three days and three nights. Certain temperature thresholds must also be reached or exceeded, which depend on the specificities of each territory and are set at the departmental level.)
Drawing. In the best case scenario, the fan provides relief from the heat. But there are other tricks. • © GUILLAUME CHHUM / FRANCE-BLEU ALSACE (+ FB ELSASS)
If necessary, this heat wave will be remarkable in two respects.
The first : it occurs after August 15 and is qualified in this case as a “late heat wave”. Normally, from mid-August, the duration of sunshine decreases as well as the temperatures, to gradually move towards autumn weather. Late heat waves have occurred in the past in 2009, 2011, 2012, 2019 and in 2020 where it occurred very late, between September 12 and 19. The second point: its duration. The 15-day forecast points to a heat wave that could last up to 10 or 12 days, which is exceptional.
It is however, for Christophe Dedieu, President of the association Weather Midi-Pyrenees, to temper these phenomena which have a degree of reliability of 60 to 70%. There would be uncertainties and the weather situation would not yet be “completely wedged» starting this Sunday, according to this weather enthusiast. A sea wind and a westerly wind should also punctually ventilate the temperatures, especially on the night of this Friday to Saturday. Nights that will be tropical and painful – also due to high humidity – with high night temperatures above 25° in the large agglomerations of the south-west, in particular that of Toulouse.
To end up concluding this meteorological moment announced as remarkable, Saharan sand dust will rise in the Pyrenees due to a vigorous southerly flow and probably coming from Morocco. They should alter the air quality.
On social networks, the subject is actively reacting, like the scientist Serge Zaka, doctor in agrometeorology: “France is about to experience one of (the?) most intense late heat waves ever observed. Values exceeding 40°C are modeled over several days (up to +12°C peak above standards.”
it will be very hot in the Occitanie region and it will be particularly painful, with however more ventilated areas. past August 15, the duration of sunshine and heat, usually and gradually, is reduced. In this, it would be an exceptional phenomenon. the heat wave could last if the forecast weather phenomenon is qualified as such. If it lasts and the phenomenon feeds itself, we could then observe a rise in temperatures to 40° among the different scenarios, a cold drop could come to refresh the time of the maximum ranging from 35 to 39° already represent an exceptional situation for a late summer.
On the rest of the territory, if there is a heat wave, it could also rage in the east, from Lyon to Burgundy going up to Alsace, or even to the Paris basin.
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