Cyclonic risk : from prevention to crisis management
“The cyclonic risk and its effects in the Caribbean basin and Saint Barthélemy” was the theme of the conference held Saturday, June 2, 2018. Fifty people attended this event given by Romain MEUNIER, crisis managment specialist and engineer within Predict Services.
The day after the opening of 2018 hurricane season, this conference aimed to draw up an inventory of the hurricane problematic and its management.
Reminder of the key points of the conference below
It is important to remember that a Hurricane can have several effects on an island:
⇨ Strong winds: wind strength and sudden changes in direction and intensity. Maximum winds blow in the eyewall. Some site effects can increase the impact of the wind. This risk concerns the entire island.
⇨ Torrential rains: floods, landslides, mudslides, scree, floods and overflowing gullies. This risk concerns low points, urbanized areas and areas of steep slopes.
⇨ Cyclonic swell: At the hurricane core, strong winds generate enormous waves that can reach 10 to 20 meters high by friction with the surface of the sea.
⇨ Storm surge: abnormal rise in mean sea level associated with the passage of the cyclone. The rise is maximum just before the hurricane eye passing through.
These last two phenomena concern low-lying coastal areas.
❖ Anticipating a cyclone for a better prevention
Since the 1980s, the increasing power of computers and the collection of measurements have increased the reliability of cyclonic forecast models. The arrival of satellite imagery has also considerably improved the analysis of the development and evolution of hurricanes.
At the island level, it is also possible to improve resilience. It contributes to the prevention and reduction of disasters by focusing on making the population actress, both ot the actions of risk reduction and the future of territories. Resilience consists of:
- a capacity of adaptation and organization of a territory to enable it to anticipate and face harmful events as much as possible
- but also in the capacity of collective and individual learning for a better adaptation to the cyclonic risk.
Resilience is a continuous and evolving process over time. It requires drawing lessons and if necessary, making adjustments to the organization of the territory.
❖ What link between cyclonic activity and climate change?
First observation: The number of cyclones observed in 2017 -17 tropical systems, including 10 hurricanes and 6 major hurricanes- is well above the normal of the last 30 years set at 12 tropical storms, 6 hurricanes and 2 major hurricanes. This makes the 2017 season one of the 10 most active seasons in the known weather history. Nevertheless, if 2017 was intense in the North Atlantic, this was not the case in previous years. Therefore, nothing allows us to draw conclusions about the activity of the 2018 season.
Second observation: 2017 was an exceptional season in terms of power and cyclonic intensity. September 2017 sets a new monthly record for cyclone energy in the Atlantic, due, in part, to the duration of the hurricane. This month has even become the most active month of all time!
Hurricane Irma, which remained in category 5 for more than three days (with 295 km / h average winds for 36 hours – a world record – and gusts winds estimated at 350 km / h), perfectly illustrates the IPCC (Intergovernmental Panel on Climate Change) projections: “It is likely that global tropical cyclone frequency will decrease or remain substantially the same, with a likely increase in the maximum speed of wind and rainfall intensity attributable to tropical cyclones. “
Romain Meunier Romain Meunier works for Predict Services, a subsidiary of Météo France. Specialist in flood, tsunami and cyclone issues, he focuses more specifically on the Caribbean.