Florence Vaysse is the territorial referent of Météo France for Languedoc-Roussillon. It details the changes in terms of forecasting and vigilance since the 2002 tragedy.
Twenty years ago, the floods in the Gard caused 22 deaths and considerable damage. In terms of meteorology, what has changed since then?
Lots of stuff. In the area of the tools we benefit from first of all: there have been great technical improvements. Radars have improved, as have satellite images or digital models, thanks to increasingly powerful computers… Forecasts are therefore more precise.
Moreover, in 2002, we were only at the very beginning of weather vigilance, which was created in 2001 following the storms of December 1999 and the floods in the Aude.
What is it about ?
Vigilance is designed to inform citizens and public authorities in the event of dangerous phenomena within the next 24 hours.
Previously, until 2001, authorities were notified if a risky event was anticipated, but there was no direct communication to the general public. In 2002, there were no smartphones and no notifications… Since this tragedy, vigilance has progressed as events unfolded.
More parameters are taken into account. Heat wave vigilance, for example, was set up in 2004 following the summer 2003 disaster. In 2006, there was the creation of flood vigilance, differentiated from that of rain: a major development terms of prevention. For each event, we provide feedback for continuous improvement. Here, we are taking stock of the episodes that have struck us in recent days.
General public: how to get informed
As Florence Vaysse recalls, in 2002, no one had a smartphone in their pocket. “On the Météo France application, everyone can subscribe to alerts by entering their geolocation to be immediately informed of vigilance in the Gard or their vacation spot, for example, via a notification.”
But it invites the general public to go further, to benefit from more precise elements. “When we are on the alert, everyone can easily go and see the constantly updated monitoring bulletin, which gives more localized information than the departmental level.” On the web: www.vigilance.meteofrance.fr.
Precisely: these recent episodes have been fairly localized, while the vigilance of Météo France is notified on a departmental scale. Isn’t this too wide?
Vigilance has been designed at the departmental level since its origin because it is the most relevant scale for our institutional interlocutors, starting with the COD (Departmental operational center, the crisis management tool available to the prefect, editor’s note) . Incidentally, I remind you that if Météo France calls for vigilance, it is the prefecture that decides on alerts and issues them…
Regarding this week’s episodes, they were called V cells, which produce stationary thunderstorms. In this case, the models make it possible to predict a stormy situation, but they have great difficulty in predicting the onset and the duration of stationarity…
For heat waves, for example, which can affect 10 or 15 departments, there is little uncertainty, we see them coming. But these Mediterranean storms are so small-scale and fast-moving that they slip through the cracks of the models. But beyond departmental vigilance, we produce continuous monitoring bulletins, accessible to everyone with, as soon as we can, more details and localized data.
People sometimes have the feeling that there are more and more alerts…
Because more parameters are taken into account. But also because in our region, studies show, the frequency of Mediterranean episodes and their intensity have increased. There is a consensus on an increase of more than 20% over 50 years and the projections for the future still point in this direction.
If it happened today, would the 2002 rainfall cause less damage or death?
I cannot answer you. There would have been, upstream, more fluid information to the general public. Since then, more information campaigns on the risks and behaviors not to have have been carried out. And there’s also the impact of the work and the developments, which I don’t know how to assess. If it is impossible to say so, I think that the consequences would probably not be the same.
In the future, more and more violent episodes
“What is exceptional in the 2002 phenomenon, in addition to the record rainfall, is the importance of the very large area that was affected”, recalls Florence Vaysse. More than 5,000km2 (almost the whole of the Gard department) received rainfall above 200mm, the maximum approaching the incredible figure of 700mm. “In recent days, continues the scientist in comparison, we have recorded bands of very heavy rain, intense but localized.”
Question: Could the vast deluge of September 8 and 9, 2002 happen again? “Yes, it will happen again, she answers without hesitation. But will it be this fall, in 20 years or in 50 years: we don’t know.”
Climate projections do not lead to optimism: if they promise “little change in annual accumulations by the end of the 21st century” (source: climat HD, on meteofrance.fr), the so-called exceptional phenomena will be at the both more frequent and more violent in the future.
It’s going to get hotter and hotter!
Ditto side dryness and heat. Since the creation of the Nîmes-Courbessac weather station in 1921, the 40°C threshold had been crossed three times in 80 years, between 1921 and 2000. It was exceeded 10 times in 20 years from 2001 to 2022, including nine times after 2017 and… three times during this summer of 2022 alone! “The records for the driest or hottest periods will become the average after 2050”, announces Florence Vaysse.
Even if political measures made it possible to significantly reduce CO2 emissions, the warming will continue in Languedoc-Roussillon, observe the climatologists of Météo France. “It could exceed 5°C in average annual temperature at the end of the century compared to the period 1976-2005.”